Friday, March 13, 2009

My First Easy Trolley Design

Today, I baby-sat three 1-1/2 hour high school classes. They were good, but had no work
to do on the day before spring break. So, while they talked and played games, I spent a
lot of time drawing and figuring.

I have come up with a simple demo loop for an N-scale traction line on a module with 'normal' TTrak tracks. The loop has a passing siding along one side. From the beginning, I had planned for the loop to run under the main lines.
To fit it on a standard-size double module (24" long x 12" deep) some games had to be played.
Rough sketches were encouraging, so I made a measured drawing today. The main lines will be relocated approximately 1-5/8" towards the rear. So, the module itself will extend this far forward of 'normal' modules.

The loop uses very small 4" (103mm) radius curves. One long side of the loop is out
front, and the other with the passing siding is 'hidden' around back. The scheme is for the loop to run through a couple of tunnel portals in a stone wall. Between the portals, in the wall, under the main lines, are to be a couple of shops and a small parking lot. The trackage will appear to run down the middle of the street in front of the stores.

I asked on the Yahoo N Traction group, and the small Tomix turnouts (all the loop trackage is Tomix) will work fine as spring switches right out of the package. By using them this way, anything running CW will always take one siding, that running CCW will take the other.

I want it to have two trams, different colors, clearly different. Then, from the front, one will appear, run R-to-L and disappear. Then the other will run L-to-R. They will alternate. With the passing siding hidden, it should be entertaining, eh?

The controls for something like this are trivial. I plan to put a diode in each tram, in series with the motor. That will make it run only one way. By facing the trams in opposite directions, and flipping track polarity (a relay, or an H-chip) the trams will take turns. A simple sensor in each passing siding detects when a tram 'arrives' in its siding and flips the power.

Simple, yes? Imagine someone walking up, seeing one run past and expecting to see it
again when the other shows in the opposite direction.
I'll probably order the track over the weekend. This should be a very fun module.

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