On Tue, 11 Apr 2006 23:24:21 -0500, Joseph Gwinn
wrote:

In article ,
Eric R Snow wrote:

On Tue, 11 Apr 2006 11:21:34 -0700, "Ken Davey"
wrote:


O.K. As long as you don't spin the bearing with the compressed
air. *That* can be disastrous.

How so?

It can spin up to a fast enough RPM so the centrifugal force (I
know -- there really is no such thing) will cause it to fly apart
-- turning it into shrapnel -- and *you* into a target. I don't
know whether there is any size limit for this to happen, but it
has been known to happen and to harm or kill people nearby.

Ahh. I can see a large bearing being driven fast enough to explode,
especially as bearing races are designed to be reinforced by being
pressed into a recess in a larger housing.

However, One would think that overspeed isn't going to be an issue
with small bearings already specified for 30,000 rpm, unless one's
air supply is something else.


Spinnning a bearing with compressed air is a complete NONO!
Firstly this practice will ruin the bearing - think no lubrication.
Dangerous - as has been mentioned the bearing can explode and sometimes the
bearing will seize.
As the handiest workholder is a finger a seizure at high speed will severely
damage said workholder.

Cleaning with air is quite allright - oil the bearing immediately after such
treatment as moisture will be present in the air and/or will condence on the
(now) cold bearing.

Regards.
Ken

--
Volunteer your idle computer time for cancer research
http//www.grid.org/download/gold/download.htm
Return address courtesy of Spammotel http://www.spammotel.com/

Years ago I was blowing out some bearings with air. Goofing off, with
the bearing on my finger, I spun one up and listened to the pitch. As
it spun the pitch got higher until I couldn't hear it. Just as it
passed into my ultrasonic range it exploded with a bang.

Ultrasonic! Wow. That implies a ball-passing frequency exceeding
20,000 per second or so. If the ball cage has ten balls in it, the cage
is rotating at 2000 rps, or 120,000 rpm, and the outer race a factor
faster. No wonder it exploded.
MY ultrasonic range. I know my high frequency hearing is damaged. But
it was still really spinning fast.

Do you recall the dimensions of the deceased ball bearing?
The ID was about 5/8 and the OD maybe 1 1/2, 1/34.


The bearing
axis was perpendicular to my body so that the bearing parts were
embedded into the wall and not me. My finger hurt like hell. I think
the bearing must have exploded pretty equally because otherwise that
finger would have probably broken instead.

Yes. Lab ultra-centrifuges are built inside a heavy steel box, to
contain the shards of the rotor, when (not if) it explodes. When this
happens, the centrifuge is totally destroyed.


I don't spin up bearings
any more. Not even a little.

It sounds like there is actually quite a wide safe range here. Just
stay in the sonic range?
No way. A small bearing may take the rpm. But a larger one will
explode much sooner. Just don't spin 'em up.

Joe Gwinn

On Wed, 12 Apr 2006 07:18:44 -0700, Eric R Snow
wrote:

On Tue, 11 Apr 2006 23:24:21 -0500, Joseph Gwinn
wrote:

In article ,
Eric R Snow wrote:

On Tue, 11 Apr 2006 11:21:34 -0700, "Ken Davey"
wrote:


O.K. As long as you don't spin the bearing with the compressed
air. *That* can be disastrous.

How so?

It can spin up to a fast enough RPM so the centrifugal force (I
know -- there really is no such thing) will cause it to fly apart
-- turning it into shrapnel -- and *you* into a target. I don't
know whether there is any size limit for this to happen, but it
has been known to happen and to harm or kill people nearby.

Ahh. I can see a large bearing being driven fast enough to explode,
especially as bearing races are designed to be reinforced by being
pressed into a recess in a larger housing.

However, One would think that overspeed isn't going to be an issue
with small bearings already specified for 30,000 rpm, unless one's
air supply is something else.


Spinnning a bearing with compressed air is a complete NONO!
Firstly this practice will ruin the bearing - think no lubrication.
Dangerous - as has been mentioned the bearing can explode and sometimes the
bearing will seize.
As the handiest workholder is a finger a seizure at high speed will severely
damage said workholder.

Cleaning with air is quite allright - oil the bearing immediately after such
treatment as moisture will be present in the air and/or will condence on the
(now) cold bearing.

Regards.
Ken

--
Volunteer your idle computer time for cancer research
http//www.grid.org/download/gold/download.htm
Return address courtesy of Spammotel http://www.spammotel.com/

Years ago I was blowing out some bearings with air. Goofing off, with
the bearing on my finger, I spun one up and listened to the pitch. As
it spun the pitch got higher until I couldn't hear it. Just as it
passed into my ultrasonic range it exploded with a bang.

Ultrasonic! Wow. That implies a ball-passing frequency exceeding
20,000 per second or so. If the ball cage has ten balls in it, the cage
is rotating at 2000 rps, or 120,000 rpm, and the outer race a factor
faster. No wonder it exploded.
MY ultrasonic range. I know my high frequency hearing is damaged. But
it was still really spinning fast.

Do you recall the dimensions of the deceased ball bearing?
The ID was about 5/8 and the OD maybe 1 1/2, 1/34.


The bearing
axis was perpendicular to my body so that the bearing parts were
embedded into the wall and not me. My finger hurt like hell. I think
the bearing must have exploded pretty equally because otherwise that
finger would have probably broken instead.

Yes. Lab ultra-centrifuges are built inside a heavy steel box, to
contain the shards of the rotor, when (not if) it explodes. When this
happens, the centrifuge is totally destroyed.


I don't spin up bearings
any more. Not even a little.

It sounds like there is actually quite a wide safe range here. Just
stay in the sonic range?
No way. A small bearing may take the rpm. But a larger one will
explode much sooner. Just don't spin 'em up.

Joe Gwinn


Im going to have to try that one of these days.

Safely of course.

Gunner

"I think this is because of your belief in biological Marxism.
As a genetic communist you feel that noticing behavioural
patterns relating to race would cause a conflict with your belief
in biological Marxism." Big Pete, famous Usenet Racist

"Eric R Snow" wrote in message
...
On Tue, 11 Apr 2006 23:24:21 -0500, Joseph Gwinn
wrote:

In article ,
Eric R Snow wrote:

On Tue, 11 Apr 2006 11:21:34 -0700, "Ken Davey"
wrote:


O.K. As long as you don't spin the bearing with the compressed
air. *That* can be disastrous.

How so?

It can spin up to a fast enough RPM so the centrifugal force (I
know -- there really is no such thing) will cause it to fly apart
-- turning it into shrapnel -- and *you* into a target. I don't
know whether there is any size limit for this to happen, but it
has been known to happen and to harm or kill people nearby.

Ahh. I can see a large bearing being driven fast enough to
explode,
especially as bearing races are designed to be reinforced by being
pressed into a recess in a larger housing.

However, One would think that overspeed isn't going to be an issue
with small bearings already specified for 30,000 rpm, unless one's
air supply is something else.


Spinnning a bearing with compressed air is a complete NONO!
Firstly this practice will ruin the bearing - think no lubrication.
Dangerous - as has been mentioned the bearing can explode and sometimes
the
bearing will seize.
As the handiest workholder is a finger a seizure at high speed will
severely
damage said workholder.

Cleaning with air is quite allright - oil the bearing immediately after
such
treatment as moisture will be present in the air and/or will condence
on the
(now) cold bearing.

Regards.
Ken

--
Volunteer your idle computer time for cancer research
http//www.grid.org/download/gold/download.htm
Return address courtesy of Spammotel http://www.spammotel.com/

Years ago I was blowing out some bearings with air. Goofing off, with
the bearing on my finger, I spun one up and listened to the pitch. As
it spun the pitch got higher until I couldn't hear it. Just as it
passed into my ultrasonic range it exploded with a bang.

Ultrasonic! Wow. That implies a ball-passing frequency exceeding
20,000 per second or so. If the ball cage has ten balls in it, the cage
is rotating at 2000 rps, or 120,000 rpm, and the outer race a factor
faster. No wonder it exploded.
MY ultrasonic range. I know my high frequency hearing is damaged. But
it was still really spinning fast.

Do you recall the dimensions of the deceased ball bearing?
The ID was about 5/8 and the OD maybe 1 1/2, 1/34.


The bearing
axis was perpendicular to my body so that the bearing parts were
embedded into the wall and not me. My finger hurt like hell. I think
the bearing must have exploded pretty equally because otherwise that
finger would have probably broken instead.

Yes. Lab ultra-centrifuges are built inside a heavy steel box, to
contain the shards of the rotor, when (not if) it explodes. When this
happens, the centrifuge is totally destroyed.


I don't spin up bearings
any more. Not even a little.

It sounds like there is actually quite a wide safe range here. Just
stay in the sonic range?
No way. A small bearing may take the rpm. But a larger one will
explode much sooner. Just don't spin 'em up.

Joe Gwinn

The other reason not to spin up a bearing with air:
Consider the setting.. You just cleaned out a nice bearing and want to dry
the solvent out. You spin it up with air to MHS speed and suddenly it
starts feeling rough and noisy. You just dislodged a piece of your favorite
hard stuff that went into the bearing race and got mashed at even a nice
"safe" 30,000 RPM. If you are spinning up a bearing dry you are running at
very high speeds with no lubrication and no shields or seals.
Having said that .. they sure make some interesting sounds and go really
fast when you release them on the garage floor Dad was NOT amused LOL
Glenn

"Joseph Gwinn" wrote in message
...
In article ,
"Glenn" wrote:

"Glenn" wrote in message
...

"DoN. Nichols" wrote in message
...
According to Joseph Gwinn :
In article ,
(DoN. Nichols) wrote:
much snippage
Got them, Thanks. Would have liked the photos to be legible.
Perhaps
we can impose on the poster to provide a high-rez scan as well.

No imposition at all. I have placed a larger file on my webspace at
http://webpages.charter.net/gsneff/
Look at that and let me know if you want it bigger. I was actually quite
suprised it came out so small when scanned to PDF. According to my
scanner
software each page was going to be about 6 meg .. something mystical
happened though and it came out at ~1.6 meg.

I got the file, and it looks good. Thanks.

Probably the 6/1.6= 3.75:1 reduction is due to compression of the image,
which is automatic unless one sets some controls to forbid compression.

Joe Gwinn
Ok .. Great
What acrobat said when I saved the file was that it was removing empty
space. ??
Glenn

On Tue, 11 Apr 2006 12:43:46 -0700, Eric R Snow
wrote:

On Tue, 11 Apr 2006 11:21:34 -0700, "Ken Davey"
wrote:


O.K. As long as you don't spin the bearing with the compressed
air. *That* can be disastrous.

How so?

It can spin up to a fast enough RPM so the centrifugal force (I
know -- there really is no such thing) will cause it to fly apart
-- turning it into shrapnel -- and *you* into a target. I don't
know whether there is any size limit for this to happen, but it
has been known to happen and to harm or kill people nearby.

Ahh. I can see a large bearing being driven fast enough to explode,
especially as bearing races are designed to be reinforced by being
pressed into a recess in a larger housing.

However, One would think that overspeed isn't going to be an issue
with small bearings already specified for 30,000 rpm, unless one's
air supply is something else.


Spinnning a bearing with compressed air is a complete NONO!
Firstly this practice will ruin the bearing - think no lubrication.
Dangerous - as has been mentioned the bearing can explode and sometimes the
bearing will seize.
As the handiest workholder is a finger a seizure at high speed will severely
damage said workholder.

Cleaning with air is quite allright - oil the bearing immediately after such
treatment as moisture will be present in the air and/or will condence on the
(now) cold bearing.

