mickoo
Western Thunderer
You're too kind,Where's the "We are not worthy" smiley..??
Ah, here it is....
It won't take much to adjust the under frame to suit the F7/F9 model either, the drag box would have to go at either end and the cast box section added. The F7/F9 is a full flat floor chassis so you'd need to get rid of the fish belly side frames and put the bigger longer and flatter box section in and then add all the cross braces.....because you can You may also need to jack the floor up a little so that it sits up inside the body shell a bit.
There are no convenient chassis to shell fixings so two new bulkheads will need to be added with flanged bases to hold the securing nuts to fix the chassis to. Whilst you're at it you mat as well etch up a new cab section, floor, front and rear bulkheads to hold your 3D printed control stands and other details.
You could leave a small depressed section in the middle for the motor mount and you could move the above floor side walls out quite a bit, probably not all the way to the side as the middle fixing plates for DCC and speaker become too wide.
You'd have to change the profile of the footplate up front for the nose curvature.
Once you have that then you have the basis for the CF7 when you square off the front footplate back to the GP-9 profile, not sure if the CF-7 has the same style drag boxes and pilot support plate behind with gussets, I suspect it might have. You'd also need to add the outer frame rails with the dropped centers, I'm fairly sure the rest of the floor remained fully flat though they may have dropped the engine center line to make it more like a GP-9.
It's a hard call to either go GP-9 to F9 then CF-7 or GP-9 to CF-7 then F9. I'm sure the latter would be many peoples preference but it might not be the most practical or time/energy efficient way.
This is a FT underframe, I'd be looking at something like this, except there would be bleedin great big holes for the model trucks to fit in. The FT differs in the rear draw bar was a solid link so the drag box is vastly simplified, later F units could be broken up so the drag box was modified like the front casting to take a buckeye. Note the big hole toward the rear for the 567 engine, there's no floor here yet so I wonder is a thin skin was added later or the FT engine sump was exposed to the underside of the engine all the time?
Copyright EMD archives.
I'm sure y'all can work out where I'll probably be heading with the next spin off chassis next weekend