Pick ups, a cautionary tail!
I have started building another locomotive to use on the club layout – Lakebank. This is a Jinty which is being made from a 3mm Society/ J M Models etched brass kit.
The chassis is compensated with a fixed rear axle. Drive is from a Mashima motor mated to a Branchlines 38:1 gearbox. I set the motor and gearbox up and had it running well. The chassis was soldered up on a jig using the coupling rods as guides. Using a set of Romford wheels the chassis ran freely. I then put on the Finescale wheels and gearbox, but without the final gear glued to the axle. After a bit of adjustments to the quartering and a touch of lubricant to the horn guides the wheels were running freely. I then glued the gear wheel and attached fly leads to the motor. On the test bed the chassis went well in both directions. I thought I had cracked it.
I then added the pick ups from .33mm phosphor bronze wire and wired it all up. Trying it on the test track I found it would go fine in one direction but the gear box seemed to jam in the other direction. Two hours and many minor adjustments later it was still the same!! Time to sleep on it…….
The next day I got out Iain Rice’s book on chassis building and reading the section on pick ups I realised my mistake. I had put short pick up wires rubbing on the back of the wheels. This was putting too much pressure on the wheels stopping the compensation functioning properly and causing the chassis to lock up. Putting on proper Bus bars with long pick up wires attached and bearing lightly on the flanges solved the problem and hey presto the chassis runs well in both directions. I have used short wires before with no problem but that was on a non compensated chassis.
The moral of the story? Consult the experts, they seem to know how to do it correctly!