Researching the air-cooled twin, I came across some facts I thought I'd share with you all.
In 1923, Stuart Turners and seven other companies were approached by the War Office to see if they could produce a light weight air cooled engine to drive a generator for military use. Five firms tried, but only the ST unit operated as it was supposed to & they got the contract. The brief was that the whole set should weigh no more than 84 lbs (38 kilos) as it was intended for forward radio positions in difficult terrain & would be carried on a pack mule. It must be unaffected by the position in which it was carried, be capable of operating in any temperature from freezing to 140oF and govern its speed to within 5%. There were other conditions too, but these are the salient details. The engine was close-coupled to a 24-volt dynamo rated at300 Watts & were together mounted on an aluminium base plate and protected by a lightweight steel tubular frame that was probably enclosed with a shaped canvas cover. The cylindrical petrol tank was fixed to the frame with leather straps before use.
Many led interesting lives & their portability took them to many an obscure corner of Empire. In the 1930's, the Admiralty, War Office, Air Ministry. the Post Office & the Crown Agents for the Colonies all used them & Sir Ernest Shackleton's Antarctic exploration ship "Endurance" carried a Stuart generating set. The 1933 Mount Everest Expedition carried one that was used at a height of 16,500 ft, probably the greatest altitude at which a stationary internal combustion engine had operated at that time. The Duke of Windsor's staff used a similar plant on his East African tour, and another was used on location in the filming of "Sanders of the River."
"Sanders of the River" ....... Gosh