Subject:
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Re: mechanical clutches
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Newsgroups:
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lugnet.robotics
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Date:
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Tue, 31 Aug 1999 01:05:43 GMT
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Viewed:
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697 times
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I agree that the adder/subtractor is the way to go (at least for now) if you
want any semblance of accuracy in your robots - I even started the thread on
what was the best design for the a/s (remember LDraw?) from which this
branched out. (I hope that doesn't render the original discussion a dead
thread?!) But to keep the creative juices at full charge, every avenue is
worth exploring, and this clutch system sounds like a worthwhile thing to
consider.
Dave wrote:
> It could work in theory, but I just tested it again with 2 motors that
> were grossly mismatched. Having both motors interconnected
> (electrically) did NOT cause their respective torques to match up as I
> had hoped. I think the key would be in a mechanical lockup between the
> two axles.
Yeah, I had figured you wouldn't be able to connect the motors electrically,
but I had hoped it might be able to work... Too bad we don't have a LEGO
equivalent of that handy magnetic clutch. On the other hand, we might be able
to hook up some couplers from a LEGO train set. :)
> 1) When going straight, the clutch is locked to the differential case
> preventing it from rotating and effectively locking A in step with B.
> 2) Before turning, dis-engage the clutch with Motor C, now A and B turn
> independently.
> 3) Do your turn.
> 4) Re-engage the clutch before going straight.
> 5) Go straight.
>
> Sure it ties up an extra output, but you now have synched outputs at
> will.
>
> Eh?
> Dave
Exactly. I propose putting two of those 1x4 gear racks on a 2x4 plate. Build
the clutch system so that you have two gears that end up next to each other
but are not connected. Motor C can raise and lower the plate/gear racks in
order to link/unlink the gears.
Unfortunately, though, while this will ensure that the robot will go straight,
it does not ensure that it will turn on a dime - the difference in motors
might cause some wander. It might be possible to construct a "see-saw"
mechanism in which first the gears would be linked to go straight ahead and
then they would be linked for steering. This might involve building an
inverter apparatus to cause the gears to be linked up correctly for turning.
(But I seem to be getting back to the a/s, and I want to see if this idea can
work in its own right.)
Sound reasonable?
-- Ian
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Message is in Reply To:
 | | Re: robotic rovers
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| It sounds like you guys are trying to re-invent the adder/subtractor system. Check out (URL) for some designs using this. In an adder/subtractor you have two motors, A and B. The wheels are then run through a mechanical linkage such that one wheel (...) (25 years ago, 31-Aug-99, to lugnet.robotics)
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