Subject:
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Re: 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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Wed, 20 Mar 2002 00:16:46 GMT
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Viewed:
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1899 times
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In lugnet.technic, Miguel Agullo writes:
> 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!
Excellent color coding in your pics. Regrettably, I have no practical
advice. When I built the differential drive in Dave Baum's book, I was
dumbfounded by the principle. I look forward to to seeing what is clearly a
demanding project.
- Kyle
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