Step 1: The Chassis
The chassis was a simple "Ladder" design made from 19mm aluminium square section tubing. This is easy to work and light as well as moderately low cost.
The various sections were joined with aluminium plates and pop rivets. We followed a Greenpower design as the basis for our car but made numerous changes along the way.
Step 2: The Steering
The front wheels have a simple bent 2 mm mild steel king pin arrangement with a 19 mm bolt though for the king pin. With plenty of grease this works well. the steering rods have trackrod ends easily available from bearing suppliers to allow a certain amount of give in the system so no complicated alignment was required just set the wheels straight ahead.
We decided not to apply any toe in or wheel camber. the wheels are a 12.5 inch by 2.25 inch wheel chair wheel. Again, aluminium for lightness and ease of obtaining new tires.
Step 3: The Brakes
The brake levers are on the steering arms and operate the rear wheel brakes independently - this isn't a problem even at speed.
Step 4: The Motor and Drive System
With the gearing we have used it gives us a top speed at present of about 25 to 30 Mph - Not super fast but when your bum is only 2 inches from the ground!!
At a later date we will raise the gearing ratio slightly to up the top speed to 30 to 40 MPH provided we can do thig without over stressing the motor.
Cycle gears are also an option but may insert a complex system into something that needs reliability.
Step 5: The Motor Control/electrical System
Although this system is very simple it is enough and reliable. Pulsing the switch on and off provided a crude speed control although for most of the race the motor is on if going in a straight line and off is the wheels are turned.
In line with the motor is a 70 amp thermal cut out to protect the motor from over current - I strongly recommend you fit this - the motor costs Â£100 new so protection seems advisable.
The motor runs at about 80 deg C in normal use but if stressed, e.g. pulling away from a slow spped too often, driving the motor when the wheels are turned, gearing up the drive too highly in the hope of attaining supersonic top speeds the motor temperature can ramp up alarmingly to the point of breakdown of the epoxy glue holding the windings in at about 200 deg C.
Some teams use water cooling as the motor is water proof, some like us use fins to provide air cooling.
Step 6: The Body
Our body is made from paper, laminated with wood glue this dries to almost wood stiffness with little weight. getting a good finish however has proved difficult and we will look at a thin fiber glass alternative.
The general shape works well but the top cover should be closer to the driver with a small aero screen and the rear should be rounded to provide a smooth exit path for the air flowing over the body.
Step 7: Batteries
They sit on the chassis and are held down with a simple bar and threaded rod arrangement to allow ease of changing.
We are allowed 4 batteries in total and can get about 60 to 100 miles out of them at about 20 Mph.
In our initial race we did 67.5 miles at an average of 18 Mph but we changed drivers 6 times during the race. Our peak speed was 26.5 Mph.
Safety is paramount in any racing sport so full 4 point seat harness was fitted and a full face crash helmet worn at all times when racing.
That's the nutshell overview of our project there are many alternatives to our design some exotic some very simple. You pay your money and take your choice and have fun.