Re: How to determine Torque from these motor numbers?

Greg-

RPM was derived by placeing a "tag" of electrical tape on the shaft
of the motor and letting it "slap" a piece of cardboard on every
rotation. This was recorded via a microphone into my computer and
then I analized the waveform with a sound editing software- 12
waveform pulses (tape "slap") per second = 720RPM. very useful for
determining pulserates of many types.. I primarily use this method
for measureing paintball gun cycle rates. :)

as for the motors, Im not sure if they are the same as the ones
around which others are selling as servo motors for CNC use or not.
From just compairing specs, they seem very similar to the "Ametek 600
oz/in motor" that Camtronics sells over on
http://www.seanet.com/~dmauch/Products2.htm .

These do not have access to the shaft from the back of the motor- the
back plates are solid... something that will soon be changed and a
shaft extension added for an encoder to be mounted on the back end of
the motor.

Thanks-
Colin

--- In CAD_CAM_EDM_DRO@yahoogroups.com, Gregory Kamysz
<smsupply@a...> wrote:

> Your motor is very similar to the Aerotech 1210 which I have specs

for.

> The size is the same. Nema 42 about 5" long. Terminal

resistance is

> 1.8 Ohm. They spec Kt=35oz-in/A and 6A continuous or 210oz-in
> continuous for this motor. I made the comment about the size of

the

> motor and even though they are the same size your motor makes 50%

more

> torque per amp. The max RPM they spec is 3000 so you should be

safe

> running your motor to 1500RPM.
>
> I do have a question. How did you measure the RPM? If your motor

has

> rare earth magnets this would account for the difference between it

and

> the 1210. There really isn't any simple way to tell what type of

magnet

> is in the motor. If the RPM measurement is accurate then the

numbers

> everyone came up with are accurate.
>
> Stalling the motor is OK. If you start with a very high current

you

> could overheat the armature before the outside of the motor gets

hot, so

> start low. I have done this to quite a few motors. As long as you

don't

> overheat it, it doesn't matter. There are basically two limits to
> electric motor operation the amount of heat it can dissipate (the
> current or torque limit) and the maximum RPM at which mechanical

issues

> limit the life of the motor (the RPM limit). Operating the motor

within

> those two limits is pretty safe. If you are trying to push the

envelope

> of both limits you can run into problems, basically as RPM

increases

> maximum current has to be derated.
>
> As far as powerful, well they make a lot of torque. If you had a

motor

> with similar torque but it ran faster it would be more powerful (it
> would also be larger). Or you could have a motor that made less

torque

> and ran faster it could make the same amount of power. I think the
> motor will work just fine. They may be slow compared to some

motors,

> but if you run a 60V supply it shouldn't be an issue. With that

much

> torque you could run a higher pitch ballscrew to make the machine

faster.

>
> Greg
>
>
> Earl wrote:
> > Thanks for all the help and numbers so far yall. You dont know

how

> > much the helps out! :)
> >
> > these motors are around 4"D x 5"L in size.. I guess from what I'm
> > hearing is that they are actaully more powerful than I thought?
> >
> > Lastly, Greg when you mention testing the motor for temperature
> > buildup, Is it OK to let the motor cook at locked shaft.. even at

(a

> > low) 3.7A? just seems that cant be good on it for any length of
> > time... but if thats what it takes! :)
> >
> > thanks again all-
> > Colin