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[DPRG] Pittman motors at Tanners

Subject: [DPRG] Pittman motors at Tanners
From: Dan Creagan dcreagan at bellevue.edu
Date: Tue Aug 21 13:32:08 CDT 2001

So,

Did you get it back together? ;-}

I just received some so I've done a few rev tests. At 12 volts they do
about 60 rpm (done by just counting '1 potato, 2 potato', etc.) so the
70 rpm figure seems about right.

I have some other 8000 series motors from another site (Allelectronics
had them for a while) and these do about 30 rpm using the same highly
accurate counting technique.

Either one seems good for a basic robot.  The .05" motor extension is
not much to work with so the super glue technique seems the only likely
one if a motor side rev counter is needed.  Too bad the rear holes
aren't threaded. Makes it a bit messier.

Dan

-----Original Message-----
>From: dprglist-admin at dprg.org [mailto:dprglist-admin at dprg.org] On Behalf
Of Jeffrey T. Birt
Sent: Monday, August 20, 2001 10:11 PM
To: David P. Anderson; DPRG List
Subject: Re: [DPRG] Pittman motors at Tanners




I received four of the Pittman motors that Tanners had in the mail
today! Many thanks to David Anderson for sending them (the check is in
the mail David)!  Now to design a new base to hold them.  Has anyone
disassembled one yet.  The three holes in the rear case will need to be
threaded to mount an encoder there.  Well, heck I'll go take one apart
now.


Jeff Birt
Halfway, Missouri

----- Original Message -----
>From: "David P. Anderson" <dpa at io.isem.smu.edu>
To: <dprglist at dprg.org>
Sent: Sunday, August 12, 2001 5:53 PM
Subject: [DPRG] Pittman motors at Tanners


>
> Hi DPRG
>
> Great data collecting Eric!!  I've played a little bit with these 
> Pittman motors purchased from Tanner's and am favorably impressed.
>
> Some months ago Barry Jordan and I began talking about designing a 
> DPRG club robot base that we could replicate for cheap for interested 
> members of the club.  The stopping point turned out to be the lack of 
> suitable motors.  Tanner's now has in stock some Pittman motors which 
> may be suitable for such a project.
>
> Eric details these motors below.  The down side of these motors is 
> that they have no shaft encoders.  I had planned to use home made 
> laser printed cardstock encoders super-glued to the rear of the motor 
> shaft, as I've done on other robots.  Eric suggests that one of the 
> HEDS encoders might fit, which would be great. The only one I've seen 
> taken apart appears to need a longer shaft to fix a tiny Allenhead 
> setscrew against, on the collar of the encoder disk.  Is .050" enough?

> Part of that .050 is beveled on the very end.  I'm not sure.
>
> Jimmy Tanner said he would make us a deal on a group purchase. I 
> haven't been able to raise Barry (are you out there Barry???) to 
> continue the club design aspect but these are cool enough motors that 
> I don't think we can go wrong buying a bunch of them.
>
> Any interest?
>
> cheers,
> dpa
>
>
> > Eric wrote:
> >
> >
> > A certain Sr. Systems Philosopher at SMU (dpa) clued me in to a new 
> > batch of gearmotors that Tanners now has on the shelf, the Pittman 
> > GM8712-31 for $10.95.  I picked up a few of them to play with (along

> > with the soon to be released Handy Board kit Jimmy is making).  So 
> > far I haven't done anything with them besides think
> > a little about making a motor mount for them...  :-(   But they
> > look really nice.  Here's the Pittman webpage for GM8700 models with

> > a decent enough spec sheet:
> >
> >          http://www.pittmannet.com/122100.html
> >
> > The spec sheet says of the 19.1V GM8712 gearmotor, with a 60.5:1 
> > reducing gearbox:
> >
> >    Gearmotor Data:
> >
> >        Gearbox Efficiency              66%
> >        No-load Speed                   128 RPM
> >
> >
> >    Motor Data:
> >
> >        Continuous Torque (Max)         1.3 oz-in
> >        Peak Torque (Stall)             5.1 oz-in
> >        No-load Speed                   7729 RPM
> >
> >    Winding Data:
> >
> >        Torque Constant                 3.06 oz-in/A
> >        Resistance                      10.80 Ohms
> >        No-load Current                 0.14 A
> >        Peak Current (Stall)            1.76 A
> >
> >
> >I take all that to mean (in theory) out the gearbox shaft:
> >
> >        Continuous Torque (Max)
> >
> >            1.3 oz-in  *  60.5:1  *  66%  =  51.9 oz-in
> >
> >        Peak Torque (Stall)
> >
> >            5.1 oz-in  *  60.5:1  *  66%  =  203.6 oz-in
> >
> >(Logic/arithmetic flaws?)
> >
> >
> >David mentioned they seemed to work nicely at 12V running about 70 
> >RPM with a stall current around 1A -- small enough to use an L293 to 
> >drive it.
> >
> >The 3/16" motor shaft sticks 0.050" out the back which I think is far

> >enough to slap one of those HEDS encoder modules on it to get up to 
> >1024 CPR (cycles per revolution) resolution, or for sure it's enough 
> >to stick on a homegrown encoder disk.
> >
> >Tanners is willing to give us a volume discount, so save your lunch 
> >money in case these turn out to work out well enough that we'd want 
> >to do a group buy.
> >
> >BTW, Automation Solutions has these gearmotors (new?) listed for a 
> >cool $73.90 a pop.
> >
> >
> >Faithfully submitting my findings,
> >
> >--
> >Eric
> _______________________________________________
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> DPRGlist at dprg.org http://nimon.ncc.com/mailman/listinfo/dprglist

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