Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work.

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Default [VIDEO] I had an interesting fail -- steel cabinet collapsedand fell

On 2017-05-19, Jon Elson wrote:
Ignoramus13612 wrote:

This cabinet had been in my shop for something like four years and its
load did not change much. It sat by the door. Then one day it suddenly
collapsed, totally unprovoked, probably due to high winds.

https://youtu.be/UGNT6i8AIGk

Kind of amazing, **** happens when you expect it the least.

i

Well, that is a little unusual, as it had a steel back, not the typical 4
verticals with just a couple cross braces. I've had a few of those either
fail completely, or start to show signs of twisting, and I readjusted the
cross braces to resist the twist. Your cabinet clearly twisted also as the
first part of the collapse.


Yes, i saw how it twisted a second before failing.

I would never have thought that it could be possible.

i

Well, sorry for the mess all over the floor.

Jon

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Default [VIDEO] I had an interesting fail -- steel cabinet collapsed and fell

On May 19, 2017, Ignoramus17154 wrote
(in ):

On 2017-05-19, Jon wrote:
Ignoramus13612 wrote:

This cabinet had been in my shop for something like four years and its
load did not change much. It sat by the door. Then one day it suddenly
collapsed, totally unprovoked, probably due to high winds.

https://youtu.be/UGNT6i8AIGk

Kind of amazing, **** happens when you expect it the least.

i

Well, that is a little unusual, as it had a steel back, not the typical 4
verticals with just a couple cross braces. I've had a few of those either
fail completely, or start to show signs of twisting, and I readjusted the
cross braces to resist the twist. Your cabinet clearly twisted also as the
first part of the collapse.


Yes, i saw how it twisted a second before failing.

I would never have thought that it could be possible.

Id bet on a busted spot weld or a missing fastener or two. With a
rectangular back panel, all four corners must have bolts, or a twist is
likely.

Joe

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Default [VIDEO] I had an interesting fail -- steel cabinet collapsed and fell

Ignoramus17154 wrote:

On 2017-05-19, Jon Elson wrote:
Ignoramus13612 wrote:

This cabinet had been in my shop for something like four years and its
load did not change much. It sat by the door. Then one day it suddenly
collapsed, totally unprovoked, probably due to high winds.

https://youtu.be/UGNT6i8AIGk

Kind of amazing, **** happens when you expect it the least.

i

Well, that is a little unusual, as it had a steel back, not the typical 4
verticals with just a couple cross braces. I've had a few of those
either fail completely, or start to show signs of twisting, and I
readjusted the
cross braces to resist the twist. Your cabinet clearly twisted also as
the first part of the collapse.


Yes, i saw how it twisted a second before failing.

I would never have thought that it could be possible.

These things are actually QUITE flimsy, without the cross braces. Also,
there is some method to doing the cross bracing properly. I do not actually
know the correct scheme. but, you want to avoid the cross braces being put
in compression, as they will buckle. I do occasionally tighten the screws
on these things, as they seem to work loose over time. If the bracing
screws get loose, it will collapse if heavily loaded. The screws for the
shelves also need to be kept tight, as they also help resist the verticals
from slanting.

Jon
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Default [VIDEO] I had an interesting fail -- steel cabinet collapsedand fell

On 2017-05-19, Joseph Gwinn wrote:
On May 19, 2017, Ignoramus17154 wrote
(in ):

On 2017-05-19, Jon wrote:
Ignoramus13612 wrote:

This cabinet had been in my shop for something like four years and its
load did not change much. It sat by the door. Then one day it suddenly
collapsed, totally unprovoked, probably due to high winds.

https://youtu.be/UGNT6i8AIGk

Kind of amazing, **** happens when you expect it the least.

i
Well, that is a little unusual, as it had a steel back, not the typical 4
verticals with just a couple cross braces. I've had a few of those either
fail completely, or start to show signs of twisting, and I readjusted the
cross braces to resist the twist. Your cabinet clearly twisted also as the
first part of the collapse.


Yes, i saw how it twisted a second before failing.

I would never have thought that it could be possible.

I???d bet on a busted spot weld or a missing fastener or two. With a
rectangular back panel, all four corners must have bolts, or a twist is
likely.

