Bristol Hercules

The Hercules was Bristol’s great wartime workhorse — a fourteen-cylinder, two-row, air-cooled radial of 38.7 litres using the sleeve-valve system that Roy Fedden’s team had pioneered, which gave smooth running and good fuel economy in place of conventional poppet valves. Power rose from about 1,300 hp to over 1,700 hp in service. It drove the Beaufighter and the Short Stirling, the bulk of the Vickers Wellingtons, and the Hercules-engined marks of the Halifax that largely cured that bomber’s early handling troubles. Around 57,000 were built, many installed as a self-contained “power egg” that could be swapped between airframes.