Privateer Helmut Fath won the 1960 sidecar championship using a BMW, the motor of choice at that time. In 1961 BMW gave him factory support but a crash ended that seasons challenge. As he recovered, he planned on building a more powerful BMW engine but parts were not available form the factory. A resourceful man, he and friends designed and built an inline four from scratch naming it the URS after their town Ursenbach.
It first ran in 1964, and though it made good power, it broke- a lot. problems were ironed out and development continued till the engine was reliable and powerful. In 1968 Fath won the championship again, beating the factory BMWs and breaking their 14 year winning streak.
The engine was a 2 valve DOHC inline four with two crankshafts connected by a common cushioned countershaft. The chain driven camshafts are driven from that countershaft and are also made in two halves. A series of gears drives a Bosch fuel injection pump intended for a Borgward car. The engine produced 78 horsepower at 13,000 rpm while maintaining a healthy spread of power. The transmission (not shown) was an Austrian make, Schaftleitner, and used 4, 5 or 6 speeds depending on the track. The engine was also tried in solo motorcycles using a frame from Seeley and later Rickman.
Drawing above by Bill Bennett.
1 comment:
At 13,000 rpm!
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