Subject:
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Re: Motorized Railroad Crossing Lift-Gate Plans
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Newsgroups:
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lugnet.trains
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Date:
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Mon, 26 Feb 2001 17:20:32 GMT
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Viewed:
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720 times
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In lugnet.trains, Brad Hamilton writes:
> I've been trying to build a dual one (i.e. a gate on each side of the
> rails), but I keep having trouble keeping the sides in synch.
>
> If I use two motors, they seem to turn at slightly different rates so the
> gates don't line up after a while.
>
> I tried to use one motor with an axel going under the tracks to drive the
> other gate, but the gearing leading to the second gate uses up a bit of
> travel so the second gate always lags behind the first and can't travel far
> enough.
>
> The rich man's solution would be to hook up a mindstorms unit with 2
> rotation sensors and 2 motors and have them independently raise and lower
> (i.e. you would have one sensor trigger both, but they would be running
> separate software threads). Unfortunately, that's big money!
>
> Have you ever attempted to syncrhonize two of these gates?
I have synchronized a pair of these gates, and it is much easier to do than
you might imagine. The drive train in my design uses a rubber-band, which
allows slippage when the gates reach their limits of motion. The rather odd
assortment of parts that I used to build the gate was selected to stop the
gate when it reaches a horizontal or vertical position.
I simply constructed two identical lift-gates and powered them off the same
motor output from an RCX. They raised and lowered essentially in sync,
because it takes them such a short amount of time to move. The clutch
action of the rubber band resets the drive train tension at each stop, so
the gates never really get out of step with each other. In practice, this
worked perfectly. Much better than I would possibly have dared to hope.
(Others who saw the NELUG train layout with their own eyes should feel free
to corroborate my biased testimony.)
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Message is in Reply To:
 | | Re: Motorized Railroad Crossing Lift-Gate Plans
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| I've been trying to build a dual one (i.e. a gate on each side of the rails), but I keep having trouble keeping the sides in synch. If I use two motors, they seem to turn at slightly different rates so the gates don't line up after a while. I tried (...) (24 years ago, 25-Feb-01, to lugnet.trains)
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