Subject:
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Re: Discontinuous motion.
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Newsgroups:
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lugnet.robotics
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Date:
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Wed, 3 Apr 2002 20:20:05 GMT
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Original-From:
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Steve Baker <sjbaker1@airmail.(StopSpammers)net>
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Reply-To:
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SJBAKER1@saynotospamAIRMAIL.NET
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Viewed:
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1661 times
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Robert Limbaugh wrote:
>
> I meant using wheels with rubber treads. Rubber treads won't have a meshing
> problem. Instead of the problem being gear mesh, the new problem should be
> speed vs. friction.
OH! I see! Very clever.
I guess I should explain why I wanted this thing in the first place.
All the talk last week about building a Turing machine using Lego - and
building primitive mechanical computers in general led me to try to build
a simple adding machine using gears and stuff. (I'm aware of the awesome
pneumatic adder someone presented recently).
So, the first step was to build a counter - like a car odometer - where you
spin one axle and when it's spun a complete revolution, a second wheel moves
1/10th of a revolution. When the second wheel has undergone a complete
revolution, a third wheel moves forward a tenth of a revolution. This
gives you the 1's, 10's and 100's numbers based on how much the wheels
have moved. It didn't need to be a base 10 system though.
The first step of that was to get a reliable mechanism that would allow
one revolution of the input axle to rotate the second wheel by 1/10th of
a revolution. A 10:1 gear ratio would do that - but car odometers don't
do that. The 10's digit stays absolutely still until the 1's wheel is
just about to clock over from '9' back to '0' - and then it moves quite
quickly onto the next 10's digit.
So, your suggestion certainly does do what I actually asked for - but it's
not accurate enough for what I actually *want*. If the system doesn't use
some kind of solid gear-based mechanism, it'll gradually accumulate error
which will be hopeless for what I ultimately want to do.
> If the drive wheel arm rotates to quickly, the drive wheel may not grip the
> 2nd wheel enough. Or, it may grip too well and make the 2nd wheel spin more
> than desired (depending on the load on it's axel).
Yes - that problem exists with the gearwheel solution too.
> Maybe I should just build an example of what I mean... The idea came from
> how the Pirate Ship carnival rides move the ship back hull back and forth...
> sets of wheels push the hull right or left.
That's interesting. I didn't know they worked like that. By an *amazing*
coincidence, my son has just finished building one of those in Lego - but
he used RCX software to alternate the direction of drive on the wheels to
sync with the speed he wants the ship to swing. Your way is *much* better!
----------------------------- Steve Baker -------------------------------
Mail : <sjbaker1@airmail.net> WorkMail: <sjbaker@link.com>
URLs : http://www.sjbaker.org
http://plib.sf.net http://tuxaqfh.sf.net http://tuxkart.sf.net
http://prettypoly.sf.net http://freeglut.sf.net
http://toobular.sf.net http://lodestone.sf.net
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Message has 3 Replies:
 | | Re: Discontinuous motion.
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| Steve, Here's an "all gear" based solution (minus the chain I used from the drive shaft): (URL) not sure how much gear lash is in the design I came up with, but the thing runs very well (much better than I thought it would). It's been quite some (...) (25 years ago, 4-Apr-02, to lugnet.robotics)
| | | Re: Discontinuous motion.
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| Steve, I don't know if this will help you at all, but I certainly had fun with it. I put together a (quite bulky) version of the Geneva Wheel. (URL) Baker" wrote in message news:3CAB63F5.7A5CF2...ail.net... <snip> (...) you (...) moves (...) I don't (...) (25 years ago, 5-Apr-02, to lugnet.robotics)
| | | Re: Discontinuous motion.
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| (...) <snipped very interesting description> Just to chime in here quickly, you could use the lego small chain links instead of tons of gears to create gear trains. Advantages: gearing ratios are retained as in trains, backlash/chatter is reduced (...) (25 years ago, 5-Apr-02, to lugnet.robotics)
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