On 10/14/10 7:01 PM, Robatoy wrote:
On Oct 14, 7:52 pm, wrote:
On 10/14/10 6:40 PM, wrote:





On Thu, 14 Oct 2010 17:26:59 -0500,
wrote:

On 10/14/10 5:06 PM, Robatoy wrote:
In ,
wrote:

Then start sawing oak, and leaving the VERY CORROSIVE sawdust caked
onto every surface of the caliper.

More corrosive than road salt?

More corrosive than brake fluid? Because calipers neeeeeever leak.
Brake fluid itself is not corrosive. When it absorbs moisture it is -
and brake fluid is highly hygroscopic.

I guess I was wrong then.
sheesh

what does it feel like, Mike?

I was being fesesiou.... phesesu... feseeshus..... sarcastic.

I thought I was wrong once, but I was mistaken.


--

-MIKE-

"Playing is not something I do at night, it's my function in life"
--Elvin Jones (1927-2004)
--
http://mikedrums.com

---remove "DOT" ^^^^ to reply

Subjest

Time for a reality check.

Take your choice, dynamic or regenerative braking will never cut it as
a safety braking system.

Toss in disk brakes if that will make you happy.

All are much too slow to respond quickly enough to compete as a safety
device against SawStop.

As far as a braking system to bring a saw blade to a stop more
quickly, the economics will kill the idea.

The cost of a DC power supply, adjustable timer and a horsepower
rated, mechanically interlocked, set of contactors for a dynamic
braking system will be equal to or exceed the cost of a motor which
will also require added stator pegging to keep it from being ripped
loose from the motor housing.

Similar cost structures are4 in play for the other options.

Back to the drawing board.

Waiting for a T/S blade to stop spinning is a good time to collect
your thoughts.

When working around woodworking tools, patience is a virtue, IMHO.

Lew

On 10/14/10 10:43 PM, Lew Hodgett wrote:
Subjest

Time for a reality check.

Take your choice, dynamic or regenerative braking will never cut it as
a safety braking system.

Toss in disk brakes if that will make you happy.

All are much too slow to respond quickly enough to compete as a safety
device against SawStop.


Reality check.
We don't give a crap because we're not talking about a safety stop.


--

-MIKE-

"Playing is not something I do at night, it's my function in life"
--Elvin Jones (1927-2004)
--
http://mikedrums.com

---remove "DOT" ^^^^ to reply

"Josepi" wrote in
:

How about a compressed air nozzle aimed at the carbide of the blade to
slow it to a stop?

It would clean it off and compressed air is usually available.


That might actually have a practical application. Point the jet of air
towards the dust collection port, and perhaps dust collection can be
improved by having the stream of air going while the saw is running. As a
bonus, it would work to slow the saw blade down after shutting off the saw.

Puckdropper
--
Never teach your apprentice everything you know.

In article , says...

Spoken like a true woodworker...LOL

Seriously that's how you compress the piston on the brakes on a Jeep--
put a c-clamp on it.

"J. Clarke" wrote in message
in.local...
C-clamp.




In article ,
says...

On 10/13/2010 02:32 PM, J. Clarke wrote:
In ,
says...

On 10/13/10 9:43 AM, J. Clarke wrote:
In , says...

J. Clarke wrote:
In , says...

J. Clarke wrote:
In ,
says...

On Mon, 11 Oct 2010 19:59:30 -0400,
wrote:

J. Clarke wrote:
In ,
says...

I would think that an emergency stop mechanism would be a
whole different
magnitude than a scheduled, everyday, stop.

For a finger saver an emergency stop mechanism would have to
stop the blade
in a few teeth passings. For everyday usage a couple dozen
blade rotations
would be OK too. These two situations would require different
tactics.

A dynamic electronic brake could vary the intensity for the
two different
scenarios and we could add the caliper to the emerg stop. A
caliper probably
wouldn't last long in everyday usage and would need to be
adjusted and/or
replaced frequently.

So how much power do you have to put into that electronic brake
to stop
the blade as fast as Sawstop's physical block?

And why would a caliper not last long? A set of brake pads on
a car
with 10" rotors lasts 40,000 miles or so, and they're getting a
Hell of
a lot more of a workout that they would stopping a little bitty
saw
blade that masses less than 1/1000 as much.

The physics on that seem interesting. A little like stopping a
speeding
bullet on a dime--it challenges my imagination. Probably not
quite as
difficult as stopping a lightning bolt, but I wouldn't want to
try that
either.

Bill
No way a caliper could stop the blade in even 4X the time
the
saw-stop does. And keeping dust out of the gap between tha "pad"
and
the blade would be quite problematic - with dust decreasing the
stopping efficiency by a very large margin.

I suspect that a small pyrotechnic pressurizing one of the calipers
off
my '76 Lincoln might surprise you.


When it snapped (seriously)? I'm not an engineer, so I don't know
for
sure. I just wouldn't be surprised. Maybe someone else can opine.

Why would something that can stop a 4000 pound car "snap" when
called on
to stop a 3 pound saw blade?

"Pyrotechnics" rather than a master cylinder with brake fluid?

To stop the saw in a fraction of a revolution, you need rapid
application. A pyro will build pressure rapidly.

I didn't think we were talking about an emergency stop.
AFAIK, we're discussing a convenience stop which, in my opinion, would
be satisfactorily done in a couple seconds, not milliseconds.

Well, geez, for that a bicycle brake will work fine.

