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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).
Summary of test results on water pumps and cooling systems, addressing cavitation and back pressure.

Identifier  ExFiles\Box 4\1\  01-page335
Date  25th April 1935
  
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Ha/Smdl.2/KW. 25.4.35.

Summarising the results of these tests, the large pump with the modified crankcase gives a satisfactory temperature rise across the engine at all speeds, but the indication of cavitation at the high speeds is undesirable. If this is overcome, the resulting increase in flow is unnecessary and also has the disadvantage of a higher back pressure in the system.

The use of the small pump in conjunction with a further reduction in the restrictions throughout the system, such as an increased flow from the rear end of the cylinder head, to overcome the higher rear end temperature, would reduce the back pressure in the system. Other than this there is not the tendency to cavitation at high speeds as compared with the larger pump.

As these tests have shown, the bottom water pipe is too small and should be increased if possible to 1 3/8" diameter, together with the radiator outlet and connection piece.

Though we have not yet had the opportunity of trying a larger pump inlet it should be logical to increase this in conformity with the bottom pipe.

Ha/L.H. Swindall.
  
  


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