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   Construction Notes for Railroad Crossing Gates, by Christopher Philips
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Not shown in these instructions is a single white o-ring style rubber band
that goes from the pulley on the micro-motor to the one on the 4-stud axle.

Also not shown is the 9V electrical connector that must be attached to the
back of the micro-motor.

The grey pulley-gears shown here may not be correct.  (I must be using an
old set of .DAT files.)  You can use either the smooth or the crown-style
small 1/2 bush on the axle.  I prefer the smooth one, but couldn't find the
right .DAT file for that.  I'm also not sure if I used the right .DAT for
the gear on the motor itself, but it was the closest thing I could find.

Build these gates in pairs, one for each side of the tracks.

One way to reverse the polarity of a micro-motor is to remove the electrical
connector, remove the motor from its base clip, flip it 180 degrees and
put everything back together.  It makes your life easier if you ensure that
all your gates have the same polarity when you are building a lot of them.

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Coming soon:
+  Building instructions for flashing-lighted "railroad crossing" signpost.
+  Use a reed switch and an RCX to detect oncoming trains and drop the gates.

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