Another reality check for all the people taking this thread off into the
wild blue yonder is
the issue of getting the blade onto the arbor in the presence of calipers
that grip either
side of the blade. My interest (and Mike's as well, I think) in using a
bicycle brake was
simply a matter of "how can I retrofit my existing table saw with a simple
convenience
brake?" I think the wide-opening jaws of a bicycle brake (maybe along
with some kind of
front-side cable disconnect to allow the calipers to drop out of the way)
would allow enough
clearance to get the blade on the arbor without too much trouble. This
heavy-duty
automotive caliber Saw-Stop alternative that everybody else is talking
about would also have
to provide a similar mechanism, which would of course add to the
complexity.

Disc brake were around for a lot longer than the ABS systems were ever
implemented.
Disc brakes were not sdesigned to "lock up" but rather be more linear than
shoe brake systems, and fade less.

"Mike Marlow" wrote in message
...
No they aren't. ABS systems are designed to prevent the wheel from locking
up, but disk brakes aren't. In fact, quite the opposite, they are designed
to lock up but rely upon the ABS to govern them so they don't.


Scott Lurndal wrote:
On the other hand, disc brakes are designed so they don't lock up,
this includes the materials used as well plus the modern ABS
electronics.


--

-Mike-

In article ,
says...

I have no idea what EU regulations state or why they would care about a
gradual stop of a saw blade.

Are these regulations involved in convenience stopping of a table saw blade
and what do they state?

The state that the blade must spin down in 10 seconds or less or else
the saw has to have permanent guard. The method they normally use won't
spin dado blades down in 10 seconds, so saws without permanent guards
are made with short arbors that can't take a dado.

"J. Clarke" wrote in message
in.local...
If it "works like a charm" then why can't it slow a dado fast enough to
meet EU regulations?



In article , says...

The electornic way would be so much gentler and easier to implement. They
work like a charm.

Maybe only because of the background of the guys proposing it.

In article ,
says...

On Thu, 14 Oct 2010 16:22:22 -0500, Steve Turner
wrote:

On 10/14/2010 2:52 PM, wrote:
On Thu, 14 Oct 2010 09:27:45 -0400, "Mike Marlow"
wrote:

Larry Jaques wrote:
On Thu, 14 Oct 2010 08:50:21 -0400, "Mike Marlow"
wrote:


As a guy who has done all of his own vehicle maintenance for 40
years now, I have to ask what you observed in your experiences, that
causes you to make this statement? I don't know if the brake
caliper idea is the most elegant solution, but I sure can't see
anything in what you are saying that would suggest it is not a
workable solution.

Suitable placement of an air nozzle tube to clear the caliper frame
every hour or so would go far into making this device work for more
than an hour. You'd have to keep the sawdust from piercing the seals
and/or building up on the frame

Not at all Larry, if you consider what a normal brake caliper in an
automobile is subject to. In comparison, the environment inside a table saw
would be a walk in the part of a caliper.


You get a splinter of oak thrown at a rubber caliper boot at 18000
feet per minute (almost 205MPH) a few times and expect the boot to
survive?. For the brake to see the same rotational RPM on a car with
24" diameter tires (pretty standard today) you would need to drive
over 250 MPH. Closer to 260MPH if the saw runs 3650 RPM.

A 10" saw runs closer to 5200 RPM - so 370 MPH.

Ever heard of "mass"? By your logic, my Dremel tool running at 30,000 RPM
would be even more impossible to stop.


No, I said nothing of the sort. I didn't even say anything about it
being hard to stop. I was comaring the speed at which particals might
possibly hit the boot on the lincoln caliper some dufus was talking
about mounting to the table saw to stop the blade, The speed at which
a sliver could be flung at that boot from a typical table saw blade
would require the above mentioned speeds with the caliper on a car -
assuming the bit was picked up from the road or thrown from the
circumference of the tire.
Also, the caliper is actually pretty well protected mounted as it is
virtually inside the wheel - with the caliper boot protected between
the pad and tha caliper frame, and usually behind a splash shield as
well.

Then start sawing oak, and leaving the VERY CORROSIVE sawdust caked
onto every surface of the caliper.

Geez Chicken Little, how many mountains are you going to make out of molehills
on this topic? Just about every point you've tried to make has had the air of
doom, disaster, and failure. This ain't that friggin' difficult, Penelope.

Nobody said it was difficult. Just saying the brake from the old
lincoln is NOT going to be anywhere close to an effective solution.
So many guys on the Wreck just make things WAY too complicated.

You want a convenience brake on an AC table saw? DC injection braking
is as simple as it gets and can be done by a reasonably adept
scrounger for less than $25 in less than an hour, with NO
modifications to the physical part of the saw. Just grabbing a few
parts out of my scrap bin I could have it working on a saw in less
than half an hour with no cash outlay at all. Not fully automated -
but hit the stop button or turn off the power and press a pushbutton
untill the blade stops (about 2 seconds) using nothing more than an
old PC power supply and a pushbutton switch. To make it a littlemore
foolproof the power switch would need to be replaces with a SPDT or
DPDT switch or augmented by a relay to prevent injecting the DC while
the AC was still connected.

But if I have to push a button to stop the blade I may as well just
shove a pushstick into the side of it.

In article ,
says...

On Thu, 14 Oct 2010 16:38:53 -0500, -MIKE-
wrote:

On 10/14/10 4:22 PM, Steve Turner wrote:
Then start sawing oak, and leaving the VERY CORROSIVE sawdust caked
onto every surface of the caliper.

Geez Chicken Little, how many mountains are you going to make out of
molehills on this topic? Just about every point you've tried to make has
had the air of doom, disaster, and failure. This ain't that friggin'
difficult, Penelope.


