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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).
Progress report on the Spectre chassis engine unit, detailing tests and modifications to components.

Identifier  ExFiles\Box 4\1\  01-page125
Date  9th October 1934
  
X6694

To E.{Mr Elliott - Chief Engineer}
c. to Wor.{Arthur Wormald - General Works Manager}
c. to By:

Rm{William Robotham - Chief Engineer}/Rm{William Robotham - Chief Engineer};11/KW. 9.10.34.

PROGRESS OF SPECTRECodename for Phantom III CHASSIS.

ENGINE UNIT.
We have now done a considerable amount of running on the test bed with this engine unit.

Bearings.
Originally we ran lead bronze main bearings. For a car engine of our present output these are not really necessary, additionally our lubrication scheme is not altogether satisfactory for this material. In consequence we have reverted to white metal main bearings and are running lead bronze big ends only.

We have had no trouble with the mechanical reliability of the engine, though we have not done any endurance tests as yet.

Cooling.
There is a certain amount of restriction in the water circulation which appears to be spread evenly over the whole system, the passages and pipes will require increasing in size.

Pistons.
The original semi-split type pistons were not very good for mechanical efficiency, we have fitted Aerolites and picked up 10 H.P. The engine now gives 195 H.P.

Camshaft & Carburetter.
We have not been able to obtain satisfactory slow running with the camshaft and carburetters at present fitted. We do not think that the fault lies entirely with the camshaft because it is very similar to that on the 20/25. The hydraulic tappets however increase the effective overlap, which is bad for this feature. However, we are fitting two SpectreCodename for Phantom III carburetters to a Bentley pipe on the 20/25 and working on them under these conditions, so that we can separate the engine characteristics from the carburetter characteristics.
  
  


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