On Friday 28 March 2008, Gene Heskett wrote:
>On Friday 28 March 2008, Ian W. Wright wrote:
>>Gene wrote...
>>
>> >>>>>>>>>>I also don't know about the
>>
>>bearings, I'd think ball cuz sleeved stuffs usually have more end-play than
>>could be tolerated in a spiral groove drive setup.>>>>>>>>>>>>
>>
>>you might need to look at those motors carefully - some of them only had
>> very rudimentary bearings in the front of the motor and relied on a simple
>> steel ball sitting in a dimple in both the motor back bearing and at the
>> end of the screwed shaft. A lot of the little 3 1/2" floppy disk motors
>> now use the same technology. Have you considered using the innards of a
>> mouse to make an encoder such as - http://tinyurl.com/3awsou ? A dead
>> computer printer will probably give you a couple of usable motors but they
>> are often only 48 step.
>
>These have oil-lite sleeve bearings on both ends, I can see them. And they
> do seem to be 200 step/rev. I believe my friend has more of them cuz when
> he gets an itch, he buys enough surplus of whatever he's going to use to
> scratch that itch to last him for his projected production run. That,
> after 8 or 9 years, is never gonna happen, and I suspect the batch this one
> was one cell occupant of an egg crate full of them can be supplanted with
> however many more I might need for a 5 dollar bill or less each. Probably
> a lot less.
The motors I had eyed have arrived, and one checked for its suitability.
They are the head steppers from the old disk drives, and seem to output a
waveform that we can use at almost zero speed, and certainly usable at 3 or 4
steps per second, possibly even slower. There is a magnetic detent you can
feel but some mass in the 'wheel' should smooth that out to where even
one 'click' per second might be feasible. OTOH, a good turn between my
fingers shows nearly 80 volts peak to peak, so arriving at a suitable
hysteresis should be an easy optimization.
I've gotten enough of them to make 2, 4 axis boxes, thinking about the lathe
at some point, but if that (putting the motors on the lathe) gets too
delayed, would someone else be interested in the second one?
The first pendent box will have one on each end, one on the front, and one on
the top. The right end I'll hook to X, the front one to Y, the top one to Z,
and the one on the left end of the box I'll run A with. They will then be in
the same relative positions as the real motors they will be controlling on my
machine, so my hand at least will naturally reach for the right one.
--
Cheers, Gene
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
There are more things in heaven and earth,
Horatio, than are dreamt of in your philosophy.
-- Wm. Shakespeare, "Hamlet"
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