Driving axle/motor problems!!

[Ozymandias]

Is there a subtle difference in size between older Farish centre drive cogs/worm gear and newer Chinese/Bachmann drive cogs and worm gear for steam locos?

I have a number of older and newer motors (three and five pole) which work fine without the wheels attached, but as soon as I put the wheels and cover plates on they can't move at all or really struggle, causing the motor to overheat. These are mainly 0-6-0s and Prairies.

Are newer centre drive wheelset cogs marginally bigger, or are the worm drives on the new five pole motors bigger? It feels as though there's too much friction between the worm and the cog for the motor.

I've checked the coupled wheels and there are no issues with coupling rods fouling, and the quartering all seems to be fine.

I hope someone can help - I'm at a bit of a loss! 

[Dr Al]

I hope someone can help - I'm at a bit of a loss! 

It's not clear. Back in the day when I started changing out pizza cutters for the newer style wheels there were various responses on lists saying it was or wasn't possible and the gears wouldn't necessarily mesh. It turns out I've never had trouble and it all appears backwards compatable - the gears appear to be the same pitch and diameter. I've never done this for early 3 pole stuff, only later 5 pole though.

However, there's no reason they shouldn't fit the 3 poles either. What may be the issue is a fractionally larger axle diameter - it's feasible that if this is the case then attaching the baseplate could lock the whole thing up, or make it stiff at any rate. Try loosening the baseplate screws and see if that helps.

Other than that, look at the pickups - these are very stiff on old early 3 pole Farish models and can put a lot of drag onto the wheels if not carefully adjusted.

Cheers,
Alan