Joe


I still have the cabinet laying in my yard. I will take a look.

i
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Default [VIDEO] I had an interesting fail -- steel cabinet collapsedand fell

On 2017-05-20, Jon Elson wrote:
Ignoramus17154 wrote:

On 2017-05-19, Jon Elson wrote:
Ignoramus13612 wrote:

This cabinet had been in my shop for something like four years and its
load did not change much. It sat by the door. Then one day it suddenly
collapsed, totally unprovoked, probably due to high winds.

https://youtu.be/UGNT6i8AIGk

Kind of amazing, **** happens when you expect it the least.

i
Well, that is a little unusual, as it had a steel back, not the typical 4
verticals with just a couple cross braces. I've had a few of those
either fail completely, or start to show signs of twisting, and I
readjusted the
cross braces to resist the twist. Your cabinet clearly twisted also as
the first part of the collapse.


Yes, i saw how it twisted a second before failing.

I would never have thought that it could be possible.

These things are actually QUITE flimsy, without the cross braces. Also,
there is some method to doing the cross bracing properly. I do not actually
know the correct scheme. but, you want to avoid the cross braces being put
in compression, as they will buckle. I do occasionally tighten the screws
on these things, as they seem to work loose over time. If the bracing
screws get loose, it will collapse if heavily loaded. The screws for the
shelves also need to be kept tight, as they also help resist the verticals
from slanting.

Jon


Much to learn on a seemingly simple subject!

By The Way your cnc boards are still working for me.


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Default [VIDEO] I had an interesting fail -- steel cabinet collapsed and fell

Ignoramus31415 wrote:


Much to learn on a seemingly simple subject!

Yeah, nothing that seems simple is actually simple! And, stuff that you
just expect to sit there and do their job, sometimes doesn't. Still don;t
know how the screws on these cabinets actually get loose over time, but when
I go around tightening them, a bunch are in fact a bit loose.
By The Way your cnc boards are still working for me.

Great. Glad it is working for you. A guy just returned a big order. I
guess when he found out how many wires were involved, he chickened out.
He has a 3-axis Fanuc-controlled mill with brushless motors and a tool
changer. No WAY he is going to find a bolt-on solution that just plugs in
and has the machine up and running over a weekend, which I guess is what he
was hoping for.

Jon
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Default [VIDEO] I had an interesting fail -- steel cabinet collapsedand fell

On 2017-05-20, Jon Elson wrote:
Ignoramus31415 wrote:


Much to learn on a seemingly simple subject!

Yeah, nothing that seems simple is actually simple! And, stuff that you
just expect to sit there and do their job, sometimes doesn't. Still don;t
know how the screws on these cabinets actually get loose over time, but when
I go around tightening them, a bunch are in fact a bit loose.
By The Way your cnc boards are still working for me.

Great. Glad it is working for you. A guy just returned a big order. I
guess when he found out how many wires were involved, he chickened out.
He has a 3-axis Fanuc-controlled mill with brushless motors and a tool
changer. No WAY he is going to find a bolt-on solution that just plugs in
and has the machine up and running over a weekend, which I guess is what he
was hoping for.

Jon


My mill had DC motors and everything worked really nicely.

All three axes work.

Except for one thing. For 4th axis, I have a rotary table made by
Troyke with a resolver (not encoder). I bought from you a "resolver to
encoder signal converter".

This worked initially, HOWEVER after a while some errors started
creeping in and sometimes I would get completely erroneous results,
for A axis jumping randomly by thousands of degrees or some such
macroscopic number of degrees.

I disabled 4th axis for now but I want to fix it. Maybe I should fit
an encoder in place of that resolver or figure out why this converter
is not working.

Overall I am happy but 4th axis would be a great plus for me.

i
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Default [VIDEO] I had an interesting fail -- steel cabinet collapsed and fell

On 2017-05-20, Ignoramus31415 wrote:
On 2017-05-20, Jon Elson wrote:
Ignoramus31415 wrote:


My mill had DC motors and everything worked really nicely.

All three axes work.

Except for one thing. For 4th axis, I have a rotary table made by
Troyke with a resolver (not encoder). I bought from you a "resolver to
encoder signal converter".


Hmm ... I've only seen resolvers in aircraft instruments. Those
require 400 Hz power (26V IIRC). Is what you have also 400 Hz, or do
they make 60 Hz resolvers, too?

If they are 400 Hz, could some subsystem which is supposed to
generate the 400 Hz failing?

Good Luck,
DoN.

