Base

The Base occupies three feet by three feet of floor space, and supports a platform which rotates a 55 gallon fiber drum. A "virtual terrain" made of foam and other materials attached to the surface of the drum. The platform is an aluminum plate with a hub bolted to its underside. The hub has two pairs of set screws securing it to a 1-1/4" diameter axle.

The stainless steel (it was a bargin) axle both supports and rotates the platform. The axle is supported by a pair of ball bearings on the top and bottom of a "cage" frame suspended from two three-foot long cross pieces.


On the top and bottom ends of the cage frame are ball-bearing pillow blocks with set screws to anchor the axle in place.

The axle is driven by a 24 volt servo gearmotor. Even though the motor is a gearmotor, the minimum speed at which it would run in a stable, reproducible manner is still too fast. The barrel rotates about 2 RPM nessitating a five to one reduction in speed using a belt and timing pulleys. Fitting these parts together required:

turning down the main axle from 1-1/4" to 1/2" to accept the large timing pulley
flatting the axle to accept the set screws in the large pulley
drilling and reaming the large pulley out to 1/2"
making a coupling to join the small timing pulley to the motor shaft
- cutting to length and facing a section of aluminum from which to form the coupling
- drilling out a bore to accept the motor shaft
- turning the coupling diameter down to fit the small pulley
- drilling and tapping the set screw hole for attaching the couplng to the motor shaft
laying out, cutting, and drilling the motor mounting bracket

Most of these operations were carried out on the metal lathe or milling machine.

After the mechanism was proved out from an operational perspective, the homing switch was mounted. It is a magnetic reed switch triggered by a rather powerful magnet fastened to the large pulley. (See Homing and Limits)

The motor mounting plate is blue in color because it still has layout dye on it. Layout dye is applied to metal so that very thin lines an be scribed on the surface to locate holes and other cuting operations.