Perplexing older GP-40 derailment problem

[Slomopiot]

I have a new-old-stock Bachmann GP-40 that has a perplexing problem with the powered rear truck assembly. I inherited this unit from my dad and it looks like it's either never ran or has been run only a few times. I ran for a minute and then it lost drive to the wheels on the back/powered truck. I took it apart and there was a lot of lubrication oil on the entire drive shaft assembly. It took several cleanings until it would stay together; but now I have a new problem: the front axle of the drive truck seems to be slightly higher than the rear axle and the engine constantly derails. I tried taking it apart and reassembling it. If I get it loose enough that it sits level, when I stop the engine, the rear axle on the drive truck almost always derails to the right. If I tighten up the assembly to where the truck sits level, it's too stiff to navigate the curves. If I run the engine in reverse, where the powered truck is leading, the engine runs fine with no derailments. Any idea what I've done wrong and/or can remedy the problem ? Should I try replacing the entire drive truck assembly ?

[rich1998]

I am assuming it has the motor in the center with a drive shaft to both geared ends.
The diagram is in a page under Parts, Service and Information.
I have a couple other brands of diesels made about the same way. Careful assembly is important. I had stripped both for grinding the chassis some.
The 44 ton and 70 ton are smaller but similar.

Rich

[Slomopiot]

Rich,

I looked at the online diagram after someone in another forum mentioned it and discovered something odd: mine is not an all wheel drive unit ! There's space for a driveshaft in the front but the motor doesn't even have a connector on the motor shaft for one and there's no gearbox in the front truck assembly. I located the paperwork that came with the engine and the diagram has it as a single-truck drive also. This was part of a set distributed by "Great Planes Model Distributors Company" that had a powered GP-40, a GP-40 dummy and a caboose. So now I wonder if Bachmann made single-drive units just for these sets ?

I am now considering replacing what's in there with a new motor & powered trucks set - there's room in the body for them.

[rich1998]

That sounds like a pancake motor in one end. No gears in the other end. Real old type drive.
You have to set up everything carefully for it to run ok.

The steamers use to come like that. Noisy all metal gears. I still have one. A Plymouth 0-6-0.
I gave two 0-6-0's away away.

Good luck.

The proper diagram should help you.

Bachmann started out with Pancake motor years ago. Single motor. Someone here can gine you more on Bachmann history. Even Google can tell you a lot.

Rich

[Slomopiot]

Rich,

I don't know if it's a pancake motor per se . . . but it's a different one from the one shown on Bachmann's parts diagram for the 'regular' GP-40. (Unfortunately I can't seem to figure out how to get attachments down to the limit of 128k here so I can't post scans of both diagrams for comparison.)

I think I'll give the Bachmann Service Department a call Monday and see what they say.

For what it's worth, this set was sold by a 3rd party "Great Planes Model Distributors" which is apparently now owned by a company "Horizon Hobby". Both are mostly RC airplane companies but I did manage to track down an old phone # that Horizon had for 'train questions'. The main thing I'm curious about is when these sets were sold; but it's like tracking down something that was made for Sears 30 years ago. . . .

Charlie

[rich1998]

All forums you need a photo hosting site like photo bucket to post photos. Here and other forums like trains.com forums.
What many call the pancake motor is a complete assembly with the wheels on one end.
If you scroll down a few forums, look for General Questions. A dated forum.
There are other photo hosting sites.

Rich

[jward]

You said this locomotive has a drive shaft from the motor to the truck. Pancake motored units have the motor mounted on the truck itself. There is no drive shaft. On this locomotive are the trucks held in place by a pin that slides through a hole in both the truck and the chassis?

[rich1998]

Wow. The photo you sent me shows a motor in the center. Probably no gears on one end but I see the worm above the truck, Really strange. I doubt Bachmann would ever do that or a custom job. That other end must have had gears at one time. Looks strange to see a worm hanging there.
Did you check the truck for gears?

Rich

[rich1998]

I Googled the company, Wikipedia says they only made model planes. I did not look any further.

Rich

[rich1998]

I am wondering if Bachmann would replace it with a dual geared loco?
They did for a 44 ton of minne with a cracked gear and a check.
Call the Parts department. Look at the Parts page for replacement policy unless it has sentimental value.
Maybe they can repair it if gears were ever in the truck.

Rich

[rich1998]

Possibly cracked gear and previous owner stripped gears out of truck. That does make sense.

Rich

[rich1998]

Did you ever get it to run decently?

Rich

[Slomopiot]

Possibly cracked gear and previous owner stripped gears out of truck. That does make sense.

Rich

I doubt it. The likely scenario was that my dad bought it and he wouldn't have even ran it much less taken the shell off. When I first took it out of the box, I looked at the wheels and there wasn't a spot on them.

Another possibility is that by virtue of it not being AWD, it's simply a defective unit via a production issue.

No, the only time it will stay on the track is if I run it in reverse with the powered truck leading . . .

[Slomopiot]

On this locomotive are the trucks held in place by a pin that slides through a hole in both the truck and the chassis?

No; the trucks are held in place by a screw that goes through the top part of the body into a circular plastic piece that attaches with two screws to the truck body. The plastic piece is circular also and so it swivels within the body above the trucks. If I tighten the screw too much, the truck assembly is too stiff, doesn't travel/steer adequately through the curves and derails. If the screw is too loose, the rear axle of the rear (and only drive) truck kicks out to the right when both starting and stopping the loco. I cannot seem to find the 'sweet spot' adjustment.

[rich1998]

Yes. Powered truck leading makes sense.
I thought I saw a worm above the un-powered truck is why I said look at the truck and see if any gears might have been in the truck at one time.

Bachmann says for $35.00 they will send you a replacement non DCC HO loco in return. Check the Parts, Service and Information page. You could get a DC loco, Call first. All the info is on that page. You have nothing to lose. Many miss that page.

I did that with a two motor HO 44 ton that I converted to DCC. It cracked a gear. I put all the parts back in and it still ran on DC. Sent a check and Bachmann sent a HO single motor 44 ton.

Rich