And since when is Oak sawdust corrosive... no, I'm sorry..."VERY
CORROSIVE?"

Never see the black staining in oak from non-galvanized nails? That is
due to corrosion. Doesn't take much corrosion to make a caliper just
fussy enough that it might not do the required job (for which it was
not designed).

What, a disk brake caliper is not designed to stop a metal disk from
turning? So for what _is_ it designed?

And when did oak in a dry shop become more corrosive than salt on a wet
road?

See also:
http://www.scribd.com/doc/36276187/C...Metals-by-Wood

Yeah, you stick a nail in a piece of oak and let it soak in water for a
few years and you'll get corrosion. There's no piece of oak here, and
no soaking in water. If corrosion from oak is an issue you should be
more worried about your blade and arbor and bearings than about the
brake caliper.

You gotta be an electrical engineer--only an EE could be so paranoid
about a simple mechanical device.

I saw my fair amount of oak and I'm not exactly a neat guy in the shop.
I clean up my saw dust when it ****es me off enough, which is usually
when it's in the way of the next project, which means, it can sit around
under the saw, on my tools, all kinds of other metal, plastic, and
rubber stuff, including the end of this run-on sentence, for months at a
time.

I haven't seen it corrode a single thing.
(This should cue some pseudo scientific diatribe about some oil in oak,
contained in a minuscule amout, which is technically an acid or oxidizer
of some sort which *can* corrode *something* on planet earth.)

In article ,
says...

How about a compressed air nozzle aimed at the carbide of the blade to slow
it to a stop?

It would clean it off and compressed air is usually available.


wrote in message
...
On Thu, 14 Oct 2010 08:50:21 -0400, "Mike Marlow"
First of all, it's just too big and heavy to fit.

Fit what, a big cabinet?

Second it's using an
atom bomb to swat a fly.

So is Sawstop by that logic.

Third, it's too complex.

More complext than Sawstop?

Exactly haw are you
going to actuate it?????

Trigger a gas generator.

Forth, how are you going to get it out of the way to change blades?

Screwdriver.

Fifth - How are you going to compensate for different blade
thicknesses - or heaven help you, a DADO blade?

Screwdriver. It already accomodates the front and rear rotors, the
fronts are about 3/4 inch thick, the rears about 1/4, and there's abut
that much difference in pad thickness between new and worn out.

Also, single piston or dual piston?

However many it has on it.

and how are you going to ensure
the pressure on both sides of the blade is equal,

The same way it happens on the car.

and application is
even..

The same way it happens on the car.

Push on one side of the blade more than the other and the blade
goes into an oscillation/wobble and you eventually break the web out
of the blade. Then you have a REAL safety issue!!!!!.

You can say the same for a brake rotor, which actually has a "web"
instead of being a piece of uniform steel plate.

Trust me - it's a BAD idea - and almost totally unworkable on so MANY
levels if you understand anything about how both the saw and the break
caliper work.

Oh, now I see the problem. We were talking about _brake_ caliper. I
guess if you use a _break_ caliper you can expect things to break.

In article , says...

Nobody wants to stop a saw blade in one rev. Convenience stop only.

This was barked at when the SawStop came into comparison.


"Scott Lurndal" wrote in message
...
A car wheel spinning at 5000RPM's isn't stopped within a single rotation
by a caliper disc brake. Why would you expect a saw blade to be?

Because the blade masses a tiny fraction of what the car does.

A car brake is designed to avoid locking up, yet that's exactly the
behavior you would want with a sawblade, and you'd want it to lock in
much less than a single revolution.

If a car brake doesn't ever lock then the car doesn't stop. In any
case, absent ABS it's possible to lock the brakes on any car on which
the brakes are in good condition. Don't believe me, put both feet on
the pedal and shove hard. If you have ABS then pull the fuse on it
first.

In article , says...

Disc brake were around for a lot longer than the ABS systems were ever
implemented.
Disc brakes were not sdesigned to "lock up" but rather be more linear than
shoe brake systems, and fade less.

"Mike Marlow" wrote in message
...
No they aren't. ABS systems are designed to prevent the wheel from locking
up, but disk brakes aren't. In fact, quite the opposite, they are designed
to lock up but rely upon the ABS to govern them so they don't.

They're not "designed to lock up", they're designed as a compromise
between maximum braking force, fade, pad wear, weight, and cost. Most
disk brakes can be locked.

ABS is intended to save your ass when there's poor traction by
preventing lock--it will also prevent lock on good surfaces but
generally isn't needed for that purpose.

Scott Lurndal wrote:
On the other hand, disc brakes are designed so they don't lock up,
this includes the materials used as well plus the modern ABS
electronics.

Funny how we keep going back to that concept...LOL


"-MIKE-" wrote in message
...
Reality check.
We don't give a crap because we're not talking about a safety stop.

Me think we will wait until somebody shows a design drawing of where the
caliper goes when the saw blade tips at a 45 degree cut.

I don't see this working well for a retrofit on a tablesaw with a
tilt...maybe a production lumber yeard saw. For a new design a custom moter
with a caliper brake would be feasible but eliminates a stock motor design
and the price would reach the SawStop price.

IMHO The dynamic brake would be more effective and less maintenance. I am
with clare on that one but then I am a "circuitry" guy.



"Mike Marlow" wrote in message
...
Too complex? On the contrary, it's very simple.

Well, one idea would be to mount it on the inside of the arbor so that it
does not even have to be removed to replace a blade.

You are going out of your way to make this appear to be complicated now.
Both sides? Why both sides? For the discussion at hand, one side would be
ample.


