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).
Issues with valve seat distortion, engine diamond mounting movement, and overheating at low speeds.
| Identifier | ExFiles\Box 5a\3\ 03-page142 | |
| Date | 30th November 1931 | |
| To He/Rm.{William Robotham - Chief Engineer} From G.F.H. Hotel de France, Chateauroux, FRANCE. 18.G.IV. Further to our memo of yesterday, we send you a sketch of the valve seats, showing the distortion of the seats, the shaded portion indicating the high part of the seat and the unshaded portion where the valve seating has sunk. We also show a sketch of the exhaust valve and guide giving an indication of the collapse or distortion of the angle of the valve guide, also where the annulus should have been turned in the valve guide to stop the capillary attraction. It would appear that where the valves in the cylinder head are situated the design is on the weak side. Either thicker castings or strutting should overcome this trouble. RE. ENGINE DIAMOND MOUNTING. We have come across a feature that may, or may not be, serious. The feature is only noticeable when turning over the engine by the starting handle. We noticed that when going over compression the front of the engine was lifted up, and upon investigation we found that it is only the O.S. of the front of the engine that was being lifted, with no movement on the N.S. This movement is caused by the bending of the supporting tube on the O.S. between the portions as shown in the sketch. We cannot discern any movement taking place in the rocking lever supporting the two tubes and the engine. It would be interesting if you could try this out on the car that you have mounted the engine in the same way. The best way to observe it is to get the engine on a good compression and bounce it, watching the fan pulley closely, and I believe you will find that this appears to move up and down as if there was slack in the bearing, and is very misleading until one traces the movement out. RE. OVERHEATING TEMPERATURES WHEN RUNNING SLOWLY. We have got down to this trouble and find that it is due to an inefficient water pump. At slow speeds, i.e. 4 M.P.H. or when idling in the shop, there was no water flow at all. We dismantled the water pump and found that there was a clearance of .045" between the vanes and the pump body. This naturally allowed, at slow speeds, the vanes to revolve without circulating the water. We have let the vanes down to within practically .001" of the body mounting and packed with aluminium washers behind the vanes. Upon trying the engine with this alteration we get a water flow at the slowest we can run the engine, and our water temperature after running for approx. 20 mins. did not rise above 75°C. We send you a rough sketch showing the pump as we have found it. Since sending you the report on 18/11/31 we have found | ||