From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Supercharger noise, fuel requirements, engine cooling, and oil temperatures.
| Identifier | ExFiles\Box 173\3\ img081 | |
| Date | 4th April 1934 | |
| -2- Other points discussed were :- SILENCE. WHAT HAS THE GREATEST DIFFICULTY ENCOUNTERED ? The supercharger runs at 5.75 engine speed and is driven off the 1.5 engine speed shaft by a single reduction worm. Their greatest difficulty has been in getting the drive quiet. The slightest inaccuracy causes noise. They have made an appreciable improvement by increasing the flexibility of the couplings. They were afraid of noisy ball races and so used plain bearings. They have tried different rotor forms and some have been noisy, but never approaching the noise of a constant displacement blower. They find that the blower reduces induction pipe roar, its own intake hiss being easily dealt with by an ordinary A.C. cleaner. FUEL. The engine will run on the ordinary American fuel (which I believe has an octane value about 74) without any trouble or serious detonation. It does not require the Ethyl Gasoline which has 78-80 octane and costs 3 cents/gal. more. COOLING. They have not increased their radiator size. They contend the increased speed balances the increased power, this however appears questionable. OIL TEMPERATURES. They are using 2 1/2" dia, big ends, 1 1/4" long. Their piston is heavy, being of the invar-strut type, and weighs 21 1/2 ozs. The engine runs up to 5000 R.P.M. before the valves bounce, and therefore, considering they are white metal, we should think that these bearings are right on the limit. However, they state that they ran last summer in the hot weather without an oil cooler and did not experience any trouble. They have also completed 100 hours bench test. | ||