Last week my sports car failed its MOT. The fault was "Excessive play in rear suspension linkage. Look I can move this with my hand. This one isn't even done up Richard." I was told to take it home and re-torque all the fasteners in the rear suspension before I re-presented it. The rear suspension on a Caterham like mine is quite interesting and quite simple. There's a strong horizontal tube that has the wheels on it. It doesn't have the differential in it to save weight. The tube is kept in the middle of the car by a triangular A frame that is bolted to the middle of the tube and to the chassis well in front of the wheels. To stop the tube from moving forwards and backwards there are a pair of "radius arms" that are bolted to the ends of the tube, and to the chassis well in front of the wheels (like the swing arm on a motorbike). If I was richer the for/aft position of the tube would be maintained by 3 part Watts linkages giving almost perfect vertical travel.
What was interesting is that only the radius arms had loose fasteners, and it's only the radius arms that you have to take the seats out and get inside the car to work on them. Coincidence? Or something less? I wonder whether Caterham forgot to nip them up when they changed the differential.
Richard "anti-sabotage lacquer" B
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