3d Printed Differential Challenge – $1,000

A differential is a collection of gears that accept one spinning shaft as an input and spin two other shafts. The trick is a differential allows the output shafts to both receive power from the input shaft, but the output shafts can spin at different speeds. This is what lets a car turn a corner while accelerating- even though both powered wheels (or all 4) are turning at different speeds in a corner.

We have a $1,000 WIKISPEED prize for a SIMPLE differential that meets the following user stories and acceptance criteria:

  • Must weigh less than 45 pounds. (demonstrated by a video of it being put on a scale).
  • Must have one input shaft and two output shafts.
  • Must handle at least 45 ft-lbs of torque peak, more is better. (demonstrated by a video of a 45 lb weight on a 1′ bar attached to input, and output shafts held in place or counterweighted).
  • Must include adapter on input shaft to 1/2″ square drive (a power-tool standard) with a 4″ circle of 5x 3/8th’s bolt holes.
  • Must include adapter on output shafts to 1/2″ square drive,  with a 4″ circle of 5x 3/8th’s bolt holes (similar to how a wheel attaches to a car with 5 bolts). (This will be demoed by a video of a 1/2″ drive ratchet turning the input shaft and 1/2″ drive sockets spinning on the output shafts.
  • 2d parts cut from aluminum plate with a waterjet cutter are also allowed for this challenge, as are 3/8ths diameter grade 8 bolts (24 thread) of any length. 1″ diameter steel washers are allowed, as are nylon locknuts for the 3/8th’s bolts.
  • A working prototype must be delivered to Team WIKISPEED Lynnwood, WA to win, ’cause that means we can use it and the challenge is solved!
  • To win, we must receive a working prototype and the Open Source CAD and code to print more

This could be 3d printed, machined from metal or a block of plastic, assembled from purchased parts, or even an off the shelf part if you can find one! To win the prize, we either need to be able to reproduce it (we have the plans and permission to do so) easily (say 3d print it) or the winner agrees to make any where from 1 to 10,000 of these for under $500 each, or the winner connects us with a supplier that agrees to make anywhere from 1 to 10,000 of these for under $500 each.

Given the light load requirement, I think this COULD be 3d printed, and that could be the best option if that works. It might be able to be as light as <5 pounds, and could be very small. I’m absolutely interested to see what folks might be able to produce!