Rolls-Royce Archives
         « Prev  Box Series  Next »        

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).
Performance and pressure characteristics of petrol pumps, including free flow, back pressure, and spring ratings.

Identifier  ExFiles\Box 20\9\  Scan134
Date  8th April 1936
  
-2-

Hs{Lord Ernest Hives - Chair}/Swdl.{Len H. Swindell}19/KW.8.4.36.

We understood that the maximum pressure exerted by the pumps was 2 lbs/sq.in., but on checking found that this was only 1 lb/sq.in., or 35 ins. head of petrol. Although the maximum free deliveries between the several pumps tested varied by no more than 15% the maximum pressure ranged from 24 to 35 ins. of petrol head.

From the attached curve SP.{Mr Spinney}29, it will be seen that the maximum pressure is as important as the free flow delivery.

This curve shows the flow against back pressure in the case of the standard pump at 1 lb/sq.in. max. pressure, against that of a pump with a 1 1/2 lbs/sq.in. max. pressure. In the former the flow begins to fall off with the slightest back pressure, whereas the latter does not begin to fall off rapidly until a restriction amounting to a back pressure of 1.5 ins/hg. is reached.

Assuming that the reliability of the pump is not impaired by increasing the pressure to 1 1/2 lbs/sq.in., more consistent flow results are obtained when there is a restriction in the delivery line as per the needle and orifice. The free flow figures are unaltered.

The control of the maximum pressure is obtained by the strength of the diaphragm return springs, the standard pump springs being of .056 wire/2 1/2 lbs. rating and the 1 1/2 lbs./sq.in. pump springs of .064 wire/4 lbs. rating, otherwise the same.

HS{Lord Ernest Hives - Chair}/L.M.Swindall.
  
  


Copyright Sustain 2025, All Rights Reserved.    whatever is rightly done, however humble, is noble
An unhandled error has occurred. Reload 🗙