Tractor Construction Set Design Guide

Basic

• Use 4"x4" square tubing, with 3/16" to 1/2" wall thickness0. It is easy to squeezed the sides of 1/8" tubing, so such a thin wall should in general be avoided. If using thin walled tubing, use a 3" or large washer, ~2x as thick as the tubing, to spread out clamping force.
• CNC torch holes, typically 1" bolt holes
• Plates are 1/2" thick
• Holes can serve as holes for pins or bolts
• Plates are in sizes that are multiples of 4"x4"
• For heavy duty joints, 3" pins are used
• 3" holes are reinforced with DOM Tubing for precision of fit
• Bolt-together XYZ corners are a basic design pattern
• To design lighter-weight structures, use aluminum.
• To optimize weight, weld the aluminum frame, as in the Wikispeed car.

Details

Scalability

• Plates may be stacked
• Tubes may be stacked

Joints

• Rotating joints are a key motion feature
• Machines may be scaled from sub-ton to 50 ton weight

Structure: XYZ Construction

• Whenever building a device, make the frame structural by assuring that bolting is done along 3 axes at each corner. This allows the construction to be a space-frame construction with all corners having equivalent strength.

Modular Wheel Units

• Whenever attaching modular wheel units to frames, attach over 12" of space to prevent twisting of tubes under heavy loads.

Calculations

• 3" pivots can be designed for 150 tons of force at the pivot