Subject:
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RE: moving in a straight line with two motors?
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Newsgroups:
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lugnet.robotics
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Date:
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Fri, 13 Nov 1998 13:38:47 GMT
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Original-From:
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Giesen, Oliver <OGIESEN@spamlessMDSINTL.COM>
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Viewed:
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2327 times
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G'Day
My 3 cents (Canadian, Eh).
The most elegant solution I have seen to this problem I believe came from an
old Milton Bradly 'Big Trak', in which the designers used a magnetic clutch.
The idea is simple , getting the forces involved to balance may be more
tricky I have not yet tried this with Lego(TM) bricks.
Basically you get two large pulleys (or bars) and mount two magnets opposite
each other on the same side, one pulley has the two north poles facing out
and one has the two south poles facing out, when the two pulleys are mounted
so that the magnets face each other the two pairs of magnates will attract
each other and then when one axle is turned the other will turn with it.
Now the tricky(?) part... the idea is that when both wheels are driving
forward together the difference in torque will be low enough and the magnets
strong enough that the two axles will stay in step. When turning by only
driving one motor and thus only side of our little clutch the torque will be
great enough to unstick the magnets and one side will spin freely.
Its kind of cool to watch.
This also seems to work better if the clutch turns faster that the wheels
being driven, so it should be placed closer to the motor than the drive
wheel end of the transmission drive chain.
I hope I have been clear in my description, it is obvious when you see
it.(sorry no web page yet)(;(
Cheers!
Oliver.
ogiesen@mdsintl.com
sent to lego-robotics@crynwr.com
Horrible ASCII art:
Top View
| < axle
| <
---------- < pulley 1
n n < two magnets mounted on pulley 1's surface
< air space
s s < two magnets mounted on pulley
---------- < pulley 2
| <
| < other axle
-----Original Message-----
From: lugnet.robotics@lugnet.com [mailto:lugnet.robotics@lugnet.com]
Sent: Thursday, November 12, 1998 10:11 PM
To: lego-robotics@crynwr.com
Subject: moving in a straight line with two motors?
Hi,
One of the first things I ran into when making a mobile 'bot using one
motor for each of two drive wheels was the mismatch in their speed.
Needless to say, it's a nice way to make curved path. Not what I want.
<snip>
Unfortunately, gear slop keeps this from working well for me. Any
suggestions?
Thanks,
-Tim
--
Tim and/or Shelley Rueger - rueger "at" io.com
WWW page: http://www.io.com/~rueger/
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Message has 2 Replies:
 | | RE: moving in a straight line with two motors?
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| Ah-Oh... Magnets in close proximity to the RCX brick may not be a wise idea. On just about all of my mobile bots, the motors are immediately adjacent to the RCX brick. Just my 2 cents (US, of course!) Carl -----Original Message----- From: Giesen, (...) (26 years ago, 13-Nov-98, to lugnet.robotics)
| | | RE: moving in a straight line with two motors?
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| Giesen, Oliver writes: > Basically you get two large pulleys (or bars) and mount two magnets opposite > each other on the same side, one pulley has the two north poles facing out > and one has the two south poles facing out, when the two pulleys are (...) (26 years ago, 13-Nov-98, to lugnet.robotics)
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