Lab 0: Progress and Successful Launch

The pitching-machine idea was chosen because we decided it gave us the best chance for a successful device given the materials we had to work with. The design consists of two wheels positioned with just enough space for a ping-pong to squeeze through; one wheel will be driven by the motor and the other will be free-spinning. When a ball is introduced, the driven wheel will accelerate it through the gap and propel the ball outward. This is a proven design used in baseball pitching machines and tennis ball throwing machines.

We had a suitable motor and gears to configure a system capable of high angular velocities, however we needed to purchase wheels to contact the ball. We found a set of rubber tires mounted on plastic rims intended for use in a toy car. The sticky, spongy rubber was perfect to grip the balls.

We used the base from our pedal set as the base for our launcher. Foam core was used to create vertical walls, between which our wheels would be mounted. Gears were selected for maximum speed; the motor was fitted to turn the largest gear directly, which then turned the smallest gear which was fixed to the tire.




Axles for each of the wheels were inserted through the foam core, with washers glued to the board to provide a rigid hole and prevent enlargement. The motor was mounted near the top of the device by re-purposing a bearing sleeve which happened to fit the motor case perfectly. The other end of the large gear was supported loosely by a round metal band. Because the shaft of the gear is roughly square at this end, this fitting causes some vibration, but does an adequate job nonetheless. We wired the motor up with a simple push-on push-off switch and a potentiometer taken from the petal setup to control motor speed. We spliced into the device's DC converter and used it to power the motor. We quickly realized that the potentiometer was meant for low-power use, as we burned it up and had to remove it from our setup. Finally, we added a curved ramp to feed ping pong balls into the rotating wheels.


The device successfully launches ping pong balls, though not with great range or accuracy. The vibrations in not-quite-matched wheels/gears and axles, causes a lot for frictional torque and slows the motor. We plan, at this point, is to "one-hop" or bounce the balls into the buckets, which this device is more than capable of doing.

Videos to follow once Vista realizes that a device can have both pics and vids on one device at the same time...