There has been a discussion on RMweb today about using riveted plywood construction in EM gauge. Here are some notes I posted there.
For riveted plywood construction in EM, there is a problem that the pre-punched sleepers have the hole centres a bit too far apart. They were originally designed for use with the larger 2.5mm dia EMGS rivets, and the idea was that you create a solder fillet on the outside to represent the chair jaws. For use with cosmetic plastic chairs the rivets need to be exactly under the rail centre, so you may find that you need to take the corners off the rivets with a Dremel disc to get the chairs to fit snug.
But the best solution is to drill or punch your own holes in the right place. There is a trick you can use in Templot to help. If Templot is set to print the rail centre-lines
instead of the rail edges, you get the rivet positions for riveted plywood construction, where the rail centres cross the timber centres, like this:
This shows a crossover in EM. One turnout has the more usual style of rail detail for comparison. Click the generator > generator settings > rails > rail centre-lines only
menu option, then rebuild
the required templates as a group (or all of them), before printing them.
Print on tracing paper
(which works fine in an inkjet printer if you load a single sheet in the tray at a time), then spray the print with Spraymount adhesive (blue can -- removable) and lay the plywood timbers in position. Then turn the whole thing over and prick through with a scriber to mark the rivet centres onto the timbers.
This saves the tedious business of marking them out individually, and gets the rivets exactly under the middle of the rail, which makes it a lot easier to fit the cosmetic chairs later. The timbers can then be peeled off for punching or jig drilling, or using a mini-drill they could be drilled directly through the tracing paper.
You then print a normal template for construction, of course, and having fixed the riveted timbers in place on it, the tracing paper version (or a fresh one) can be laid over the rivets to check for any riveting or timber alignment errors before adding the rails.
Templot lets you set the printed line thicknesses to suit your printer. For precision marking like this it's probably best to set thinner lines than usual, as in the above print. That's at output > line thickness >
Notice also that when you print the rails as centre-lines, Templot makes the timber centre-lines solid instead of the usual dashed centre-lines.
for the greatest accuracy, do a separate printer calibration
for the tracing paper.
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