Subject:
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Re: Lego Breaks
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Newsgroups:
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lugnet.robotics
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Date:
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Thu, 17 Aug 2000 19:26:35 GMT
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Original-From:
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Steve Baker <sjbaker1@airmail.%spamcake%net>
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Reply-To:
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sjbaker1@airmail.SPAMCAKEnet
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Viewed:
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938 times
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John Barnes wrote:
>
> The answer to good casters seems to revolve (excuse the pun) around
> the caster radius. Using a narrow wheel (to limit turning friction) helps.
> The real key is the distance from the wheel's axle to the caster's axis
> of rotation. The bigger the better, since the required torque goes down.
>
> But, as in all things, its a trade off. Make the distance too large and the
> wheel tucks too far under and shortens the height of the three wheel
> triangle that everything is balancing on. (You can of course use two casters
> most people do, but you still end up with the leading triangle being small
> which can cause toppling if the thing stops abruptly.)
Hmmm - so could you mount TWO wheels on the caster - one with a relatively
wide tyre mounted a large distance from the vertical caster axle - and another
(close to the center of the caster axle) with a thin tyre?
The thin wheel would bear the weight of the robot - without reducing the wheelbase
by 'tucking under' the machine.
The wide wheel (having more friction) would provide the torque to rotate the
entire mechanism...it would tuck under the robot - but since it's only there
to rotate the caster, you don't care.
Something like this:
Caster
axel
||
____ ||
| | || ||
| |_______||_||
|| |__________|||
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|____| ||
^ ^
Fat wheel Skinny wheel
-
Steve Baker HomeEmail: <sjbaker1@airmail.net>
WorkEmail: <sjbaker@link.com>
HomePage : http://web2.airmail.net/sjbaker1
Projects : http://plib.sourceforge.net
http://tuxaqfh.sourceforge.net
http://tuxkart.sourceforge.net
http://prettypoly.sourceforge.net
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Message is in Reply To:
 | | RE: Lego Breaks
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| The answer to good casters seems to revolve (excuse the pun) around the caster radius. Using a narrow wheel (to limit turning friction) helps. The real key is the distance from the wheel's axle to the caster's axis of rotation. The bigger the (...) (24 years ago, 17-Aug-00, to lugnet.robotics)
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