Subject:
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Re: Backlash in Lego Gear Trains
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Newsgroups:
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lugnet.technic
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Date:
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Tue, 9 Jan 2001 01:20:47 GMT
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Viewed:
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1068 times
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In lugnet.technic, Derek Raycraft writes:
> The way to eliminate backlash it to find a way to maintain a constant torque on
> the drive train in one direction only. This way the gears only run off one
> side of the teeth. The slop in the gear train is caused when the teeth switch
> contact from one side to the other. If you can maintain contact to one side
> only then the backlash will be greatly reduced.
If you are building a scanning thing, this works really well. I built a
camera that used the Lego light sensor, and I would get zig-zags between
scan lines. I changed the software to wind it all the way back and scan from
the same direction every time instead of back and forth, and the problem was
gone.
I have also used closed-loop systems. You can do some pretty sensitive
measurements with the light sensor, and use that for feedback.
The brute-force method for positioners is to use gear reduction and worms
meshed with racks. I made a 2-axis stage that could always hit a position
within about a mil. I made a tiny little plotter that could perfectly fill
regions with a ball point pen, but it only had a working area of about a
square inch. Everything was as tight as possible, and I built it like a
tank, with beams cross-pegged at every possible point. I accidentally
over-drove the stage, and it literally exploded, sending parts all over the
room.
What is your application? Do you need linear positioning or rotational
positioning? What sort of load?
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Message is in Reply To:
 | | Re: Backlash in Lego Gear Trains
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| If you working on a Mindstorms project, then measure your position as close to the output of your gear train as possible. This will eliminate the effect of backlash on your positioning. However if the gear train is expected to hold the final (...) (24 years ago, 8-Jan-01, to lugnet.technic)
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