I'll be the first to admit very legit question I'll go through the logic here, which also explains how this thing can take so long to get built.
OK, basically the Atlas GP7 chassis is exactly one foot too long in the wheelbase. CF7 is 30' centers, GP7 is 31'. The overall GP7 is seriously a lot longer:
http://research.nprha.org/Diesel%20Diagrams/EMD%20GP-7%20569.jpgMy old scratchbuilt CF7's were done on Atlas Roco GP7 frames and steps, and yeah, I had to add a good two feet behind the cab. So, this time, the question was, could I do it tighter?
I seriously, seriously, tried to reuse the Atlas step assemblies, and came to the conclusion you all did- it made it WAY too long, and just the wrong steps anyway. One of the odd things about the CF7 is the really short - try 18" - end platforms. The GP7 is much longer. Sigh, forget it, start from scratch, and they are bears to design with four steps and compound angles.
So the question got to be just exactly how far I could push it - could I get the end-to-end dimensions close enough on the Atlas frame and still pivot the trucks? The CF7 trucks are tucked quite under the steps at the brake shoes.
One of my criteria on this project was NO FRAME HACKING. So given that, I was able to get the 'nose to tail' (hood) dimensions within what I scale about 3" - model 47' 6" - drawing 47' 3". The end-sill to end-sill dimensions are about 6" over - model 49' 9" vs drawing 49' 3" . The compromise is that the 6" on either truck center is basically 3" over on each end with the trucks closer to the ends. It is a TIGHT FIT on that frame! And right now, you have to loosen one of the 1015 truck boxes slightly to get the shell off. I'm still concerned that the nose brake shoes may have to be trimmed to clear the steps.
The nose is definitely fat (wide) by 9". I made it as thin as I could, but the alternative was to grind the frame.
I'll be putting photos up on my web page of the unit shot in gray primer so you can see the detail better, and also the dimensions and ruler shots to prove it.
Basically, Daniel, it is over, but no two feet here. I think I've kept it to the 9" and under group all around except for the truck centers. The debate since this project started has been "how much is too much?" because to make it exact require really, an entirely new cast mechanism, milling the tanks of a GP15, or something else expensive to everybody.
Rails, grabs, steps & other goodies will all be etched. This is the most expensive part of the entire project- getting the etched parts right - and Chris333 has been a HUGE help on calculating and designing steps that will work. Those have to be run in batches, the bigger the batches the less the per-unit cost, so thats why I'm trying to get a handle - now - on what you all think.
I'm not claiming perfection, remember this is home-brew scratchbuilding at its core.