Regards.
Ken

--
Volunteer your idle computer time for cancer research
http//www.grid.org/download/gold/download.htm
Return address courtesy of Spammotel http://www.spammotel.com/

Years ago I was blowing out some bearings with air. Goofing off, with
the bearing on my finger, I spun one up and listened to the pitch. As
it spun the pitch got higher until I couldn't hear it. Just as it
passed into my ultrasonic range it exploded with a bang. The bearing
axis was perpendicular to my body so that the bearing parts were
embedded into the wall and not me. My finger hurt like hell. I think
the bearing must have exploded pretty equally because otherwise that
finger would have probably broken instead. I don't spin up bearings
any more. Not even a little.
ERS

Hi Eric,

I was maybe ~14 when I did this. The farmer I worked for had
the airgun in his hand and I had the old wheel bearing
(roller bearing) on my finger like a ring. He had a hold of
the end of my finger. One of the airguns we had been using
could really make it sing, but it would top out. There was
another airgun attachment though that had a bigger hole and
put out more cfm. Much like your episode, about time the
singing noise went above our hearing level the bearing blew.
It cut by finger twice, clear around at the edges of the
bearing. My farmer buddy got a nice bruise on his thigh
about the size of a silver dollar. Both of us learned a
valuable lesson and luckily neither of us had to get medical
attention. Doggone finger hurt for quite awhile though

I can still remember saying, "leave the air on, let's see
how fast it will go!"

--
Leon Fisk
Grand Rapids MI/Zone 5b
Remove no.spam for email

On Wed, 12 Apr 2006 08:50:19 -0700, "Glenn"
wrote:



The other reason not to spin up a bearing with air:
Consider the setting.. You just cleaned out a nice bearing and want to dry
the solvent out. You spin it up with air to MHS speed and suddenly it
starts feeling rough and noisy. You just dislodged a piece of your favorite
hard stuff that went into the bearing race and got mashed at even a nice
"safe" 30,000 RPM. If you are spinning up a bearing dry you are running at
very high speeds with no lubrication and no shields or seals.
Having said that .. they sure make some interesting sounds and go really
fast when you release them on the garage floor Dad was NOT amused LOL
Glenn

IIRC there was a post some years back about a fair sized, spun up
bearing released to travel down the street with startling (to some
innocent drivers) results.
Gerry :-)}
London, Canada

According to Glenn :

"DoN. Nichols" wrote in message

[ ... ]

I believe that it will do for the task.

Thank you for this.

Quite Welcome

[ ... ]

And also on page 2 is the all upper case:

"WARNING: DO NOT EXCEED WHEEL SPEED RECOMMENDATIONS."

(But no exclamation point at the end. :-)

The manual is obviously older than my grinder, because of the
lack of 3-pin power connectors. But it is obviously for the same
grinder, as the model number (first four digits of the serial number)
matches.

Kinda fun looking at these old manuals .. especially the price list :-)

Yep! I wish that we could still get things at those prices. :-)

[ ... ]

The added info in the .txt file will help as well. I am glad to
get confirmation that the spindle thread was originally 1/4-32.

Was there only the one "Chuck assembly" with a 1/8" bore? That
would appear to be the case, based on the parts list and drawing.

Only 1 chuck came with mine. There is a hombrew thing in there for holding
a stone but it has no threads and the stone is glued to the brass.

O.K. The manual only shows the one chuck.

I am now most of the way through making the chuck for mine. I
need to make a D-reamer to cut the taper inside the nut, and then I need
to slot the collet, and cut the wrench flats on both. I had to
single-point cut the threads in the nut -- I wish that I had known to
order a 5/16-32 tap while I was ordering the 1/4-32. :-)

And -- I have verified that the arbor nut (and the pulley nuts)
on mine are all 7/16" across flats.

Also -- I have verified that the height range will bring it up
to center height with no problems on my Clausing -- and that I need to
make a T-nut to fit the Clasuing, as the one which is there is too tiny
and has to be inserted rotated to bite at all.

So -- the largest wheel really was a 2" one. I've got some
larger ones which I have adapted to the spindle which are still well
within their speed rating -- but perhaps the motor does not have the
horsepower to drive the larger wheels. I guess that I'll find out.

Mine drives a 2.5" wheel ok.

I've got a pair of wheels (which did not come with it) which are
nearly 3" diameter, and which finally defined the ID of the guard.

The design of the diamond holder is different than I had
expected -- but makes sense if you have to re-dress the wheel part-way
through the task.

I don't see the diamond holder listed in the parts list, nor in
the drawing.

Mine dosen't have the wheel dresser either but I intend to make one.

As do I -- though I may try some other ideas for initial
dressing (mount in the collet before the workpiece goes in, not on the
workpiece), and save the shape shown in the manual for dressing in the
middle of a project.

Again, thanks,
DoN.



--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

According to Joseph Gwinn :
In article ,
Eric R Snow wrote:

[ ... ]

Years ago I was blowing out some bearings with air. Goofing off, with
the bearing on my finger, I spun one up and listened to the pitch. As
it spun the pitch got higher until I couldn't hear it. Just as it
passed into my ultrasonic range it exploded with a bang.

Ultrasonic! Wow. That implies a ball-passing frequency exceeding
20,000 per second or so. If the ball cage has ten balls in it, the cage
is rotating at 2000 rps, or 120,000 rpm, and the outer race a factor
faster. No wonder it exploded.

Do you recall the dimensions of the deceased ball bearing?

Since it was on his finger, a guess says that the ID of the
inner race was probably on the order of 5/8". Scale the rest to that.


The bearing
axis was perpendicular to my body so that the bearing parts were
embedded into the wall and not me. My finger hurt like hell. I think
the bearing must have exploded pretty equally because otherwise that
finger would have probably broken instead.

[ ... ]

I don't spin up bearings
any more. Not even a little.

It sounds like there is actually quite a wide safe range here. Just
stay in the sonic range?

That depends on the size of the bearing -- and your personal
hearing range. :-)

A large bearing (say 1-1/2" ID on the inner race) could probably
get to dangerous speeds while the tone remained in the audible range.
And -- it is affected in part by the number of balls in the race. Some
(for heavy loads) have completely full races, others have fewer balls,
with some mechanism to space them out. I've seen ribbons of steel
formed into cups around both sides riveted together. I've seen bakelite
machined to slip in from one side once the bearings are properly spaced.
I've even seen bearings with little coil springs set between the balls
to keep them spaced out. This was in a vary slow, and very low
operating force setup -- like a gimbal gyro cage.

Enjoy,
DoN.
--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

In article , "Glenn"
wrote:

"Joseph Gwinn" wrote in message
...
In article ,
"Glenn" wrote:

"Glenn" wrote in message
...

"DoN. Nichols" wrote in message
...
According to Joseph Gwinn :
In article ,
(DoN. Nichols) wrote:
much snippage
Got them, Thanks. Would have liked the photos to be legible.
Perhaps
we can impose on the poster to provide a high-rez scan as well.

No imposition at all. I have placed a larger file on my webspace at
http://webpages.charter.net/gsneff/
Look at that and let me know if you want it bigger. I was actually quite
suprised it came out so small when scanned to PDF. According to my
scanner
software each page was going to be about 6 meg .. something mystical
happened though and it came out at ~1.6 meg.

I got the file, and it looks good. Thanks.

Probably the 6/1.6= 3.75:1 reduction is due to compression of the image,
which is automatic unless one sets some controls to forbid compression.

Joe Gwinn
Ok .. Great
What acrobat said when I saved the file was that it was removing empty
space. ??

I don't really know what acrobat means by this, but speculate that it
uses a convenient temporary file format while building the file, then
goes back and closes up the space that turned out not to be needed.

Joe Gwinn

Okay, so I'm late and catching up, but Gunner
wrote on Wed, 12 Apr 2006 15:18:35 GMT in rec.crafts.metalworking :
On Wed, 12 Apr 2006 07:18:44 -0700, Eric R Snow
wrote:

On Tue, 11 Apr 2006 23:24:21 -0500, Joseph Gwinn
wrote:

In article ,
Eric R Snow wrote:

On Tue, 11 Apr 2006 11:21:34 -0700, "Ken Davey"
wrote:


O.K. As long as you don't spin the bearing with the compressed
air. *That* can be disastrous.

How so?

It can spin up to a fast enough RPM so the centrifugal force (I
know -- there really is no such thing) will cause it to fly apart
-- turning it into shrapnel -- and *you* into a target. I don't
know whether there is any size limit for this to happen, but it
has been known to happen and to harm or kill people nearby.

Ahh. I can see a large bearing being driven fast enough to explode,
especially as bearing races are designed to be reinforced by being
pressed into a recess in a larger housing.

However, One would think that overspeed isn't going to be an issue
with small bearings already specified for 30,000 rpm, unless one's
air supply is something else.


Spinnning a bearing with compressed air is a complete NONO!
Firstly this practice will ruin the bearing - think no lubrication.
Dangerous - as has been mentioned the bearing can explode and sometimes the
bearing will seize.
As the handiest workholder is a finger a seizure at high speed will severely
damage said workholder.

Cleaning with air is quite allright - oil the bearing immediately after such
treatment as moisture will be present in the air and/or will condence on the
(now) cold bearing.

Regards.
Ken

--
Volunteer your idle computer time for cancer research
http//www.grid.org/download/gold/download.htm
Return address courtesy of Spammotel http://www.spammotel.com/

Years ago I was blowing out some bearings with air. Goofing off, with
the bearing on my finger, I spun one up and listened to the pitch. As
it spun the pitch got higher until I couldn't hear it. Just as it
passed into my ultrasonic range it exploded with a bang.

Ultrasonic! Wow. That implies a ball-passing frequency exceeding
20,000 per second or so. If the ball cage has ten balls in it, the cage
is rotating at 2000 rps, or 120,000 rpm, and the outer race a factor
faster. No wonder it exploded.
MY ultrasonic range. I know my high frequency hearing is damaged. But
it was still really spinning fast.

Do you recall the dimensions of the deceased ball bearing?
The ID was about 5/8 and the OD maybe 1 1/2, 1/34.


The bearing
axis was perpendicular to my body so that the bearing parts were
embedded into the wall and not me. My finger hurt like hell. I think
the bearing must have exploded pretty equally because otherwise that
finger would have probably broken instead.

Yes. Lab ultra-centrifuges are built inside a heavy steel box, to
contain the shards of the rotor, when (not if) it explodes. When this
happens, the centrifuge is totally destroyed.


I don't spin up bearings
any more. Not even a little.

It sounds like there is actually quite a wide safe range here. Just
stay in the sonic range?
No way. A small bearing may take the rpm. But a larger one will
explode much sooner. Just don't spin 'em up.

Joe Gwinn


Im going to have to try that one of these days.

Safely of course.

After watching the video of the guy spinning up CDs on his Dremel, and
having a few explode on the wheel ... bearings seem to be a logical next
step. Should be simple to whomp up a bearing holder so that you can do
this with your hands in your pockets.
--
pyotr filipivich.
as an explaination for the decline in the US's tech edge, James
Niccol wrote "It used to be that the USA was pretty good at
producing stuff teenaged boys could lose a finger or two playing with."

According to Joseph Gwinn :
In article ,
(DoN. Nichols) wrote:

According to Joseph Gwinn :
In article ,
(DoN. Nichols) wrote:

[ ... ]

As you probably have seen already -- there was a followup posted
which strongly supports my warning.

Yes. With the siren song from balls passing through the air jet going
into the ultrasonic. I suppose it shouldn't be a surprise, as many
gyroscopes are spun up with compressed air (or helium).

Right.


O.K. At least the manual (I presume that you downloaded it as
well) does not say to not disassemble it.

I just downloaded the manual. Quite interesting.

Even if it does not precisely cover your version. How do the
model numbers compare? (The first four digits of the serial number).
Mine are an exact match.

Mine does not follow the rule in the Series 11 manual, but looks like
the parts breakdown diagram.

O.K.

[ ... ]

Right -- but that should not make any difference. Perhaps the
difference in the motor bearings is because only the pulley end of the
motor experiences side loads, while both ends of the spindle do.

Or -- the bearings *may* be identical. :-)

I haven't had the motor apart, so have no opinion.

And while I have had my motor apart -- the bearing at the pulley
end did not want to come out of the housing, and I did not want to try
too hard while I was working on other things.

