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).
Tests carried out on Wraith III valve gear springs on a Bentley unit.
| Identifier | ExFiles\Box 10\3\ 03-page017 | |
| Date | 16th March 1937 | |
| 654. E.{Mr Elliott - Chief Engineer} from Rm{William Robotham - Chief Engineer}/Mths.{Reg Matthews} c. E/Psn. c. Rm{William Robotham - Chief Engineer}/Swdl.{Len H. Swindell} Rm{William Robotham - Chief Engineer}/Mths{Reg Matthews}9/R.16.3.37. WRAITH III VALVE GEAR. This report is in reply to your memo E/Psnl/MN. 1.3.37. in which you requested us to carry out certain tests on valve springs, with and without the bottom tappet springs, on Bentley unit. For our first tests the unit was run with bottom tappet springs, and the following arrangement of valve springs. No. 1 & 2 Cylinders - Rm.{William Robotham - Chief Engineer}260 close coiled Swedish wire produced by Tempered Spring Co. No. 3 & 4 Cylinders - Rm.{William Robotham - Chief Engineer}260 close coiled Swedish wire produced by R.R. No. 5 & 6 Cylinders - Lec.5417 Chrome-Vanadium Springs produced by R.R. the results of the first tests are tabulated below:- BOTTOM TAPPET SPRINGS FITTED. R.P.M. | Rm.{William Robotham - Chief Engineer}260 Tempered Spring Co. | Rm.{William Robotham - Chief Engineer}260 By R.R. | Lec.5417 by R.R. ---|---|---|--- 3900 | - | - | Springs Surge. No.5 Inlet surges badly. No.5 Inlet Valve bouncing. 4000 | Very slight surge | Very slight surge. | Slight surge. 4100 | Very slight surge | Very slight surge. | Slight surge. 4200 | Very slight surge | Very slight surge. | Surging. No.5 Inlet surges badly, others not so much. All valves bounce slightly. 4250 | Very slight surge. No.1 Exhaust valve bounces slightly. | Very slight surge | 4300 | Springs surging No.1 Exh. No.3 Inlet Valves bouncing. | Springs surging. | No.5 Inlet surges badly. All springs surge and valves bouncing. | ||