--
Remove oil spill source from e-mail
Email: | (KV4PH) 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 ---
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Default [VIDEO] I had an interesting fail -- steel cabinet collapsed andfell

On 5/20/2017 6:25 PM, DoN. Nichols wrote:
On 2017-05-20, Ignoramus31415 wrote:
On 2017-05-20, Jon Elson wrote:
Ignoramus31415 wrote:


My mill had DC motors and everything worked really nicely.

All three axes work.

Except for one thing. For 4th axis, I have a rotary table made by
Troyke with a resolver (not encoder). I bought from you a "resolver to
encoder signal converter".


Hmm ... I've only seen resolvers in aircraft instruments. Those
require 400 Hz power (26V IIRC). Is what you have also 400 Hz, or do
they make 60 Hz resolvers, too?

If they are 400 Hz, could some subsystem which is supposed to
generate the 400 Hz failing?

Good Luck,
DoN.

I want to say if you have a slave pair - one is a encoder and the other
a resolver. in other words - transmit and receiver.

One on a knob that is rotary or on a rack - and the other on a surface
that is moving. Sometimes in reverse the surface 'tells' the pointer
where to point.

Martin
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Default [VIDEO] I had an interesting fail -- steel cabinet collapsed and fell

On 2017-05-21, Martin E wrote:
On 5/20/2017 6:25 PM, DoN. Nichols wrote:
On 2017-05-20, Ignoramus31415 wrote:
On 2017-05-20, Jon Elson wrote:
Ignoramus31415 wrote:


My mill had DC motors and everything worked really nicely.

All three axes work.

Except for one thing. For 4th axis, I have a rotary table made by
Troyke with a resolver (not encoder). I bought from you a "resolver to
encoder signal converter".


Hmm ... I've only seen resolvers in aircraft instruments. Those
require 400 Hz power (26V IIRC). Is what you have also 400 Hz, or do
they make 60 Hz resolvers, too?

If they are 400 Hz, could some subsystem which is supposed to
generate the 400 Hz failing?

Good Luck,
DoN.

I want to say if you have a slave pair - one is a encoder and the other
a resolver. in other words - transmit and receiver.

One on a knob that is rotary or on a rack - and the other on a surface
that is moving. Sometimes in reverse the surface 'tells' the pointer
where to point.


Hmm ... that sounds more like synchros (AKA "selsyn"). An ac
signal applied to the rotor, and three phases (Wye connection) of
output. Thus the synchros had five leads, two for the rotor, and three
for the Wye connection of the stator.

Apply power to both rotors, and one will move to track the
other. Instead, take the second rotor, connect it to the input of a
servo amplifier, and the servo will rotate the one to which it is
connected until at 90 degrees, at which there is zero output, and a
slight motion will provide signal either at 0 degrees phase or at 180
degrees phase, causing the motor to rotate the servo until the output is
zero again. (This allows driving things which are heavier than the
synchro is capable of driving directly.)

A resolver, however, has one rotor signal with two stators at 90
degrees, and isolated from each other electrically. This produces
output signals on the two stators as a sine and a cosine of the rotor's
angle. (Some resolvers have two rotors at 90 degrees, so they can
process the output of a normal resolver with only one rotor winding, so
you can add two angles. (The resolvers which I am describing are quite
small, to fid in aircraft instruments.) I don't know whether there are
larger 60 Hz resolvers as there are larger 60 Hz synchros (the 60 Hz
ones were commonly used on shipboard, where the extra weight of the 60
Hz versions was not a significant penalty. They were the ones called
"Selsyn"s. And while all 400 Hz synchros which I have seen are all
pretty much the same, the receivers on the 60 Hz ones had an inertial
damper on the shaft, while the transmitters did not)

The resolvers have either six leads (two for the rotor, four for
the two independent windings) or eight leads (two for each winding in
the rotor, and two for each winding in the stator.

So -- I would really expect the Troyke rotating table to have a
synchro and a servo amp, but it could be a resolver, and some way to
connect that to a servo motor and amplifier.

Enjoy,
DoN.