It may depend on what you call "removable". Certainly the ones
which started this thread were designed to screw into a hollow spindle
with a taper, based on the photos. (Hmm ... has that auction closed,
yet? :-)

I think that the hollow spindle is a later design.

O.K. But the manual does show that for this model at least, the
same spindle is used for both larger wheels and smaller mounted ones --
with a screw-on single-sized collet adaptor.

Yes. It appears to be the earlier design. The hollow spindle design
allows one to change the business end without disassembling the grinder.

Right -- but you can change the business end with the screw-on
"chuck" just as easily.

True, but replacing the whole spindle is faster, and works even for
holes smaller than the spindle diameter. Quick change seems to be the
issue.

That depends on what you call "the whole spindle". If you mean
from the pulley to the stone mount, I would suggest that the "chuck"
(really a single-size collet" which screws onto the arbor in place of
the normal stone and its end plates (and possible centering adaptors as
well -- as is the case with my stones)) is quicker to screw onto the end
of the spindle than changing the *whole* spindle, involving removing the
pulley, both bearing caps, spacers, and bearings, withdrawing the
spindle, and replacing it with a different spindle with all of the
bearings and such (risking exposing the bearings to grit in the process)
is much more trouble prone than screwing on the "chuck".

The "chuck" is designed to accept stones with 1/8" shanks, and
there were several in the case with the grinder (but no chuck -- so I
just finished making a replacement as close to the original as I could
manage). A couple of those stones even were as large as 1-3/4", and the
shank was closer to 3/16" or maybe even 1/4", stepping down to 1/8"
(actually, slightly oversized at 0.126"). Those last ones would not fit
into the reamed hole in the chuck-in-progress, but once I slit it with
two slits at right angles, the stresses opened it enough so those
stones dropped right in.

The one real advantage which I can see to the design implied by
the screw-in ends for the hollow spindles is that a stone can stay
mounted on its arbor, and will not need to be re-trued when it is
re-mounted, if the stone has little enough wear.

[ ... ]

And -- I think that I'll also make a support collar so it will
be easy to restore to the proper height each time, since this is the
only lathe which I expect to use it on. It seems a bit too big for the
little Emco-Maier Compact-5/CNC -- a 5" swing machine. :-)

Right. Now, Ill have to get a big enough lathe.

O.K. Good luck with that. I've been known to collect
accessories when I could, in hopes of acquiring a machine with which
they could be used later.

[ ... ]

The thing is that most flashlamps use external trigger -- a wire
wrapped around the outside of the envelope. This one, however, has
internal trigger electrodes, and may operate with a much lower trigger
voltage.

I think that the trigger is 4KV, but such things are far from critical.
I recently built a special-purpose strobe (for illuminating a coil
winder in motion), and couldn't initially get the right parts, using a
trigger transformer that was too weak for the right flashtube, and a
flashtube that required more trigger voltage than the correct tube, the
net deficit being (2:1)(6:4)= 3:1.

It worked anyway, albeit with the occasional misfire. When I rewired it
to double the trigger voltage, the misfires went away. This is with new
tubes. The problems will occur later, as things age. (I now have the
correct flashtube.) This uses an ordinary cheap flashtube, and runs at
up to about 40 Hz (2,400 rpm).

A bigger issue is how fast the tube deionizes. If it isn't fast enough,
one cannot flash the tube fast enough, as it stops flashing and instead
remains always on. Deionization time is mostly determined by flash tube
design.

This may be one of the reasons for the internal trigger
electrodes, and the extra volume (of unionized xenon) to quickly replace
the ionized stuff.

If it does not deionize quickly enough, and the capacitor
charging current is high enough, it will indeed remain on full time.
Part of the problem is the deionization time, part is the voltage to
which the tube discharges the capacitor.

[ ... ]

I have a question in at Perkin-Elmer asking if the FX-6A is still made,
and if not what is it's replacement (perhaps Series 1100), and what they
cost. We shall see.

O.K. Good luck.

[ ... ]

The only other current auction is # 7607451350 -- one of the
older ones, with a less bright flash lamp, and (IIRC) a much lower speed
limit. None of the photos are from an orientation to show the
"soupbowl" reflector -- which may suggest problems with it. Normally, I
would expect, even from the views show, the bulge of the large crystal
to be visible. Since it is not -- it may be broken. And while it
*looks* like a GR unit from the views given -- it may not be by GR --
they say "Electric Brazing" -- which may have been a secondary
contract manufacturer during wartime or something similar.

I saw that one. Never heard of the company.

Nor did I. But it looks like one of the wartime unknowns which
got contracts to make a product known to come from a larger company --
simply because they could not turn them out in the quantities needed.
I've seen Tektronix scope clones made under such contracts -- they
looked almost identical to the Tektronix, other than the maker's name.

[ ... ]

Sam Goldwasser has published a circuit for a three-range strobe that
goes to 6,000 flashes per second. Search for "strobex.pdf". This
circuit could achieve 25,000 fpm with the right tube, and some circuit
adjustments.

O.K. Part of the problem, of course, is stability of the
timebase. A really good one could be made with a crystal oscillator, a
bunch of counter chips and comparators -- load in a count (period, not
frequency) and it would be very stable. Even the nice little GR
Strobotac which I have drifts for the first minute or so. And that one
is solid state. The older (soupbowl) one takes longer to stabilize, and
it is run from tubes.

[ ... ]

I can understand ditching the repair parts after 50 years, but how much
trouble would it have been to scan and post the old manuals? These old
units are quite well made, and so will always be with us.

They used to make them available -- for free. (At least the one
for the drill grinder was free.) They seem to have tossed all of the
old parts and manuals now.

Annoying.

Indeed so.

[ ... ]

But -- I'm not going to complain when he didn't have to do this
at all. I'm just passing on thanks.

True enough. If he wishes, he can email to me, and I will post the
files for him. I have no 30K limit. He can email to me, and I will
post the files. The email address above is real.

As you already know -- he has scanned them to a higher
resolution, and put them in his private web space.

Enjoy,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

According to Glenn :

[ ... ]

Just checked .. I have 20Meg or so left on my FTP space so I will scan it in
high res suitable for framing and post it there. I will post a link when it
is in place.

It turned out to be your web space -- but that was a nice
improvement.

Thanks again,
DoN.
--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

According to Joseph Gwinn :
In article , "Glenn"
wrote:

"Joseph Gwinn" wrote in message
...

No wonder I've been having trouble keeping track of which of
you posted what. Both of you have names which start with 'G', end in
'n', and are in the 4-5 character range. :-)

[ ... ]

What acrobat said when I saved the file was that it was removing empty
space. ??

I don't really know what acrobat means by this, but speculate that it
uses a convenient temporary file format while building the file, then
goes back and closes up the space that turned out not to be needed.

If you have scanned a B&W line drawing -- no colors, just B&W,
and saved to TIFF (which unlike JPEG does not cloud the space near lines
with various shades of gray), you will have a quite large file, as TIFF
has no compression.

One way to save space in this sort of situation is to skip over
areas which are plain white. I don't think that TIFF or JPEG have this
option, but PostScript may, and PDF (which you reach through an
intermediate PostScript conversion -- hidden from you by the Adobe
software). So -- "removing empty space" means exactly that -- deleting
all of those bytes of white, and replacing them with code to "treat the
next N bytes as white". I wonder whether it can do the same with an
image which is white text on a black background?

BTW I've now made my copy of the "chuck" -- thanks to your scans and
measurements.

Enjoy,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

"DoN. Nichols" wrote in message
...
According to Glenn :

[ ... ]

Just checked .. I have 20Meg or so left on my FTP space so I will scan it
in
high res suitable for framing and post it there. I will post a link when
it
is in place.

It turned out to be your web space -- but that was a nice
improvement.

Funny that, When I go to upload files I have to go to an ftp site and
login, then to download them you go to the web space. I may get a hair to
play with the scanner more and see how nice I can make it. The scanner
lives on the wife's machine so I have to schedual time to use it May
have to go buy one for me too just so I can figure out how to do it right
the first time.

Glenn

"DoN. Nichols" wrote in message
...
According to Joseph Gwinn :
In article , "Glenn"
wrote:

"Joseph Gwinn" wrote in message
...

No wonder I've been having trouble keeping track of which of
you posted what. Both of you have names which start with 'G', end in
'n', and are in the 4-5 character range. :-)

Amazing how easily the mind can fill in the letters to be what you expect
There is an e-mail floating around with all the letters munged around but
starting and ending correctly and with the right number of letters.
Interesting


What acrobat said when I saved the file was that it was removing empty
space. ??

I don't really know what acrobat means by this, but speculate that it
uses a convenient temporary file format while building the file, then
goes back and closes up the space that turned out not to be needed.

If you have scanned a B&W line drawing -- no colors, just B&W,
and saved to TIFF (which unlike JPEG does not cloud the space near lines
with various shades of gray), you will have a quite large file, as TIFF
has no compression.

One way to save space in this sort of situation is to skip over
areas which are plain white. I don't think that TIFF or JPEG have this
option, but PostScript may, and PDF (which you reach through an
intermediate PostScript conversion -- hidden from you by the Adobe
software). So -- "removing empty space" means exactly that -- deleting
all of those bytes of white, and replacing them with code to "treat the
next N bytes as white". I wonder whether it can do the same with an
image which is white text on a black background?

BTW I've now made my copy of the "chuck" -- thanks to your scans and
measurements.

That's pretty much what I thought but had nothing to base it on but logic.
Your chuck is probably better than the original one anyway I was not
overly impressed with the one in my kit. To take the burr off from cutting
the slots they just ground down the threads so it has 4 flat spots where the
slots are.
Glad ya got'er done
Glenn

According to Glenn :

"DoN. Nichols" wrote in message
...

[ ... ]

No wonder I've been having trouble keeping track of which of
you posted what. Both of you have names which start with 'G', end in
'n', and are in the 4-5 character range. :-)

Amazing how easily the mind can fill in the letters to be what you expect
There is an e-mail floating around with all the letters munged around but
starting and ending correctly and with the right number of letters.
Interesting

:-)

[ ... ]

BTW I've now made my copy of the "chuck" -- thanks to your scans and
measurements.

That's pretty much what I thought but had nothing to base it on but logic.
Your chuck is probably better than the original one anyway I was not
overly impressed with the one in my kit. To take the burr off from cutting
the slots they just ground down the threads so it has 4 flat spots where the
slots are.

I used some narrow slitting saws on the horizontal mill. (Well,
I only *used* one, but there are four on that arbor in a setup for
another recurring project.

The body of the chuck was held in a 3-jaw chuck on a dividing
head for the Emco-Maier Compact-5 lathe's milling attachment, which was
held in the vise on the horizontal mill. I cut twice for each slot at
each depth -- once with the dividing head rotated 180 degrees from the
other (so I cut at 0 degrees, 90 degrees, 180 degrees and 270 degrees).
This way, whatever very small error I may have had in centering the
slitting saw blade over the end of the body was translated into very
slightly wider slots.

So -- to make this, I have used:

1) Clausing 12" lathe (with collets, for turning body to
desired diameter, drilling, reaming and tapping (hand tapping,
but using the tailstock to get it right.

2) Same -- for turning it around in the collet after parting off,
drilling undersized and reaming to 0.125", then turning to major
thread diameter, then threading, and finally turning off half
of the threaded length to minor diameter using the threading
tool still set up in the lathe. Then turn a 15 degree taper
with the compound.

3) Same -- for turning end cap to diameter,knurling, and drilling
through hole, and part it off with a bit of the parent stock to
take it to and chuck it in ...

4) Compact-5/CNC -- to bore to minor diameter, and single-point
the internal 5/16-32 thread (testing against the male already
made in the Clausing for the body.)

Next -- make a tapered D reamer.

5) Back to the Clausing, to turn a length of 5/16" Water hardening
drill rod to the minor diameter, and to turn a taper on the end.

6) To the Nichols horizontal mill -- to slab mill that drill rod
to half diameter.

