Saturday, October 13, 2007

Connecting the motor

The motor will need to collect current from the rails via the wheels.

This aspect isn't illustrated in the instructions, presumably being considered standard procedure, but I now find myself wishing that I'd thought more about it earlier.

Because of the split-frame design, both sides of the chassis are live, so wires can in principle be led from any part of the chassis to the motor terminals.

In practice things like axles, gears and the motor itself get in the way and of course the wires should be unseen on the finished model. So I find myself with a tricky job soldering around wheels to access a small area on the top of the chassis, at the same time shielding the nearest wheel from flux and solder.

The left-hand wire is only a few mills from the wheel and the gear.

Now to connect the wires to the motor. Had to do this twice as first time the polarity was opposite to that on my converted Farish 08.

My "mid-air" soldering never looks tidy.

But it runs. The chassis trundles along comfortably at about 8-10 scale mph. Any slower and it's stop-start, but perhaps a bit of weight in the body will improve things.


Thank you to those who showed interest in this blog at the recent 2mm Scale Association AGM. I was inspired as always by the general standard of modelling on show there, but staying on-topic I took the opportunity to see Mick’s prototype model 08 running. It ran smoother and more slowly than mine, so I came home determined to match it.

I’ve cleaned off the dirty oil and gunk from the gear train and axles, polished the wheels with fine wet-and-dry paper and now on my new, flatter test-track with KPC controller the chassis plus coupling rods runs pretty well down to about 1.7 scale mph.

I still feel there’s an issue with my gears, but it looks as though it’s not going to prevent the loco running reasonably well for a first attempt. Mick has made sure that his wheels can be removed if he needs to check the gears for example - definitely something I’ll try to do if I tackle another loco.


Anonymous said...

Should run slower once you've fettled things, and some weight will help. Check that the track is dead flat, and that the wheels really are picking up all the time.

- Nigel

Anonymous said...


Your locomotive is coming along nicely! I'm glad to see that you have progressed more since painting the hood.

I was surprised to read that your chassis won't run smoothly below 8-10smph. With the apparent gear ratio and coreless motor, I would expect much better performance.

Is is a mechanical bind that creates the stop/start? One way to isolate a mechanical bind, verses a electrical continuity issue, is to hook the motor leads directly to the controller. If it runs smoothly, at super slow speeds on the controller, but not on the track, it's a continiuty issue. If it runs the same off the controller, as it does off the track, you might have some mechanical binding to sort out...
Your locomotive should run well smoothly in the 1-3smph range with the motor and gearing it has.

Good luck and keep up the good work!


Gram said...

Hello again Jeff. Hope the move went well...

After Nigel’s comment I threw away my ad-hoc test track and built a decent length of really flat track. With rails and wheels polished within an inch of their lives, gears oiled and some extra weight placed on the chassis I can get below 3 mph.

I do know there’s an issue with the gears binding. They haven't been perfect since day one, so it's never going to be an ultra-slow runner. I’ll keep working at it, but I'm not sure I can face taking it apart to look at the gears again.

Cheers, Graham