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R1122 B12 4-6-0 motor worm loose


CDRC

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Hi,

I have acquired a R1122 LNER B12. The loco wasn’t running although there is the sound of the motor running. On removing the body I discovered the worm was loose on the spindle of the motor shaft although the motor itself was turning. (the motor is the X8777SK) When I removed the body I found the previous owner had placed 2 washers under the screw at the rear of the motor that holds it on the chassis. This was to raise the rear of the motor and had the effect of pushing the front of the motor where the worm is into the drive gear? I removed these and tried to seat the motor back at its proper angle, needless to say this didn’t work as it jams the worm further into the gear wheel locking it solid. The worm is loose on its spindle, I have tried finding a replacement X8777SK but to no avail. Does any of you fine folk have…….

1) any ideas how I can fix the worm to the spindle, permanently.

2) why the wheel gear locks (the wheels run smoothly when the motor is removed, I thought it might be a quartering issue)

3) A replacement motor that will fit the B12 instead of the X8777SK

i have photos if it would help

Thanks

Charles

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The two washers inserted under the rear end of the motor carrier would indeed increase the pressure of the worm on the wormwheel and their removal should therefore increase the gap between them rather than press them tighter together.

I am wondering whether the teeth on the wormwheel have been worn away by the worm which is the more normal damage encountered and this prompted the previous owner to add the washers to restore meshing but at the same time has caused the splines on the motor shaft to eat away the bore of the worm thereby loosening it on the shaft.

A new motor/worm/carrier assembly is available in pack X8809M but if you also need the wormwheel, it was included in pack X8199 but this seems almost impossible to find at the moment.


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Thanks Going Spare,

I think your right about the pressure. Is the wormwheel the cog that meshes with the worn and is connected to the axle?

I’ve re-examined the worm itself and it doesn’t seem to be worn but it is difficult to assess without having one to compare it with. I’ll have a look at the X8809M and take it from there.

I was hoping I could find a complete replacement motor but if the axle cog/wormwheel is worn it would be a bit fruitless replacing it.

thanks

Charles

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Yes, the wormwheel is the 'gear' mounted on the driven axle and meshes with the worm on the motor shaft. The teeth on the wormwheel often wear to a concave shape with a pronounced dip in the centre of each tooth or with a definite angle across the teeth if the wormwheel is not positioned on the axle directly below the motor shaft - i.e. slightly offset to one side. While wear to the worm is not unknown - it is essential that the worm is positioned on the motor shaft such that it meshes smoothly with the wormwheel teeth - damaged teeth on the wormwheel are more common in my experience.

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