7) Fire up the heat treating oven, and wrap the drill rod in
stainless with some paper to use up the oxygen, and quench.
(Also deal with the leftover leaves just outside the shop
(garage) door, to avoid a chance of fire if I drop it while
still hot).

8) Eat dinner while the oven cools back down to tempering
temperature -- then temper and shut off the oven.

9) Go to Taig lathe (yes -- a third lathe), and chuck the tool
made from the drill rod in the tailstock chuck, and the knurled
nut in the aluminum soft jaws, and use the Taig and the just
finished tapered D reamer to machine a taper inside the nut to
close the collet.

10) Back to Clausing -- screw nut onto body, and hold body in
collet while turning a taper on the end of the nut to remove
half of the knurling (as per photo).

11) To Nichols horizontal mill with assembled body and nut in
dividing head to cut wrench flats on the nut, and then the body.

12) Still Nichols horizontal -- but change the arbor to install the
thin slitting saws, and cut the slots as described above.

So -- this used how many machines?

Clausing
Compact-5/CNC
Taig
Nichols horizontal mill
heat treating oven.

All to make a little 2-piece part.

I was half-way expecting to need to use the little surface
grinder to finish that D-shaped tapered reamer I made to make the
internal taper. But it was sharp enough as finished. I had to make
that because I did not have any boring bars which I could trust at that
small a bore. I was lucky to have a threading insert which could be
used for the 5/16-32 thread. (I really need to add that tap to my
collection. :-)

But -- I've tried it on the toolpost grinder, and it works
nicely with all of the mounted stones which I have -- the larger ones
(1-3/4") spun up only with the slower pulley combination, the 3/4" and
smaller spun with the faster pulley combination.

BTW -- I've discovered that both the black stamped steel wrench
with the Dumore name stamped in it, and the standard small forged wrench
have one end at 7/16" (for the arbor and pulley nuts), and the other end
at 3/8" (for the "chuck" flats). So -- I didn't even need to add a
wrench to the toolbox.

Now -- left to make:

1) The spacer so it will always mount at the center height on the
Clausing.

2) A better T-nut for mounting it on the Clausing.

3) Dressing diamond holder.

And then to find a project which really *needs* the TP grinder
to do properly. :-)

Glad ya got'er done

Thanks -- so am I.

But I'm falling way behind here in rec.crafts.metalworking. If
it were not for the scoring feature of my newsreader moving threads in
which I have been participating to the front, I would probably not have
found these articles until tomorrow -- or the next day. There are
nearly 400 articles left to read -- even *after* my killfile does away
with known political threads. :-)

Thanks again,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

According to Glenn :

"DoN. Nichols" wrote in message

[ ... ]

Just checked .. I have 20Meg or so left on my FTP space so I will scan it
in
high res suitable for framing and post it there. I will post a link when
it
is in place.

It turned out to be your web space -- but that was a nice
improvement.

Funny that, When I go to upload files I have to go to an ftp site and
login, then to download them you go to the web space.

That is probably so I (and the rest of the world) can't upload
to your space. I don't know whether they offer anonymous FTP for
downloads, but with the URL you gave, the brower (or wget) was the only
choice.

I may get a hair to
play with the scanner more and see how nice I can make it. The scanner
lives on the wife's machine so I have to schedual time to use it May
have to go buy one for me too just so I can figure out how to do it right
the first time.

What kind of scanner does she have?

I find an old HP ScanJet II (color) works very nicely for this.
I've got a SCSI adaptor on the computer, and the HP software lets me
scan to TIFF with pure B&W -- and adjusting the threshold between black
and white to tune it to drop most light stains and smudges. Once I have
the scans made, they get moved to one of the unix machines, and
combined, turned into PostScript, and from there into PDF -- all using
unix tools -- not Adobe ones.

I've got a spare ScanJet II (one from hamfest, the other from
eBay -- both really cheap), so some of these days I will try the various
unix scanning software to see what will work better for me, and keep me
clear of that Windows machine except for on income tax prepration day. :-)

Enjoy,
DoN.


P.S. What Time zone are you in? It is currently 2:36 AM for me, in
EDT -- and I am now going to bed. :-)
--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

On Thu, 13 Apr 2006 22:30:31 -0700, with neither quill nor qualm,
"Glenn" quickly quoth:


"DoN. Nichols" wrote in message
...
According to Glenn :

[ ... ]

Just checked .. I have 20Meg or so left on my FTP space so I will scan it
in
high res suitable for framing and post it there. I will post a link when
it
is in place.

It turned out to be your web space -- but that was a nice
improvement.

Funny that, When I go to upload files I have to go to an ftp site and
login, then to download them you go to the web space. I may get a hair to
play with the scanner more and see how nice I can make it. The scanner
lives on the wife's machine so I have to schedual time to use it May
have to go buy one for me too just so I can figure out how to do it right
the first time.

http://www.pricewatch.com/scanners/281713-1.htm From $59.

I have a book on scanning if you'd like to borrow it. (My office has a
stack of 100+ books which I'm sorting to sell on Ebay, etc.) I'll be
down in your area (the airport) Tuesday morning so let me know.

I may be in Medford today to sign my tax docs if the tax critter I
hired ever gets well, goes to her office, and does my return. sigh


--
"Given the low level of competence among politicians,
every American should become a Libertarian."
-- Charley Reese, Alameda Times-Star (California), June 17, 2003

On Fri, 14 Apr 2006 10:09:37 -0500, Joseph Gwinn
wrote:

In article ,
Eric R Snow wrote:

On Tue, 11 Apr 2006 23:24:21 -0500, Joseph Gwinn
wrote:

In article ,
Eric R Snow wrote:

[snip]
Years ago I was blowing out some bearings with air. Goofing off, with
the bearing on my finger, I spun one up and listened to the pitch. As
it spun the pitch got higher until I couldn't hear it. Just as it
passed into my ultrasonic range it exploded with a bang.

Ultrasonic! Wow. That implies a ball-passing frequency exceeding
20,000 per second or so. If the ball cage has ten balls in it, the cage
is rotating at 2000 rps, or 120,000 rpm, and the outer race a factor
faster. No wonder it exploded.

MY ultrasonic range. I know my high frequency hearing is damaged. But
it was still really spinning fast.

How old were you when this bearing died?

In my 20s and 30s, I could hear to 20 KHz, and sense 26 KHz (used by
some burglar alarms) as a pressure.


Do you recall the dimensions of the deceased ball bearing?
The ID was about 5/8 and the OD maybe 1-1/2, 1-3/4.

OK. Not that large.


The bearing
axis was perpendicular to my body so that the bearing parts were
embedded into the wall and not me. My finger hurt like hell. I think
the bearing must have exploded pretty equally because otherwise that
finger would have probably broken instead.

Yes. Lab ultra-centrifuges are built inside a heavy steel box, to
contain the shards of the rotor, when (not if) it explodes. When this
happens, the centrifuge is totally destroyed.


I don't spin up bearings
any more. Not even a little.

It sounds like there is actually quite a wide safe range here. Just
stay in the sonic range?

No way. A small bearing may take the rpm. But a larger one will
explode much sooner. Just don't spin 'em up.

The tone indicates rotation rate. The larger the outer diameter, the
greater the centrifugal force on the outer race. The effect is very
much like a gravitational field pulling outward, and can easily be tens
of thousands of times stronger than Earth's gravity.

Making the race heavier doesn't help, because while the cross sectional
area (and thus strength) increases, so does the weight (and thus outward
force). My recollection from discussions of energy-storage flywheels is
that these effects cancel more or less perfectly, so all that matters is
the strength-to-weight ratio of the material from which the outer race
is made. Only hoop stress matters, so storage flywheels are often made
of boron fiber.

What alloy are bearing races made of? What's the tensile strength?

Joe Gwinn
Greetings Joe,
I was in my early twenties when I blew up the bearing. However, I
already had some hearing loss by then. When I was about 12 I could
hear all sorts of high frequency sound that others around me couldn't.
Used to drive me nuts. High pitch coming out of the TV. And my grandma
had a remote control that used sound (remember those?) to switch
channels on the TV that bugged me too. I couldn't really hear it, I
mean it didn't sound like "sound", but when the hammer in the remote
struck the little metal bar inside it was sorta like the pressure you
wrote about.
ERS

In article ,
Eric R Snow wrote:

On Tue, 11 Apr 2006 23:24:21 -0500, Joseph Gwinn
wrote:

In article ,
Eric R Snow wrote:

[snip]
Years ago I was blowing out some bearings with air. Goofing off, with
the bearing on my finger, I spun one up and listened to the pitch. As
it spun the pitch got higher until I couldn't hear it. Just as it
passed into my ultrasonic range it exploded with a bang.

Ultrasonic! Wow. That implies a ball-passing frequency exceeding
20,000 per second or so. If the ball cage has ten balls in it, the cage
is rotating at 2000 rps, or 120,000 rpm, and the outer race a factor
faster. No wonder it exploded.

MY ultrasonic range. I know my high frequency hearing is damaged. But
it was still really spinning fast.

How old were you when this bearing died?

In my 20s and 30s, I could hear to 20 KHz, and sense 26 KHz (used by
some burglar alarms) as a pressure.


Do you recall the dimensions of the deceased ball bearing?
The ID was about 5/8 and the OD maybe 1-1/2, 1-3/4.

OK. Not that large.


The bearing
axis was perpendicular to my body so that the bearing parts were
embedded into the wall and not me. My finger hurt like hell. I think
the bearing must have exploded pretty equally because otherwise that
finger would have probably broken instead.

Yes. Lab ultra-centrifuges are built inside a heavy steel box, to
contain the shards of the rotor, when (not if) it explodes. When this
happens, the centrifuge is totally destroyed.


I don't spin up bearings
any more. Not even a little.

It sounds like there is actually quite a wide safe range here. Just
stay in the sonic range?

No way. A small bearing may take the rpm. But a larger one will
explode much sooner. Just don't spin 'em up.

The tone indicates rotation rate. The larger the outer diameter, the
greater the centrifugal force on the outer race. The effect is very
much like a gravitational field pulling outward, and can easily be tens
of thousands of times stronger than Earth's gravity.

Making the race heavier doesn't help, because while the cross sectional
area (and thus strength) increases, so does the weight (and thus outward
force). My recollection from discussions of energy-storage flywheels is
that these effects cancel more or less perfectly, so all that matters is
the strength-to-weight ratio of the material from which the outer race
is made. Only hoop stress matters, so storage flywheels are often made
of boron fiber.

What alloy are bearing races made of? What's the tensile strength?

Joe Gwinn

In article ,
(DoN. Nichols) wrote:

According to Joseph Gwinn :
In article ,
Eric R Snow wrote:

[ ... ]

Years ago I was blowing out some bearings with air. Goofing off, with
the bearing on my finger, I spun one up and listened to the pitch. As
it spun the pitch got higher until I couldn't hear it. Just as it
passed into my ultrasonic range it exploded with a bang.

Ultrasonic! Wow. That implies a ball-passing frequency exceeding
20,000 per second or so. If the ball cage has ten balls in it, the cage
is rotating at 2000 rps, or 120,000 rpm, and the outer race a factor
faster. No wonder it exploded.

Do you recall the dimensions of the deceased ball bearing?

Since it was on his finger, a guess says that the ID of the
inner race was probably on the order of 5/8". Scale the rest to that.


The bearing
axis was perpendicular to my body so that the bearing parts were
embedded into the wall and not me. My finger hurt like hell. I think
the bearing must have exploded pretty equally because otherwise that
finger would have probably broken instead.

[ ... ]

I don't spin up bearings
any more. Not even a little.

It sounds like there is actually quite a wide safe range here. Just
stay in the sonic range?

That depends on the size of the bearing -- and your personal
hearing range. :-)

A large bearing (say 1-1/2" ID on the inner race) could probably
get to dangerous speeds while the tone remained in the audible range.

