Earlier today I had silver soldered up the blocks for the boom base onto the mounting plate. After a soak in the pickel solution, here it is mounted on the shovel platform, with the boom set in place. The three axles on the main boom have brass bearings. A piece of the 'cable' that will be used is holding the upper end of the boom in the air - it will be able to tilt with one of the motors to adjust the angle like the original did. For cable, I have a spool of gray 250 pound test braided fishing line (synthetic fiber, not metal cable, for flexibility). On the table under the boom you can see the plastic prototype bucket, for a sense of size of it.
Lots more to do on the main boom - sets of pulley sheaves, axle support extensions, and the dipper shaft assembly still to go, but its looking more and more like an excavator!