Sure - it you push it hard enough. No need for that level of pressure
though. Think about what forces your blade sees as you cut through a
knarley hunk of hardwood. It sees more lateral force than would be required
for a simple blade brake - which is the discussion at hand.


Sorry Clare - cannot trust you on this point. I see it as perfectly
workable and not subject to any of the concerns you've outlined. I do
understand both how the saw works and how calipers work but you have not
argued anything to make the idea impractical.

--

-Mike-

Should have read. (I didn't write the attributed text)

"Mike Marlow" wrote in message
...
ABS is designed to prevent lock up - car brakes are not.

--


"Josepi" wrote in message
...
Nobody wants to stop a saw blade in one rev. Convenience stop only.

This was barked at when the SawStop came into comparison.


"Scott Lurndal" wrote in message
...
A car wheel spinning at 5000RPM's isn't stopped within a single rotation
by a caliper disc brake. Why would you expect a saw blade to be?

A car brake is designed to avoid locking up, yet that's exactly the
behavior you would want with a sawblade, and you'd want it to lock in
much less than a single revolution.

The name "anti-lock" is a misnomer as the brakes successively lock and
release each pulse. On each release steering control is regained. Braking
distance is not improved as admitted in later research.


"J. Clarke" wrote in message
in.local...
They're not "designed to lock up", they're designed as a compromise
between maximum braking force, fade, pad wear, weight, and cost. Most
disk brakes can be locked.

ABS is intended to save your ass when there's poor traction by
preventing lock--it will also prevent lock on good surfaces but
generally isn't needed for that purpose.

I assume these regs are not enforced on saw sales then?

I know my sliding saw (cheapo) has a dynamic brake in it that slows it down
after a few seconds of power down but I do not have a T/S. The ones I have
seen (probably old units) spin forever after power off.



"J. Clarke" wrote in message
in.local...
The state that the blade must spin down in 10 seconds or less or else
the saw has to have permanent guard. The method they normally use won't
spin dado blades down in 10 seconds, so saws without permanent guards
are made with short arbors that can't take a dado.



In article ,
says...

I have no idea what EU regulations state or why they would care about a
gradual stop of a saw blade.

Are these regulations involved in convenience stopping of a table saw
blade
and what do they state?

I believe there would be a definite danger factor difference parameter in
that one.

Usually convenient though.




"J. Clarke" wrote in message
in.local...

But if I have to push a button to stop the blade I may as well just
shove a pushstick into the side of it.

Now we know what the "J." stands for...."Jeep"


"J. Clarke" wrote in message
in.local...
Seriously that's how you compress the piston on the brakes on a Jeep--
put a c-clamp on it.


In article , says...

Spoken like a true woodworker...LOL

On 10/15/10 8:32 AM, J. Clarke wrote:
You want a convenience brake on an AC table saw? DC injection braking
is as simple as it gets and can be done by a reasonably adept
scrounger for less than $25 in less than an hour, with NO
modifications to the physical part of the saw. Just grabbing a few
parts out of my scrap bin I could have it working on a saw in less
than half an hour with no cash outlay at all. Not fully automated -
but hit the stop button or turn off the power and press a pushbutton
untill the blade stops (about 2 seconds) using nothing more than an
old PC power supply and a pushbutton switch. To make it a littlemore
foolproof the power switch would need to be replaces with a SPDT or
DPDT switch or augmented by a relay to prevent injecting the DC while
the AC was still connected.

But if I have to push a button to stop the blade I may as well just
shove a pushstick into the side of it.


Exactly, unless it's incorporated into the off switch.

If you do use a push stick, don't use oak.
It's VERY CORROSIVE and will disintegrate your saw blade.


--

-MIKE-

"Playing is not something I do at night, it's my function in life"
--Elvin Jones (1927-2004)
--
http://mikedrums.com

---remove "DOT" ^^^^ to reply

On Thu, 14 Oct 2010 22:06:25 -0400, "Mike Marlow"
wrote:

Scott Lurndal wrote:


On the other hand, disc brakes are designed so they don't lock up,
this includes the materials used as well plus the modern ABS
electronics.


No they aren't. ABS systems are designed to prevent the wheel from locking
up, but disk brakes aren't. In fact, quite the opposite, they are designed
to lock up but rely upon the ABS to govern them so they don't.
Not true. Drum brakes are much more powerfull on the first
application, and more likely to lock up due to their self-energizing
servo action (virtually every drum brake on a vehicle in the last 40
years) The only advantage of disks is faster cooling and less fade.

On Fri, 15 Oct 2010 09:49:34 -0400, "J. Clarke"
wrote:

In article , says...

Disc brake were around for a lot longer than the ABS systems were ever
implemented.
Disc brakes were not sdesigned to "lock up" but rather be more linear than
shoe brake systems, and fade less.

"Mike Marlow" wrote in message
...
No they aren't. ABS systems are designed to prevent the wheel from locking
up, but disk brakes aren't. In fact, quite the opposite, they are designed
to lock up but rely upon the ABS to govern them so they don't.

They're not "designed to lock up", they're designed as a compromise
between maximum braking force, fade, pad wear, weight, and cost. Most
disk brakes can be locked.

ABS is intended to save your ass when there's poor traction by
preventing lock--it will also prevent lock on good surfaces but
generally isn't needed for that purpose.

Scott Lurndal wrote:
On the other hand, disc brakes are designed so they don't lock up,
this includes the materials used as well plus the modern ABS
electronics.


I've had more "success" locking drum brakes on dry pavement than
disks. For CAFE reasons they put the lightest disk brake assembly they
can get away with on most vehicles.

