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Sunbeam S7

American Government Special Collections Reference Desk

Motorcycles

S7
Vehicle Model

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Wikipedia: Sunbeam S7 and S8

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A motorcycle produced by Sunbeam.

History

The following section is an excerpt from Wikipedia's Sunbeam S7 and S8 page on 22 August 2020, text available via the Creative Commons Attribution-ShareAlike 3.0 Unported License.

The Sunbeam S7 and S8 are British motorcycles designed by Erling Poppe with styling loosely based on the BMW R75 designs that were acquired as war reparations by BSA (full rights to the Sunbeam brand had been acquired from AMC in 1943). Built in Redditch, the unusual engine layout was similar to that of a car. The engine was a longitudinally mounted inline vertical OHC 500 cc twin based on an experimental 1932 BSA design (the Line-Ahead-Twin - LAT) with coil ignition and wet sump lubrication which, through a dry clutch, drove a shaft drive to the rear wheel. The inline engine made this technologically feasible—horizontally-opposed ("flat") twin engines on BMW motorcycles had already used shaft drives following the system employed by Nimbus in 1918. The early S7 was expensive and over engineered, which is why it is now the most sought-after and commands a premium over the S7 De Luxe and the S8, which were produced with fewer features to reduce costs, while retaining many of the innovative parts of the early Sunbeam and updating some ideas.

Three models were produced, the S7, S7 "de luxe" and the S8. All three were very expensive with only modest performance resulting in low sales. The original model was the S7 (the "Tourer") (2,104 produced from 1946 to 1948), in 1949 the S7 was updated to become the S7 de luxe (5,554 produced) and the S8 (8,530 produced). Both had new cylinder linings, redesigned frames and increased oil capacity. The lighter S8 was sold as a "sportier" model with a top speed of 85 mph (137 km/h). It also had new (BSA) forks, a cast aluminium silencer and chromed wheels (with narrower tyres to replace the 'balloon' tyres which had led to uncertain handling at speed). S9 and S10 models were planned but never made as BSA decided to concentrate on the more traditional twins. Another "sports" model was also tested but never put into production. This had a much higher compression ratio with a different OHC design but was never sold, reputedly because of the undampened front fork system which affected handling. There were also trials with a rigid version for a cheaper model but this design was also abandoned.

The original S7 was produced in black. The S7 de luxe came in either "Mist Green" or black and the S8 in "Silver Grey" or black. For export abroad BSA would supply Sunbeams in any BSA colour.


Photographs

1968 Sunbeam S7 500cc Subject:  1968 Sunbeam S7 500cc
Photographer:  Bill Crittenden
Event:  Woodstock VFW "Remember Our Heroes" Car Show
View photo of 1968 Sunbeam S7 500cc - 5,081KB
1968 Sunbeam S7 500cc Subject:  1968 Sunbeam S7 500cc
Photographer:  Bill Crittenden
Event:  Woodstock VFW "Remember Our Heroes" Car Show
View photo of 1968 Sunbeam S7 500cc - 4,535KB
1968 Sunbeam S7 500cc Subject:  1968 Sunbeam S7 500cc
Photographer:  Bill Crittenden
Event:  Woodstock VFW "Remember Our Heroes" Car Show
View photo of 1968 Sunbeam S7 500cc - 3,545KB


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