I've got a machine that must keep constant tension on a stretchy roving.

I've got a slip-clutch on the takeup spool right now, but when it slips
(sliding friction being less that starting friction) it "unwinds" some of
the tension in the roving before it stops slipping... so it doesn't keep
the material in the right state for one of the intermediate operations.

Are there any over-torque protection clutches that maintain a constant
torque from their break-free settings? I'd really rather see this thing
slipping constantly than starting and stopping.

LLoyd

"Lloyd E. Sponenburgh" lloydspinsidemindspring.com fired this volley in
. 3.70:

I've got a machine that must keep constant tension on a stretchy roving.



I should have added (my current byline these days) that so far, this is a
completely mechanical machine. I could do this with a servo motor takeup
and a tension arm, like an old computer tape deck, but I'd like to not
modify it that much. The existing clutch is co-axial on the takeup spool
shaft.

LLoyd

"Lloyd E. Sponenburgh" wrote:

"Lloyd E. Sponenburgh" lloydspinsidemindspring.com fired this volley in
. 3.70:

I've got a machine that must keep constant tension on a stretchy roving.



I should have added (my current byline these days) that so far, this is a
completely mechanical machine. I could do this with a servo motor takeup
and a tension arm, like an old computer tape deck, but I'd like to not
modify it that much. The existing clutch is co-axial on the takeup spool
shaft.

LLoyd

Tension arm and band brake?

On Tue, 15 Jun 2010 15:29:27 -0500, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:

"Lloyd E. Sponenburgh" lloydspinsidemindspring.com fired this volley in
.3.70:

I've got a machine that must keep constant tension on a stretchy roving.



I should have added (my current byline these days) that so far, this is a
completely mechanical machine. I could do this with a servo motor takeup
and a tension arm, like an old computer tape deck, but I'd like to not
modify it that much. The existing clutch is co-axial on the takeup spool
shaft.


I've used several of these in unwinds myself and seen a bunch more in
use for the same purpose.
http://www.polyclutch.com/polyclutch...slip-clutches/

--
Ned Simmons

Lloyd E. Sponenburgh wrote:
I've got a machine that must keep constant tension on a stretchy roving.

I've got a slip-clutch on the takeup spool right now, but when it slips
(sliding friction being less that starting friction) it "unwinds" some of
the tension in the roving before it stops slipping... so it doesn't keep
the material in the right state for one of the intermediate operations.

Are there any over-torque protection clutches that maintain a constant
torque from their break-free settings? I'd really rather see this thing
slipping constantly than starting and stopping.

LLoyd

Fishing reel drag mechanism?



--
Steve Walker
(remove wallet to reply)

Can your current clutch be run with continuous slip? I.e., can it
dissipate the heat? If so, can you run your take up motor faster?

BTW - constant torque does not equal constant tension on the roving.
(Cause the diameter increases as the roving is taken up.) A dancer arm
would give you constant tension.

Bob

Bob Engelhardt fired this volley in
:

BTW - constant torque does not equal constant tension on the roving.
(Cause the diameter increases as the roving is taken up.) A dancer arm
would give you constant tension.


correct, and the way it's set up, it's a "constant"(not so) torque takeup.
I'd like to make it constant-tension, but still can't find a mechanical
detail on a "dancer arm". I know how to do it electronically, but it would
be nice to fit it in the same layout. If the "dancer" could alter the
torque of the clutch, that would (I think) accomplish my goal.

LLoyd

On Tue, 15 Jun 2010 15:27:33 -0500, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:

I've got a machine that must keep constant tension on a stretchy roving.

I've got a slip-clutch on the takeup spool right now, but when it slips
(sliding friction being less that starting friction) it "unwinds" some of
the tension in the roving before it stops slipping... so it doesn't keep
the material in the right state for one of the intermediate operations.

Are there any over-torque protection clutches that maintain a constant
torque from their break-free settings? I'd really rather see this thing
slipping constantly than starting and stopping.

LLoyd


Something like this?

https://sdp-si.com/estore/..%5Css%5CPDF%5C78013006.PDF

Pricing seems reasonable.

