I wanted a class 31 to haul the small goods train. So finding a new one on ebay with fitted sound decoder led me to purchase it.
Unfortunately, the model arrived with a drivetrain fault. A cracked axle gear meant the mechanism jams after one full turn of the drivewheels. This can be diagnosed easily:
- Remove both bogies and use wires to power the body. Check the motor runs OK.
- Replace one bogie at a time, to find which bogie causes the mechanism to jam.
- Remove the bogie causing the problem and turn the driving wheels by hand. In my case, one of the wheels could be turned continuously; the other would only turn one full turn. It is the opposite one (which when turned by hand rotes OK) that has the fault.
- Look carefully at the gear on the axle. There will be one of the gaps between teeth appears slightly too large; and it won't allow the gear to mesh with the driving gear.I was able to use a scalpel to expand the gap between teeth to prove this was the problem.
The fix is simple: order a replacement axle with gear and wheels. The axles are held in place by a removable "base" under the axles; this also holds the bogie sideframes. There is a clip at each end. With that open, the affected wheel can be snapped out and removed.