Yes. I'm tempted to figure out the rough limit. I would guess that it
will be a ratio on the max allowed rpm in service.

Right away we know that the service speed is safe for all but bearings
sold as designed to work only while pressed into a recess. So, if a
bearing is rated to 12,000 rpm, the balls travel at half that, or 6,000
rpm, and there are 10 balls (just count them), then the max tone
frequency is (6000/60)*10= 1,000 Hz.

That said, I don't have perfect pitch (few do), so I would keep it far
lower, a few hundred Hertz - a low hum, rather than a whine or a clear
tone.


And -- it is affected in part by the number of balls in the race. Some
(for heavy loads) have completely full races, others have fewer balls,
with some mechanism to space them out. I've seen ribbons of steel
formed into cups around both sides riveted together. I've seen bakelite
machined to slip in from one side once the bearings are properly spaced.
I've even seen bearings with little coil springs set between the balls
to keep them spaced out. This was in a vary slow, and very low
operating force setup -- like a gimbal gyro cage.

I've seen all these variants except the one with the little springs.
What are the springs made of?

I don't know that I would be tempted to spin such a bearing at all - the
little springs would get pulled under the balls, and the whole affair
would jam up, or the balls would end up all to one side, allowing the
bearing to disassemble itself long before the outer race could explode.

Joe Gwinn

In article ,
(DoN. Nichols) wrote:

According to Joseph Gwinn :
In article ,
(DoN. Nichols) wrote:

According to Joseph Gwinn :
In article ,
(DoN. Nichols) wrote:

[snip]
Right -- but that should not make any difference. Perhaps the
difference in the motor bearings is because only the pulley end of the
motor experiences side loads, while both ends of the spindle do.

Or -- the bearings *may* be identical. :-)

I haven't had the motor apart, so have no opinion.

And while I have had my motor apart -- the bearing at the pulley
end did not want to come out of the housing, and I did not want to try
too hard while I was working on other things.

I assume it is designed to allow removal at least.


It may depend on what you call "removable". Certainly the ones
which started this thread were designed to screw into a hollow spindle
with a taper, based on the photos. (Hmm ... has that auction
closed, yet? :-)

I think that the hollow spindle is a later design.

O.K. But the manual does show that for this model at least, the
same spindle is used for both larger wheels and smaller mounted ones
--
with a screw-on single-sized collet adaptor.

Yes. It appears to be the earlier design. The hollow spindle design
allows one to change the business end without disassembling the
grinder.

Right -- but you can change the business end with the screw-on
"chuck" just as easily.

True, but replacing the whole spindle is faster, and works even for
holes smaller than the spindle diameter. Quick change seems to be the
issue.

That depends on what you call "the whole spindle". If you mean
from the pulley to the stone mount, I would suggest that the "chuck"
(really a single-size collet" which screws onto the arbor in place of
the normal stone and its end plates (and possible centering adaptors as
well -- as is the case with my stones)) is quicker to screw onto the end
of the spindle than changing the *whole* spindle, involving removing the
pulley, both bearing caps, spacers, and bearings, withdrawing the
spindle, and replacing it with a different spindle with all of the
bearings and such (risking exposing the bearings to grit in the process)
is much more trouble prone than screwing on the "chuck".

I meant the conical thing to which the stone is attached.


The "chuck" is designed to accept stones with 1/8" shanks, and
there were several in the case with the grinder (but no chuck -- so I
just finished making a replacement as close to the original as I could
manage). A couple of those stones even were as large as 1-3/4", and the
shank was closer to 3/16" or maybe even 1/4", stepping down to 1/8"
(actually, slightly oversized at 0.126"). Those last ones would not fit
into the reamed hole in the chuck-in-progress, but once I slit it with
two slits at right angles, the stresses opened it enough so those
stones dropped right in.

The one real advantage which I can see to the design implied by
the screw-in ends for the hollow spindles is that a stone can stay
mounted on its arbor, and will not need to be re-trued when it is
re-mounted, if the stone has little enough wear.

I think that's the reason to do it this way. The assembly with bearings
and pulleys seems quite expensive, ~$1,000. I assume (hope) that the
removable part is cheaper. But I don't know that I understand their
pricing structure.


And -- I think that I'll also make a support collar so it will
be easy to restore to the proper height each time, since this is the
only lathe which I expect to use it on. It seems a bit too big for the
little Emco-Maier Compact-5/CNC -- a 5" swing machine. :-)

Right. Now, Ill have to get a big enough lathe.

O.K. Good luck with that. I've been known to collect
accessories when I could, in hopes of acquiring a machine with which
they could be used later.

But did you inherit a tool that caused lathe acquisition?


The thing is that most flashlamps use external trigger -- a wire
wrapped around the outside of the envelope. This one, however, has
internal trigger electrodes, and may operate with a much lower trigger
voltage.

I think that the trigger is 4KV, but such things are far from critical.
I recently built a special-purpose strobe (for illuminating a coil
winder in motion), and couldn't initially get the right parts, using a
trigger transformer that was too weak for the right flashtube, and a
flashtube that required more trigger voltage than the correct tube, the
net deficit being (2:1)(6:4)= 3:1.

It worked anyway, albeit with the occasional misfire. When I rewired it
to double the trigger voltage, the misfires went away. This is with new
tubes. The problems will occur later, as things age. (I now have the
correct flashtube.) This uses an ordinary cheap flashtube, and runs at
up to about 40 Hz (2,400 rpm).

A bigger issue is how fast the tube deionizes. If it isn't fast enough,
one cannot flash the tube fast enough, as it stops flashing and instead
remains always on. Deionization time is mostly determined by flash tube
design.

This may be one of the reasons for the internal trigger
electrodes, and the extra volume (of unionized xenon) to quickly replace
the ionized stuff.

Exactly. It's the nearby masses of metal that does the job.


If it does not deionize quickly enough, and the capacitor
charging current is high enough, it will indeed remain on full time.
Part of the problem is the deionization time, part is the voltage to
which the tube discharges the capacitor.

Edgerton's book "Flash, Strobe" goes into the details of how the
Strobotac and allied devices work.


I have a question in at Perkin-Elmer asking if the FX-6A is still made,
and if not what is it's replacement (perhaps Series 1100), and what they
cost. We shall see.

O.K. Good luck.

So far, no response.


The only other current auction is # 7607451350 -- one of the
older ones, with a less bright flash lamp, and (IIRC) a much lower speed
limit. None of the photos are from an orientation to show the
"soupbowl" reflector -- which may suggest problems with it. Normally, I
would expect, even from the views show, the bulge of the large crystal
to be visible. Since it is not -- it may be broken. And while it
*looks* like a GR unit from the views given -- it may not be by GR --
they say "Electric Brazing" -- which may have been a secondary
contract manufacturer during wartime or something similar.

I saw that one. Never heard of the company.

Nor did I. But it looks like one of the wartime unknowns which
got contracts to make a product known to come from a larger company --
simply because they could not turn them out in the quantities needed.
I've seen Tektronix scope clones made under such contracts -- they
looked almost identical to the Tektronix, other than the maker's name.

Yes. Don't know how good a job they did.


Sam Goldwasser has published a circuit for a three-range strobe that
goes to 6,000 flashes per second. Search for "strobex.pdf". This
circuit could achieve 25,000 fpm with the right tube, and some circuit
adjustments.

O.K. Part of the problem, of course, is stability of the
timebase. A really good one could be made with a crystal oscillator, a
bunch of counter chips and comparators -- load in a count (period, not
frequency) and it would be very stable. Even the nice little GR
Strobotac which I have drifts for the first minute or so. And that one
is solid state. The older (soupbowl) one takes longer to stabilize, and
it is run from tubes.

Yes. The strobe I built is triggered by an optical encoder on the
winder's main axle, so the image stands absolutely still as the rotation
rate is varied.


I can understand ditching the repair parts after 50 years, but how much
trouble would it have been to scan and post the old manuals? These old
units are quite well made, and so will always be with us.

They used to make them available -- for free. (At least the one
for the drill grinder was free.) They seem to have tossed all of the
old parts and manuals now.

Annoying.

Indeed so.

[ ... ]

But -- I'm not going to complain when he didn't have to do this
at all. I'm just passing on thanks.

True enough. If he wishes, he can email to me, and I will post the
files for him. I have no 30K limit. He can email to me, and I will
post the files. The email address above is real.

As you already know -- he has scanned them to a higher
resolution, and put them in his private web space.

I got it; looks good.


Joe Gwinn

On Fri, 14 Apr 2006 07:22:29 -0700, Larry Jaques
wrote:

Funny that, When I go to upload files I have to go to an ftp site and
login, then to download them you go to the web space. I may get a hair to
play with the scanner more and see how nice I can make it. The scanner
lives on the wife's machine so I have to schedual time to use it May
have to go buy one for me too just so I can figure out how to do it right
the first time.

http://www.pricewatch.com/scanners/281713-1.htm From $59.

I have a book on scanning if you'd like to borrow it. (My office has a
stack of 100+ books which I'm sorting to sell on Ebay, etc.) I'll be
down in your area (the airport) Tuesday morning so let me know.

I may be in Medford today to sign my tax docs if the tax critter I
hired ever gets well, goes to her office, and does my return. sigh


if one goes to the various thrift stores, Salvation army etc etc..one
may purchase perfectly ggood and in some cases extremely high quality
flat bed scanners for $5 or less. Drivers are freely available on the
net

Gunner

In article ,
says...

Making the race heavier doesn't help, because while the cross sectional
area (and thus strength) increases, so does the weight (and thus outward
force). My recollection from discussions of energy-storage flywheels is
that these effects cancel more or less perfectly, so all that matters is
the strength-to-weight ratio of the material from which the outer race
is made. Only hoop stress matters, so storage flywheels are often made
of boron fiber.

Yes, the stress on a rotating thin cylinder is dependent only on density
and peripheral speed.


What alloy are bearing races made of? What's the tensile strength?


By far the most common material is AISI 52100, UTS is around 300,000
psi. I don't believe that centrifugal force alone is enough to burst the
bearing race. I figure a peripheral speed of around 1700 FPS would be
required to reach 300 ksi stress. That's close to 2x the speed of sound,
almost 20 miles/second, or about 250,000 RPM for a common 6203 (17x40mm)
bearing. (Those numbers may be a bit high, depending on how chunky the
bearing is, i.e., how far it deviates from a "thin cylinder.")

I suspect that lubrication failure leading to galling of the balls and
consequently jamming is the big culprit. Perhaps the race expands enough
from the centrifugal force to rattle around and hasten the failure, but
it seems unlikely to me that it's possible to get the bearing spinning
fast enough for this to be much of a factor. The strain in the
hypothetical 6203 race would be about .15% at 100 KRPM - in other words
the bearing might loosen up a thousandth or two at that speed.

Ned Simmons

According to Joseph Gwinn :
In article ,
(DoN. Nichols) wrote:

According to Joseph Gwinn :

[ ... ]

Do you recall the dimensions of the deceased ball bearing?

Since it was on his finger, a guess says that the ID of the
inner race was probably on the order of 5/8". Scale the rest to that.

[ ... ]

It sounds like there is actually quite a wide safe range here. Just
stay in the sonic range?

That depends on the size of the bearing -- and your personal
hearing range. :-)

A large bearing (say 1-1/2" ID on the inner race) could probably
get to dangerous speeds while the tone remained in the audible range.

Yes. I'm tempted to figure out the rough limit. I would guess that it
will be a ratio on the max allowed rpm in service.

Right away we know that the service speed is safe for all but bearings
sold as designed to work only while pressed into a recess. So, if a
bearing is rated to 12,000 rpm, the balls travel at half that, or 6,000
rpm, and there are 10 balls (just count them), then the max tone
frequency is (6000/60)*10= 1,000 Hz.

That said, I don't have perfect pitch (few do), so I would keep it far
lower, a few hundred Hertz - a low hum, rather than a whine or a clear
tone.

That *might* work. I still would not place myself (or anything
that I cared about) in the plane of the rotation.

