Subject:
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Re: Fishing for a tasty linkage/gearing/robotic building thread...
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Newsgroups:
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lugnet.robotics
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Date:
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Thu, 13 May 1999 13:34:33 GMT
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Original-From:
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S. Crawshaw <sc10003@eng.cam.ac^spamcake^.uk>
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Viewed:
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1619 times
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On Thu, 13 May 1999, Paul Speed wrote:
> Or third, a synchro drive constrained to a ninety degree
> throw. This is simpler than the independent wheels since it doesn't • <snip>
> The most complicated part of this will be getting the drive train
> snaked through whatever rotation assembly you have. Most of the
> synchro drives you will see examples of use the turntable pieces.
Surely the only reason there's usually complication is that the assembly
needs to be able to rotate any amount in either direction. If 0-90 degrees
is the total range, then there are lots of really simple solutions.
[This next bit is irrelevant to the 0-90 constrained synchro drive]
> I do not have any of these so I have experimented with several
> other linkages. I won't go into them here... they are an
> implementation detail.
That's a bit of an understatement - and I'd love to hear how many other
ways you found to make a synchro drive: I've only heard of one way
that doesn't use a turntable (uses a differential instead)
Incidentally, apart from Dacta and the (rather expensive) tow truck, where
else can you get turntables?
[Back on topic]
> The other hardest part is usually getting the rotation linked. With
Why link the rotation assemblies? So long as all the rotation assemblies
_eventually_ get to either 0 or 90, before the drive is engaged, then it
doesn't matter if they rotated at different speeds.
Seems to me that the only problem is if the robot drifts slightly while
the rotation assemblies are turning ...
... oops. Have spotted a flaw - if the synchro drive is constrained to
0-90 degrees, then it needs to turn *both* ways - so you would need a
second motor to drive the wheels. (OK, I accept that you could use a
mechanical solution to reverse the turn without reversing the motor *but*
then you would need sensor(s) to know when to stop the turn)
Sounds to me like you need two motors/no sensors or one motor/two sensors.
But at least you don't need a rotation sensor.
Stuart
--
Did you check the web site first?: http://www.crynwr.com/lego-robotics
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