Suspension

The suspension is important to keep the car stable and significantly affects the cornering ability of the car. The Serlby Park Racing suspension is a unique design, which fits into the wheel.

Both the front and rear suspension blocks have been re-engineered. These now move in a phosphor bronze tube bearing made on the school CNC machine. Dampening has been added using a split ring and spring mounted in the tube fitted onto the front and rear suspension bar. The spring forces a cone into the split ring forcing it out and creating friction between the tube and the ring. The more the spring is pushed the more friction is created and hence dampening provided.

The components are machined on the school mini-CNC machine using computer generated drawings.

The rear axle is to be driven using a direct drive from a gear arrangement connected directly to the engine. Drive will only be to the rear wheels and a differential will be mounted on bearings from which drive shafts will connect to the independent suspension mounted in the wheels. The shafts will have ball joints which allow the wheel to move up and down while not impeding the drive of the engine to the rear wheels.

A lubricant has been added to the phosphor bronze bearings to reduce friction and extend life (thanks to Esterchem). To avoid fluid friction (a thick oil stopping movement) a low viscosity fluid was selected, approximately 32cSt (ISO 32). Conventional lubricants could not be used as they are manufactured from mineral oil which contains sulphur. Many sulphur based extreme pressure additives like ZDDP's are added to lubricants to improve performance. Unfortunately sulphur additives react with yellow metals to form sticky black deposits, which themselves cause friction.

To lubricate the bearings while avoiding these black deposits an ester based on a synthetic alcohol and a C12/C14 saturated fatty acid was used. This fluid was obtained from Esterchem Chemicals and is commercially known as TMP Cocoate. The TMP alcohol provides a liquid ester (melting point 5°C) despite the use of a saturated fatty chain. The last advantage is that any decomposition will lead to the formation of fatty acids which are themselves excellent lubricants with yellow metals.

The latest development is to add dampening to the suspension to reduce bounce and further improve cornering by making the suspension more positive.

  

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