The Mercury was a 9 cylinder one-row radial aircraft engine that was developed by the Bristol Aeroplane Company in 1927, as their Bristol Jupiter was reaching the end of its lifespan. While the Pegasus was essentially a faster cranking (and thus higher power) version of the Jupiter, the Mercury was intended to fill the same performance range as the original Jupiter while still being based on the same production system as the Pegasus.
In order to do this, the Mercury cut down the stroke by one inch, and added a reduction gear to the prop. This allowed it to be used as a drop-in replacement for the earlier Jupiter, using the same propellor, which would otherwise have to change to adapt to the higher RPM.
Its smaller size was aimed at fighter use, and it powered the Gloster Gauntlet and then its successor, the Gloster Gladiator. It was intended that the larger Pegasus would be for bombers, but as the power ratings of both engines rose the Mercury found itself being used in almost all roles. Perhaps its most famous use was in a twin-engine light bomber, the Bristol Blenheim.
Specifications
For the Mercury VIII:
- Bore / Stroke / Displacement: 5.75" x 6.5", 1519 cu in
- Compression ratio: 5:1
- HP: 840 hp at 2750 RPM (max continuous), 730 hp at 2650 RPM (take-off)
- Weight: 980 lbs
The Bristol Mercury was a newspaper from Bristol, published in the 1800s.