Ok, I know what folk are thinking. A self uncoupling wagon? We have all got one of those, a wagon which uncouples in the middle of a train at the most inconvenient part of the layout when folk are watching for no apparent reason. Indeed I have had a few over the years.

Ah, but how about a wagon which uncouples where you want it to when you want it? Anywhere, not just at a specific point. Could be a fun idea.

The starting point for this was me looking at bits direct from China on ebay. I found these tiny six channel transceiver modules,  4 pounds a pair. Couldn’t resist, bought some and had a play with them over christmas, decided that they worked and then wondered what to actually do with them.

Which got me thinking about a self uncoupling wagon. Some pics of progress so far.

Basic frame soldered up from brass and copperclad.

A coat of primer, some internal assembly.

The mechanism is basically a duff servo. The usual failure mode for servos is dead driver board or feedback potentiometer wear causing excessive jitter. At which point they get chucked in a box labelled duff servos. However it is still a motor and gearbox with lots of torque. Remove the driver and add a couple of microswitches and diodes and it becomes  a mechanism that moves from a to b when you reverse polarity , and uses almost no power when it isn’t moving, unlike a conventionally driven servo. When not moving it takes just the reverse leakage of the diodes . (typically < 5 microamp) Works down to about 3V , useful if you are running the lot with 3 aaa cells.

This is the circuit. The trailing wires in the pic will be for body leds via magnetic contacts.

I am thinking about the body. Some sort of road van, brake compartment one end, the rest a van covering the mechanism. Silhouette time.