Subject:
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Problem with auto-steering mechanism.
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Newsgroups:
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lugnet.robotics
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Date:
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Fri, 25 Oct 2002 17:38:22 GMT
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Original-From:
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Steve Baker <sjbaker1@airmail.&spamcake&net>
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Viewed:
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615 times
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I've been trying to build a mechanism I remember seeing on a kids toy.
What I'm thinking of is a vehicle with two un-driven wheels at the
back and two wheels at the front that are mounted on a turntable
such that they normally pull the vehicle forwards - but which
rotate when the vehicle hits something to drive it automatically
away from the obstacle.
This toy would drive around in a room in more or less random directions,
managing to extricate itself from tight corners and obstacles with
zero onboard intelligence and just a single motor.
The thing I've built *almost* works.
There is a picture here:
http://www.sjbaker.org/toy.jpg
The two front wheels are connected via a differential whose
body is rotated by the motor via a drive shaft that runs down
through the middle of the turntable. The crown gear in the
center drives a 16t on the right of the picture which drives
the body of the differential.
Theoretically both wheels will drive forwards until the vehicle
hits something - at which point one wheel stalls and the other
one rotates. This causes the turntable to rotate until the drive
direction has rotated enough to allow it to move away from the
obstruction.
On paper, it looks like my mechanism should work - and to some
extent it does. However, I can't seem to quite get the thing
to prefer to drive straight. It'll go forwards for a while
and then a particularly stubborn air molecule will get in it's
way and the front wheels will start spinning.
I don't have one of the original toys that do this so I can't
see what trick I've missed.
I hope it's not some 'iffy' deal with subtly adjusting the friction
in the drive versus the friction of the turntable - but I suspect it
might be.
Any ideas?
---------------------------- Steve Baker -------------------------
HomeEmail: <sjbaker1@airmail.net> WorkEmail: <sjbaker@link.com>
HomePage : http://web2.airmail.net/sjbaker1
Projects : http://plib.sf.net http://tuxaqfh.sf.net
http://tuxkart.sf.net http://prettypoly.sf.net
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Message has 3 Replies:
 | | Re: Problem with auto-steering mechanism.
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| (...) I find it hard to believe some 'iffy' condition would be required for a mass-producted childs toy. (so you hope) I have two suggestions. 1) Limit the rotation of the turntable to 180 degrees. (or 180 each direction) That should keep it from (...) (22 years ago, 25-Oct-02, to lugnet.robotics)
| | | Re: Problem with auto-steering mechanism.
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| (...) The "Cy-Purr Mouse" cat toy seems to be sold just about everywhere (including my local supermarket) for $9 US or so. See, for example*: (URL) employs the principle you are describing about as precisely as I can imagine. The only problem I've (...) (22 years ago, 25-Oct-02, to lugnet.robotics)
| | | Re: Problem with auto-steering mechanism.
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| May I give it a go?..... I'm not exactly sure of the Toy you speak of, Hmmm. I also have seen a Toy that does this. I brought a gift from Zany Brainy for my Friends Son's Birthday. The thing was neat! It was a Clear Ball and had a little I think, (...) (22 years ago, 25-Oct-02, to lugnet.robotics)
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