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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).
And finalising new experimental fan ratios.

Identifier  ExFiles\Box 75\3\  scan0078
Date  24th March 1925
  
To BY.{R.W. Bailey - Chief Engineer} from EFC.
c. BY/SS.{S. Smith}
c. Hs.{Lord Ernest Hives - Chair}

X1017
EFC3/T24.3.25.

X.1017. RE EAC. FANS. V8220

We are in receipt of your BY18/H23.3.25.

With reference to the originally suggested ratios of 1.05 to 1, 1.12 to 1, and 1.20 to 1, the smallest and largest of these may be taken to correspond approximately to the same thrust and the same speed respectively, comparing the present No.18 fan with the old 40/50 fan, the intermediate ratio being an intermediate case.

On talking this matter over with Mr. Hives, he has expressed a desire to omit the 1.05 ratio, in which case the same thrust and same cooling is obtained, and instead, to introduce another and higher ratio which corresponds to the absorption of the same amount of power as the old fan, this being roughly speaking 1.3 to 1.

Therefore, our final recommendations in the matter for the three experimental ratios are 1.12 to 1, 1.20 to 1 and 1.28 to 1, these being in arithmetical progression.

Perhaps you would kindly have the experimental instructions altered accordingly.

EFC.
  
  


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