Lotus Mk4 was a trials car by Colin Chapman built on a Austin 7 chassis. Chapman’s success at building trials cars brought another previous customer, Mike Lawson, to order a second trials car in 1952 to replace his Lotus Mk2, in which he won the Wrotham Cup. Once again Chapman chose an Austin Seven as the starting point, reinforcing the frame and installing a four-cylinder 1172cc (71.5ci) Ford sidevalve engine. Chapman used all the tricks he had learned in his previous cars, constructing a lightweight aluminum body with a rounded nosecone. He fitted a 3-speed transmission taken from a Ford 8 and the divided front axle as on his previous cars.
Lawson won his class in the very first attempt in this car, following up with others, solidifying Chapman’s reputation as a designer and engineer. The success of this car, and other requests for more cars, led Chapman and Michael Allen to establish Lotus Engineering in a disused stable in Hornsey.
Ford Sidevalve Motor
Config: S4 SV
Displacement: 1172 cc
Bore/Stroke: 63.5mm x 92.456mm (2.5x3.64")
1 commento:
It is stated:
"The success of this car, and other requests for more cars, led Chapman and Michael Allen to establish Lotus Engineering in a disused stable in Hornsey."
The time sequence is wrong. Colin and Michael established Lotus Engineering at Hornsey on 1st January 1952, and then started to build the Mk IV which was finished in early March 1952.
There are two features of this car which make it noteworthy and have not been mentiond:
Engine position
The regulations in those days allowed the engine to be positioned a long way back in the chassis frame to get more weight on the rear wheels. This would normally have made the car difficult to drive as a road car, but Chapman fitted two 20 litre Jerricans of water ahead of the engine which could be removed before the hill was climbed, and then fitted back for the road journey to the next hill.
Jelly Joint
Trials required a front suspension rather like a farm tractor in which the front axle can freely pivot around a single point. However this made it almost impossible to drive at any speed on the road. Chapman devised a method of fixing the spring by tightening down two wing bolts which locked the spring rigidly for road use, and then, by undoing the wing bolts on either side of the pivot, it was made loose for the hill climb.
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