Team Scooter Thursday

In the Fall of 2001, a group named "Does Everybody Know What Time it Is?" participated in the "Amish Scooter Challenge." This consisted of designing an electric scooter and using it in an all-terrain race. The group faired quite well in the challenge, and their final product is a powerful electric scooter designed for a grown person.  Our job is to take this racing machine, and make it more practical for everyday use.

We first explored many aspects of everyday use of the scooter. The problems that we decided to solve are the following:

1. Redesign the throttle control.
2. Install a battery charging system.
3. Weatherproof the electrical components.

These improvements will improve the safety, performance, and convenience of the overall product.

Throttle
The preexisting design for the throttle was not functioning at all.  The choice of diodes in the pulse width modulation (PWM) circuit caused the diodes to fail, rendering the throttle useless.  Thus the main constraint for the throttle was finding a transistor with proper specifications to avoid the same problem that happened before.  At maximum power, the control system requires 41 amperes.

Battery Charger
The scooter did not have any method of charging the battery before we received it. Since the battery life is approximately 30 minutes, a charging system is a must in improving the convenience of the scooter.  We also agreed that extending battery life would be a great addition to this portion of the project.

Weatherproofing
If the scooter were to encounter rain, there was great risk to both the rider and the scooter. If the scooter is to be used by a common person, this risk MUST be minimized as much as possible. Weatherproofing is the best way to accomplish this task. The difficulty here is that we must weatherproof the electrical components from both the top and the bottom of the scooter.

Throttle
We found an IGBT that would meet the necessary specifications. It is an Advanced Power Technology (APT50GF60B2RD) suited for 80 amperes and up to 600 volts. With these attributes the IGBT will be able to handle the current and voltage the system requires.

The other parts we ordered were the PWM chip, the flyback diode, and the gate driver. We ordered these specific parts because that is what the pervious group used without any problems. For the pulse width modulation, we purchased a LM556 Dual Timer. The flyback diode is a 06F8689 and the gate driver is 27C6938. We purchased all of these parts from Newark Electronics.

On-Board Battery Charger
We simply purchased an on-board charger to meet the needs of the scooter. It is the light-weight onboard, 24 volt, 3 ampere version of the Battery Tender. It will be placed on the fender within the weatherproofing enclosure to ensure its safety.

Solar Battery Charger
In addition to the on-board charger, we implemented solar panels to charge the battery as well.  These panels provide extended to the battery life of the system. The solar cells are 10 watt framed panels from BatteryStuff.com. They will be placed on the weatherproofing enclosure, allowing them to gather as much sunlight as possible. The solar charge controller is a 24V Sun Saver from Morningstar. It will be placed on the fender. A battery charge meter will be mounted on the back side of the enclosure, so that it can be easily viewed.

Weatherproofing
The weatherproofing will be made of sheet metal. It will be used to form rear and front fenders, and an enclosure over the rear fender. The sheet metal will be cut, bent and pop-riveted to form the fenders and enclosure. A frame to reinforce the enclosure will be made from half inch metal tubing. The enclosure frame will also be attached to the scooter frame using sliders. This will allow easy removal of the frame in order to perform routine maintenance on components of the power system and drive train.