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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).
Engine and body modifications for a 100 MPH demonstration vehicle.

Identifier  WestWitteringFiles\V\March1931-September1931\  Scan204
Date  20th May 1931
  
HS.{Lord Ernest Hives - Chair} FROM R.{Sir Henry Royce} & E.{Mr Elliott - Chief Engineer}
C. to SG.{Arthur F. Sidgreaves - MD} WOR.{Arthur Wormald - General Works Manager} BY.{R.W. Bailey - Chief Engineer} [Struck through]
C. to C. OK. PN.{Mr Northey} [Struck through]
[Stamped]: ORIGINAL
re. P. 2. 100 MPH.
DEMONSTRATION.
[Handwritten]: 8/4/4/0
[Handwritten]: X7771
It would appear that with the present sports body this will take say 175 BHP., and we should aim at getting 100 BMEP. at 3300 RPM.
The gear ratio should be increased from the present 12 pinion to 14 teeth.
To get the HP. we may have to use benzol mixture, anda compression ratio of 5.5 to 1.
E.{Mr Elliott - Chief Engineer} is looking into the profile of the cam to give the maximum lift and long duration. This helps with detonations, to get good filling at high speed, and it will be necessary to have the short induction pipes and two separate carburetters, either vertical or down-draught, as we think the horizontal would be difficult to get in.
The throttles would be 50 to 55 m/m.{Mr Moon / Mr Moore} which equals from 2 to 2.125 dia.
The engine should be fitted up freely and every care taken to get good mechanical efficiency because at these high speeds much power is lost in viscosity of the oil. Thin oil should be used throughout the car. I have had very excellent results from the Shell 'R' thin oil on my small engine both as regards power and wear.
Some advantage might be obtained by smaller area of contact with the pistons and we might have to do something special in the way of piston rings to keep the oil down.
In consequence of the loss in mechanical friction I do not think it is wise to run faster than 3300 RPM. At this speed balance weights equal to the crankpin and web would appear possible on the 8 balance weight scheme.
I suggest the possibility of testing a model of the body and wings in the wind tunnel. I do not know how much difficulty this would entail. It might be found that some form of complete undershield would help the speed without altering the appearance. and we should naturally cut off every atom of wing that was possible, and we do not know whether discs over the wire wheels would be safe, and if they would be a decided advantage.
R.{Sir Henry Royce} & E.{Mr Elliott - Chief Engineer}
[Stamped]: RECEIVED 22 MAY 1931
  
  


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