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).
The cause of valve failure due to decreasing clearance over mileage during continental touring.
Identifier | ExFiles\Box 11\3\ 03-page047 | |
Date | 2nd April 1930 | |
To Hs{Lord Ernest Hives - Chair} From G.W.H. Handwritten: Ac (in a circle) E Da{Bernard Day - Chassis Design} Seen Dr X7940c Bq Seen Bq Hôtel de France Chateauroux Indre 2/4/30 Return to HS{Lord Ernest Hives - Chair} RE: FAILURE OF THE VALVES. We can now state fairly docurate the cause of the failure of the valves. We find after running 3.500 miles the clearance of the exhaust valves begins to decrease and at 5.000 miles we come to a state when there are one or two exhaust valves with only .001" clearance when cold. When this condition is arrived at we get the following cycle during the mileage, the valve quickly become red hot whilst the high speed is maintained, the expansion of the valve is not equal to the expansion of the cylinder head and valve mechanism. We then have the valves open say .001" during the remaining time of the high speed and for a few seconds the valve clearance is increased which brings the valve on to its seat whilst it is still red hot. A few lightening hammer blows under this condition slightly tulips the valve which makes the valve clearance less, when again opening up, and a worse condition then arrises, the valve being more open say .002" whilst again running at high speed and we say it is this condition which produces effect of burning. If the valve clearance is kept to .004" dead cold there is no fear of the valves burning It looks as if the life of the clearance of the valve is approx. 3.500 miles for continental touring. G.W.H. (Signature of G.W.H.) (Stamp: RECEIVED 3 APR 1930) | ||