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).
Endurance test report on Spectre Fully Split Skirt Pistons.
| Identifier | ExFiles\Box 94\5\ scan0101 | |
| Date | 21th October 1935 | |
| To E.{Mr Elliott - Chief Engineer} c. to Wor.{Arthur Wormald - General Works Manager} c. to By.{R.W. Bailey - Chief Engineer} SpectreCodename for Phantom III Fully Split Skirt Pistons. We have now successfully completed our usual endurance test on a set of SpectreCodename for Phantom III pistons having a full split skirt to Lec.4617. The pistons tested were the original set to Lec.4617 and were produced from existing castings of E.86672 semi-split pistons and ground similar to Bentley EB.1299 pistons. The pistons had previously done a little running in SpectreCodename for Phantom III 10 unit and when removed from this unit showed as good a bedding as EB.1299 pistons on Bentley and there were no knocks. When fitted to the Bentley unit the gudgeon pin bores were bushed in order that Bentley gudgeon pins could be used and longer connecting rods were used to suit the higher position of the gudgeon pin relative to the crown on the SpectreCodename for Phantom III piston compared with Bentley. The pistons completed 28 hrs. of our endurance test which is run as follows for each hour :- 30 mins. at 4,000 r.p.m. full throttle. 25 mins. at 4,250 " 5 mins. at 4,500 " At completion of test the pistons were perfectly free from cracks of any kind. From our experience with tests on Bentley pistons each hour of the endurance test is equivalent to approximately 1,250 miles of the standardisation test in France, so that we can say the pistons have run the equivalent of 35,000 miles in France. The conditions under which the pistons were run were more severe than they are likely to be subjected to in SpectreCodename for Phantom III, since the compression ratio of the Bentley unit was higher and at these speeds the B.M.E.P. is of course much higher on Bentley than SpectreCodename for Phantom III. | ||