Building a competition car

Mark Mansell

A look at building a competition car from scratch.

The original Evans Special, car 33 VIC was sent to me to see if I could sort it out and get it going properly. This was not possible due to the fuel tank being in the wrong position. For the tank to be in the correct position it would have ended up being out side the car. Or the car had to be extensively modified to make it run in the opposite direction. As previously stated, result = just as easy to make a new car.

Off to the foundry with the patterns and core boxes for a new chassis, front axle and engine mount / back axle mount in AD601.

Left: The front axle pattern, casting and finished part.

Right:The chassis casting was put in the milling machine and this is the result. Also shown are the ignition switch, the battery mounting, the fuel shut-off valve and the tail skid. It’s a good idea to use worn out tungsten carbide tips silver soldered onto the ends of tail skids because the concrete of the running surface will soon wear through the spring steel in no time.

The body was made by first making a pattern in wood. This was actually many pieces or laminations glued together and carved and sanded to the desired shape. The shape of bumps or bubbles to clear things like cylinder heads and fuel tanks are determined by cardboard templates. Then, having a split parting line like the chassis pattern, it had to be mounted on an "odd-side" or follow board. Around this pattern a box was constructed and release agent sprayed into the mould immediately before the plaster of Paris was poured in.

Here is the resultant mould with the pattern removed. I forgot to get a picture of the "Raw" fibre glass body before painting.

Here is the body after painting. Only use alcohol proof paint. The methanol will simply act as paint stripper to anything else.

The un-machined chassis casting is shown with a mock-up plywood fuel tank. (Also shown along side the finished tank.) The shape of the tank was determined by making templates and by a process known as "scribe to fit". The shape of the end pieces was determined to make the tank fit the chassis and body as closely as possible to maximize the volume. The plywood mock-up was then used to help "mark-out" the development of the tank on the 0.5mm brass sheet. The curved surfaces were easily determined simply by rolling the mock-up on the brass. Then the whole thing was silver soldered together.

Front and back wheels were turned from solid aluminium 2011-T6 bar, holes drilled and tapped and mounted on the axles. The car now with its body yet to be fitted.

The finished car. Complete car with battery and fuel has a mass of 1762 grams, well inside the 2000 gram limit for this class.

Achieved 164.17kph on its first run.