On Thu, 14 Oct 2010 22:18:51 -0400, "Mike Marlow"
wrote:

wrote:


Never see the black staining in oak from non-galvanized nails? That is
due to corrosion. Doesn't take much corrosion to make a caliper just
fussy enough that it might not do the required job (for which it was
not designed).


I thought you worked on cars Clare. Have you ever seen a caliper that was
*not corroded*? You're exagerating things in attempt to bolster your point
but again, it's just not true.
The outer frame of the caliper can be corroded all to heck - no
problem. If the slider mechanism is corroded (which it often is)
braking is less linear, and less predictable. They can (and do) drag.
They can also apply late.

If the piston gets corroded, all the same, but a lot worse.

On Fri, 15 Oct 2010 09:32:43 -0400, "J. Clarke"
wrote:

In article ,
says...

On Thu, 14 Oct 2010 16:22:22 -0500, Steve Turner
wrote:

On 10/14/2010 2:52 PM, wrote:
On Thu, 14 Oct 2010 09:27:45 -0400, "Mike Marlow"
wrote:

Larry Jaques wrote:
On Thu, 14 Oct 2010 08:50:21 -0400, "Mike Marlow"
wrote:


As a guy who has done all of his own vehicle maintenance for 40
years now, I have to ask what you observed in your experiences, that
causes you to make this statement? I don't know if the brake
caliper idea is the most elegant solution, but I sure can't see
anything in what you are saying that would suggest it is not a
workable solution.

Suitable placement of an air nozzle tube to clear the caliper frame
every hour or so would go far into making this device work for more
than an hour. You'd have to keep the sawdust from piercing the seals
and/or building up on the frame

Not at all Larry, if you consider what a normal brake caliper in an
automobile is subject to. In comparison, the environment inside a table saw
would be a walk in the part of a caliper.


You get a splinter of oak thrown at a rubber caliper boot at 18000
feet per minute (almost 205MPH) a few times and expect the boot to
survive?. For the brake to see the same rotational RPM on a car with
24" diameter tires (pretty standard today) you would need to drive
over 250 MPH. Closer to 260MPH if the saw runs 3650 RPM.

A 10" saw runs closer to 5200 RPM - so 370 MPH.

Ever heard of "mass"? By your logic, my Dremel tool running at 30,000 RPM
would be even more impossible to stop.


No, I said nothing of the sort. I didn't even say anything about it
being hard to stop. I was comaring the speed at which particals might
possibly hit the boot on the lincoln caliper some dufus was talking
about mounting to the table saw to stop the blade, The speed at which
a sliver could be flung at that boot from a typical table saw blade
would require the above mentioned speeds with the caliper on a car -
assuming the bit was picked up from the road or thrown from the
circumference of the tire.
Also, the caliper is actually pretty well protected mounted as it is
virtually inside the wheel - with the caliper boot protected between
the pad and tha caliper frame, and usually behind a splash shield as
well.

Then start sawing oak, and leaving the VERY CORROSIVE sawdust caked
onto every surface of the caliper.

Geez Chicken Little, how many mountains are you going to make out of molehills
on this topic? Just about every point you've tried to make has had the air of
doom, disaster, and failure. This ain't that friggin' difficult, Penelope.

Nobody said it was difficult. Just saying the brake from the old
lincoln is NOT going to be anywhere close to an effective solution.
So many guys on the Wreck just make things WAY too complicated.

You want a convenience brake on an AC table saw? DC injection braking
is as simple as it gets and can be done by a reasonably adept
scrounger for less than $25 in less than an hour, with NO
modifications to the physical part of the saw. Just grabbing a few
parts out of my scrap bin I could have it working on a saw in less
than half an hour with no cash outlay at all. Not fully automated -
but hit the stop button or turn off the power and press a pushbutton
untill the blade stops (about 2 seconds) using nothing more than an
old PC power supply and a pushbutton switch. To make it a littlemore
foolproof the power switch would need to be replaces with a SPDT or
DPDT switch or augmented by a relay to prevent injecting the DC while
the AC was still connected.

But if I have to push a button to stop the blade I may as well just
shove a pushstick into the side of it.

Which is why using the DPDT switch makes it foolproof. and simple
circuitry can handle the injection current timing.

On Thu, 14 Oct 2010 22:08:03 -0500, -MIKE-
wrote:

On 10/14/10 7:01 PM, Robatoy wrote:
On Oct 14, 7:52 pm, wrote:
On 10/14/10 6:40 PM, wrote:





On Thu, 14 Oct 2010 17:26:59 -0500,
wrote:

On 10/14/10 5:06 PM, Robatoy wrote:
In ,
wrote:

Then start sawing oak, and leaving the VERY CORROSIVE sawdust caked
onto every surface of the caliper.

More corrosive than road salt?

More corrosive than brake fluid? Because calipers neeeeeever leak.
Brake fluid itself is not corrosive. When it absorbs moisture it is -
and brake fluid is highly hygroscopic.

I guess I was wrong then.
sheesh

what does it feel like, Mike?

I was being fesesiou.... phesesu... feseeshus..... sarcastic.

I thought I was wrong once, but I was mistaken.
so THAT time you WERE wrong - admit it. You actually thought you were
wrong when you weren't.

On Thu, 14 Oct 2010 22:14:49 -0400, "Mike Marlow"
wrote:

wrote:


First of all, it's just too big and heavy to fit.

Why so? A caliper does not have to be large.

One from a lincoln is!!!

Second it's using an
atom bomb to swat a fly. Third, it's too complex. Exactly haw are you
going to actuate it?????

Too complex? On the contrary, it's very simple.

