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).
Comparison of G.1 and G.3 material diaphragms, tested with and without air bottles on a pump.
| Identifier | ExFiles\Box 149\4\ scan0110 | |
| Date | 18th November 1936 | |
| To E.{Mr Elliott - Chief Engineer} from Rm{William Robotham - Chief Engineer}/JBD.{John B. Dixon - Fuel Systems} Hs.{Lord Ernest Hives - Chair} COMPARISON BETWEEN THE G.1. & G.3. material diaphragms with and without air bottles. The pump was fitted up with filter and standard length of suction pipe as on the Phantom III. chassis having a 30" lift from the Tank. The delivery pipe was fitted with a tap and a connection to a glass stand pipe taken between the pump and the tap. The head against which the pump was operating could then be regulated by the tap, and read directly in the glass tube. The attached graph gives delivery plotted against head. Graph No.1. With both diaphragm materials the double pump tended worked in step, that is to say both sides delivering at the same time giving a very pulsating delivery, this did not cease when the gauge glass was disconnected. This pumping in step happened on both pumps used, though both of them at times functioned correctly, when the delivery was approximately the same as when the air bottles were fitted. The delivery of the G.3. as compared with the G.1. fell off rapidly as the delivery head was increased and the pump cut out at a lower pressure. This must be due to the stiffer G.3. diaphragm having larger effective area because with low pressure heads there is only slight difference in delivery which may be due to the increased stiffness of the material. Air bottles were fitted on the top of the pump with a total capacity of 2 cubic inches, this gave a very steady delivery throughout the pressure range and a very substantial increase in delivery when only one unit was working and either multiplied the effect of the units working in step or prevented it, but did not increase the flow beyond that delivered by both pumps working correctly. We feel the fitting of air bottles to pumps would be justified insomuch as they increase the delivery of one unit and prevent the possibility of a reduced output from the pumps if they function in step. By using the G.3. material, we have we hope got rid of all the shrinkage troubles, but we have now a pump with a diminished margin to deal with vapour in hot weather. continued. | ||