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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).
Wind tunnel tests performed on a 1/8th scale model of a 3 1/4 litre Bentley saloon.

Identifier  ExFiles\Box 160\2\  scan0127
Date  27th June 1933
  
To Mer. From EV.{Ivan Evernden - coachwork}
C. Sg.{Arthur F. Sidgreaves - MD} C.
C. Cx.{Major Len W. Cox - Advertising Manager} HS.{Lord Ernest Hives - Chair}
C. S. De.
C. PN.{Mr Northey} Bn.{W.O. Bentley / Mr Barrington}

EV.{Ivan Evernden - coachwork}14/KT.27.6.33.

WIND TUNNEL TESTS - BENTLEY
AT VICKERS AVIATION LTD. WEYBRIDGE.

Purposes of the Tests.

It was considered that the purpose of these tests was to discover ways and means of improving the shape of the 3 1/4 litre Bentley saloon, as seen on the green car 2.B.4, with a view to obtaining greater maximum speed with the present maximum horse power at 91 HP. at 4000 R.P.M.

For the tests we used model I as shown on N.sch.3738, which represented this body very accurately in detail, even including front and rear axle, wells for the feet, engine sump and petrol tank.

Six types of front wings were available, four screens and two tails. The second tail was of the same length as the standard back end, but the re-entrant angle was replaced by a straight sweep, from the roof down to the rear of the body. The scale of the model was 1/8.

The Tests on Front Wings. (Group I)

From the table herewith the following deductions can be made.

(1) The addition of rear wings appears to reduce the drag by a small percentage.

(2) The addition of normal standard front wings adds to the drag approx. 14.5%.

(3) Of all the other types of front wings the Panhard Type are the best, being even better than the Birdwing (10-EX Type), being approx. 6%.

(4) With the standard tail and standard front wings with outside valances, the spare wheel recessed and not recessed showed only a very small difference.
  
  


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