Forth, how are you going to get it out of the way to change blades?

Well, one idea would be to mount it on the inside of the arbor so that it
does not even have to be removed to replace a blade.

That's one solution I said COULD work, isn't it?

Fifth - How are you going to compensate for different blade
thicknesses - or heaven help you, a DADO blade?

See above answer.

Also, single piston or dual piston?

You are going out of your way to make this appear to be complicated now.

and how are you going to ensure
the pressure on both sides of the blade is equal, and application is
even..

Both sides? Why both sides? For the discussion at hand, one side would be
ample.

Push on one side of the blade more than the other and the blade
goes into an oscillation/wobble and you eventually break the web out
of the blade. Then you have a REAL safety issue!!!!!.

Sure - it you push it hard enough. No need for that level of pressure
though. Think about what forces your blade sees as you cut through a
knarley hunk of hardwood. It sees more lateral force than would be required
for a simple blade brake - which is the discussion at hand.


Trust me - it's a BAD idea - and almost totally unworkable on so MANY
levels if you understand anything about how both the saw and the break
caliper work.

Sorry Clare - cannot trust you on this point. I see it as perfectly
workable and not subject to any of the concerns you've outlined. I do
understand both how the saw works and how calipers work but you have not
argued anything to make the idea impractical.


It all depends on how fast you are stopping the blade, how big a pad
you are using, what pressure you are using, etc.

I never said you could not desin a caliper type stopping device as a
convenience brake.

I DID say there is NO WAY to effectivel use an automotive caliper
(lincoln) to do the job, and I DID say dynamic braking of one type or
other would be simpler, more effective, and more reliable.

DONE

On 10/15/2010 10:52 AM, -MIKE- wrote:
On 10/15/10 8:32 AM, J. Clarke wrote:
But if I have to push a button to stop the blade I may as well just
shove a pushstick into the side of it.

Exactly, unless it's incorporated into the off switch.

If you do use a push stick, don't use oak.
It's VERY CORROSIVE and will disintegrate your saw blade.

LOL!

--
Free bad advice available here.
To reply, eat the taco.
http://www.flickr.com/photos/bbqboyee/

Lew Hodgett wrote:
Subjest

Time for a reality check.

Take your choice, dynamic or regenerative braking will never cut it as
a safety braking system.

Toss in disk brakes if that will make you happy.

All are much too slow to respond quickly enough to compete as a safety
device against SawStop.

That has never been the intent of this discussion. So - you are correct,
but it's not relevant.



--

-Mike-

Josepi wrote:

Disc brake were around for a lot longer than the ABS systems were ever
implemented.
Disc brakes were not sdesigned to "lock up" but rather be more linear
than shoe brake systems, and fade less.


You are correct that disk brakes have been around a lot longer than ABS has,
but if you believe that disk brakes will not lock up then you simply need to
drive a car that pre-dates ABS. Disk brakes will most certainly lock up.
Why do you think ABS exists?

--

-Mike-

Josepi wrote:
Should have read. (I didn't write the attributed text)

"Mike Marlow" wrote in message
...
ABS is designed to prevent lock up - car brakes are not.


Not sure what you are trying to point out. I did a simple reply all. The
problems come in when people like yourself insist on replying in a manner
that defies normal attributions. Really do not understand what your
statement "Should have read" means.

--

-Mike-

wrote:
On Thu, 14 Oct 2010 22:06:25 -0400, "Mike Marlow"
wrote:

Scott Lurndal wrote:


On the other hand, disc brakes are designed so they don't lock up,
this includes the materials used as well plus the modern ABS
electronics.


No they aren't. ABS systems are designed to prevent the wheel from
locking up, but disk brakes aren't. In fact, quite the opposite,
they are designed to lock up but rely upon the ABS to govern them so
they don't.
Not true. Drum brakes are much more powerfull on the first
application, and more likely to lock up due to their self-energizing
servo action (virtually every drum brake on a vehicle in the last 40
years) The only advantage of disks is faster cooling and less fade.

You are incorrect sir. What I stated is very correct. Disk brakes are not
designed so that they will not lock up. In fact - they will lock up.
Pointing out any difference in the lock up characteristic between disk and
rotor does nothing to argue that point. All that says is that there is a
difference, not that disks will not lock up. Anyone who says that disk
brakes will not lock up has no familiarity with disk brakes. I agree with
your statement that the advantage to disks is that they fade less due to
better cooling, but that very statement in itself, a contradiction to your
very assertion.

--

-Mike-

wrote:
On Thu, 14 Oct 2010 22:18:51 -0400, "Mike Marlow"
wrote:

wrote:


Never see the black staining in oak from non-galvanized nails? That
is due to corrosion. Doesn't take much corrosion to make a caliper
just fussy enough that it might not do the required job (for which
it was not designed).


I thought you worked on cars Clare. Have you ever seen a caliper
that was *not corroded*? You're exagerating things in attempt to
bolster your point but again, it's just not true.
The outer frame of the caliper can be corroded all to heck - no
problem. If the slider mechanism is corroded (which it often is)
braking is less linear, and less predictable. They can (and do) drag.
They can also apply late.

If the piston gets corroded, all the same, but a lot worse.

You are thinking of car brakes and not of calipers in general. That said -
every piece of metal on a car caliper assembly corrodes, yet they continue
to work until the corrosion on the slide becomes excessive. Not something a
table saw would likely see. I agree that with a corroded slider, braking is
less linear, but again, a table saw would not even require a slider, so the
direct comparison to a car caliper need not be made. Calipers exist outside
of the world of automobiles and calipers could make a perfectly acceptable
solution (one of many options) for a table saw. No one has suggested a car
caliper for a table saw, but instead has compared a comparatively hostile
environment where one type of caliper has proven itself.

