Rear-engined car tried to take on Mini

Tag : Carburetor Joints

Very early cars had their engines in various locations such asunder the seat or behind the driver. But the 1900 Mercedes, withits front engine followed by a four-speed transmission sendingpower to the rear axle -- albeit through chains -- established theautomobile's general configuration.
Then, during the 1930s, along came Ferdinand Porsche with hispowerful Auto-Union race cars with the engine behind the driver.And Porsche's design office engineered the Volkswagen in themid-1930s with the engine in the rear, a configuration alsofollowed by Porsche cars. Porsche, as well as Hans Ledwinka ofCzechoslovakia's Tatra, were the leading proponents of rearenginelayouts.
Following the Second World War, the Volkswagen became so popularthat several manufacturers, including Fiat of Italy, Renault andSimca of France and NSU and BMW of Germany, took up the idea.American Preston Tucker had a rear engine in his late-1940s Tucker"Car of Tomorrow" that was supposed to revolutionize the automotiveindustry. Even mighty General Motors succumbed to Dr. Porsche'sspell with the 1960 Chevrolet Corvair.
The British were largely unmoved, although some smaller makers suchas Lotus and Lola did produce rearengine cars. Then, in 1963, theEnglish Rootes Group -- makers of Hillman, Singer, Sunbeam andHumber cars -- surprised the industry with its rear-engine Imp,sold as a Hillman in England and a Sunbeam in North America. It wasRootes' Mini fighter and was as technically novel as the Mini.
The Imp used unit construction and measured just 3.5 metres long,with a 2,083-millimetre wheelbase (the Volkswagen measured 4,064 mmand 2,388 mm, respectively). It was not as tiny as a Mini, but itwasn't much bigger. Despite its diminutive size, it carried off its"shrunk-down Corvair" styling very well.
With rear-engine placement in such a small car, the drivetrain hadto be light and compact. The Imp was powered by an all-aluminum,overhead-cam, water-cooled four-cylinder of just 875 cubiccentimetres, which had originally been developed by Coventry Climaxto power fire pumps. To avoid a long, circuitous throttleconnection, it had a pneumatically operated throttle, which provedtroublesome and was soon replaced with a cable. With 42 horsepoweron tap, the engine could propel the 744-kilogram sedan to 96kilometres an hour in 25.2 seconds and on to a top speed of 122km/h (according to Road & Track, 6/'64).
The longitudinally positioned engine was slanted 45 degrees to theright for a lower profile and was located behind the rear axle. Itdrove the rear wheels through a floor-shifted, manual, four-speed,synchromesh transmission with an aluminum case. An interestingfeature was that instead of conventional universal joints, innerdrive axle angularity was taken up by big rubber doughnuts calledRotoflex couplings. There were regular universals at the outer endsof the axles.
The all-independent coil spring suspension was also unusual in thatthe front wheels were carried on swing axles, which gave them adecidedly cambered look, rather like the Volkswagen Beetle'sbow-legged rear wheels. Semi-trailing arms were used at the rearand the wheels were just 12 inches in diameter with 5.90x12 tires.Braking was by drums all around.
Steering was rack-and-pinion, but, with the tie rod ends, they wereattached to the middle of the rack, not to the ends as inconventional designs. This allowed the tie rods to exactly followthe path of the suspension arms.
Accommodation for four passengers was adequate, if a bit short onrear legroom. There was a small space for luggage under the hoodand another bin at the rear accessed by a top-hinged rear window.With the rear seat folded, the Imp became a generous little hauler.
The Imp was built in Linwood, Scotland, from 1963 to 1976. Intypical British fashion, it evolved into several badge-engineeredversions such as the aforementioned Hillman Imp, Singer Chamois,Sunbeam Stiletto and Husky station wagon. Few, if any, of thesereached North America.
Although it was technically interesting, the Imp didn't achieve thepopularity of the British Motors Corp. Mini. Cars of Imp and Minisize were considered too small by most North American motorists.They would accept the Volkswagen, but there was a limited marketfor anything much smaller. And, with cheaper gasoline, fuel economywas not as urgent as in Europe. Also, the Imp suffered some earlyproblems with the pneumatic throttle and carburetor, although thesewere corrected.
Over a 14-year period, approximately 500,000 Imps and derivativeswere produced.
bvance1@cogeco.ca