--
Remove oil spill source from e-mail
Email: | (KV4PH) 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 ---


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Default [VIDEO] I had an interesting fail -- steel cabinet collapsed and fell

On Fri, 19 May 2017 19:40:12 -0400, Joseph Gwinn
wrote:

On May 19, 2017, Ignoramus17154 wrote
(in ):

On 2017-05-19, Jon wrote:
Ignoramus13612 wrote:

This cabinet had been in my shop for something like four years and its
load did not change much. It sat by the door. Then one day it suddenly
collapsed, totally unprovoked, probably due to high winds.

https://youtu.be/UGNT6i8AIGk

Kind of amazing, **** happens when you expect it the least.

i
Well, that is a little unusual, as it had a steel back, not the typical 4
verticals with just a couple cross braces. I've had a few of those either
fail completely, or start to show signs of twisting, and I readjusted the
cross braces to resist the twist. Your cabinet clearly twisted also as the
first part of the collapse.


Yes, i saw how it twisted a second before failing.

I would never have thought that it could be possible.

I’d bet on a busted spot weld or a missing fastener or two. With a
rectangular back panel, all four corners must have bolts, or a twist is
likely.


I have always fastened (at the top) tall bookcases to the wall. I
guess cabinets should be fastened as well. They tend to be overloaded
by default.

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In today’s academia and mainstream media,
we’re all guilty of hate until proven leftist.

--Robert Knight, senior fellow, American Civil Rights Union
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Default [VIDEO] I had an interesting fail -- steel cabinet collapsed andfell

On 5/20/2017 9:50 PM, DoN. Nichols wrote:
On 2017-05-21, Martin E wrote:
On 5/20/2017 6:25 PM, DoN. Nichols wrote:
On 2017-05-20, Ignoramus31415 wrote:
On 2017-05-20, Jon Elson wrote:
Ignoramus31415 wrote:

My mill had DC motors and everything worked really nicely.

All three axes work.

Except for one thing. For 4th axis, I have a rotary table made by
Troyke with a resolver (not encoder). I bought from you a "resolver to
encoder signal converter".

Hmm ... I've only seen resolvers in aircraft instruments. Those
require 400 Hz power (26V IIRC). Is what you have also 400 Hz, or do
they make 60 Hz resolvers, too?

If they are 400 Hz, could some subsystem which is supposed to
generate the 400 Hz failing?

Good Luck,
DoN.

I want to say if you have a slave pair - one is a encoder and the other
a resolver. in other words - transmit and receiver.

One on a knob that is rotary or on a rack - and the other on a surface
that is moving. Sometimes in reverse the surface 'tells' the pointer
where to point.


Hmm ... that sounds more like synchros (AKA "selsyn"). An ac
signal applied to the rotor, and three phases (Wye connection) of
output. Thus the synchros had five leads, two for the rotor, and three
for the Wye connection of the stator.

Apply power to both rotors, and one will move to track the
other. Instead, take the second rotor, connect it to the input of a
servo amplifier, and the servo will rotate the one to which it is
connected until at 90 degrees, at which there is zero output, and a
slight motion will provide signal either at 0 degrees phase or at 180
degrees phase, causing the motor to rotate the servo until the output is
zero again. (This allows driving things which are heavier than the
synchro is capable of driving directly.)

A resolver, however, has one rotor signal with two stators at 90
degrees, and isolated from each other electrically. This produces
output signals on the two stators as a sine and a cosine of the rotor's
angle. (Some resolvers have two rotors at 90 degrees, so they can
process the output of a normal resolver with only one rotor winding, so
you can add two angles. (The resolvers which I am describing are quite
small, to fid in aircraft instruments.) I don't know whether there are
larger 60 Hz resolvers as there are larger 60 Hz synchros (the 60 Hz
ones were commonly used on shipboard, where the extra weight of the 60
Hz versions was not a significant penalty. They were the ones called
"Selsyn"s. And while all 400 Hz synchros which I have seen are all
pretty much the same, the receivers on the 60 Hz ones had an inertial
damper on the shaft, while the transmitters did not)

The resolvers have either six leads (two for the rotor, four for
the two independent windings) or eight leads (two for each winding in
the rotor, and two for each winding in the stator.

So -- I would really expect the Troyke rotating table to have a
synchro and a servo amp, but it could be a resolver, and some way to
connect that to a servo motor and amplifier.

Enjoy,
DoN.

That was good Don.
The 60 cycles/per/second - they were of that age - off B-36 or B-52
frames. The Bronze bodies are like 5 pound coffee cans. Heavy. I have
to drag them out and check the wires...

Air force used many of them in various Analog systems...

Martin
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