[ ... ]

I've even seen bearings with little coil springs set between the balls
to keep them spaced out. This was in a vary slow, and very low
operating force setup -- like a gimbal gyro cage.

I've seen all these variants except the one with the little springs.
What are the springs made of?

I don't know for sure. I've seen them in equipment from the
mid to late 1950s at a guess, and did not test them to destruction.

I don't know that I would be tempted to spin such a bearing at all - the
little springs would get pulled under the balls, and the whole affair
would jam up, or the balls would end up all to one side, allowing the
bearing to disassemble itself long before the outer race could explode.

the springs were coil springs, about 2/3 the diameter of the
balls, so the balls would hold the springs fairly well centered at low
speeds. As I said -- it was run only at very slow speeds. The bearings
in the actual gyroscope (powered by three phase 400 Hz, FWIW) were
fitted with some red/orange synthetic separator -- phenolic, at a guess.

Enjoy,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

According to Joseph Gwinn :
In article ,
(DoN. Nichols) wrote:


[ ... ]

And while I have had my motor apart -- the bearing at the pulley
end did not want to come out of the housing, and I did not want to try
too hard while I was working on other things.

I assume it is designed to allow removal at least.

Yes -- but something is wedged I think. What I'll need to do is
to thread a chunk of mild steel to protect the threads for the pulley
securing nut and then try pressing (and driving) it out -- once I have
spare bearings on hand.

[ ... ]

Right -- but you can change the business end with the screw-on
"chuck" just as easily.

True, but replacing the whole spindle is faster, and works even for
holes smaller than the spindle diameter. Quick change seems to be the
issue.

That depends on what you call "the whole spindle". If you mean
from the pulley to the stone mount, I would suggest that the "chuck"
(really a single-size collet" which screws onto the arbor in place of
the normal stone and its end plates (and possible centering adaptors as
well -- as is the case with my stones)) is quicker to screw onto the end
of the spindle than changing the *whole* spindle, involving removing the
pulley, both bearing caps, spacers, and bearings, withdrawing the
spindle, and replacing it with a different spindle with all of the
bearings and such (risking exposing the bearings to grit in the process)
is much more trouble prone than screwing on the "chuck".

I meant the conical thing to which the stone is attached.

O.K. But I still fail to see why that is faster than the
screw-on chuck -- other than not having to unmount the wheel and flanges
and put them aside.

[ ... ]

The one real advantage which I can see to the design implied by
the screw-in ends for the hollow spindles is that a stone can stay
mounted on its arbor, and will not need to be re-trued when it is
re-mounted, if the stone has little enough wear.

I think that's the reason to do it this way. The assembly with bearings
and pulleys seems quite expensive, ~$1,000. I assume (hope) that the
removable part is cheaper. But I don't know that I understand their
pricing structure.

Well ... first off -- the manual for my model of the grinder
puts the price of the spindle at $5.45, and the bearings at $1.95 each.
The chuck assembly is $2.90.

In contrast, the current MSC price for the screw-in spindle ends
ranges from $160.45 to $213.75, while the price for the spindle was
something like $1050.00.

Of course, we don't know the date of that price list. :-)

[ ... ]

Right. Now, Ill have to get a big enough lathe.

O.K. Good luck with that. I've been known to collect
accessories when I could, in hopes of acquiring a machine with which
they could be used later.

But did you inherit a tool that caused lathe acquisition?

Not a chance. The only tools which my father had were a couple
of tiny claw hammers with at least one claw broken off each, two very
rusty screwdrivers, and eventually an electric drill with a circular
sanding pad for work on the boat.

I was the tool user in the family. My father, and his father
were both lawyers (and later, a judge, for my father).

[ ... ]

A bigger issue is how fast the tube deionizes. If it isn't fast enough,
one cannot flash the tube fast enough, as it stops flashing and instead
remains always on. Deionization time is mostly determined by flash tube
design.

This may be one of the reasons for the internal trigger
electrodes, and the extra volume (of unionized xenon) to quickly replace
the ionized stuff.

Exactly. It's the nearby masses of metal that does the job.

That -- and perhaps the greater volume of Xenon surrounding the
arc path?

If it does not deionize quickly enough, and the capacitor
charging current is high enough, it will indeed remain on full time.
Part of the problem is the deionization time, part is the voltage to
which the tube discharges the capacitor.

Edgerton's book "Flash, Strobe" goes into the details of how the
Strobotac and allied devices work.

O.K. Do you have access to that book? I've never seen it --
though I have met and talked to the man. Is it still in print?


I have a question in at Perkin-Elmer asking if the FX-6A is still made,
and if not what is it's replacement (perhaps Series 1100), and what they
cost. We shall see.

O.K. Good luck.

So far, no response.

Sigh!

[ ... "Electric Brazing" ... ]

I saw that one. Never heard of the company.

Nor did I. But it looks like one of the wartime unknowns which
got contracts to make a product known to come from a larger company --
simply because they could not turn them out in the quantities needed.
I've seen Tektronix scope clones made under such contracts -- they
looked almost identical to the Tektronix, other than the maker's name.

Yes. Don't know how good a job they did.

Nor do I -- but they had to match the specs or they would lose
the contract. And they *should* have had copies of the GR prints and
schematics for the purpose. The lack of a large "crystal" dome over the
soupbowl reflector may have been a part of the money-savings and
material savings during wartime.

[ ... ]

O.K. Part of the problem, of course, is stability of the
timebase. A really good one could be made with a crystal oscillator, a
bunch of counter chips and comparators -- load in a count (period, not
frequency) and it would be very stable. Even the nice little GR
Strobotac which I have drifts for the first minute or so. And that one
is solid state. The older (soupbowl) one takes longer to stabilize, and
it is run from tubes.

Yes. The strobe I built is triggered by an optical encoder on the
winder's main axle, so the image stands absolutely still as the rotation
rate is varied.

Any idea what the maximum flash rate was?

[ ... ]

As you already know -- he has scanned them to a higher
resolution, and put them in his private web space.

I got it; looks good.

Yep -- much better than the first pass -- though the first pass
was enough to get me started.

Enjoy,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

In article , DoN. Nichols says...

I saw that one. Never heard of the company.

Nor did I. But it looks like one of the wartime unknowns which
got contracts to make a product known to come from a larger company --
simply because they could not turn them out in the quantities needed.
I've seen Tektronix scope clones made under such contracts -- they
looked almost identical to the Tektronix, other than the maker's name.

LOL. Tek was *not* happy when Hickock was given the plans and specs
for all the tektronix plug-ins, and the contracts to produce them.

I've worked on both kinds, the Hickock ones were strictly second
rate when it came to quality. Actually, third rate compared with
the originals! :^)

Jim


--
==================================================
please reply to:
JRR(zero) at pkmfgvm4 (dot) vnet (dot) ibm (dot) com
==================================================

In article ,
Ned Simmons wrote:

In article ,
says...

Making the race heavier doesn't help, because while the cross sectional
area (and thus strength) increases, so does the weight (and thus outward
force). My recollection from discussions of energy-storage flywheels is
that these effects cancel more or less perfectly, so all that matters is
the strength-to-weight ratio of the material from which the outer race
is made. Only hoop stress matters, so storage flywheels are often made
of boron fiber.

Yes, the stress on a rotating thin cylinder is dependent only on density
and peripheral speed.


What alloy are bearing races made of? What's the tensile strength?


By far the most common material is AISI 52100, UTS is around 300,000
psi. I don't believe that centrifugal force alone is enough to burst the
bearing race. I figure a peripheral speed of around 1700 FPS would be
required to reach 300 ksi stress. That's close to 2x the speed of sound,
almost 20 miles/second, or about 250,000 RPM for a common 6203 (17x40mm)
bearing. (Those numbers may be a bit high, depending on how chunky the
bearing is, i.e., how far it deviates from a "thin cylinder.")

I doubt that the airstream from a hand blowoff nozzle is supersonic, so
twice this speed might be hard to attain.

My recollection is that in rocket engines, the flow "chokes" (speed
limited by the speed of sound) in the throat of the engine, and then
goes supersonic only while expanding in the bell.

Blowoff nozzles have a throat, but no expansion bell.


I suspect that lubrication failure leading to galling of the balls and
consequently jamming is the big culprit. Perhaps the race expands enough
from the centrifugal force to rattle around and hasten the failure, but
it seems unlikely to me that it's possible to get the bearing spinning
fast enough for this to be much of a factor. The strain in the
hypothetical 6203 race would be about 0.15% at 100 KRPM - in other words
the bearing might loosen up a thousandth or two at that speed.

This mechanism would have a hard time managing the very precisely
symmetric explosions we have heard reported, so uniform that the finger
isn't torn off.

Joe Gwinn

In article , says...
According to Ned Simmons :
In article ,
says...

[ ... ]

What alloy are bearing races made of? What's the tensile strength?


By far the most common material is AISI 52100, UTS is around 300,000
psi. I don't believe that centrifugal force alone is enough to burst the
bearing race. I figure a peripheral speed of around 1700 FPS would be
required to reach 300 ksi stress. That's close to 2x the speed of sound,
almost 20 miles/second, or about 250,000 RPM for a common 6203 (17x40mm)
bearing.

Hmm ... assuming eight balls in the race, that would get you to
33.3 KHz frequency from the balls modulating the airflow.

I have a very hard time accepting that the air at the outlet of a
blowgun supplied with shop air is traveling at close to Mach2.


And the bearing which failed on somebody's finger was 5/8" ID
(15.875mm) -- slightly smaller than the one which you postulated.

Eric said, "The ID was about 5/8 and the OD maybe 1 1/2, 1/34," which is
pretty close to a 6203, and 6203s are common as dirt - much more so than
any radial bearing with an inch dimension bore.


But
we don't know how many balls it had. No doubt, no fewer than 6, which
would get us to 25 KHz. And we don't know exactly when his hearing
dropped out at that time in his life, nor how much more speed the
bearing got in the time since it passed his hearing range.

(Those numbers may be a bit high, depending on how chunky the
bearing is, i.e., how far it deviates from a "thin cylinder.")

I suspect that lubrication failure leading to galling of the balls and
consequently jamming is the big culprit. Perhaps the race expands enough
from the centrifugal force to rattle around and hasten the failure,

That might hasten the failure of the surface of the balls, but
if they *really* failed, all of that energy stored in the spinning outer
race would be transferred to the finger on which the bearing was
mounted, perhaps twisting it off.

Not if the race fractures and the pieces fly off, which is apparently
what happened.


Hmm ... the story did not describe whether the bearing's inner
race remained on his finger -- nor what happened to all of the balls.

but
it seems unlikely to me that it's possible to get the bearing spinning
fast enough for this to be much of a factor. The strain in the
hypothetical 6203 race would be about .15% at 100 KRPM - in other words
the bearing might loosen up a thousandth or two at that speed.

I would expect the outer race to be spinning faster than the
ball cage (think of it as a planetary gear setup with the planet gears
being driven),

That assumes that there's no slip between the inner race, the balls, and
the outer race, which is not the case even at rest. If you hold the
races of an open bearing stationary and push on the ball and cage
assembly it'll slide around easily. That's the reason that a ball
bearing is not happy operating with a load that's very small compared to
its capacity. As the bearing's outer race spins faster the clearance
between the various parts will only increase.

But that last thought does point up something I neglected. The balls are
being thrown against the outer race, so are adding to the force on the
race without adding any strength. If you do the numbers, doubling the
density of the outer race to account for the balls (which I think is
conservative for a couple reasons), you still need to go supersonic,
1300FPS, to burst the race.

Here's another couple possible failure modes related to the retainer.
The retainer, typically mild steel or plastic, distorts or disintegrates
from the centrifugal force and either jams the bearing or frees the
balls to crowd together and the races separate.

so a six-ball race at ultrasonic could indeed have the
outer race spinning fast enough to fail explosively.

I don't buy it, at least not yet. A reference to a common blowgun
producing supersonic flow would be a start.

