Frames for the 2-8-2 cut
Finally, I have some real frames. First I cut two pieces of copperclad pcb material to size then spray glued a copy of the frame "comic" to the top piece. These were then clamped to some 12mm mdf. Holes were bench drilled to take some 4ba screws right through the sandwich to secure everything once the clamp was removed.
1.6mm pilot holes were drilled through at the axle locations. I've done this so that I can use crankpins fitted in the mdf as a jig for setting up the coupling rods. As the frames and jig were all drilled at the same time, the theory is that the rods should fit!
The frame material was removed from the mdf and clamped back together with the original screws and the bearing holes opened out to 3.5mm. These two halves could then be clamped together with 6ba screws for shaping.
Here's a photo of the "jig" and the two frames bolted together after intial rough shaping.
Note arrow showing which way is "front"
Here's a photo of the frames held up against the body
And here's a frame against the original drawing, with one of the Kemilway 8F hornblock/spring etches that will be soldered to the frames. Note I've used the hole in the etch to scribe a circular gap in the copper to isolate the bearing from the rest of the frame. I will have to do similar around the cylinder strecher and motion support bracket to prevent shorts.
Next step is to machine up some 8.5mm spacers for a set of Comet frame jigs. As I'm using quite thick double sided PCB material the spacers are correspondingly thin. The figure of 8.5mm was derived from a formula in Iain Rice's book on chassis construction.
The "EM" spacers from the tender chassis will be pressed into service for the loco as soon as I've cut them down to 8.5mm too. Now, where did I put that lathe .......
EDIT:
Thanks to micknich2003 for agreeing to machine up the 8.5mm frame jig spacers, saves me digging the lathe out of the garage
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