Project: RoboButler 3000 – Part 1

As our project for EMFCamp 2014 (August 29th – 31st near Bletchley), Jim and I have decided to build a robotic butler to bring us drinks and generally bounce around the field getting in the way.


I started off by spending some time CADing up a model using parts we have lying around, and also things bought from ebay:

  • Motors – Invacare Wheelchair Motors
  • Motor Control – Invacare Wheelchair Power Module
  • Wheels – 145/70-6 Quad Bike Wheels, 6″ Pneumatic Casters
  • Frame – 20mm Steel Box
  • Batteries – Hawker PC680 17Ah 12V lead acid batteries

My second task was making something to connect the wheels, which had a standard 6 bolt pattern (3 of which hold the wheel together), with the keyed shaft of our motors.  I decided to 3d print the connector, as it should be plenty strong enough.  I based my design on the existing wheel hub for the old 4-bolt wheelchair motors, and made it in openscad:

I printed this out using 50% infill, with black PLA on the Mendel90 3D printer at Hackspace Manchester, a 15 hour print!  I assembled the wheel units using M8 bolts for holding the wheels on, and used the existing M6 allen bolt for mounting the hub to the shaft:

I’m pretty happy with how they came out, they seem strong enough to hold everything together, and the bolts go far enough through to hopefully stop delamination.

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