I started by pocketing the solid aluminum pulleys to make them lighter. To get rid of any slop in the arm, the arm is supported by a pair of tapered roller bearings.
The arm, the first length of which for now is a thin-walled aluminum tube, is clamped in place with this aluminum block. This arrangement allows the arm to be taken off the belt reduction by the removal of one bolt. That way I can do the programming and control side of things without the arm in place. This will stop the arm from self destructing by smashing into its physical limits.
A long bolt passes through the bearings, aluminum block, and pulley to preload the tapered roller bearings:
The two reductions will look roughly like this when assembled. I still need to make the plates that connect the output pulley of the smaller reduction to a linkage. Unfortunately, the 1/8" endmill I've been using to machine all these parts snapped 3/4 the way through making the first of those plates.
Next up is making the second link of the arm, as well as the linkage that actuates it. More updates can be expected in early January.
In other news, Cambridge got snow this weekend. SkiScooter pictures and videos will appear shortly.