Tractor Construction Set Design Guide

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  • 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.



  • Plates may be stacked
  • Tubes may be stacked


  • 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.


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