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).
Investigation into a Goshawk-11 car's lack of power, identifying a burnt exhaust valve due to incorrect tappet adjustment.
| Identifier | ExFiles\Box 53\1\ Scan096 | |
| Date | 24th November 1922 | |
| TN. from Hs. {Lord Ernest Hives - Chair} X4545 Hs {Lord Ernest Hives - Chair} 5/LG24.11.22 HS. {Lord Ernest Hives - Chair} 4. Goshawk-11. X4219 X4545 We have received 4. Goshawk.11 car at the Works and we are keenly interested in your complaint as regards lack of power, because after this car had been back to the Works to have the low geared axle fitted, we tested it over the roads on which all the production Goshawks are tested, and found that it gave slightly above the average performance. When the car arrived it appeared to be fairly good at high speeds; the driver who brought it said that he came from Conduit Street to Derby in just over 3 1/4 hours. We found the power at low speeds was bad and that one cylinder was practically missing fire. It was soon apparent that one of the cylinders had practically no compression and further investigation showed that the seating on the exhaust valve in that cylinder was badly burnt. What we wish to point out is that we think the driver who has been in charge of this car should have realized what was wrong. We also feel certain that the cause of the exhaust valve burning is because the tappets have been set too closely. The tappet adjustment on the 20 HP. cannot be treated in the same way as the 40/50 - there must be a minimum clearance of .004". We believe also that there is a tendency on the part of the drivers to only remove the side tappet doors from the engine and adjust the tappets by the feel in the tappet rod. The only safe way of adjusting the tappets is to take off the top cover as well as the side covers and insert the feeler gauge. We think the drivers should at least take sufficient interest in their cars so as to know whether there are 6 compressions, and if not, to go into it and find the reason why. Hs. {Lord Ernest Hives - Chair} | ||