Subject:
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Re: 2 Motors -> 1 axle
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Newsgroups:
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lugnet.robotics
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Date:
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Fri, 7 Jan 2000 16:37:46 GMT
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Original-From:
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The WordMeister <dwilcox@wordsmithdigital.[IHateSpam]com>
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Viewed:
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2155 times
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Will your design work using shorter axles and a bunch of the "axle
connector" pieces? That should keep the axle train from flexing too much.
--Doug Wilcox
http://www.wordsmithdigital.com/mindstorms/
-----Original Message-----
From: Dave Johnson <djohnson@sirius.com>
To: lego-robotics@crynwr.com <lego-robotics@crynwr.com>
Date: Friday, January 07, 2000 11:34 AM
Subject: 2 Motors -> 1 axle
> After the good suggestions from folks (see the Balancing Bots thread) I
> did some experiments with using 2 motors to drive one axle (to double the
> power to the axle) and thought the results might be of interest to others.
>
> I first tried having the motors separately drive the same axle. That is,
> the motors weren't directly connected to each other at all, except
> through the axle. Each motor drove a 24t crown gear, and each crown gear
> drove a separate 24t gear on the axle. The idea was that even if the
> motors weren't matched exactly, there would simply be a bit of a load on
> the "fast" motor.
>
> Unfortunately, the motors were different enough that the gears actually
> skipped teeth occasionally. Running in one direction would probably be
> OK, but in this application I'm switching direction constantly, and it
> didn't work. Also, even if the gears remained meshed, it's not an
> effective use of the power in the motors: one of them is always pulling
> the other one along, robbing the whole system of power.
>
> Then I tried using a differential "backwards": I used a motor to drive
> each of the outside axles, and the body of the differential to drive the
> output. MUCH better, though bulkier. In this case, each motor contributes
> what it can, and any difference between the motors just means the middle
> gear in the differential spins a bit to absorb the difference, but no
> power is lost fighting a mis-matched motor. I think this is the way to go.
>
> Now if I could just figure out how to stiffen the axle torsionally. I
> need a wide base for stability, but the long axle means that the wheels
> aren't locked together very well, there's lots of springy torsional
> wiggle between them, which twists my bot around a lot when it's whipping
> the wheels back and forth. I'm thinking maybe a tripod base with only one
> drive wheel would be good, or maybe treads. Or maybe I should just bug my
> machinist friends to carve me some steel axles :-)
>
> Dave Johnson
> Still trying to balance
>
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