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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).
Air Ministry's empirical formula for crankshaft stiffness and comparing calculated versus test results.

Identifier  ExFiles\Box 65\4\  scan0208
Date  24th November 1927
  
RG{Mr Rowledge}
BY
X8010
Hs{Lord Ernest Hives - Chair}/Tsnl/LG24.11.27.

AIR MINISTRY EMPIRICAL FORMULA FOR
CRANKSHAFT STIFFNESS.
X5010

The following are a few notes on the method
of obtaining a comparison between the calculated and test
stiffness in crankshafts.

The last column on the right gives the stiffness
of one complete crank as shewn in the sketch. The torsional
deflection of all six cranks will be six radians for the torque
in lbs.ins. given here.

To this must be added the deflections that will
occur in the nose extension for the spring drive, and also in
the extra amount of main bearing journal not included in the
formula, which only takes account of one half of a short bearing
on each side of the crank. These last two items usually
amount to about 20% of the total deflection.

To obtain the actual stiffness of one crank
therefore from the test on the complete shaft, the reverse
procedure has to be followed, and the various deflections sub-
tracted.

The car crankshafts given in the table were cal{Mr Calvert}-
culated by Major Carter from data supplied by us, and are :

13 c Standard Phantom.
14 c " 20 HP.
15 c Special stiff experimental 20 HP.
16 c 1-G-1
17 c Lorraine Dietrich.

Hs{Lord Ernest Hives - Chair}/S.S.Tresilian.
  
  


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