On Jun 15, 1:29*pm, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:
"Lloyd E. Sponenburgh" lloydspinsidemindspring.com fired this volley 8.3.70:

I've got a machine that must keep constant tension on a stretchy roving..

I should have added (my current byline these days) that so far, this is a
completely mechanical machine. *I could do this with a servo motor takeup
and a tension arm, like an old computer tape deck, but I'd like to not
modify it that much. *The existing clutch is co-axial on the takeup spool
shaft.

LLoyd

Just got back from a little vacation on the Northern California coast.
No internet access.

Have you given any thought to a clutch such as used for newer
automobile fans? I know the one on our old MB 300SD turns pretty hard
when moved by hand, but seems to be the same resistance no matter how
quickly I move it by hand.

Paul

A dancer arm won't help here. It only makes up for momentary,
short-lived changes in the system.

Pete Stanaitis
-------------------

Lloyd E. Sponenburgh wrote:

Bob Engelhardt fired this volley in
:


BTW - constant torque does not equal constant tension on the roving.
(Cause the diameter increases as the roving is taken up.) A dancer arm
would give you constant tension.



correct, and the way it's set up, it's a "constant"(not so) torque takeup.
I'd like to make it constant-tension, but still can't find a mechanical
detail on a "dancer arm". I know how to do it electronically, but it would
be nice to fit it in the same layout. If the "dancer" could alter the
torque of the clutch, that would (I think) accomplish my goal.

LLoyd

spaco wrote:
A dancer arm won't help here. It only makes up for momentary,
short-lived changes in the system.

Yeah, I didn't put much thought in my response G.

What would work is what I think Lloyd meant by a tension arm. That is,
an arm riding on the roving, with a spring tension on it (the arm). The
angular position of the arm is measured by a pot which is the feedback
to a servo amp which is controlling a dc motor. That motor turns the
spool. The pot is basically the tach feedback for speed control.

'Course a new system is what Lloyd wanted to avoid & there have been
several links to devices that should do what he wants, I think. But ...
if he really wants constant _tension_, this would be easy. A big
question, though, is how big the takeup motor is.

Bob

Spehro Pefhany fired this volley in
:

https://sdp-si.com/estore/..%5Css%5CPDF%5C78013006.PDF

That's a great concept, and I almost fell for it... but the device in the
torque rating I need would weigh 94 lb! g

LLoyd

Bob Engelhardt fired this volley in
:

A big
question, though, is how big the takeup motor is.

It wouldn't have to be very large. The spool runs at about 3 rpm.

I'm getting close to trashing the mechanical idea and reverting to simple
servo technology.

LLoyd

On Tue, 15 Jun 2010 17:31:06 -0500, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:

Spehro Pefhany fired this volley in
:

https://sdp-si.com/estore/..%5Css%5CPDF%5C78013006.PDF

That's a great concept, and I almost fell for it... but the device in the
torque rating I need would weigh 94 lb! g

LLoyd

A powered one would probably weigh less. I used one once, analog 24V
signal, relatively high current in. I'd done the dancer arm-pot
thing, but this had to account for lumps, sticky stuff, etc. I ran
the web over a roller mounted on load cells which gave tension
directly. I think I used a 120 deg. contact. Worked a treat. When a
lump of gels hit the takeup, the lessening in tension would be
detected and the slip clutch would tighten up until it passed the
lump.

Pete Keillor

Pete Keillor fired this volley in
news
A powered one would probably weigh less.

That was the powered version.
250W at 100RPM, so obviously less at my 3-or-so.

LLoyd

"Lloyd E. Sponenburgh" wrote:

Bob Engelhardt fired this volley in
:

A big
question, though, is how big the takeup motor is.

It wouldn't have to be very large. The spool runs at about 3 rpm.

I'm getting close to trashing the mechanical idea and reverting to simple
servo technology.

LLoyd

The tension arm connected to band brake is a mechanical servo, applying
more braking to the spool as the tension drops.

