Saturday, February 03, 2007

The footplate

First I'll need a jig

This will hold the sideframes, bufferbeams and footplate in place.

Plan view from underneath the footplate.

This shows how, when the bufferbeams and outside frames are soldered on, the gaps will divide the underside into 4 electrically isolated sections.

The underside must also be isolated from the top side, hence the need to file back the PCB from the edge of the bufferbeams.

The instructions say the bufferbeams should be “centralised on the footplate, flush with the top surface, and vertical.

With a steel square clamped to my board and a line drawn perpendicular, to it, I can position the bufferbeam then hold the footplate firmly against it with a cocktail stick while I solder.

The angles are OK, and the isolation gaps all correspond. But it's too long for the jig. I take a bufferbeam off, file the footplate back and solder the bufferbeam back on. Now it fits the jig perfectly, but the sideframes won't fit inside. I file a fraction off the sideframes and rather more from the inside edges of the bufferbeam until it all goes together.

bufferbeam inside edges reduced

Now the footplate fits over the sideframes in the jig.

There's only a small area of footplate between the frame and the isolating gap, so soldering will be tricky. This shows one of the easier corners.

Managed to solder three corners together, but the gap was too close on this one, so I had to slide some solder underneath the frame near the axlebox.

Not sure why the gaps have to be so close to the frames, but at least its done, and with all the sections isolated.

Only needs wheels and a body.

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