Re: Two related questions, Sherlines and Steppers

Alan,

Speed certainly won't be an issue with those motors because there
won't be any particularly with a 4:1 reduction.

What you have there are some size 17 motors, probably about 30 in-oz
in holding torque. I'm guessing you have a 20TPI leadscrew so you can
calculate "push" in lbs as being 2pi * 20TPI * 4 * 30 in-oz /16 or
942 lbs (neglecting screw efficiency). The problem will be speed; at
24VDC those motors may manage 3 revs per second at best. Figuring 80
revs per inch (TPI * reduction ratio of 4:1) you will get 3/80 inches
per second or 2.25" per minute.

There isn't much point in rewiring the motors because you will still
have way to much inductance to make it worthwhile to run them with a
switching type drive.

You may wish to think about re-motoring with higher current motors.
If you insist on running them anyway, plan on using an R/L drive.

Mariss

--- In CAD_CAM_EDM_DRO@y..., Alan Rothenbush <beer@s...> wrote:
I have a number of small steppers once used in 5.25" hard
> drives. The largest of these is
>
> Unipolar
> rated ( on the case ) at 24 volts, .25amps
> 1.5" x 1/5" x 1.5"
> .9 degree/step ( I think )
> torque unknown
>
> So, here's the questions
>
> 1. Is this motor likely to be strong enough, given about a 4:1
reduction ?
> ( Speed is not an issue )
>
> 2. How do I rewire this for bipolar operation ? It's currently 5
wire
> unipolar, but the back plate comes off and the wiring is visible
and reworkable.
>
> There are eight physical windings, evenly spaced, and 4 electrical
windings,
> all on one side of the motor.
>
> Obviously, I'm going to parallel two pairs of windings, but I can't
quite get
> my head around which pair AND the phase of those pairs ( relative
to their
> current unipolar connection )
>
> Any help/thoughts appreciated.
>
> Alan
>
>
> --
>
> Alan Rothenbush | The Spartans do not ask the number
of the
> Academic Computing Services | enemy, only where they are.
> Simon Fraser University |
> Burnaby, B.C., Canada | Agix of
Sparta