Mechanical
Car Track
In order to achieve the
effect of two independent cars racing around an oval track, we used a system of
two stacked v-belt pulleys. The system is built from laser cut masonite, steel corner braces,
wooden dowels, limit switches, large flat washers, and dc motors.
Each pulley is constructed
from a small drive gear mounted on a shaft hub, a larger gear, a large pulley
disc of equal diameter, a drive motor mounted on a corner brace, and a v-belt.
The v-belt is slung around both the large gear and the large pulley disc to
form an oval shape. The belt is constrained on the gear and pulley by larger
discs affixed on both faces of the gear and the pulley disc. Both the gear and
pulley disc are mounted onto two wooden dowels embedded perpendicularly into a
1’ x 2’ masonite base plate.
Flat metal washers are used
for spacing. The drive gear is mounted on the motor shaft using a shaft hub.
Due to imperfections in masonite
thickness and construction, the drive motors are mounted with hose clamps on
corner braces affixed to the base plate. This allows the drive gear to be
adjusted for acceptable meshing. By locating all components within the area
enclosed by the v-belts, two of these pulley systems can be stacked on top of
each other without the complications of twisting wires and colliding parts. Space
permitting, a third or forth car could be added.
Receiving various PWM
signals from the C32, the motors are able to drive the pulleys at several
distinct speeds. The cars were propped up off of each v-belt using reinforced
drinking straws. The straws allow enough flex to accommodate for some
inconsistencies around the track edges while providing enough support to
prevent the cars from drooping. The straws also serve as the mechanical
triggers for two limit switches, which are used to sense when each car
completes a lap.
Speedometer
The speedometer is a HiTec
HS-311 analog servo controlled by a PWM signal from the C32. The PWM duty cycle
is varied to reflect the speed of the player controlled car – the faster the
car, the higher the duty cycle and vice versa. The player car can reach a
maximum speed of 240mph and never drops below 20mph even when at a standstill.
Electrical
Schematic of pacer, player and speedometer
motors
Schematic of player and pacer car finish
limit switches