On Tue, 15 Jun 2010 19:52:18 -0500, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:

Pete Keillor fired this volley in
news
A powered one would probably weigh less.

That was the powered version.
250W at 100RPM, so obviously less at my 3-or-so.

LLoyd

Wow. I went back and looked at the one I used 20 yrs ago or so, it
was a Magpowr C-100, about 154 lb. That was a relatively small part
of the weight of the whole rig. Mine ran pretty slow, 2000 rpm max DC
motor through ~3400:1 double reduction. So yeah, I didn't need water
cooling.

Pete

"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote in message
. 3.70...
I've got a machine that must keep constant tension on a stretchy roving.

I've got a slip-clutch on the takeup spool right now, but when it slips
(sliding friction being less that starting friction) it "unwinds" some of
the tension in the roving before it stops slipping... so it doesn't keep
the material in the right state for one of the intermediate operations.

Are there any over-torque protection clutches that maintain a constant
torque from their break-free settings? I'd really rather see this thing
slipping constantly than starting and stopping.

LLoyd

Fluid couplings will allow a constant slip. Also known as a hydrulic clutch
sometimes.

Bob Engelhardt wrote:

spaco wrote:
A dancer arm won't help here. It only makes up for momentary,
short-lived changes in the system.

Yeah, I didn't put much thought in my response G.

What would work is what I think Lloyd meant by a tension arm. That is,
an arm riding on the roving, with a spring tension on it (the arm). The
angular position of the arm is measured by a pot which is the feedback
to a servo amp which is controlling a dc motor. That motor turns the
spool. The pot is basically the tach feedback for speed control.


The RCA film chain projectors I serviced had a small variac that was
driven by the tension arm. With proper adjustment, it kept a fairly
constant tension on the 16 mm film, through an entire reel. The variacs
were connected in line with the takeup and supply reel motors.


'Course a new system is what Lloyd wanted to avoid & there have been
several links to devices that should do what he wants, I think. But ...
if he really wants constant _tension_, this would be easy. A big
question, though, is how big the takeup motor is.

Bob


--
Anyone wanting to run for any political office in the US should have to
have a DD214, and a honorable discharge.

"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote in message
. 3.70...
I've got a machine that must keep constant tension on a stretchy roving.

I've got a slip-clutch on the takeup spool right now, but when it slips
(sliding friction being less that starting friction) it "unwinds" some of
the tension in the roving before it stops slipping... so it doesn't keep
the material in the right state for one of the intermediate operations.

Are there any over-torque protection clutches that maintain a constant
torque from their break-free settings? I'd really rather see this thing
slipping constantly than starting and stopping.

LLoyd

This isn't mechanical but it might help
http://www.sew-eurodrive.com/produkt...calculator.htm

Larry Jaques fired this volley in
:

Fluid couplings will allow a constant slip. Also known as a hydrulic
clutch sometimes.

...or a torque convertor, as in all automatic transmichigans.


Constant slip, yes; constant torque, no. The coupling efficiency
diminishes with speed.

I need something that maintains a constant or controllable torque at all
speeds from stall to 3 rpm.

LLoyd

In article . com,
"Pete C." wrote:

"Lloyd E. Sponenburgh" wrote:

Bob Engelhardt fired this volley in
:

A big
question, though, is how big the takeup motor is.

It wouldn't have to be very large. The spool runs at about 3 rpm.

I'm getting close to trashing the mechanical idea and reverting to simple
servo technology.

LLoyd

The tension arm connected to band brake is a mechanical servo, applying
more braking to the spool as the tension drops.

This is how most wire tensioners used in coil winders work.

Here are some US patent numbers: Gerest 3,707,269; Gerest 4,912,274; and Takeda
4,526,329.

Joe Gwinn

Joseph Gwinn fired this volley in news:joegwinn-
:

This is how most wire tensioners used in coil winders work.

yep. Thanks, Joe.

I have that series of patents.

The main problem here is that there is a substantial amount of stretch in
the roving I'm spooling, and it is in its fully elastic domain, so that
any hysteresis in the tensioning clutch will cause (first) excess
stretch, followed (second) by sudden recovery when the clutch slips.

