7. - Rice Pudding Units

How does one quantify the power of an engine? Does it depend on what it is used for or maybe the units that people are familiar with?

Power Jets, circa 1940

John Coplin, Chief Designer of the Rolls-Royce RB-211, has been quoted as saying that Lord Hives, Chairman of Rolls-Royce, had been invited to inspect Frank Whittle's prototype jet engine. Hives asked what horsepower was being produced by the engine but Whittle said he was only interested in the thrust that it produced, currently about 800 lbf.

Hives was clearly not impressed, remarking that "that would not be enough to pull the skin off a rice pudding". John Coplin suggests it was Frank Whittle, but others say it was Stanley Hooker, who pointed out that this was slightly better than that effectively produced by the 1,500 h.p. Merlin 45, as used in the Spitfire.

From that moment Hives became determined to take on the new technology for Roll-Royce. It is not clear though whether he was influenced by Whittle's comments that his engine, basically a long combustion tube, compressor and turbine, achieved Merlin-like power but without the 'up down bits', cranks, valves and sodium cooled valve stems of the Merlin.

Undoubtably the jet engine has proved its worth as a powerplant for aircraft, far exceeding anything that a reciprocating engine could achieve. The Roll-Royce Trent 1000, for instance, produces 78,000 lbf. thrust, some 100 times better than Merlin 45, while the static Trent 60 produces 79,120 s.h.p. 50 times better. But was Whittle's dream of a simple, powerful jet engine fulfilled? Only 10% of the Trent 1000's thrust is truly 'jet' thrust, the bulk being produced by bypass air. The difficulty of working with sodium cooling of valve stems etc. are trivial compared to the problems to be solved when working with the forces and temperature differentials within a modern jet engine!

As to the original question, it is surely always a good idea to talk to customers in the language they understand.