Chapter 2. Busloads of Nonsense
The trains aspect of the Postage Stamp Central is dirt simple: one train running laps. End of story. But the bus system I devised was a whole other ball of wax: two buses running in opposite directions, alternately parking at the station. This was not going to be a trivial bit of nonsense to pull off.
The problem is that there's no off-the-shelf solution—Faller never made any detectors for the bus system, so I had to make them myself. Each detector triggers a relay to de-energize the track with the arriving bus, and energize the opposite track. Incidentally, the bus track polarity won't need to change when the swap takes place; one of the buses will have its motor flipped so it'll run in the other direction—a much simpler solution.
Then there's the grade crossing: when the train—which is always running counter-clockwise—hits the "stop trigger," it kills the bus track power in the "stop zone" corresponding to the direction of the approaching bus (the crossing itself is always energized so the bus doesn't stall on the railroad tracks). After the train passes, it hits the "resume trigger," which restores bus track power. It sounds like an awful lot of work for a silly little project, but what's a project worth if it doesn't offer some sort of challenge?
Here's a finished homemade bus trigger. It's simply a piece of thin music wire bent into the shape of a staple and inserted into two small holes drilled into the track. The trip wire is very slightly higher than the rail so the bus pickup shoe is sure to make contact with it. In order to prevent a bus from stalling on it, the relay system will energize the trip wire the instant it's hit, which will cause the bus to coast past it. The entire system is controlled by two Trix relays—one for the bus swap, and one for the grade crossing.
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