Very neat. I'm looking at the CAD right now, and a lot of stuff is very well incorporated. The weight seems to be around 6.7lbs after I went through and checked the weights on the motors and stuff, although I'm sure I missed a lot. ~7lbs would be a closer estimate I think.
Cool stuff:
1. Clamping bearing block for rotation
2. 8mm to hex adapter for a pulley instead of gear reduction
3. Encoder mount doubles as a spacer
4. Use of versatube for the top of the module
5. Bearing gussets for spacing out gears in module
5a. Supported by C-channel
5b. The only precise gear-thing on the whole module
6. No need for precision except on a few parts
5c. Mostly drill press and chopsaw work, and not that much of either
Some possible improvements:
1. To make it more feasible for teams without a mill/lathe (or those who want to assemble faster), a few parts screw things up: the module rotation/support tube, and the block that mounts the aforementioned to the module. Both are relatively precise parts unfortunately, and I think it would be possible to convert it to low-precision and remove them.
1a. Why the custom U-gusset instead of two right-angle gussets on each side?
2. The encoder mounts are cool, but 3D printers are expensive. It seems to be possible to replace them with simpler pieces.
3. Encoder-shaft coupler on the versaplanetary can be removed and replaced with a versaplanetary encoder. This also removes the MA3, so it doesn't cost too much extra.
4. The square slot in the tube. I think like this can just be a 1.25" diameter hole, or even 1.375" to allow for more tensioning.
5. The slot for the bearing tensioner for the belt. You already have a tensioner with a WCP cam.
According to SDP-SI's belt calculator you don't need the tensioner to achieve good contact with the 18t pulley anyway; what pushed you to have it?
6. 5/16-18 taps on the bottom shaft instead of 1/4-20 (thunderhex makes the latter easy) and the hole running all the way through the 3/8" shaft on the upper shaft of the module.
7. Bronze thrust bearings instead of roller. A completely personal preference, but they only cost a few dollars more so I like the tradeoff.
8. Use of a 48t gear as a faux versahub for the timing belt pulley. I had to do this once and did not like it.
There has to be a better way...