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 detailing the findings from an examination of a cylinder head from car 12-MC, including rust, thickness, and proposed design changes.
| Identifier | ExFiles\Box 72\2\ scan0071 | |
| Date | 7th May 1926 | |
| ROLLS-ROYCE OF AMERICA, INC. SPRINGFIELD, MASS. X8991 Oy5-E-5726 May 7th, 1926 Mr. E.{Mr Elliott - Chief Engineer} W. Hives, Rolls-Royce, Ltd., Derby, England. Dear Hives: Re Cylinder head We have just taken the cylinder head off 12-MC which has run 14,000 miles, and cut it up to see the condition of the water jacket core-spaces, etc. We have put the model head on the car. It is too early yet to say whether we find any difference with the new head. The idea was to see whether the water passages had become filled with rust or scale. We have been using glycerine anti-freeze mixtures which tend to scour the jackets, and our water is very soft, so that we did not expect to find much scale. There was considerable rust on the jacket walls however and in particular the three small passages between and at the sides of the two spark plug bosses, were almost or completely closed on all cylinders. Thus a steam pocket is liable to form on the lower side of the spark plug bosses. I attach a print A-9069 showing a proposal to use three long core prints and covers to make it possible to core these spots more rigidly, to clean them out on a new head and to clean them out on service. We further found that the thickness of metal above each cylinder head was .400 to .425, instead of .300 as on drawing. On the S.G. we have found a thick cylinder head the principal cause of detonation and roughness and for some time have been working to a limit of .250+30. We are putting a limit on the new head of .300-50. It can be measured at the center through a core hole above each cylinder, by means of a special indicating calliper. | ||