Hello, I thought I might save somebody 3 hours of work by sharing my Hornby Q1 engine "shorting mystery". This was a near mint condition locomotive I'd bought at auction and was around 10 years old. It intermittently shorted when placed on the track - which it did 95% of the time, going a few further prototypical feet if you jiggled it, before shorting again. To cut a very long story short, I found that the problem was the middle gear pin (or axle) was made of steel and had slid out of it's chassis bearing and was touching the wheel. It was doing this because there was a crack in the middle of the gear wheel that was invisible to the naked eye and needed an eye glass to see it. So a cracked gear wheel led to a gear pin sliding out of the chassis touching a wheel which shorted the loco. This is not the first time I have seen cracked gear wheels on little used Chinese built Hornby locos. Something to look out...with an eyeglass! This is my first time at fully disassembling a modern Hornby loco as I am still largely stuck in the Tri-ang, Lima, Wrenn Era and I must say that although it was daunting, it proved possible using the same old skills of patience and attention to detail. So don't be put off fixing these yourself