Skateboard Tow

Mechanical: To make the mechanical part of my project I got

an old electric scooter wheel and hinge and nailed it a wooden frame that had two other wheels on an axle on it. I needed the project to be heavy so that the wheels would have good traction so I used a heavy car battery to power the scooter wheel (originally). One of the main problems was the steering becuase when tested it tended to turn way more than it needed to so it would go out of control. To fix this I clamped two wooden blocks behind the bar that turned the wheel and i attached bungee cords to the same bar so it would always stay straight if I wasn’t turning it. To steer I made rein-like ropes running from the cart to me (on the skateboard).

Electrical: To power this contraption I originally planned on using a 12-volt car battery. After testing it out I found that it wasn’t fast enough for my liking so I changed the battery to an 18-volt cordless drill battery. I still kept the car battery on for the sole purpose that it did an excellent job keeping the cart’s center of gravity low and giving it good traction. Unfortunately, the drill battery doesn’t have as much endurance as the car battery so it lasts not nearly as long, but that doesn’t really matter to me because I don’t plan on using it to get somewhere and it is more fun to go fast. To control the speed of the motor I used a 555 timer. I originally planned on using three resistors for three speeds but after researching that a little bit I learned that that way of setting it up would put low voltage to the motor constantly and cause the motor to heat up quickly. After a little more research I found out that it would be easier to control with pulse width modulation (PWM). With PWM the full voltage of the battery is pulsed very quickly. The amount of time between each pulse can be changed, with short periods of time making the motor move slower and long periods of time making the motor go faster. A simple way to harness PWM is a 555 timer. The voltage going into the timer is varied by a device built into it called a potentiometer. The 555 timer can’t handle the full current of the motor so high current switching transistors use the output of the timer to change speed.