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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).
Report discussing engine cooling, radiator airflow, and bonnet ventilation at various speeds and conditions.

Identifier  ExFiles\Box 24\4\  Scan194
Date  25th August 1924
  
- 2 - BY17/H.{Arthur M. Hanbury - Head Complaints} 25.8.24.

not under direct fan control normally will replace
the covered area and no serious inconvenience is
suffered so long as enough radiator area to meet
fan area, and therefore fan requirements, is
available.

From the last paragraph on first page of PN{Mr Northey}2/DN.
22.8.24. it would appear that FN. has taken my
demand for "air speed" to be synonymous with
"fan speed" but I was particularly careful to
avoid the term "fan speed" all through my report,
as being an ambiguous term, and replaced it by
one which is accurate; but more than that, I
carefully pointed out that increased air speed
does not necessarily mean increased fan speeds at
all but :-

a/- increased efficiency of the fan itself,

b/- giving free vent from bonnet to the air
handled by the fan,

more especially the latter, precisely as urged by
FN.

So far I have dealt with hill-climbing conditions.
I now propose to deal with criticism that my
deductions are'all put"out of court" when the car is
driven along the road. Whilst admittedly some change
takes place at certain speeds, at high speeds the
conditions are not materially altered owing to the
fact, repeatedly pointed out in my report, that there
is a totally inadequate area provided to allow the
air to escape from the bonnet, and therefore it would
appear that the fan in adding to the pressure of air
in bonnet set up by speed of car, practically prevents
air flowing through radiator at any reasonable speed
except where matrix is beneath the influence of the
fan. This point is clearly indicated by the fact
that at any speed above 50 MPH. the bonnet if
unsecured will lift up under the internal pressure
set up, and since pressure of this magnitude would
oppose the pressure on the matrix face set up by
car speed, obviously little, if any, air can be
flowing through radiator except where fan controlled.

The increased undershield clearances arranged on
latest 40/50 do not prevent boiling even with
shutters on bonnet open at full speed level road
conditions if temperature is at or above 30oC.

Contd.
  
  


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