Subject:
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How much can you shrink a dual differential drive?
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Newsgroups:
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lugnet.technic, lugnet.robotics
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Date:
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Tue, 19 Mar 2002 23:40:10 GMT
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Viewed:
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3367 times
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Hi all,
I've got an intriguing little MOC coming up that hopefully will interest
both the technicheads and the robogeeks. It is a tracked vehicle with a
twist, but you'll have to wait to learn all the details ;-)
In the meantime, here is something I could use some help on. For precise
operation, I'm using a dual differential drive as described by the Ferrari
brothers in their book. My setup is farily different from theirs, mostly
because I need to save space. I've uploaded to brickshelf 2 dats and 4 POV
jpegs of how it looks right now. You might want to take a look.
http://www.brickshelf.com/cgi-bin/gallery.cgi?f=13856
(For those of you who, like me 4 months ago, don't know what a double
differential drive does, it's a mechanism that mechanically links 2 motors
to an axle so that one motor rotates both wheels on the ends of the axle in
the same direction and the other motor rotates them in opposite directions.
In practice, this means that a vehicle fitted with this drive will go in a
stright line if one of the motors is used or rotate in place if the other is
activated. If both motors are activated, rotation still occurs.)
So, a couple of things about my design. First, it's meant to be as small as
possible. Second, the two input axles (yellow and green in the jpegs) rotate
the output axle (blue) at different speeds - the green one uses a double
bevel 20 tooth gear/24 gear crown combination for reduction, the yellow one
a 8/24 tooth combination. I have not attached motors to this drive, but
nothing seems to break or even creak when I rotate the axles with my fingers
in any direction simultaneaously.
Anybody can come up with a more compact design? Can anybody solve the dual
speed issue? I could add studs in width (distance between wheels) and one
stud in height to what already rises above the wheel axle (and maybe another
stud below). Height is critical, but losing some length is even more so.
OK, I hope you enjoy it and come up with some ideas.
Chao for now!
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