B12 drive gear worn - how to replace

[Will-360191]

Hi all, very new to model railways. I bought a second hand Mainline Steam set and everything is on good condition visually, but the drive gear on the B12 loco is work to the point it's not catching the motor.

Is there a way to replace this? And if so, is there a guide or video guide online I can use? I'm struggling to find anything.

Thanks,

Will

[Fazy]

Peter spares do parts for the old Mainline models. Might be worth checking them out. They have their own website and are also on eBay. But not everything is shown on eBay. If you can’t find it might need to phone them up.

[Going Spare]

The B12 loco in this China-made set was first introduced way back in 1963 and, as a result, the chassis is not so easy to work on as more modern designs because the driving wheel axles pass through the main chassis block.

The replacement gear you need is included in parts pack X8199 and an exploded diagram of the chassis is shown on Service Sheet 218C which can be viewed and downloaded via the Support drop-down menu, selecting Product Support, Service Sheets, Hornby.

To replace the gear you will need to release the motor assembly from the chassis then remove the coupling rod bolts from the front driving wheels, ideally using a R913 spanner which fits the hexagonal bolt head. Then it will be necessary to remove one wheel from the axle so that the remaining wheel and axle can be slid out of the chassis to release the existing gear and fit the new one. Reconstruction is the reverse of this procedure but you may find it advisable to remove the plastic chassis bottom plate and pick-ups to avoid the latter getting trapped or mis-shaped as the wheels are replaced.

When refitting the wheel on the axle, make sure the position of the coupling rod bolt hole is exactly in line with those on the other two wheels on that side of the loco and, in both the removal and refitting of the wheel, do not twist it on the axle as the splines on the axle can damage the plastic wheel boss leading to an insecure fit.

[Will-360191]

Thank you so much for the detailed description! I'm going to order the spare and the correct tool and have a go.