Huh, look what a google on - supersonic air flow blowgun - turned up...
http://yarchive.net/metal/ball_bearing_spinup.html

Ned Simmons

On 14 Apr 2006 20:04:38 GMT, (DoN. Nichols)
wrote:

According to Ned Simmons :
In article ,
says...

[ ... ]

What alloy are bearing races made of? What's the tensile strength?


By far the most common material is AISI 52100, UTS is around 300,000
psi. I don't believe that centrifugal force alone is enough to burst the
bearing race. I figure a peripheral speed of around 1700 FPS would be
required to reach 300 ksi stress. That's close to 2x the speed of sound,
almost 20 miles/second, or about 250,000 RPM for a common 6203 (17x40mm)
bearing.

Hmm ... assuming eight balls in the race, that would get you to
33.3 KHz frequency from the balls modulating the airflow.

And the bearing which failed on somebody's finger was 5/8" ID
(15.875mm) -- slightly smaller than the one which you postulated. But
we don't know how many balls it had. No doubt, no fewer than 6, which
would get us to 25 KHz. And we don't know exactly when his hearing
dropped out at that time in his life, nor how much more speed the
bearing got in the time since it passed his hearing range.

(Those numbers may be a bit high, depending on how chunky the
bearing is, i.e., how far it deviates from a "thin cylinder.")

I suspect that lubrication failure leading to galling of the balls and
consequently jamming is the big culprit. Perhaps the race expands enough
from the centrifugal force to rattle around and hasten the failure,

That might hasten the failure of the surface of the balls, but
if they *really* failed, all of that energy stored in the spinning outer
race would be transferred to the finger on which the bearing was
mounted, perhaps twisting it off.

Hmm ... the story did not describe whether the bearing's inner
race remained on his finger -- nor what happened to all of the balls.

but
it seems unlikely to me that it's possible to get the bearing spinning
fast enough for this to be much of a factor. The strain in the
hypothetical 6203 race would be about .15% at 100 KRPM - in other words
the bearing might loosen up a thousandth or two at that speed.

I would expect the outer race to be spinning faster than the
ball cage (think of it as a planetary gear setup with the planet gears
being driven), so a six-ball race at ultrasonic could indeed have the
outer race spinning fast enough to fail explosively.

Enjoy,
DoN.
Greetings DoN,
It was me who posted about the exploding bearing. The inner race came
off my finger but it was intact. I'm not sure if it came off because
the bearing came apart or because when the bearing did its thing I
jerked my hand back. The rollers disappeared into the insulation on
the walls. The walls didn't have sheetrock on them where the pieces
struck. I always thought the reason the thing came apart is because
something jammed. A friend's father worked at a lab where things were
spun up in centrifuges until the spinning objects failed. They were
spinning at tremendous speeds. This was when I was about 16 so the 34
year old details are sketchy. But his dad told me how much energy the
small centrifuges used and it required lots of horsepower to spin
small items to the bursting point. Way more than the air coming out of
my nozzle.
ERS

According to Ned Simmons :
In article , says...

[ ... ]

Hmm ... assuming eight balls in the race, that would get you to
33.3 KHz frequency from the balls modulating the airflow.

I have a very hard time accepting that the air at the outlet of a
blowgun supplied with shop air is traveling at close to Mach2.

It could simply be giving a little kick to each ball as it
rotates past -- picking a different part of the sloping trailing edge of
the balls depending on speed, so the actual speed of the bearings could
exceed the airflow velocity.

[ ... ]

That might hasten the failure of the surface of the balls, but
if they *really* failed, all of that energy stored in the spinning outer
race would be transferred to the finger on which the bearing was
mounted, perhaps twisting it off.

Not if the race fractures and the pieces fly off, which is apparently
what happened.

You mean the outer race only, I presume.

[ ... ]

I would expect the outer race to be spinning faster than the
ball cage (think of it as a planetary gear setup with the planet gears
being driven),

That assumes that there's no slip between the inner race, the balls, and
the outer race, which is not the case even at rest. If you hold the
races of an open bearing stationary and push on the ball and cage
assembly it'll slide around easily. That's the reason that a ball
bearing is not happy operating with a load that's very small compared to
its capacity. As the bearing's outer race spins faster the clearance
between the various parts will only increase.

It will slip -- but it can still give a little drive. Try
holding only the inner race and pushing on the bearing cage while the
outer race is unconstrained and see what happens.

[ ... ]

so a six-ball race at ultrasonic could indeed have the
outer race spinning fast enough to fail explosively.

I don't buy it, at least not yet. A reference to a common blowgun
producing supersonic flow would be a start.

Huh, look what a google on - supersonic air flow blowgun - turned up...
http://yarchive.net/metal/ball_bearing_spinup.html

Interesting, I get a:

================================================== ====================
Not Found

The requested URL /metal/ball_bearing_spinup.htm was not
found on this server.
================================================== ====================

when I try that URL. What is it -- this discussion?

Enjoy,
DoN.
--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

According to Eric R Snow :
On 14 Apr 2006 20:04:38 GMT, (DoN. Nichols)
wrote:

[ ... ]

Hmm ... assuming eight balls in the race, that would get you to
33.3 KHz frequency from the balls modulating the airflow.

And the bearing which failed on somebody's finger was 5/8" ID
(15.875mm) -- slightly smaller than the one which you postulated. But
we don't know how many balls it had. No doubt, no fewer than 6, which
would get us to 25 KHz. And we don't know exactly when his hearing
dropped out at that time in his life, nor how much more speed the
bearing got in the time since it passed his hearing range.

[ ... ]

That might hasten the failure of the surface of the balls, but
if they *really* failed, all of that energy stored in the spinning outer
race would be transferred to the finger on which the bearing was
mounted, perhaps twisting it off.

Hmm ... the story did not describe whether the bearing's inner
race remained on his finger -- nor what happened to all of the balls.

[ ... ]

Greetings DoN,

It was me who posted about the exploding bearing. The inner race came
off my finger but it was intact. I'm not sure if it came off because
the bearing came apart or because when the bearing did its thing I
jerked my hand back. The rollers disappeared into the insulation on
the walls. The walls didn't have sheetrock on them where the pieces
struck. I always thought the reason the thing came apart is because
something jammed. A friend's father worked at a lab where things were
spun up in centrifuges until the spinning objects failed. They were
spinning at tremendous speeds. This was when I was about 16 so the 34
year old details are sketchy. But his dad told me how much energy the
small centrifuges used and it required lots of horsepower to spin
small items to the bursting point. Way more than the air coming out of
my nozzle.

Hmm ... you mention the inner race and the rollers -- but not an
outer race. Was this the typical tapered roller bearing, with the cage
traveling with the inner race, and there was no outer race involved? In
that case, yes, you were working with something a lot weaker than the
outer race, so it was more likely to explode at lower speeds.

Anyway -- I'm glad that you were not hurt by this.

Thanks,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

According to Joseph Gwinn :
In article ,
Ned Simmons wrote:

In article ,
says...

[ ... ]

I doubt that the airstream from a hand blowoff nozzle is supersonic, so
twice this speed might be hard to attain.

My recollection is that in rocket engines, the flow "chokes" (speed
limited by the speed of sound) in the throat of the engine, and then
goes supersonic only while expanding in the bell.

But -- that limiting speed is the speed of sound in the medium
and at the pressure that occurs in the throat. At the higher pressure,
that may be significantly above the speed of sound at atmospheric
pressure.

Blowoff nozzles have a throat, but no expansion bell.

Well ... modern ones have sort of a bell -- that OSHA mandated
collar with side holes to keep the full pressure from being applied to
someone's skin. :-)


I suspect that lubrication failure leading to galling of the balls and
consequently jamming is the big culprit. Perhaps the race expands enough
from the centrifugal force to rattle around and hasten the failure, but
it seems unlikely to me that it's possible to get the bearing spinning
fast enough for this to be much of a factor. The strain in the
hypothetical 6203 race would be about 0.15% at 100 KRPM - in other words
the bearing might loosen up a thousandth or two at that speed.

This mechanism would have a hard time managing the very precisely
symmetric explosions we have heard reported, so uniform that the finger
isn't torn off.

A recent posting from the individual involved implies that it was
just the inner race and the roller cage, without an outer race involved.

Enjoy,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

In article ,
says...
In article ,
Ned Simmons wrote:

In article ,
says...

Making the race heavier doesn't help, because while the cross sectional
area (and thus strength) increases, so does the weight (and thus outward
force). My recollection from discussions of energy-storage flywheels is
that these effects cancel more or less perfectly, so all that matters is
the strength-to-weight ratio of the material from which the outer race
is made. Only hoop stress matters, so storage flywheels are often made
of boron fiber.

Yes, the stress on a rotating thin cylinder is dependent only on density
and peripheral speed.


What alloy are bearing races made of? What's the tensile strength?


By far the most common material is AISI 52100, UTS is around 300,000
psi. I don't believe that centrifugal force alone is enough to burst the
bearing race. I figure a peripheral speed of around 1700 FPS would be
required to reach 300 ksi stress. That's close to 2x the speed of sound,
almost 20 miles/second, or about 250,000 RPM for a common 6203 (17x40mm)
bearing. (Those numbers may be a bit high, depending on how chunky the
bearing is, i.e., how far it deviates from a "thin cylinder.")

I doubt that the airstream from a hand blowoff nozzle is supersonic, so
twice this speed might be hard to attain.

Exactly.


My recollection is that in rocket engines, the flow "chokes" (speed
limited by the speed of sound) in the throat of the engine, and then
goes supersonic only while expanding in the bell.

Blowoff nozzles have a throat, but no expansion bell.


I suspect that lubrication failure leading to galling of the balls and
consequently jamming is the big culprit. Perhaps the race expands enough
from the centrifugal force to rattle around and hasten the failure, but
it seems unlikely to me that it's possible to get the bearing spinning
fast enough for this to be much of a factor. The strain in the
hypothetical 6203 race would be about 0.15% at 100 KRPM - in other words
the bearing might loosen up a thousandth or two at that speed.

This mechanism would have a hard time managing the very precisely
symmetric explosions we have heard reported, so uniform that the finger
isn't torn off.

I didn't see any claims that the explosions of the bearings were
symmetric; in fact, if they were perfectly symmetrical there would have
been no finger injuries at all, and Eric and Leon would have been
tempted to repeat their experiments g. I don't have any idea how much
energy is required to sever a finger, but I'm sure a bearing race
spinning at tens of thousands of RPMS is up to the job *if* the finger
is restrained and the bearing can't leave the finger. And while a broken
or severed finger doesn't seem an unreasonable outcome, it also seems
plausible that the impulse of the disintegrating bearing could slew your
whole arm around til your finger is in an orientation where the bearing
slips off. The velocities are vastly different, so it's not a great
analogy, but think of the difference between hitting your finger with a
hammer while it's on the workbench as opposed to while it's held out at
arm's length.

Ned Simmons

In article , says...
According to Ned Simmons :
In article , says...

[ ... ]

Hmm ... assuming eight balls in the race, that would get you to
33.3 KHz frequency from the balls modulating the airflow.

I have a very hard time accepting that the air at the outlet of a
blowgun supplied with shop air is traveling at close to Mach2.

It could simply be giving a little kick to each ball as it
rotates past -- picking a different part of the sloping trailing edge of
the balls depending on speed, so the actual speed of the bearings could
exceed the airflow velocity.

I think it much more likely that air bouncing back off the balls and
retainer interferes with the airstream from the nozzle. I'd be surprised
if the balls reached anywhere near the velocity of the air, and I doubt
the airsteam approaches the speed of sound.


[ ... ]

That might hasten the failure of the surface of the balls, but
if they *really* failed, all of that energy stored in the spinning outer
race would be transferred to the finger on which the bearing was
mounted, perhaps twisting it off.

Not if the race fractures and the pieces fly off, which is apparently
what happened.

You mean the outer race only, I presume.

Initially, yes. In his last post Eric says the inner race also came off
his finger after the bearing disintegrated, which would further explain
why his finger was not more seriously injured.