The use of a magnetic hysteresis clutch obviates the mechanical problems,
since they are continuous-slip devices. But clutches in the 20 ft-lb
torque range cost thousands of dollars.

I'm going to employ a dumbed-down electro-mechanical servo system. A
tensioning arm that can swing a fairly long arc over a small tension
differential, limit switches to sense "spool on/spool off" limits, and a
slow gear motor that has torque in excess of that required to maintain
the limit tension.

Including the metal work to remove the existing clutch system and replace
it with this, the solution comes in at about 1/6 the price of a magnetic
hysteresis or magnetic particle slip clutch of that required torque.

LLoyd

--Ya know this sounds like a perfect opportunity to retask the film
feed apparatus from an old motion picture camera. They're a dime a dozen at
swap meets, too.

--
"Steamboat Ed" Haas : Didja see my stuff
Hacking the Trailing Edge! : at 2010 Maker Faire??
www.nmpproducts.com
---Decks a-wash in a sea of words---

On Jun 15, 4:27*pm, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:
I've got a machine that must keep constant tension on a stretchy roving.

I've got a slip-clutch on the takeup spool right now, but when it slips
(sliding friction being less that starting friction) it "unwinds" some of
the tension in the roving before it stops slipping... so it doesn't keep
the material in the right state for one of the intermediate operations.

Are there any over-torque protection clutches that maintain a constant
torque from their break-free settings? *I'd really rather see this thing
slipping constantly than starting and stopping.

LLoyd

Ideally, aren't there constant-torque AC motors that can be stalled
indefinitely?

So far your method is coming out a lot cheaper, I'm sure.

Dave

steamer fired this volley in
:

--Ya know this sounds like a perfect opportunity to retask the film
feed apparatus from an old motion picture camera. They're a dime a
dozen at swap meets, too.


A 20ft-lb camera? Wouldn't that -um...- BREAK the film?

G
LLoyd

Dave__67 fired this volley in news:ba0b6aec-e956-
:


Ideally, aren't there constant-torque AC motors that can be stalled
indefinitely?

yep... So called "impedance protected" motors. I've been looking for one
that would produce about 20ft-lb torque at around 5 rpm.

No luck so far. But I'm thinking I can run a split-phase induction gear
motor on reduced voltage and accomplish the same thing. Most split phase
motors don't really care if they're running, so long as you don't
overheat them. Reducing the input voltage would be one way to set the
stall torque and keep one from burning up.

But that still only gives me constant torque, and what I really want is
constant tension. so my dancer arm will need to control the motor
voltage.

LLoyd


LLoyd

On Fri, 18 Jun 2010 12:21:55 -0500, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:

Dave__67 fired this volley in news:ba0b6aec-e956-
:


Ideally, aren't there constant-torque AC motors that can be stalled
indefinitely?

yep... So called "impedance protected" motors. I've been looking for one
that would produce about 20ft-lb torque at around 5 rpm.


Bodine calls them "torque motors," but they suffer the same size
shortcoming as mag particle brakes. A 20 ft-lb torque motor would be
enormous. When I was a kid I had a pair of torque motors I scavenged
from a Univac 2 tape drive. They were about the size of a cast iron
1/3 HP induction motor and could be stalled by grabbing the shaft.

http://www.bodine-electric.com/Asp/P....asp?Context=7

--
Ned Simmons

Ned Simmons fired this volley in
:

. A 20 ft-lb torque motor would be
enormous. When I was a kid I had a pair of torque motors I scavenged
from a Univac 2 tape drive. They were about the size of a cast iron
1/3 HP induction motor and could be stalled by grabbing the shaft.


But Ned, keep in mind that those motors were designed to produce that
torque all the way up to several hundred RPMs.

Mine only needs 3+ RPM... so I multiply the motor torque with belting or
sprocket drives.

