Re: [Emc-users] Minimally printed rotary. Initial torque testing..

[Chris Albertson]

Yes, I agree with the words below. I better way to measure torque is to
make a drumwrape a cable around it and lift a bucket.  Run the drum at
different PPMs and load the bucket until the drum slows from it's
programmed RPM.  THis will allow you to plot an RPM vs torque curve.

What you have with a torque wrench is only one point on that curve.   For a
stepper motor this is the "best case" point on the curve, all other points
would be lower. Static torque is important but mostly these drives are
meant to move.

Along to same line.  Measuring longevity under zero load is not as
interesting as if measured at say 50% of max torque and running it in both
directions.  I know, testing takes time.

That said, I'm watching these experiments closely because I want to make
some of these reduction drives myself.  I meed at least 100:1 reduction in
a very smallspace.  I want to use a motor like one of these (but likely
notthis exact one)  amazon.com/Hobbypower-1000kv-Brushless...
<https://www.amazon.com/Hobbypower-1000kv-Brushless-Multicopter-Quadcopter/dp/B00E7LG85O>
  The "1000 KV" means 1000 RPM per volt and it comes with a digital
controller.  I Would mount the motor almost inside the flex cut of the
harmonic drive and maek an effective 10KV motor system

On Mon, Sep 13, 2021 at 10:26 AM John Dammeyer 
wrote:

> Nice update.
> My math works out as follows:
> 35 lb-ft is 35 * 12"/ft * 16 oz/lb = 6720 oz-in.
> You said the ratio is 100:1 so that means to get 6720 you only input 67.2
> oz-in.  That's about 1/3 of what you suspect your motor can do.
>
> Something is wrong with this picture then.  Especially since you were
> effectively using static torque rather than the much lower torque when the
> motor is turning at say 400 RPM.  With micro-stepping you also get a
> reduction in full step torque because the max current is now 0.707 x full
> torque.  And without closed loop encoder feedback you can quite easily have
> to micro-step a number of times before you see physical motion.
>
> None of that matters other than that you have shown your mechanics can
> handle 35 lb-ft which is all in all pretty cool !
>
> John
>
>
>
>
> > -Original Message-
> > From: Sam Sokolik [mailto:samco...@gmail.com]
> > Sent: September-12-21 5:50 PM
> > To: Enhanced Machine Controller (EMC)
> > Subject: [Emc-users] Minimally printed rotary. Initial torque testing..
> >
> > Small update
> >
> > https://youtu.be/eW1GGI55Epc
> >
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> > https://lists.sourceforge.net/lists/listinfo/emc-users
>
>
>
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-- 

Chris Albertson
Redondo Beach, California

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Re: [Emc-users] Minimally printed rotary. Initial torque testing..

[Matthew Herd]

Friction and elasticity in the ring gear likely account for most of the
difference.  I would imagine that the elasticity in the gear would be a
fairly strong impediment to motion.  Though calculations seem to be too
much trouble.

On Mon, Sep 13, 2021 at 2:00 PM Sam Sokolik  wrote:

> I agree with the quick math I did yesterday...   But again I have no info
> on these steppers..
>
> And yes - I think it is totally usable at 35 ft-lbs..  there is some
> friction there also running the 'wave' generator...
>
> On Mon, Sep 13, 2021, 12:26 PM John Dammeyer 
> wrote:
>
> > Nice update.
> > My math works out as follows:
> > 35 lb-ft is 35 * 12"/ft * 16 oz/lb = 6720 oz-in.
> > You said the ratio is 100:1 so that means to get 6720 you only input 67.2
> > oz-in.  That's about 1/3 of what you suspect your motor can do.
> >
> > Something is wrong with this picture then.  Especially since you were
> > effectively using static torque rather than the much lower torque when
> the
> > motor is turning at say 400 RPM.  With micro-stepping you also get a
> > reduction in full step torque because the max current is now 0.707 x full
> > torque.  And without closed loop encoder feedback you can quite easily
> have
> > to micro-step a number of times before you see physical motion.
> >
> > None of that matters other than that you have shown your mechanics can
> > handle 35 lb-ft which is all in all pretty cool !
> >
> > John
> >
> >
> >
> >
> > > -----Original Message-----
> > > From: Sam Sokolik [mailto:samco...@gmail.com]
> > > Sent: September-12-21 5:50 PM
> > > To: Enhanced Machine Controller (EMC)
> > > Subject: [Emc-users] Minimally printed rotary. Initial torque testing..
> > >
> > > Small update
> > >
> > > https://youtu.be/eW1GGI55Epc
> > >
> > > ___
> > > Emc-users mailing list
> > > Emc-users@lists.sourceforge.net
> > > https://lists.sourceforge.net/lists/listinfo/emc-users
> >
> >
> >
> > ___
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> >
>
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-- 
Matthew Herd
Email:  herd.m...@gmail.com
Cell:  610-608-8930

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Re: [Emc-users] Minimally printed rotary. Initial torque testing..

[Sam Sokolik]

I agree with the quick math I did yesterday...   But again I have no info
on these steppers..

And yes - I think it is totally usable at 35 ft-lbs..  there is some
friction there also running the 'wave' generator...