[ ... ]

I would expect the outer race to be spinning faster than the
ball cage (think of it as a planetary gear setup with the planet gears
being driven),

That assumes that there's no slip between the inner race, the balls, and
the outer race, which is not the case even at rest. If you hold the
races of an open bearing stationary and push on the ball and cage
assembly it'll slide around easily. That's the reason that a ball
bearing is not happy operating with a load that's very small compared to
its capacity. As the bearing's outer race spins faster the clearance
between the various parts will only increase.

It will slip -- but it can still give a little drive. Try
holding only the inner race and pushing on the bearing cage while the
outer race is unconstrained and see what happens.

But a little drive isn't going to get the race to 180 KRPM (to use my
revised number).


[ ... ]

so a six-ball race at ultrasonic could indeed have the
outer race spinning fast enough to fail explosively.

I don't buy it, at least not yet. A reference to a common blowgun
producing supersonic flow would be a start.

Huh, look what a google on - supersonic air flow blowgun - turned up...
http://yarchive.net/metal/ball_bearing_spinup.html

Interesting, I get a:

================================================== ====================
Not Found

The requested URL /metal/ball_bearing_spinup.htm was not
found on this server.
================================================== ====================

when I try that URL. What is it -- this discussion?


In a strange sense, yes. But 13 years ago on this very group. This is
the thread on google...
http://tinyurl.com/loxlq

Ned Simmons

According to Ned Simmons :
In article , says...

[ ... ]

It could simply be giving a little kick to each ball as it
rotates past -- picking a different part of the sloping trailing edge of
the balls depending on speed, so the actual speed of the bearings could
exceed the airflow velocity.

I think it much more likely that air bouncing back off the balls and
retainer interferes with the airstream from the nozzle. I'd be surprised
if the balls reached anywhere near the velocity of the air, and I doubt
the airsteam approaches the speed of sound.

Possible -- I have no way to prove any of this -- nor any desire
to explode bearings in the test process. :-)

[ ... ]

Huh, look what a google on - supersonic air flow blowgun - turned up...
http://yarchive.net/metal/ball_bearing_spinup.html

Interesting, I get a:

================================================== ====================
Not Found

The requested URL /metal/ball_bearing_spinup.htm was not
found on this server.
================================================== ====================

when I try that URL. What is it -- this discussion?


In a strange sense, yes. But 13 years ago on this very group. This is
the thread on google...
http://tinyurl.com/loxlq

O.K. That one worked.

It seems that nothing was settled that time, either. :-)

Thanks,
DoN.
--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

"DoN. Nichols" wrote in message
...
According to Glenn :

"DoN. Nichols" wrote in message

[ ... ]

I may get a hair
to
play with the scanner more and see how nice I can make it. The scanner
lives on the wife's machine so I have to schedual time to use it May
have to go buy one for me too just so I can figure out how to do it right
the first time.

What kind of scanner does she have?

It is an LIDE 80 I believe from Cannon. It has the Negative/Slide adapter
and that was the main selling point. She has lots of old slides and
negative she wanted to scan and print. Some required a bit of restoring to
get the colors back. Most scans I have done from the negatives come out
better than the ones from the original prints

I find an old HP ScanJet II (color) works very nicely for this.
I've got a SCSI adaptor on the computer, and the HP software lets me
scan to TIFF with pure B&W -- and adjusting the threshold between black
and white to tune it to drop most light stains and smudges. Once I have
the scans made, they get moved to one of the unix machines, and
combined, turned into PostScript, and from there into PDF -- all using
unix tools -- not Adobe ones.

I've got a spare ScanJet II (one from hamfest, the other from
eBay -- both really cheap), so some of these days I will try the various
unix scanning software to see what will work better for me, and keep me
clear of that Windows machine except for on income tax prepration day. :-)

I had a Scanjet fo awhile but the scuzzi , adapter gave me fits and I
scraped that.

Enjoy,
DoN.


P.S. What Time zone are you in? It is currently 2:36 AM for me, in
EDT -- and I am now going to bed. :-)

Pacific Daylight Time Medford, OR

Glenn

"Larry Jaques" wrote in message
...
On Thu, 13 Apr 2006 22:30:31 -0700, with neither quill nor qualm,
"Glenn" quickly quoth:


"DoN. Nichols" wrote in message
...
According to Glenn :

[ ... ]

Just checked .. I have 20Meg or so left on my FTP space so I will scan
it
in
high res suitable for framing and post it there. I will post a link
when
it
is in place.

It turned out to be your web space -- but that was a nice
improvement.

Funny that, When I go to upload files I have to go to an ftp site and
login, then to download them you go to the web space. I may get a hair to
play with the scanner more and see how nice I can make it. The scanner
lives on the wife's machine so I have to schedual time to use it May
have to go buy one for me too just so I can figure out how to do it right
the first time.

http://www.pricewatch.com/scanners/281713-1.htm From $59.

I have a book on scanning if you'd like to borrow it. (My office has a
stack of 100+ books which I'm sorting to sell on Ebay, etc.) I'll be
down in your area (the airport) Tuesday morning so let me know.

I may be in Medford today to sign my tax docs if the tax critter I
hired ever gets well, goes to her office, and does my return. sigh

I would like to look at it Larry. I should be at home though. I have been
off work for about a month now with back troubles. I won't be going back
untill Monday the 24th and then it will be on light duty untill my
retirerment papers go through.
You are welcome to drop by anytime you are in the neghiborhood
Glenn

"DoN. Nichols" wrote in message
...
According to Ned Simmons :
In article , says...

[ ... ]

It could simply be giving a little kick to each ball as it
rotates past -- picking a different part of the sloping trailing edge
of
the balls depending on speed, so the actual speed of the bearings could
exceed the airflow velocity.

I think it much more likely that air bouncing back off the balls and
retainer interferes with the airstream from the nozzle. I'd be surprised
if the balls reached anywhere near the velocity of the air, and I doubt
the airsteam approaches the speed of sound.

Possible -- I have no way to prove any of this -- nor any desire
to explode bearings in the test process. :-)

[ ... ]

Huh, look what a google on - supersonic air flow blowgun - turned
up...
http://yarchive.net/metal/ball_bearing_spinup.html

Interesting, I get a:

================================================== ====================
Not Found

The requested URL /metal/ball_bearing_spinup.htm was not
found on this server.
================================================== ====================

when I try that URL. What is it -- this discussion?


In a strange sense, yes. But 13 years ago on this very group. This is
the thread on google...
http://tinyurl.com/loxlq

O.K. That one worked.

It seems that nothing was settled that time, either. :-)

Thanks,
DoN.

The thing that stands out is the fellow that ran some tests on bearings said
after his testing the bearing was worn out and useless. That pretty well
substantiates my position that even if you don't explode the bearing you are
causing harm to the bearing.
Also supporting your position that spinning it with air is a bad idea if you
want to use the bearing again.
Add to that several examples of the bearings exploding for whatever reason
while spinning them with air and I feel like your point is proven. Granted
I have only heard of used bearings exploding when cleaned and then spun up
with air so it is probable that there were small fractures in the outer race
that allowed it to come apart sooner than all the math would suggest.
It was still cool to watch those suckers fly down the road shooting a
rooster tail of sparks

Glenn
Reformed bearing spinner

In article ,
(DoN. Nichols) wrote:

According to Joseph Gwinn :
In article ,
(DoN. Nichols) wrote:


[ ... ]

[ ... ]

Right. Now, Ill have to get a big enough lathe.

O.K. Good luck with that. I've been known to collect
accessories when I could, in hopes of acquiring a machine with which
they could be used later.

But did you inherit a tool that caused lathe acquisition?

Not a chance. The only tools which my father had were a couple
of tiny claw hammers with at least one claw broken off each, two very
rusty screwdrivers, and eventually an electric drill with a circular
sanding pad for work on the boat.

I was the tool user in the family. My father, and his father
were both lawyers (and later, a judge, for my father).

My father has a reasonable number of tools, but he is no machinist.


A bigger issue is how fast the tube deionizes. If it isn't fast enough,
one cannot flash the tube fast enough, as it stops flashing and instead
remains always on. Deionization time is mostly determined by flash
tube
design.

This may be one of the reasons for the internal trigger
electrodes, and the extra volume (of unionized xenon) to quickly replace
the ionized stuff.

Exactly. It's the nearby masses of metal that does the job.

That -- and perhaps the greater volume of Xenon surrounding the
arc path?

Not unless it's moving. Ions diffuse too slowly.


If it does not deionize quickly enough, and the capacitor
charging current is high enough, it will indeed remain on full time.
Part of the problem is the deionization time, part is the voltage to
which the tube discharges the capacitor.

Edgerton's book "Flash, Strobe" goes into the details of how the
Strobotac and allied devices work.

O.K. Do you have access to that book? I've never seen it --
though I have met and talked to the man. Is it still in print?

Bought in my copy in 1983: "Electronic Flash, Strobe", 2nd edition,
Harold E. Edgerton, MIT Press, 1979, 366 pages, ISBN 0-262-55008-3.

I looked on Amazon.com. There is a 3rd edition, with used copies going
for ~$120.00. Ouch! I had no idea. It must have become a classic. My
copy of the 2nd edition cost $10.00 new. No mention on Amazon of
anything other than the 3rd edition.

There are a lot of patents listed in the back of the book. I bet the
theory is described there. I'll look. The application notes from the
various flashtube makers aren't too bad, but the book pulls it all
together.

I wonder if there are any other textbooks in print. I have not heard of
any, but wasn't looking.

The best online source I know of is Sam Goldwasser's electronic repair
website, and his bookmarks:
http://www.eio.com/repairfaq/sam/sambook.htm. Look down the list the
the section titled "Strobe/Camera Sites/Information" about 3/4 of the
way down.


I have a question in at Perkin-Elmer asking if the FX-6A is still made,
and if not what is it's replacement (perhaps Series 1100), and what
they
cost. We shall see.

O.K. Good luck.

So far, no response.

Sigh!

[ ... "Electric Brazing" ... ]

I saw that one. Never heard of the company.

Nor did I. But it looks like one of the wartime unknowns which
got contracts to make a product known to come from a larger company --
simply because they could not turn them out in the quantities needed.
I've seen Tektronix scope clones made under such contracts -- they
looked almost identical to the Tektronix, other than the maker's name.

Yes. Don't know how good a job they did.

Nor do I -- but they had to match the specs or they would lose
the contract. And they *should* have had copies of the GR prints and
schematics for the purpose. The lack of a large "crystal" dome over the
soupbowl reflector may have been a part of the money-savings and
material savings during wartime.

They will have had the full manufacturing documentation set.


O.K. Part of the problem, of course, is stability of the
timebase. A really good one could be made with a crystal oscillator, a
bunch of counter chips and comparators -- load in a count (period, not
frequency) and it would be very stable. Even the nice little GR
Strobotac which I have drifts for the first minute or so. And that one
is solid state. The older (soupbowl) one takes longer to stabilize, and
it is run from tubes.

Yes. The strobe I built is triggered by an optical encoder on the
winder's main axle, so the image stands absolutely still as the rotation
rate is varied.

Any idea what the maximum flash rate was?

I designed it for 20 Hz (1200 rpm) max, have run it at twice that
without difficulty, although the flash energy is too high to run at that
speed for long without overheating the flashtube. It's easy to fix (use
smaller flash capacitor), but I haven't bothered yet.

The tube I designed for is the Xicon unit sold by Mouser for timing
lights (361-4425) and the trigger transformer (422-2304). The max flash
rate spec (60 per minute) is for the max flash energy (4 Joules/flash).
One can go faster if one respects the power limit, 4 watts average. I
don't know the deionization limit to speed, but have flashed a Mouser
36FT106 (what I could get at the time) at 28.14 Hz (1,688 rpm), and the
limit is the circuit not the tube. Given that the Extech strobe unit
goes to 10,000 rpm (167 Hz), it should be possible to go far higher.


Joe