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 21:14:09 GMT
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Original-From:
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JED_ANDERSON@OTI.nospamCOM
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Viewed:
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765 times
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Could you post some pictures of these new gears?
jkca
Robert Limbaugh
<rlimbaugh@greenfiel To: "'sjbaker1@airmail.net'" <sjbaker1@airmail.net>
dgroup.com> cc: Lego Robotics <lego-robotics@crynwr.com>
Subject: RE: Discontinuous motion.
04/03/2002 03:03 PM
In that case, get one of the new Bionicle Bohrok (the big one's, not the
"Va's") figures. They have two new gear pieces... one is a 1/4 of a full
gear (hard to explain... but it would effectively be a partial circular
gear
of sorts) and the other new gear piece's are 2 arms with gears on each end
(they look like bones).
These pieces are used to lift the heads up.
I'll goof off with some idea's later...
-----Original Message-----
From: Steve Baker [mailto:sjbaker1@airmail.net]
Sent: Wednesday, April 03, 2002 3:20 PM
To: Robert Limbaugh
Cc: Lego Robotics
Subject: Re: Discontinuous motion.
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
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