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).
Letter discussing issues with electrical petrol pumps and hydraulic tappets.
| Identifier | ExFiles\Box 140\4\ scan0304 | |
| Date | 23th October 1940 | |
| Rm.{William Robotham - Chief Engineer}2/ET. V.W. PILKINGTON Esq., Leyland Motors Ltd., LEYLAND. Lancashire. 23rd October, 1940. Dear Pilkington, Thank you so much for your letter of the 18th October. I have already sent off a sample of the electrical petrol pump which was developed from the original S.U. article. We had endless troubles with it, but it is now reasonably reliable and has a useful delivery against a two foot head, which I expect is about what you will get on the "Meadows" engine, if you put the pump level with the bottom of the tank. I think two of these units should cope with the output of the "Meadows" engine, unless it is prodigally extravagant with petrol. You ought to be able to get supplies of these pumps from S.U.; failing this we have a number in stock which we could let you have if they turned out to be what you wanted. With regard to the follow up of the hydraulic tappets which you are experiencing, during our five years contact with these devices, we suffered from this trouble on many occasions. Basically, if the cam form is so perfect that the tappet does not leave it at any speed within the running range and the valve springs do not surge sufficiently to give incipient valve bounce at any speed, then the phenomenon will not occur. With any given valve gear, the leakage factor in the Hydraulic tappet is the controlling factor. Since, however, if the tappet is to keep the valve gear quiet under maximum oil temperatures, the leakage factor must necessarily be very low under cold starting conditions, though you get satisfactory operation when the power plant is warm, you will still have to get it right when the oil is cold. As you do not mind a bit of noise at high speeds, you may with advantage be able to increase the plunger clearance of the tappet and help yourselves out of the trouble if you want to retain these devices. I still maintain that, on a petrol engine where the best practice is followed with regard to the valve itself, i.e. stellited or bright-ray seat inserts in the block, a hydraulic tappet is an unnecessary complication. But having little or no experience of oil engines, I am in no position to pass an opinion upon their requirements. | ||