Thanks, everyone.
I was told it weighs 3.6 lbs. as shown.
The drive itself isn't anything very fancy -- it's 6WD using VexPro VersaWheels. The back (rightmost) wheels are gear driven from 2-stage ball-shifters (34:64, I believe) and everything is chained together from there. We're using 3/8" hex standoffs from McMaster-Carr as axles and the VexPro shaft collars to keep everything spaced out on those.
The gearboxes mount to a small sheet metal part that sandwiches the inside channel so they can be easily removed by loosening 4 bolts. I made the mounting holes too small on those parts, so we need to open those up on Thursday.
