Bradshaw"s early work was involved with the early pioneers of flight, which led him to become an expert on stressing. He designed the Star Monoplane including the engine for Star Aircraft when he was 19, which he later flew. The American Broadcasting Company radial aero-engines designed and built during the First World War were extremely advanced and the government placed large orders for the Dragonfly.
A number of aircraft were designed to use the Dragonfly, but the engines were plagued by problems and failed to live up to the promises.
The design was taken over by the Royal Aircraft Establishment at Farnborough to try to resolve the issues, but with the end of the war, it was abandoned. He was appointed an Officer of the Order of the British Empire for his war work in 1918.
At the end of 1918 it was announced that American Broadcasting Company Motors Limited had transferred its motor cycle manufacturing and selling rights to Sopwith Aviation Company Limited, with Granville Bradshaw of American Broadcasting Company Motors Limited concentrating on design. This allowed him to sell his designs to other companies.
He designed a number of engines for Panther motorcycles.
He also designed motorcycle engines where the cylinder barrels were oil cooled, and these were made under licence by J Walmsley & Company (Preston) Limited. The flat-twin 500cc version of this engine was utilised from 1921 on the Zenith-Bradshaw motorcycle. A single cylinder 348cc version was optional for Oklahoma-Supreme, Sheffield-Henderson, Dot, Orbit, and Coventry-Mascot in 1922.
And a 1100cc V-twin version of this oil-cooled engine was adopted for the Belsize light car.
His biggest seller was selling patents for gambling machines, although he lost all the money he made in further business deals. He later concentrated on torodial internal-combustion engines.
A biography Granville Bradshaw: a flawed genius? by Barry Jones was published in 2008. Violet petitioned for divorce in 1926.
Bradshaw married again in 1927 to Muriel Mathieson in Kensington, London.
He died in 1969 at Hitchin in Hertfordshire.