Author Topic: Grade Crossing Gates  (Read 185 times)

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    • David's Modeling Journey
Grade Crossing Gates
« on: September 20, 2020, 07:05:17 AM »

The crossing gates I'm using I'd built for the White River & Northern IV 22 years ago; I'd kept them just in case I might find a use for them again. They may be just a tad modern for the layout's era, but ask me if I care. Note that the flashers are built on mini-phono plugs: this makes them removable from the layout to avoid damage it during construction, maintenance or cleaning. The gates operate by gravity: the arm naturally drops down; a pin that passes under the assembly engages a lever that lifts it, raising the gate.

I installed them on 15 April 2020. Just as on the WR&N IV, they plug into mini-phono jacks mounted on the layout.


Making them function was quite the challenge, due to the fact that I'm very limited as to what I can do mechanism-wise because I can't put much of anything under the layout surface: there's only a one-inch space between the base and the layout surface. I wound up installing the mechanism inside the brewery, and I actually built it twice. The first one was a large, complex linear device:

On 28 May I tore out the linear drive because I installed the turbine vents in the brewery, since the factory building for which they were originally built was removed from the layout during a building reshuffle. Also, the old drive was quite noisy. The new rotary drive (below) is a about one third the size of the linear drive, is quieter, and can be operated by a single pushbutton.

The large gear has two index pins on the underside, one twice as long as the other. The longer pin trips two microswitches simultaneously, and the shorter pin only trips one. The microswitch that's tripped twice with each rotation stops the drive at the raised and lowered positions; the microswitch that's only tripped once turns the flashers on and off, so they remain on while the gates are down. The mechanism was designed so that the lights come on a short time before the gates start to move, just as it happens in life—a bonus, as this wasn't possible with the linear drive. Another bonus is that there was room for the flasher circuit (below, center right), even with the turbine vent mechanism.

Note that I built a new slider, too: the old styrene one was in the way of the turbine vents motor. Made from brass tubing, the new one works more smoothly, and is adjustable since the levers that actuate the gates are moved by wires which can be bent, as opposed to fixed squares of styrene.