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I've got a King Tiger here at the moment with various issues, but the main one was a locked up sprocket.

Having found a broken fuse, I thought that might be all it was.

Having dug a little deeper, and in the process removed the tracks, I found there was an odd noise coming from the sprocket, once per revolution.

I removed the motor, and found that was nice and smooth, but the sprocket had a couple of obvious sticking points.

Next off, I removed the sprocket - which was loose on the taper lock - and then the final drive housing.

This is the state of the main drive gear:



When I first saw it, I though someone had skimmed the gear to prevent the teeth from hitting the hull.
Then I noticed the teeth were higher as well.

The reason for this groove ? Check out the cap head bolt in the centre of this picture:


It is working its way out of the motor mount and, because it is a toughened bolt, it is wearing a groove in the main drive gear.

So now I need to strip down the other side and see if the same is happening there.

When they go back in, I'll be adding some Loctite to ensure they stay in position.

Adrian.

Holy macaroni!
It is important that the motors are securely fastened from the inside as well. If they work loose, they will sag in their mounts, fouling up the gear mesh and wearing out the gears.

Wow, good to know. I’m putting together my PIII right now and it really drives home why they want loctite in other locations too.

Interesting. My tiger one does not have those screw heads and the motor mount screws themselves have lockwashers. The king tiger is a bit different in this case I’ll be interested to see if the future model has the same design. Naturally loctite should Be required here.

On a side note the teeth of the drive gears look great.