Alt-BEAM Archive
Message #05259
To: beam@sgiblab.sgi.com
From: Bruce Robinson Bruce_Robinson@bc.sympatico.ca
Date: Sun, 11 Jul 1999 20:53:00 -0700
Subject: [alt-beam] Re: Nu(tating) Motor
Wilf Rigter wrote:
>
> I mentioned Nutating gears earlier so here something to wrap you head
> around...
> ... When the magnetic force has moved through 360', the rotor will have
> advanced one tooth since it has one more tooth than the torroid gear.
A couple of years ago I picked up 5 surplus Allis Chalmers engine hour
meters for less than $3.00 each, thinking they would make useful
mechanical counters. However, turning the input shaft didn't seem to do
anything. Mounting it in my lathe and running it at 2000 RPM didn't seem
to do anything either, so I dismantled one -- 1,920,000 to one
reduction, in 4 stages!! And that was just to drive the first digit in a
5 digit meter.
The principle is very similar to the one described. In this case a
40-tooth outer gear (with the teeth moving inward), and a 39-tooth inner
gear meshing with it. The inner gear is prevented from rotating but is
otherwise free to move. This gear is instead revolved around the
centerpoint of the outer gear. One revolution of the inner gear produces
1/40 revolution of the outer gear. In a tiny volume, they have stacked 3
- 40:1 and 1 - 30:1 reduction.
Unfortunately, these parts are plastic (delrin, I suspect), and so will
not be able to handle a lot of torque. However, with a little mechanical
skill you could probably dismantle a unit and build yourself a nice,
compact reduction unit for light duty work.
For those of you in Canada, I picked mine up from Princess Auto, and
last I looked these were still in the catalogue.
I'd be interested in hearing from anyone who adapts one of these units
to make a walker.
Regards,
Bruce
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