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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).
Letter to Major B.C. Carter discussing the method for correcting and calculating the stiffness of a single crank from tests on a complete shaft.

Identifier  ExFiles\Box 137\4\  scan0006
Date  28th March 1929
  
Y634

Hs{Lord Ernest Hives - Chair}/SEL/T.

28th March, 1929.

Y634
X.4498

Major B.C. Carter,
Royal Aircraft Establishment,
South Farnborough, Hants.

Dear Major Carter,

I enclose some further information which I hope will cover the ground you require. I regret the delay in sending it, but we are rather rushed here now.

Table 1, shows the method by which I correct to obtain the stiffness of a single crank from tests on a complete shaft.

I believe that when you were supplied with the dimensions and test results on the shafts 13 C etc. they did not tell you that -

(a) the main bearings were not all the same length along each shaft.

(b) the shafts had "noses" of various sizes on which are fixed spring drives and dampers.

When calculating the stiffness of one by means of your formula, I always put "b" equal to half the width of a short main bearing. Thus there is usually about 1¼" of journal that does not get included in an estimate of the shaft stiffness.

My method of correcting a test on a complete shaft is as follows (taking 13 C as an example):-

Under a torque of 45,000 lbs.ft. the nose deflects .1648 radians, and the extra length of journal deflects .0494 radian. The six cranks must have twisted .7858 radian, and then stiffness must be 45,000 divided by .7858 = 57,250 lbs.ft./radian, or 4.120 x 10^6 lbs.ins/radian/crank.

Contd.
  
  


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