The Rolling Stone
A Spherical Wheel Drive Mechanism
Software, Control and Electronics
The Build
-Structure
-Friction Drive
-Tension Wheel
-Electronics
-Assembly
Materials Used
Raw materials:
Aluminum 1/8th inch sheet. (for top plate, equatorial mounting plate, and dsp mount)
Aluminum 1/2in rod (for risers+ driveshafts)
Aluminum 20ga sheet (small strip for the encoder brace)
Aluminum plate, several ½ in thick rectangular pieces( for bearing mounts, motor mounts, and tensioner body)
Self lubricating bronze sleeve (for the tensioner shaft to slide in)
Hardware:
(4) 3/8 in. roller bearings (to support the drive axle, we needed roller bearings for their small profile)
(1) 3/8 in ball bearing (for the tensioner contact)
(1) 3/16 brass rod (as a shaft for the tensioner bearing)
(2) 1 in. double seal O-rings (friction wheels)
(29) ¼-20 nuts and bolts (1/4-20 was used throughout, for simplicity in assembly and manufacturing
(4) 4-40 setscrews (for securing the motor shafts and encoder shafts within the axles)
Electronics:
(2) pittman motors, 6:1 gearing, 12V
(2) digitial potentiometers (encoders)
(2) H-bridge circuit boards
(1) DSP board
(various) Wire, resistors, regulators, buttons, etc…