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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).
Differences between blueprint specifications and a supplied sample of American main springs.

Identifier  ExFiles\Box 43\2\  Scan238
Date  28th December 1927
  
RECEIVED DEC 29 1927

Hs.{Lord Ernest Hives - Chair} C. Wcr. X3900
BY2/G.28.12.27.

AMERICAN MAIN SPRINGS.

Referring to my recent visit to Messrs. Firths to discuss with Mr. Wortley Fawcett and Mr. Stansfield the question of the apparent variation between the American sample spring we supplied and the detail blueprints, to which we had previously asked them to work, I found that there was a very distinct difference between the two sets of requirements as outlined :-

a/- In the blueprints and CY's memo which we supplied to Messrs. Firths,

and

b/- The sample American spring we supplied later which was supposed to conform to the blueprints and information referred to in (a).

The difference consisted in mainly the following points :-

1/- The top plate was not made to one single radius as called for in the details and CY's memo, but was made up of three radii, a large radius in the centre approximately 108", and two curves of greater curvature forming the ends, the radius of the two curves being 70" approximately.

2/- The ends of each plate in the sample spring showed greater length of tangential ends than on the blueprint, but generally speaking it was possible to pass a .003" feeler 1 1/2" in inwards from each end along the length of the spring.

3/- The initial camber of the spring made to the drawings was distinctly greater than that shown on the sample spring.

4/- The stiffness of the spring made to drawing was distinctly greater than that of the sample spring.

The result of the differences exhibited between the detail drawings and the sample spring was that the top plate would not lie flat under any conditions, there was a gap of as much as 5/32" between the top plate and the second plate at a certain position along its length.
  
  


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