Atlas GP38/GP40 Mech

[ljudice]

I was attempting to mate some Ca. 1999 or so Atlas GP40 gray trucks to a very recent Atlas GP40 frame - and found that despite the fact that there seems to be no differences - the older trucks don't sit freely inside the newer mechanism.

Is this a known problem/feature?  I actually tried two sets of trucks and two sets of mechanisms - and same problem every time.

Everything fits - but when you tighten down the screws holding the frame halves together the trucks bind (somewhat - certainly enough to cause problems)

[AVR Mark]

I have four ca1997 or so GP40s (2 CB&Q, 2 BN) that I upgraded to the newer style DCC ready frames so that they could easily run with the newer GP38s and GP40s that I bought. I replaced the Frame halves, Motors, Light Boards, and Fuel Tanks but not the drive shafts or trucks. On my units I had no problems with the old trucks on the new frames, but the old fuel tanks wouldn't properly fit on the new frames. The old motors were used to upgrade other older units. If your trucks are binding, I would suspect that there may be some flash on the frame(s) in the truck area. I compared the "old" and "new" trucks and can't see any difference. If all else fails, the old and new sideframes are easily interchangeable.

Mark

[Walkercolt]

Lou, we've done the frame swap for people at the shop for DCCing GP-40's, sometimes a swipe with a very, very fine file or a sanding stick will clean a burr off the frame. The metal part of the trucks with the holes in them, also sometimes have burrs in them that a hobby knife and a bit of patience can clear out. Actually, the holes in the trucks have given me more problems than the frames for fit and binding. Get the bright light and the magnifiers out, and you may see some "stuff" in that hole. And (GASP!!!!) I've had the same problem with a couple of new Kato's too. We're talking thousandths of inches here. I can see that much change in cutting new dies in what, 8-10 years? Not making excuses, but stuff happens.
Mark, it's possible to make the GP-40 tank fit onto the GP-38/38-2 frame with some careful Demel work (or very tedious file work). I think I remember needing to glue the GP-40 tank to the GP-38 frame using silcone sealer because it was a very loose fit, but I may have slept since then.

[ljudice]

Thanks guys, I was starting to think I was going nuts...

I did find another pair of trucks that ended up fitting perfectly, but oddly they seem of the same vintage of the ones that did not fit...

[Walkercolt]

Yeah Lou, that's "production tolerences". You take a "max" piece inside a "max" piece and it binds, or, I have an Atlas that has "minimum" pieces on it, and I can remove the trucks by turning them to the side and wiggling them(not even pulling), but they drop back in the same way. I have a bad , bad story about a brand of DCC decoder and a particular engine related to this. After several times of "letting the magic smoke out" the instructions were changed for installation and finally a new model decoder came along. Just a few hundreths of an inch....