Cosmos Mercury
Brazil Straker Mercury

Designed by Roy Fedden of Cosmos Engineering and built at Bristol by Brazil-Straker under the direction of Roy Fedden, and first run in July 1917. The Cosmos Mercury fourteen-cylinder twin-row air-cooled radial Mercury featured an unusual crankshaft and connecting rod arrangement that dispensed with the more normal design of a single master rod linking to individual rods for each cylinder. It produced 347 horsepower (259 kW). It was said to run well without vibration and set an unofficial time to climb record while fitted to a Bristol 21A Scout F.1, the aircraft achieving 10,000 ft (3,000 m) in 5.4 minutes and 20,000 ft (6,000 m) in 16.25 minutes.
 
An Admiralty order for 200 engines was placed in 1917 but was later cancelled by Lord Weir due to the end of World War I, it is also stated that Lord Weir had a preference for the ABC Dragonfly. It did not enter production.

The name was re-used by Fedden for the later nine-cylinder Bristol Mercury radial engine.

Mercury
Type: 14-cylinder air-cooled two-row radial engine
Bore: 4.375 in (111.1 mm)
Stroke: 5.8 in (147.3 mm)
Displacement: 1,223 cu in (20.0 l)
Diameter: 41.625 in (1,057.3 mm)
Dry weight: 587 lb (266 kg)
Valvetrain: 3 poppet valve per cylinder; 2 exhaust and 1 inlet
Fuel type: Petrol
Oil system: Pressure feed to main bearings
Cooling system: Air-cooled
Power output: Normal: 315 hp (235 kW) at 1,800 rpm at sea level, Maximum: 347 hp (259 kW) at 2,000 rpm at sea level
Compression ratio: 5.3:1