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Friday, 11 August 2017

Project 17 - 3 more cassettes and a conundrum

Three more fiddle yard cassettes have been made for the station end of the loco yard. All now working. But here is the rub. I must have spent an hour trying to understand an electrical fault.

As I drove an engine off the scenic module onto one of the cassette roads it ground to a halt. A short circuit was quickly realised but the cause was proving difficult to trace. No visual signs of a short and the wiring looked correct. I disconnected the wiring to the offending section and to my amazement the meter still showed an electrical connection. How can this be with no wires connected and no other signs of a short circuit?

After much faffing around I happened to put the meter probes between the isolated rail and the track ballast and the meter showed a connection! What seems to have happened is the ballast was touching a live rail and the copper clad sleeper of the isolated section  Scrapping away the ballast from the copper clad sleeper cured the problem. Something in the ballast was conductive!

The ballast comprises a mix of Woodland Scenics grey ballast, ground up coal and ground up cork all fixed in place with a weak mix of PVA glue (dried). My thoughts turned to the coal being the culprit since it contains carbon but I read carbon in coal exists in hydrocarbon compounds that don’t conduct electricity.

So, there is the conundrum.

To explain the photo:

Left cassette - Temporarily connected to Scenic Module; represents the road to Swanage Goods Yard.

Middle Cassette - Parked; connects to the Loco Yard.

Right Cassette - Parked; represents No.1 and No 2. roads to Swanage Station.

These cassettes are not interchangeable because the tracks exiting the scenic module are not all parallel with each other.

To Part 26

To Part 1.

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