Great thread! Some information on our drivetrain:
-6 wheel tank drivetrain, .25" center drop, 4 CIMs
-10" Harbor Freight pneumatic wheels on laser-cut plywood hubs (for reduced weight, integrated VersaKey pattern and bearing bore)
-32x23" to fit on a single batter segment but accommodate 6 10"wheels and electronics. A cutout at the front provides clearance for the shooter
-Removable panels compactly mount electronic components
-Integrated (but removable) 11:72 single-speed gearboxes with encoder mounts
-4.25" ground clearance, 6" high center of mass
-#35 Chain, 12:36 reduction from gearbox output to middle and front wheels, 30:30 chain between middle and back wheels. CNC-routed HDPE cam chain tensioners are adjusted by tightening screws on the top plate
-Dead axles made from 1/2" Vex tube stock, 1/4" 5052 axle supports laser-cut by sponsor
-Superstructure mounts to 1x1x1/16" square aluminum tubes and can easily be tilted up for access or removed.
-Drivetrain including all electronics except battery weighs ~50 lbs. Wood chassis weighs ~9 lbs
For the second year, the structure was made from 1/4" baltic birch plywood laser-cut in-house on our Trotec Speedy 300 laser. Several refinements were made to our design and manufacturing process, including bolting the plywood to a flat MDF table in the laser to eliminate warping and improve accuracy and using only square nuts pressed flush with one side of the plywood for easier assembly than the centered nuts in last year's robot. The biggest improvement was development of a workflow for production of parts of up to 29x34" on our 29x17" laser cutter by flipping and realigning the plywood. By engraving markers for alignment on the wood, we were able to maintain <~.01" offsets between the two rounds of cutting.
The drivetrain performed essentially flawlessly through the season, allowing quick maneuvering around the field and crossing of all the defenses. No damage was sustained through three events. The only maintenance required was occasional chain tensioner adjustment, chain lubrication and the addition of small aluminum plates to retain improperly installed bearings in the gearboxes.
Some more information can be found in our
engineering journal.