DEWBOT III Drive Train
Dewbot III possesses a drive-train and chassis having good performance and reliability. Drive-train is four-wheel-drive (4wd) Tank with Traction Wheels forward and Omni Wheels aft.
We used AndyMark Shiftboxes with (1) CIM motor per side. Taking into account 12-tooth drive sprockets and 42-tooth driven, overall gear reduction ratios were 14.6:1 and 37.3:1. Maximum robot speeds (@ max efficiency) was 11.4 and 4.4 ft/s (in high & low gears, respectively). Servo motors were used for gear shifting. We found these to be unsatisfactory and used pneumatic actuators on subsequent robots.
Type 35 polymer chain was used for power transmission to save weight. Polymer chain weighs 0.0105 lb/in, as opposed to steel chain at 0.0175 lb/in. This can represent a significant weight savings (although this weight savings was not needed on Dewbot III). We experienced a lot of chain breaks with the polymer chain, so we are reluctanct to use this is critcal applications. Fortunately, each wheel has its own drive chain so the failure of any one chain during competition did not have a large impact on out ability to compete successfully.
Front wheels are 8" Diameter x 2" wide IFI Traction Wheels (IFI-WHEEL-820-50) with Roughtop treads (µ = 1.3).
