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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).
Page summarizing radiator test results, detailing improvements from matrix heights and ventilation.

Identifier  ExFiles\Box 22\1\  Scan213
Date  25th November 1924
  
R.R. 493A (20H) (D.A. 652 20-3-24) J.H.D.
-4-
EXPERIMENTAL REPORT.
Expl. No.
REFHS/Rm{William Robotham - Chief Engineer}/LG25.11.24.

The critical atmospheric temperature therefore is 95°C - St.{Capt. P. R. Strong}

SUMMARY OF RADIATOR RESULTS.

Improvements due to matrix heights.

Four different heights of radiator matrix were tried in the test. It will be observed that the improvement resulting from increasing the height of the matrix is not directly proportional to the increase in face area, but rather less.

Improvements due to ventilation.

It will be observed that the limit of improvement that can be obtained by ventilation at 30 m.p.h. is 15% when the bonnet top panels are removed - 19% when the side panels are removed. Standard shutters give 7% improvement - louvres very little more at the speed in question.

We had some extra large shutters made for the tests whose area was more than double that of the standard shutters. The additional improvement obtained however only amounted to about 4% at 30 m.p.h., at high speeds it will be more.

We found that shutters at the front of the bonnet are rather more effective than those at the rear. Also, as one would expect, the value of ventilation increases as the road speed increases. We find that there is a very slight increase in the value of any given size of shutter when employed with a larger matrix, but this only amounts to about 1%.

Fan efficiency.

These tests confirm what has been demonstrated previously in other over-heating tests - i.e. that the

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