--

-Mike-

wrote:
On Thu, 14 Oct 2010 22:14:49 -0400, "Mike Marlow"
wrote:

wrote:


First of all, it's just too big and heavy to fit.

Why so? A caliper does not have to be large.

One from a lincoln is!!!

But Clare - no one is seriously suggesting a Lincold caliper. That was
offered up tongue in cheek to provide an example of a solution. You really
do not believe that this discussion has been about using a Lincoln caliper,
do you?

Sorry Clare - cannot trust you on this point. I see it as perfectly
workable and not subject to any of the concerns you've outlined. I
do understand both how the saw works and how calipers work but you
have not argued anything to make the idea impractical.


It all depends on how fast you are stopping the blade, how big a pad
you are using, what pressure you are using, etc.

I never said you could not desin a caliper type stopping device as a
convenience brake.

I might be misunderstanding your position then. I have read what you wrote
to be an ardent position against the viability of a caliper as a solution
alternative. In my eyes, you seemed to have been rather adamant about that.
If I misunderstood, then I apologize.


I DID say there is NO WAY to effectivel use an automotive caliper
(lincoln) to do the job, and I DID say dynamic braking of one type or
other would be simpler, more effective, and more reliable.

I have agreed that there could be alternative and potentially better ways,
but I did not see your position as agruing against a Lincoln caliper as much
as arguing against calipers in general.


DONE

Don't tell me when I'm done damnit!...

--

-Mike-

Sorry you asre twisting words and playing with semantics.

Brake lock-up is not when the wheel stops turning. It is when the brakes
will not let go and cease to act linearly.

ABS was not created for brake lock-up. ABS would not help this problem.



"Mike Marlow" wrote in message
...
You are correct that disk brakes have been around a lot longer than ABS has,
but if you believe that disk brakes will not lock up then you simply need to
drive a car that pre-dates ABS. Disk brakes will most certainly lock up.
Why do you think ABS exists?


Josepi wrote:

Disc brake were around for a lot longer than the ABS systems were ever
implemented.
Disc brakes were not sdesigned to "lock up" but rather be more linear
than shoe brake systems, and fade less.



--

-Mike-

On Fri, 15 Oct 2010 12:54:44 -0400, "Mike Marlow"
wrote:

Josepi wrote:

Disc brake were around for a lot longer than the ABS systems were ever
implemented.
Disc brakes were not sdesigned to "lock up" but rather be more linear
than shoe brake systems, and fade less.


You are correct that disk brakes have been around a lot longer than ABS has,
but if you believe that disk brakes will not lock up then you simply need to
drive a car that pre-dates ABS. Disk brakes will most certainly lock up.
Why do you think ABS exists?
Because most drivers don't (according to our governments and highway
safety people) have the brains to release their brakes when the wheels
start to slide.

On Fri, 15 Oct 2010 13:13:27 -0400, "Mike Marlow"
wrote:

wrote:
On Thu, 14 Oct 2010 22:06:25 -0400, "Mike Marlow"
wrote:

Scott Lurndal wrote:


On the other hand, disc brakes are designed so they don't lock up,
this includes the materials used as well plus the modern ABS
electronics.


No they aren't. ABS systems are designed to prevent the wheel from
locking up, but disk brakes aren't. In fact, quite the opposite,
they are designed to lock up but rely upon the ABS to govern them so
they don't.
Not true. Drum brakes are much more powerfull on the first
application, and more likely to lock up due to their self-energizing
servo action (virtually every drum brake on a vehicle in the last 40
years) The only advantage of disks is faster cooling and less fade.

You are incorrect sir. What I stated is very correct. Disk brakes are not
designed so that they will not lock up. In fact - they will lock up.
Pointing out any difference in the lock up characteristic between disk and
rotor does nothing to argue that point. All that says is that there is a
difference, not that disks will not lock up. Anyone who says that disk
brakes will not lock up has no familiarity with disk brakes. I agree with
your statement that the advantage to disks is that they fade less due to
better cooling, but that very statement in itself, a contradiction to your
very assertion.
Pardon? What are you dissagreeing with?? Did I say disk brakes won't
lock up? NO

And there is NO contadiction to my statement. On first application, a
drum brake will ALWAYS outperform a disk on first application. Many
times also on second application. Disk brakes only outstop drum brakes
when both are hot.
Disk brakes are not "designed to lock up" They are designed that you
CAN (in many, but not all cases) lock the wheels on clean dry pavement
with hard brake application. You CAN lock the brakes in poor traction
conditions, but the locking capability is only due to their stopping
power being excessive foe some conditions. They are, by design, LESS
likely to lock than a Bendix type self energizing drum brake.

On Fri, 15 Oct 2010 13:23:47 -0400, "Mike Marlow"
wrote:

wrote:
On Thu, 14 Oct 2010 22:18:51 -0400, "Mike Marlow"
wrote:

wrote:


Never see the black staining in oak from non-galvanized nails? That
is due to corrosion. Doesn't take much corrosion to make a caliper
just fussy enough that it might not do the required job (for which
it was not designed).


I thought you worked on cars Clare. Have you ever seen a caliper
that was *not corroded*? You're exagerating things in attempt to
bolster your point but again, it's just not true.
The outer frame of the caliper can be corroded all to heck - no
problem. If the slider mechanism is corroded (which it often is)
braking is less linear, and less predictable. They can (and do) drag.
They can also apply late.

If the piston gets corroded, all the same, but a lot worse.

