What holds the extensions to the mainframe? I was looking for pins, screws, or attachment to an intermediate section (maybe the ashpan?) but nothing is obvious. That probably means you did a very good job. -- Russ
Well, I didn't shoot pix at every little step of the way ... cuz it was kinda tricky and I didn't want to loose my train of thought!
But ... these photos might help a little.
You can see a bit of metal under the styrene strip between B & C (above) -- that's a tab for mounting screw that holds the original metal frame piece. The extensions were built up of various styrene strip and laminations. The first piece has a simple butt joint against the metal frame at A -- plastic and metal surfaces roughed up, glued with ACC. The lower strip (B/C) is made of two laminated pieces. The thicker piece in back butts against the metal screw-mount tab at B. A thinner piece over that overlaps the face of the screw tab along C. Styrene pieces have solvent-welded joints along the lines D & E.
So, at right: there are butt joints shown in pink, a surface joint shown in orange and solvent joints between plastic parts shown in blue ...
The combination of butt joints and surface joint makes a sort of T-shaped joint as shown in pink here. That and the diagonal brace go a long way to reinforcing the inherent weakness of simple butt joints. Then I joined the two separate sides with a sub-floor between the cab and ashpan. Again, the styrene parts are all solvent welded ... and this assembly creates an L-shaped joint between styrene and metal parts as shown in orange. So, the combination of the T-shape and L-shaped gluing reinforcements makes it all rather sturdy ... despite the absence of pins and such.
Repeating one of the previous photos, you can see where the two separate metal pieces were unified with the extensions and the subfloor that goes between the cab and ashpan. It took a LOT of concentration to make sure that this was all removable, as I'll probably have to disassemble/reassemble the whole lot a few times at various stages of painting/detailing. (Yeah, I mean I really had to concentrate ... caught myself several times starting add little bits that would have "trapped" the assembly that has to be removable against the actual mechanical frame of the lokie!)
Speaking of assembly/disassembly ... the ashpan fits over the screws that hold the outside-frame assembly in place, so that had to be removable too. There are divets in the front (upper right of photo) that are shaped around the screw tabs and screw heads ... the little ears sticking up in front are bits of the pan that will show thru the opening in the frame behind the rear driver ... so those are there to insure that they'll be painted the same as the actual ashpan and it will appear to have the appropriate continuity.
And once the chassis is pretty much together and painted, the decoder and wires have to be tucked into the ashpan, so the bottom of that slides in place from the rear. The little ash grate is very delicate, so I drilled two little holes in the bottom which allow it to be placed with tweezers instead of big fat fingers that will smash the little grate!
(This is probably pretty obvious, but just so you know that I know ... those little holes were added after this photo was taken)
Have to do a few more little details on the frame and rig up some brake shoes and such, then hope to get some primer on the various components to see where additional putty/fill and other corrections might be needed ... oh, also forgot to mention that I re-worked the cab drawings and have that nearly sorted out. More on that after the frame stuff gets straightened up.