Peter, just reread your message. Dave Goodson solved the problem with the center drivers dropping off the track on sharpe curves.
"I've seen it, where the center driver drops off the rails on a curve, and read about it numerous times by others.
So, last night's operating sesion, I decided to drag mine out and run it.
Today, after all the other things I had to do, I decided to tear it down and fix it.
First, I grabbed my big framing square, popped the temp shims out, depressed the lead driver axle down, and checked down all three axles on one side.
I checked the running board angle, still angled up, even without the shims in place (center of board to benchwork with loco on rails).
Then, I flipped the loco over, pulled the bottom cover on #2 and #3 axles, removed the crankpin bolts on #3 axle, and pulled #3 axle out of the chassis.
Then I inspected it.
First, I noticed the top (top being away from the part that contacts the rails) of the journal has a small pin that sits into a hole in the top of the frame.
Okay, now we're oriented.
Pulled the driver caps, screws, and pulled the wheels off (this is a good time to check your back-to-back for G1MRA 1.575" and install washers between driver stubs and contact drum) and looked at the journal boxes.
I pulled the boxes, held them together, with one pin up, one down, and there is about .040" offset in the bearings.
So, I re-assembled the journals and drivers (look at the boxes...there is a "flat" side and a "humped" side...."hump" to driver....keeps the drivers from rubbing on the frame) and dropped the assembly back into the frame with the pins facing out of the chassis.
Put it all back together and on the track, running board is dead level, and center driver......I can just see light between it and rail.
You can tell how yours is put together without taking anything apart.
Rotate the drivers so you can see through the spokes of #3 driver (either side) at the bottom of the journal box.
You will always see a round peg just forward of the centerline, about 1/8" o.d., and a similar square peg just aft of the centerline.
If yours is put together with the pin down (high cab) the pin will just be visible between the square and round pegs."
I was still confused and asked ave for clarification.
"I had to double-check.
Yes, if you have 3 pins in a row, NOT counting the narrow supports at the
very edge of the journal box, you're fine.
iII Ii correct looks like that, with the "i" being the narrow supports at
iI Ii is incorrect.