You are thinking of car brakes and not of calipers in general. That said -
every piece of metal on a car caliper assembly corrodes, yet they continue
to work until the corrosion on the slide becomes excessive. Not something a
table saw would likely see. I agree that with a corroded slider, braking is
less linear, but again, a table saw would not even require a slider, so the
direct comparison to a car caliper need not be made. Calipers exist outside
of the world of automobiles and calipers could make a perfectly acceptable
solution (one of many options) for a table saw. No one has suggested a car
caliper for a table saw, but instead has compared a comparatively hostile
environment where one type of caliper has proven itself.
By definition a "caliper" squeeses - so by definition it requires
some sort of equalization between the forces from side to side of the
"rotor" which means either a slider or a dual piston type caliper.

And the "lincoln" caloper was the first suggestion of a caliper for
saw stopping in this thread.

On Fri, 15 Oct 2010 13:28:28 -0400, "Mike Marlow"
wrote:

wrote:
On Thu, 14 Oct 2010 22:14:49 -0400, "Mike Marlow"
wrote:

wrote:


First of all, it's just too big and heavy to fit.

Why so? A caliper does not have to be large.

One from a lincoln is!!!

But Clare - no one is seriously suggesting a Lincold caliper. That was
offered up tongue in cheek to provide an example of a solution. You really
do not believe that this discussion has been about using a Lincoln caliper,
do you?

Sorry Clare - cannot trust you on this point. I see it as perfectly
workable and not subject to any of the concerns you've outlined. I
do understand both how the saw works and how calipers work but you
have not argued anything to make the idea impractical.


It all depends on how fast you are stopping the blade, how big a pad
you are using, what pressure you are using, etc.

I never said you could not desin a caliper type stopping device as a
convenience brake.

I might be misunderstanding your position then. I have read what you wrote
to be an ardent position against the viability of a caliper as a solution
alternative. In my eyes, you seemed to have been rather adamant about that.
If I misunderstood, then I apologize.


I DID say there is NO WAY to effectivel use an automotive caliper
(lincoln) to do the job, and I DID say dynamic braking of one type or
other would be simpler, more effective, and more reliable.

I have agreed that there could be alternative and potentially better ways,
but I did not see your position as agruing against a Lincoln caliper as much
as arguing against calipers in general.


DONE

Don't tell me when I'm done damnit!...
OK - the whole premise of using a caliper, regardless of the source
of the caliper, for a retrofit to an existing saw has all the
drawbacks I have stated. OK, the corrosion might be a bit overstated -
but it IS an issue that would have to be dealt with -nas it has to be
dealt with in automotive, bicycle, and motorcycle applications. Using
a caliper of any sort on the blade, even on a purpose built clean
sheet saw design has engineering problems that would be best avoided
due to complexity (like blade changing, adjustment for dado use, etc.)
Putting the caliper (or drum) on the opposite end of the arbour
handles most of those issues, but again, on a clean sheet design. As a
retrofit it is still problematic. Putting the brake on the motor is
the simplest solution - wheather mechanical or electrical, and
wheather direct drive or belt drive.
Either way, electrical application is the simplest, cheapest
alternative (compared to hydraulic, mechanical, pneumatic, or
percussive application) - and if you are going to use electical or
electronic controls anyway, why not use electrical braking all the
way?

That's my point. Nobody else, so far, has addressed how they would
control the application of this "convenience brake", however
implemented. My pushbutton solution was rejected out of hand - but how
would any of the other suggested possibilities be implemented???

It is the only virtually universally implementable retrofit or add-on
solution that does not require custom engineering for every saw it
might possibly be applicable to.

A lot of dreamers on the wreck - but how many implementers?

Also, if electrical convenience braking is such a bad idea, why is it
virtually the ONLY method used on commercially available table saws,
particularly in the "consumer grade", "contractor", or "semi-pro"
lines?

Virtually every hand held circular saw on the market today has a
"dynamic blade brake" as a standard feature as well.
So does virtually every quality cut-off or miter saw.

Best of all, it COULD be made as a simple plug-in module that you plug
the saw into - replacing the existing power switch, on all but the
higher end saws that use contactors instead of a simple switch.

It could be made offshore, in reasonable quantities, to sell for less
than $50 retail.
It could be implemented, from scratch, by a reasonably competent
tinkerer for under $100 buying all the parts new from local or online
sources, and could be installed on ANY saw. Either as a plug in as
above, or wired directly into the saw. Contacter controlled mabee add
another $50.

Again - we are talking convenience brake - not emergency stop

On Oct 15, 1:31*pm, "Josepi" wrote:
Sorry you asre twisting words and playing with semantics.

Brake lock-up is not when the wheel stops turning. It is when the brakes
will not let go and cease to act linearly.

ABS was not created for brake lock-up. ABS would not help this problem.


You are completely and totally wrong and incorrect.

ABS, by definition, stands for Anti-lock Braking System. Now apply
this little bit of knowledge to your position, and you will see that
you are wrong, incorrect and mistaken.
Brake lock-up is lock-up caused by a brake, NOT a brake locking up.
ABS does not stand for Anti Brake Locking Up System.
With me yet?

Also, when you find yourself in a hole, stop digging.

On 10/15/10 12:31 PM, Josepi wrote:
Sorry you asre twisting words and playing with semantics.


You mean, like this,

"The name "anti-lock" is a misnomer as the brakes successively lock and
release each pulse."


--

-MIKE-

"Playing is not something I do at night, it's my function in life"
--Elvin Jones (1927-2004)
--
http://mikedrums.com

---remove "DOT" ^^^^ to reply