On Mon, Sep 13, 2021, 12:26 PM John Dammeyer  wrote:

> Nice update.
> My math works out as follows:
> 35 lb-ft is 35 * 12"/ft * 16 oz/lb = 6720 oz-in.
> You said the ratio is 100:1 so that means to get 6720 you only input 67.2
> oz-in.  That's about 1/3 of what you suspect your motor can do.
>
> Something is wrong with this picture then.  Especially since you were
> effectively using static torque rather than the much lower torque when the
> motor is turning at say 400 RPM.  With micro-stepping you also get a
> reduction in full step torque because the max current is now 0.707 x full
> torque.  And without closed loop encoder feedback you can quite easily have
> to micro-step a number of times before you see physical motion.
>
> None of that matters other than that you have shown your mechanics can
> handle 35 lb-ft which is all in all pretty cool !
>
> John
>
>
>
>
> > -Original Message-
> > From: Sam Sokolik [mailto:samco...@gmail.com]
> > Sent: September-12-21 5:50 PM
> > To: Enhanced Machine Controller (EMC)
> > Subject: [Emc-users] Minimally printed rotary. Initial torque testing..
> >
> > Small update
> >
> > https://youtu.be/eW1GGI55Epc
> >
> > ___
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> > Emc-users@lists.sourceforge.net
> > https://lists.sourceforge.net/lists/listinfo/emc-users
>
>
>
> ___
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Re: [Emc-users] Minimally printed rotary. Initial torque testing..

[John Dammeyer]

Nice update.  
My math works out as follows:
35 lb-ft is 35 * 12"/ft * 16 oz/lb = 6720 oz-in.
You said the ratio is 100:1 so that means to get 6720 you only input 67.2 
oz-in.  That's about 1/3 of what you suspect your motor can do.  

Something is wrong with this picture then.  Especially since you were 
effectively using static torque rather than the much lower torque when the 
motor is turning at say 400 RPM.  With micro-stepping you also get a reduction 
in full step torque because the max current is now 0.707 x full torque.  And 
without closed loop encoder feedback you can quite easily have to micro-step a 
number of times before you see physical motion.

None of that matters other than that you have shown your mechanics can handle 
35 lb-ft which is all in all pretty cool !

John




> -Original Message-
> From: Sam Sokolik [mailto:samco...@gmail.com]
> Sent: September-12-21 5:50 PM
> To: Enhanced Machine Controller (EMC)
> Subject: [Emc-users] Minimally printed rotary. Initial torque testing..
> 
> Small update
> 
> https://youtu.be/eW1GGI55Epc
> 
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Re: [Emc-users] Minimally printed rotary. Initial torque testing..

[Gene Heskett]

On Monday 13 September 2021 06:00:25 Gregg Eshelman via Emc-users wrote:

> You almost sound disappointed that you couldn't break it. ;)

I noticed that too. I haven't broken my version but once, tried to make 
it from PLA, but I had a different idea because I wanted a smaller 
version, and I have the attitude that I can print another for 10 bucks 
worth of plastic and 3 bucks worth of bb's.  But since I switched to 
PETG, and that caused a few thou $ in printers to find one that could 
handle a steady diet of PETG, most can't. But PETG can make a very 
servicable loose belt as its lots more flexible than PLA. But in the 
interests of cheap, I didn't use an armature with off the shelf 
bearings. My armature is printed, including the hub which because the 
motor I chose has an 8mm shaft that I put on the 0704's table and ground 
the d-flat much wider, needs no alu or steel insert hub, the PETG as a 
press fit on the 8mm shaft has not failed. That armature is printed, and 
eccentric by 1.1mm. Its wrapped by two printed ball bearings, which in 
turn distort the loose belt in the same manner that Sam's much more 
expensive off the shelf bearings do. Probably with less flex stress on 
the loose belt because the push is fully distributed.

The drive I made is aimed at the A drive supplied with cheap gantry mills 
as the kit supplied has virtually zero holding power and 100x the rpms 
needed for such duties. Designed for a 30/1 ratio, and another nominally 
4/1 between it and the A axle, by way of a small pitch timing belt. Its 
a hair loose and needs a tensioner idler designed and built that I 
haven't found the round tuit to do yet.

I've had it running on the kitchen counter at about 3 rpm at the chuck 
for something over a month now. All except the bearing balls which are 
crosmann bb's, is 3d printed. Currently driven by a 1NM 3 phase 
stepper/servo, I think it will do the job on my 6040 mill. And if I 
break it, a $20 bill prints another. Its also got about an hours worth 
of running at just short of that small motors stall speed, 2000+ rpms 
for about a minute at a time so the armature bearings don't get too hot.  
At that speed, the bb's are probably spinning in the 100,000 rpms 
category.

The output end houseing and shaft only have 1 bearing,, another row of 
bb's, 75mm in diameter. There is more flex in the 3mm thick disk holding 
the output sprocket than anyplace else. It is less than 4" in diameter, 
and under 20mm thick not including the output sprocket, it is plenty 
strong enough to do _that_ job.
>
>On Sunday, September 12, 2021, 06:52:23 PM MDT, Sam Sokolik
>  wrote:
>
>  Small update
>
> https://youtu.be/eW1GGI55Epc
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Cheers, Gene Heskett
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
If we desire respect for the law, we must first make the law respectable.
 - Louis D. Brandeis
Genes Web page 


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Re: [Emc-users] Minimally printed rotary. Initial torque testing..

[Gregg Eshelman via Emc-users]

You almost sound disappointed that you couldn't break it. ;)


   On Sunday, September 12, 2021, 06:52:23 PM MDT, Sam Sokolik 
 wrote:  
 
 Small update

https://youtu.be/eW1GGI55Epc  
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[Emc-users] Minimally printed rotary. Initial torque testing..

[Sam Sokolik]

Small update

https://youtu.be/eW1GGI55Epc

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