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).
Bench test report on the first Wraith III unit, detailing performance and camshaft issues.
| Identifier | ExFiles\Box 6\6\ 06-page227 | |
| Date | 22th June 1937 | |
| 600 To E.{Mr Elliott - Chief Engineer} from Rs{Sir Henry Royce's Secretary}/Swdl.{Len H. Swindell} c. to Sg.{Arthur F. Sidgreaves - MD} c. to Hs.{Lord Ernest Hives - Chair} c. to Hy.{Tom Haldenby - Plant Engineer} Rs{Sir Henry Royce's Secretary}/Swd1.1/VS.{J. Vickers}22.6.37. BENCH TEST REPORT OF 1ST WRAITH III UNIT. The following is a summarised report of the results obtained up-to-date on the above unit, which is now dismantled in preparation for 10,000 miles test. Performance. (1) In comparison with the average 30 H.P. unit the Wraith has identical power between 1500 and 3000 R.P.M. (2) Owing to valve bounce above 3600 R.P.M., Wraith power is not comparable. Stronger valve springs were not available in time to repeat power. (3) At low speeds from 500 - 1500 R.P.M. the Wraith has an advantage of 5 lbs/sq.in. M.E.P. or approx. 4%. (4) From previous experience the timing at which the curve was taken, i.e. 8° early for best all round power. (5) One tooth on existing cam wheel makes 12° alteration to the valve timing, which is excessive when finding what the best timing is. (6) By cutting an extra keyway interposed between teeth on cam wheel as per Phantom III, finer adjustment of timing can be made. Further tests to be carried out on second unit. Camshaft. (1) At .006 tappet clearance and above, the valve gear is very noisy and it is necessary to run at .002 in order to be on a par with the degree of quietness obtained on the 30 H.P. up to clearances of .008. continued. | ||