Lionel Visionline Big Boy derailing on Atlas 072 curves, what's our next step?

@MED posted:

So I looked at my JLC Big Boy from the early 2000s, assuming mechanically would be very similar to the problem Vision Line Engine. I believe the cylinder I point to in your photo is incorrectly mounted under the boiler.

Here is a pic of my engine making a right hand turn, looking at the right side of the engine. Notice that the steam cylinder pointed to by the Red Arrow and the "Lionel Cylinder" (for making the model function) pointed to by the Yellow Arrow are running parallel, and the Lionel Cylinder end appears to be affixed under the boiler - within blue circle, not coming close to the steam cylinder.

Here are a couple pics of the engine's left side at the same turn position as the right side pic. Notice that the Lionel Cylinder can barely be seen.

So I have to believe that a screw is missing, or some pin is dropped in correct hole, or??? Maybe somebody braver than I handling this big model engine can turn theirs over and get a pic of how the Lionel Cylinder is connected under the boiler.

it appears that the spring is attached to the end hole on the black pipe and the bottom hole on the yellow one.

@Engineer-Joe posted:

Well...?

That says that a good engine can do it. It doesn't say that this engine might not be the actual problem.

Yes, a good hump in the track can cause this issue. Yet, all of his other engines are fine.

I would bet something is hitting the front driver assembly, and it can't swing freely. That's just a big guess from here. That yellow paint flaking is bugging me.

Might have just been assembled incorrectly at the factory, or something is in the wrong placement. Even a missing pressure spring not putting force down on the front drivers. You really have to start from scratch. I would not rule out anything yet.

That yellow paint flake also really bothers me. We bought and installed new track, bolted down, posted our pics of our levels actually sitting dead center on the track, seems level. When I go frame by frame, seems as if the boiler hits that 4th driver wheel when it swings back in. The boiler hits those two yellow rods underneath it when it swings back in and I suspect that causing the paint flecks. There is a spring but another point has no spring, just an attachment point.  Im about to set up an oval of my old lionel tubular track, 072 curves, in my kitchen vs the atlas 0 072 curves on our trainboard, in case its my curves not being natural,  perhaps a 2/16 off.  Your comments are very much appreciated. Im a train guy forever and big time since 1990, 1991, although usually mth. Very, very frustrating. We dont know anyone in nj where we might test run this engine, unless we drive 2 hours to the hirailers in paterson, nj and ask them to test run it there.  Really wish I had more lionel experience. 40 of my other engines, many large like the triplex, the yellowstone, mostly mth, have no problem. Very Vexing.