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Subject: 
RE: More Directional transmissions...
Newsgroups: 
lugnet.robotics
Date: 
Wed, 1 Dec 1999 22:54:29 GMT
Original-From: 
Jim Thomas <Jim.Thomas@trw.&stopspam&com>
Viewed: 
703 times
  
I'm not exactly sure how, but I think the white torque limiting gear might
work here...

JT

-----Original Message-----
From: Dave Johnson [mailto:djohnson@sirius.com]
Sent: Wednesday, December 01, 1999 1:28 PM
To: lego-robotics@crynwr.com
Subject: More Directional transmissions...


At the risk of boring folks with my mechanical tinkerings...

I want to create a transmission such that drivng the input
shaft one way
gives me very slow rotation on the output, but driving it the
other way
gives me fast rotation in the opposite direction on the same
output axle.

I've got several working models, but they all have the same
problem: in
the slow rotation case it's fine, I have a long reducing gear
train to
give me very slow rotation on the output. But in the fast
rotation case,
the entire gear train is "back driven" by the output axle,
and since the
gear train from this direction is "gearing up", the load on
the motor is
very heavy, and there are lots of gears spinning VERY fast
for no good
reason.

So I've been trying to come up with a way to disconnect the
output axle
from the gear train in that case, but the usual "gear on a swing arm"
method can't work. In fact, it's this very principle that makes "pull
back" motors work at all. Those who have messed with this stuff a lot
will understand why. It was a revelation for me, I admit, but
that's a
big part of why this is so much fun :-)

Incidentally, if the output shaft can rotate the same
direction in both
cases (fast and slow), I can make it work fine. But I really
need a "fast
reverse".

So I guess the question is this: are there other ways to disconnect a
gear train besides the swing arm? Or is there any way to connect or
disconnect a gear based on speed of rotation? Does anyone
have any ideas
and/or references for this kind of thing? Does anyone even
know what I'm
talking about? :-)

Dave Johnson
Amateur Mindstormist




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