Subject:
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Re: Rack spacing problem
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Newsgroups:
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lugnet.technic
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Date:
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Mon, 6 Nov 2000 18:17:25 GMT
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Viewed:
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932 times
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I've done this lots of times, but I don't know if I have any pictures. It
takes some fiddling to get these to mesh smoothly. One trick you can use is
to lug connect beams at right angles to your assembly. This lets you use the
spacing difference between the height and the length of the Lego units,
which has units of the 1/2 plate which you want. First find the spacing any
ugly way you can, and then go back and make it elegant.
I made a microscope stage device with tightly meshed racks and worms, and a
snug, highly reduced gear train. The resolution of the stage was a fraction
of a millimeter. I mounted a paper card on it, and I mounted a ballpoint pen
above the card. When it stepped through its full range, the pen colored in a
perfect square of solid ink. Everything was as strong as possible,
cross-lugged everywhere, to help improve its precision. When I let it sit
for a while drawing, it over-ran the stage, and it literally exploded,
sending parts all the way across the room.
In lugnet.technic, Jack Gregory writes:
> I have a technic problem that I would like to put out for advice. I am
> trying to drive a sliding "carriage" via a 24t gear over a rack. Something
> like this:
>
> worm ---- motor
> 24t gear
> rack
>
> That is, the motor drive the worm overhead. The worm engages the 24t gear
> (which drives a differential, but that is not part of the problem). Now I
> want this entire upper assembly to move linearly. So I put a rack below it.
>
> The problem is that I can't get the rack and gear to mesh at the proper
> spacing. It seems like it is 1/2 plate thickness off. How can I get that
> proper spacing?
>
> As a side problem, the spacing is also a function of the sliding parts
> contact. That is, whatever the solution is, it has to allow the upper
> assemly to slide over the fixed assembly for at least one rack length (about
> an inch).
>
> I am open to other ideas for a linear drive, but I need the gear-down
> inherent in the worm. Any ideas or pointers appreciated.
>
> --Jack Gregory
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Message is in Reply To:
 | | Rack spacing problem
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| I have a technic problem that I would like to put out for advice. I am trying to drive a sliding "carriage" via a 24t gear over a rack. Something like this: worm ---- motor 24t gear rack That is, the motor drive the worm overhead. The worm engages (...) (24 years ago, 6-Nov-00, to lugnet.technic)
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