Alt-BEAM Archive
Message #01764
To: Richard Piotter richfile@rconnect.com
From: Bruce Robinson Bruce_Robinson@bc.sympatico.ca
Date: Thu, 25 Mar 1999 12:57:12 -0800
Subject: [alt-beam] Re: small parts....
"G.R.Reddy" wrote:
> Can someone point me to gears, rack and pinions, etc. resources on web
> please.
Richard Piotter wrote (in part):
> ... Has anyone tried the tear shaped timers (2 inch diameter AC motor on
> a tear shaped gear box)??? How do they work?
I've taken apart quite a few. In general, most of them consist of a gear
train of between 3 and 8 pairs of gears. These are often arranged in a
circular configuration -- central motor drives a gear on the periphery
of the large part of the teardrop, and then the gear train wraps around
this central gear and finishes at the small end of the teardrop, where
it drives the output shaft.
Two common configuration: a series of fixed shafts mounted securely on a
plate with hollow centred gears that fit over the shafts; or a series of
gear pairs on shafts, which run in small holes bored in a pair of
parallel plates. Gear pairs are typically a small brass gear attached to
a large diameter steel one. It's not unusual for the gears at the motor
end of a train to be plastic or fibre, with the driven (slower speed)
gears being metal. Typically these are gearing down from 60 Hz (3600
RPM) to 1 or 2 revolutions per hour, or about 200,000 to one! Most of
the time the gears have the same tooth configuration within a single
gearbox. Sometimes the gears from entirely different devices mesh well.
I also found a beautiful set of gears in a couple of very old oven timer
units. There was very little reduction in the teardrop gear train, so I
carefully filed apart the motor housing. Jackpot! A complete,
self-contained gearbox pressed into the case (60,000 to one reduction).
The entire motor case was filled with light oil, so the first one was a
mess to take apart.
If you've got access to a small lathe and a set of number drills, you
can custom build some very useful gear reducers out of these things.
Failing that, you can just remove gear pairs starting at one end until
you get the approximate reduction you're after. This leaves you with the
often difficult task of attaching your motor and legs (or whatever).
Getting enough identical reducers is a problem, unless you like
asymmetry in your robots.
Regards,
Bruce
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