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In this "Tips from the Pros" installment Jason Dante Bardis gives his insights into the world of BattleBot wheels and casters. Robot Wheel Comparison Guide Brief by Jason Dante Bardis (full version at the Infernolab) Things to look for in a wheel for a combat robot: Light weight: makes it easier for your drive motor to quickly speed up, slow down, and reverse direction; heavy wheels also use up valuable weight that could be better used elsewhere on the robot Sturdiness: Needs to take a beating and not break up. Tread: The stickier the better for pushing and high acceleration/deceleration. Diameter: For a given drivetrain setup, smaller wheels give more pushing force and lower top speed, larger wheels give less pushing force but higher top speed; driving smaller wheels should also tend to draw less current from your drive batteries, letting your robot run longer on a battery charge. Core/Hub: Want it to be sturdy yet easy to machine, with enough area to attach to driveshaft or hub. Tread Stiffness: Cushy wheels will have a larger contact patch, give your robot a smoother ride, absorb shocks, and accommodate mounting flaws (tweaked chassis, bent axles, etc.) but may wear faster than hard wheels. Cost: Try not to let cost influence your decision too much; then again, you always want to be able to afford to have spares on hand; all prices quoted below are from March 2000. Application: Wheels designed to support push-carts or to catch landing model airplanes are not designed to be driven by motors--reworking of the hubs is probably necessary. Robot Wheel Examples: Aluminum Hub, Rubber Tread (recommended) Wheel Detail: Tread on solid/spoked aluminum core, smooth tread, 5"-14" dia x 1.5"-5" wide Available At: McMaster-Carr part #2322T31: 3"dia x 1.25" wide, 0.5lb, $22.24 Wheel Comments: Light, grippy tread, tough hub, rounded tread, good for all sizes of bots Colson Thermo-Cushion Rubber Performa (recommended) Wheel Detail: Polyurethane tread interlocked on smooth/ribbed polyolefin core, 2"-12" dia x 0.125"-3" wide Available At: McMaster-Carr part #2829T54: 3.5"dia x 1.25" wide, 0.3lb, $7.13. Used on Dr. Inferno Jr. at BattleBots Las Vegas 2000 Wheel Comments: Very light, grippy tread, tough hub, compressible tread, plastic hub durability questionable, good for most sizes of bots, but maybe not super heavyweights Aluminum Hub, Rubber Tread Wheel Detail: Polyurethane tread interlocked on solid/ribbed cast aluminum core, 4"-10" dia x 1.5"-2.5" wide Available At: McMaster-Carr part #22865T11: 5"dia x 1.5" wide, 1.5lb, $22.24 Wheel Comments: Average weight, fairly grippy, very durable, raised ridge on tread should be removed, good for big bots CB/Tatone Foam-Filled R/C Airplane Wheel Wheel Detail: Smooth/textured tread clamped on by hard plastic hub, 3.5"-5" dia Available At: Tower Hobbies part #CBAQ3010: 3.5"dia x 1.5" wide, 0.1lb, $21.39/pair. Used successfully on 30lb Overpowered Box at BotBash 2000, but shredded on 58lb Dr. Inferno Jr. at BattleBots San Francisco 2000 Wheel Comments: Super light, grippy, cushy, weak plastic hub, tires wear considerably (buy spares!) & can crumble, good only for very small bots (lighter than BattleBots lightweights) Dave Brown Lite Flite Foam-Filled R/C Airplane Wheel Wheel Detail: Smooth/textured flat/rounded tread on hard plastic hub, 4"-6" dia Available At: Tower Hobbies part #DAVQ5540: 4"dia x 1.125" wide, 0.1lb, $8.59/pair Wheel Comments: Super light, fairly grippy, smaller wheels cushy, weak plastic hub, tires probably wear considerably (buy spares!) & can crumble, good only for very small bots (lighter than BattleBots lightweights) DO NOT CONSTRUCT OR OPERATE A ROBOT OR BATTLEBOT UNLESS SUPERVISED BY A QUALIFIED ADULT. CONTESTANTS ARE SOLELY RESPONSIBLE FOR THEIR ROBOT OR BATTLEBOT WHETHER OR NOT IT COMPLIES WITH THE RULES OF BATTLEBOTS, INC. (COMPANY) OR HAS BEEN INSPECTED FOR SAFETY OR OTHERWISE BY THE COMPANY. THE CONTESTANTS' RESPONSIBILITY INCLUDES ALL MATTERS OF SAFETY, CONDITION, DESIGN, CONFORMITY TO LAW, OPERATION, MERCHANTABILITY AND FITNESS FOR USE AND FOR ANY PARTICULAR PURPOSE. BY ACCESSING THE COMPANY RULES OR PARTICIPATING IN ANY EVENT EACH CONTESTANT WAIVES ALL AGREEMENTS, WARRANTIES, GUARANTEES, RIGHTS AND REMEDIES, EXPRESS OR IMPLIED (IF ANY), INCLUDING BUT NOT LIMITED TO, ANY OBLIGATION OR LIABILITY OF THE COMPANY WITH RESPECT TO ANY MATTER DESCRIBED ABOVE AND ANY DIRECT, INCIDENTAL OR CONSEQUENTIAL DAMAGES OF ANY KIND OR NATURE, WHETHER OR NOT ARISING FROM THE NEGLIGENCE OF THE COMPANY OR ANY OTHER PERSON, AND ANY RISKS WITH RESPECT THERETO ARE HEREBY ASSUMED BY CONTESTANTS.