LLoyd

On Fri, 18 Jun 2010 12:21:55 -0500, Lloyd E. Sponenburgh wrote:
Dave__67 wrote:
Ideally, aren't there constant-torque AC motors that can be stalled
indefinitely?

yep... So called "impedance protected" motors. I've been looking for
one that would produce about 20ft-lb torque at around 5 rpm.

[snip re impedance protected vs split-phase induction gear motor]

But that still only gives me constant torque, and what I really want is
constant tension. so my dancer arm will need to control the motor
voltage.

Do you need the roving in constant tension when something is being
done to it, or does it need to be spooled up at constant tension?

In the former case, it seems like you could have two drums set up
with constant-torque motors or clutches. The roving would be
stretched at constant tension between these fixed-diameter drums,
wouldn't it? Might need idler rollers to pressed the roving against
them.

--
jiw

On Jun 18, 12:21*pm, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:
Dave__67 fired this volley in news:ba0b6aec-e956-
:



Ideally, aren't there constant-torque AC motors that can be stalled
indefinitely?

yep... So called "impedance protected" motors. *I've been looking for one
that would produce about 20ft-lb torque at around 5 rpm.

No luck so far. *But I'm thinking I can run a split-phase induction gear
motor on reduced voltage and accomplish the same thing. *Most split phase
motors don't really care if they're running, so long as you don't
overheat them. *Reducing the input voltage would be one way to set the
stall torque and keep one from burning up.

But that still only gives me constant torque, and what I really want is
constant tension. *so my dancer arm will need to control the motor
voltage.

LLoyd

LLoyd

A DC motor has torque proportional to the Current. The dancer arm
could control the Current command to the motor, but with a fair amount
of low pass Filtering so that it does not hunt.
A DC motor and drive may well be cheaper, simpler and easier than
mechanical brakes etc.

The split phase motor may not enjoy the constant stalled condition.
The DC motor shouldn't care.

James Waldby fired this volley in news:hvgkkd$2oh$1
@news.eternal-september.org:


Do you need the roving in constant tension when something is being
done to it, or does it need to be spooled up at constant tension?

In the former case, it seems like you could have two drums set up
with constant-torque motors or clutches. The roving would be
stretched at constant tension between these fixed-diameter drums,
wouldn't it? Might need idler rollers to pressed the roving against
them.


yep, that's one very proper way to do it, and if the real estate inside
the (existing) machine would permit, I'd add a shaft with a "windlass
drum" running at constant torque. No room, though.

LLoyd

Cross-Slide fired this volley in news:a806363e-
:

The split phase motor may not enjoy the constant stalled condition.
The DC motor shouldn't care.

Primarily, it would not enjoy it because they're (gear motors) usually
fan cooled, and the fan wouldn't be running during stall.

But I forgot something important, anyway. Split phase motors don't mind
being stalled OR operating at reduced voltages, but they don't develop
much starting torque below a certain saturation voltage. Only a "bang-
bang" control would work with a typical split-phase type motor.

A DC motor would be perfect -- don't have one that fits my gear reducer,
but I can get one. A 3-phase motor would be OK too, with the dancer
driving the frequency pot of a VFC.

LLoyd

What's that Lassie? You say that Lloyd E. Sponenburgh fell down the
old rec.crafts.metalworking mine and will die if we don't mount a
rescue by Fri, 18 Jun 2010 12:21:55 -0500:

Dave__67 fired this volley in news:ba0b6aec-e956-
:


Ideally, aren't there constant-torque AC motors that can be stalled
indefinitely?

yep... So called "impedance protected" motors. I've been looking for one
that would produce about 20ft-lb torque at around 5 rpm.


Could you find one that would produce 10ft-lb at 10 rpm, and gear it
down

Or one at 5ft.-lb at 20rpm?
Or one at 2.5ft-lb at 40rpm?
Etc.


--

Dan H.
northshore MA.

(dan) fired this volley in news:4c1eede3.3077001
@news20.forteinc.com:

Could you find one that would produce 10ft-lb at 10 rpm, and gear it
down


Yep... probably. Already dealt with multiplying the torque via belting or
chain drive in another post.

