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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 endurance tests to determine the necessity of an oil cooler based on bearing type and oil temperatures.

Identifier  ExFiles\Box 107\2\  scan0135
Date  25th May 1938
  
-3-

We have not yet ascertained the reason for this but are making tests in connection with this discrepancy.

Summary.

The above tests taken in conjunction with the test bed endurance runs at high oil inlet temperatures, indicate that the oil cooler can be dispensed with on engines fitted with AC.B big ends. It may be mentioned that in all approximately 175 miles were covered on the track with 35-BX (with bearings fitted up in this manner) at maximum speeds and that continuous full throttle max. speed runs of 20-30 miles at a time were made repeatedly.

As regards existing cars A, B and C series, fitted with W/M bearings only, above tests indicate that it is not safe to dispense with the oil cooler on these chassis, at any rate until test bed endurance is completed to establish the relative effect on bearing life of oil inlet temperatures of 125 and 107°C respectively.

The maximum oil temperature which is ever likely to be reached on a Ph.III engine without oil cooler in hot weather, even when driven at maximum speed continuously is 142°C.

Rm{William Robotham - Chief Engineer}/Std.
  
  


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