Alaska GP40-2

Model Railroader General Discussion (Model Railroader)
1

Hi all,

I have a new HO Athearn RTR Alaska GP40-2 that I got off of eBay at a descent price a while ago.

It runs well but sometimes slows just a bit and gives a quick high pictched whine.

It does this for 2 or 3 seconds then returns to normal operation.

I have taken the whole thing apart thinking maybe some ballast got up into the gearing, but this is not the case.

It seems to something too tight with the flywheels, armature or something, but I can not find out.

Any of you had this problem before?

2

I have an Atlas N MP15 doing the samething. It ran fine this summer but in my cold basement now, it is doing the same. I think it needs to be lubricated but I need to find a lightweight lubricant that works well in the cold (40 - 50) degree range. Oils are just too heavy and sticky in the cold.

Hope we get more input.

Peter

3

Check the metal spring that electrically connects the elecrical pickup on the trucks with the top of the motor. If this spring gets slightly bent out of shape it can rub against one (sometimes both) of the flywheel and can make a squeaking/squealling sound.

I think the slowing may be a different problem. Check the cleanliness of your rails and the wheels on your loco (yeah, I know you said it was “new” check them anyhow, you might be surprised) [;)]. Also, check all of the metal conductor parts of your loco for signs of rust or dirt.

Sorry, I know nothing about N scale locos.

-George

4

OK, I have the body off and the the metal conducting strip is not interferring.

Wheels are definately clean.

It slows at the same time for the 2-3 seconds same duration as the whine.

I’m pretty sure it has to do with the motor itself being out of spec.

And it is HO scale.

5

Does this happen on a curve, perhaps a tight one?

-George

6

George,

No it does not happen on a curve, it happens totally at random, going up a grade, down a grade and on the straight and level.

It’s very perplexing!

7

I would suspect that the motor bushings are dry and in need of lubrication. Also check that there is some end play on the motor shaft as well. Any light plastic compatible oil should do the job. I prefer Labell.

If a lighter oil is needed, as mentioed above (running in extreme cold) use automatic trans fluid instead.

8

Try running it without the shell on and see what happens.

-George

9

OK, I figured it out!!!

Remember this is my HO Athearn RTR Alaska GP40-2

It turns out to be an out of spec motor.

It also happens to be the problem that I thought at first.

I will try to explain.

I took off the shell, placed leads from my test track to the loco’s coupler screw and the other lead to the wiring harness (not a real harness).

When running the motor I pushed the front flywheel, with a small screwdriver so the motor will keep turning freely, to slide the whole armature towards the back.

The brushes seem to be freed up. If I let go and let the motor pushed forward, the cummutator (goldpart on the armature) must have a bit of a fan out shape, and causes the noise and subsequent slow down. But only on ocassions.

So this is how I fixed it.

I removed the the motor and put two ends of a cotton swab in the whole of the front flywheel to take up the slack with the axle coupling, hence pushing back the armature and motor to the sweet spot.

I did have go back and take a little cotton out so the front wheel assembly had the correct amount of play in it.

I did try shortening the brush springs to no evail.

I do not know much about N scale, but you might give it a try.