LLoyd

In article ,
"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote:

Joseph Gwinn fired this volley in news:joegwinn-
:

This is how most wire tensioners used in coil winders work.

yep. Thanks, Joe.

I have that series of patents.

OK. What other tensioner patent numbers do you have?


The main problem here is that there is a substantial amount of stretch in
the roving I'm spooling, and it is in its fully elastic domain, so that
any hysteresis in the tensioning clutch will cause (first) excess
stretch, followed (second) by sudden recovery when the clutch slips.

This sounds like the real problem is that the moving parts are too heavy and
slow, and so we are well into mechanical resonance. If the dancer is made very
stiff and light, and thus fast, it may be possible to achieve stability.

What is the roving made of?


The use of a magnetic hysteresis clutch obviates the mechanical problems,
since they are continuous-slip devices. But clutches in the 20 ft-lb
torque range cost thousands of dollars.

I'm going to employ a dumbed-down electro-mechanical servo system. A
tensioning arm that can swing a fairly long arc over a small tension
differential, limit switches to sense "spool on/spool off" limits, and a
slow gear motor that has torque in excess of that required to maintain
the limit tension.

My above comments about stiff and light also apply here.


Including the metal work to remove the existing clutch system and replace
it with this, the solution comes in at about 1/6 the price of a magnetic
hysteresis or magnetic particle slip clutch of that required torque.

That's enough of a savings to provide some motivation for sure.


Joe Gwinn

Joseph Gwinn fired this volley in news:joegwinn-
:

What is the roving made of?

Joe, it's a very slightly twisted bundle of jute and cotton yarns and
cotton bias tape. VERY stretchy. Over the processing length of the
machine (about 80'), it will undergo about a foot of stretch at 20lbf
tension, and recover virtually all of it if released.

The tensioning requirement is not for the spooling -- the takeup spool
merely provides the necessary process tension. As the tension varies,
the overwrap of bias tape changes its spiral angle (from sideways
"yanking" of the roving in the wrapping area), and becomes uneven in
overlap and lay.

Only under fairly strict constant tension will the overwrap be as uniform
as customers demand for the product.

Stiff and light -- High resonant frequency.

LLoyd

On Fri, 18 Jun 2010 12:21:55 -0500, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:

Dave__67 fired this volley in news:ba0b6aec-e956-
:


Ideally, aren't there constant-torque AC motors that can be stalled
indefinitely?

yep... So called "impedance protected" motors. I've been looking for one
that would produce about 20ft-lb torque at around 5 rpm.

No luck so far. But I'm thinking I can run a split-phase induction gear
motor on reduced voltage and accomplish the same thing. Most split phase
motors don't really care if they're running, so long as you don't
overheat them. Reducing the input voltage would be one way to set the
stall torque and keep one from burning up.

But that still only gives me constant torque, and what I really want is
constant tension. so my dancer arm will need to control the motor
voltage.

LLoyd

The torque of a DC permanent magnet (DCPM) motor is proportional to
current regardless of speed. The motor won't overheat as long as it's
operated within its max current rating, even if stalled.

If you could rig up a 10:1 speed reducer with timing belts and pulleys
(zero backlash) then your torque requirement would be 2 lbf*ft at
about 50 RPM. A DC motor capable of delivering 2 lbf*ft at 2000 RPM
(a more usful speed for motors in general) would be a 90 watt (0.121
HP) motor. I don't think that'd be hard to find on the surplus
market. Or, you could go with a DCPM gear, e.g. power seat motors,
power window motors, windshield wiper motors, etc. Some windshield
wiper motors run at about 50 RPM. 20 ft-lbf at 50 RPM is about 23
watts, which is not quite 2 amps at 12 volts. Wiper motors are rated
for more like 5 amps.

Not all DC motors in automobiles are PM motors, though. Some are
series-wound. They'd work, but they're a bit trickier to control
because their torque is not linearly proportional to current.

Another possibility might be an inexpensive cordless drill operated
from a current regulator. Even a modest drill can deliver 200 in-lbf
which is 22.5 ft-lbf, and it can do that at low to stall speeds all
day.