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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).
Page discussing engine dimensions, thermal losses, and radiator size, including a comparative graph.

Identifier  ExFiles\Box 178\1\  img023
Date  15th February 1926 guessed
  
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goes up as the cube of the dimensions, while the area of the walls exposed to the burning charge only increases as the square of the dimensions. Again, a long stroke engine gains over a short stroke engine because with the former it is possible to make the combustion chamber more nearly hemispherical which is the desirable form for low thermal losses. Again, the combustion chamber of a small engine suggests a greater disturbance of symmetry due to the location of the sparking plug.

GRAPH IV

B.TH.U. TO COOLING WATER
PER MIN. PER ROAD WHEEL H.P.
20 H.P. R.R
E.A.C.

ENGINE R.P.M

It should not be assumed from this that over-heating troubles will be less with a large car than a small one. On the contrary, in practice, the reverse holds good owing to the restrictions on the size of the radiator which can be employed on a large car. (This is discussed later). It does shew, however, why the 20 HP. is not immune from boiling troubles in spite of the fact that it has much better area of radiator face per unit displacement than the 40/50 HP.

contd.
  
  


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