Building a General Models Pacific

1) Determine how much extra clearance is needed for the drivers to rotate freely.

2) Insert thin washers between the plate and the frame or

3) Fabricate thin gaskets to install between the plate and the frame. Possibly use gasket material, styrene or metal (brass shim).

Just a suggestion. Not sure how either would work.

MELGAR

Hmm, I could try that. Is the plate normally supposed to clamp down on the driver bearings or should it clamp down on the frame or something else?

From your description, I assumed the plate would lay flat against the frame. How much additional clearance do you think you need? You could experiment by adding some layers of paper (one at a time) until the spacing seems correct. A picture would help.

MELGAR

Is in possible the bearings have a flat side, that should be down against the plate, while the rest is in the slot.   I built an AN 4-4-0 years ago and did not have any issues like this.  

Another solution if there is not enough height for the axles is to file the top of the slot in the frame to gain a few thousandths.    And I would suggest bolting the two frame halves together and filing both sides at the same time to keep them as much the same as possible.

Doesn't look like there is a flat side to the bearings, so I don't think that's it. What I'm wondering is if the slots for the bearings in my frame aren't deep enough. I don't want to file them away until I'm sure that's the issue, though. Attached is a picture of how much the bearings stick out from the bottom.

How about several more pictures that show the situation more clearly?

MELGAR

@Johnbeere posted:

Hmm, I could try that. Is the plate normally supposed to clamp down on the driver bearings or should it clamp down on the frame or something else?

Think on the frame but looks like in your photo it's hitting the bearings.....

Yeah, it's definitely hitting the bearings on mine. Maybe someone could look at their All-Nation locomotive for me and see if it does clamp on the frame? The slots for the bearings may not be milled deep enough on my locomotive. It would be really appreciated if someone could measure how deep those slots go for them so I know for sure that's my issue.

It's hard to take pictures of this - there's not really any good angles. The last photo I posted shows the locomotive upside down, looking between the frame and plate to show how much the bearings protrude.

Please take pictures of the individual pieces looking upward from the bottom of the locomotive. I want to see the screw holes in the plate and the frame, the bearings and axles, and the slots....

MELGAR

Maybe one of these helps?

I think you may be missing some sort of spacer piece that goes between the plate and the frame. There are four holes in the mounting plate that go into the cross-members. The plate has three additional holes. For what are they used? Do the holes in the plate align with the holes in the cross-members? If the motor is mounted to the top of the plate, the plate height may be critical for proper engagement of the motor worm gear to the spur gear. It may be possible to put three washers between the plate and the cross-members. The front cross-member is at a different height and looks like it needs a longer screw. Are there drawings in the instructions?

MELGAR

Two of those additional holes are for the motor, though I'm not sure what the smallest one is for, it's threaded. That's part of what confuses me, the instructions don't show any spacers. Here's a photo of the instructions.

I was just about to post that same photo; I'm sure someone will be able to weigh in and help you with this.

Mark in Oregon

I can disassemble an A-N frame and look.  I am inclined to think that your bearings need a flat spot on the bottom.

That would be really appreciated if you can confirm that.

Something is not right. Is the frame assembled perfectly square? Do the bearings fit snugly or tightly into the frame slots? They should not be free to rotate within the frame. Your original complaint was that installing the plate caused the drivers to bind, even without fully tightening the screws. It's hard to believe that slight tightening of the four mounting screws squeezed the bearings enough to cause binding. Are there spacers in the kit?

MELGAR

As suggested by Bob2, a flat spot on the bearings (trapping them inside the plate) will keep them from rotating. That is necessary.

MELGAR

Yes, the frame is as perfectly square as I could get it - in my troubleshooting I held a straight edge to both sides and got it as close to square as possible. The bearings are a loose fit in the frame, until the plate is lightly tightened on. All the axles spin freely in their bearings - with the plate removed, and rotating the wheels by hand, the bearings aren't turning. The kit did come with two sets of two different kinds of spacers - I'm not sure what they're for, but since they're not shown or specified to be used for this purpose, I don't think they're to be used here.

My thought of what is actually happening is that the bearings might be twisting a little in the frame when the plate is tightened on them.

There are no flat spots on my bearings, so I'm inclined to think that that is probably my issue. Before I go filing away at my bearings, though, a photo proving that that's what needs to be done would be really appreciated.