Alt-BEAM Archive
Message #01870
To: Victor Snesarev vsn@eel.ufl.edu
From: Steven Bolt sbolt@xs4all.nl
Date: Tue, 30 Mar 1999 11:07:30 +0200 (CEST)
Subject: [alt-beam] Re: Walkman motors
On Mon, 29 Mar 1999, Victor Snesarev wrote:
> How correct is it to assume that all motors found in 2
> AA-battery-powered walkmen are efficient and powerful enough for a
> walker?
Their efficiency is fine. The main problem is weight. For my Spider,
(http://www.xs4all.nl/~sbolt/e-spider.html)
I use little Bertsch motors with a built-on gearbox; they weigh 14
grams each. The micro-cassette motors used on SunEater_III weigh
exactly twice as much, *excluding* the weight of the gearbox you'd
have to add for driving legs.
And walkers demand much of their gearboxes. You tend to need a ratio
of about 400:1. Despite the high ratio, the gearbox must allow a
reverse force to turn the motor or at least not allow such forces to
strip the gears. If you connect legs directly to the gearbox, there
will also be high lateral and push/pull forces on the bearings of the
output shaft, which they may not be designed to handle.
Add to all this the fact that your robot is unlikely to walk efficiently,
which makes low all-up weight essential.
On Mon, 29 Mar 1999, Victor Snesarev wrote:
> The reason I am asking is that I can buy a new walkman for $10 (I'll try
> looking for used/broken ones first though). The store manager would probably
> get irritated if I started testing his merchandise with a meter. :)
Note that those little Bertsch motors I mentioned cost about $10 a
piece. However, the output shaft bearings can't take leg loads
directly. You have to add one external gear to drive a separate
output shaft.
Best,
Steve
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# sbolt@xs4all.nl # Steven Bolt # popular science monthly KIJK #
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