Greenwatts

Drive

The drive unit consist of two DC motors, two spur gears, a worm gear, a Canuckle bearing made from ABS fittings and housings and plates made from ABS flat stock. You can convert ABS pipe into flat stock by simply heating it to around 225degF in an oven, cutting it lengthwise and pressing it until it cools.

Flat stock can be cut to size by simply scoring with a utility knife and bending until the material breaks. When drilling ABS use a low speed drill to prevent overheating and melting of the ABS plastic. When bonding with ABS cement ensure good contact between surfaces and use plenty of bonding cement. You can also create ABS liquid to mold pieces by melting shaved ABS in acetone.

When assembling the drive unit alignment of the motors, shafts and gears is critical. Bad alignment will cause the drive to bind when torque is applied resulting in stalled motors and possible burnouts. During assembly test the alignment by driving the motors with 5 volts, at 5 volts the motors will rotate slower and with less torque (In use the motors will run off of 12 or 24 volts).

The Spur gears can be found in most inkjet printers on the end of the paper feed mechanism. The worm gear can be made from a large bolt or threaded rod that matches the thread pitch on the spur gears. The Canuckle bearing is made entirely from ABS fittings. The height of the Canuckle bearing must be adjusted to fit the dimensions of the drive housing which is in turn determined by the size of the DC motors. The DC motors should be identical including identical shaft lengths.