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).
Design of a single inlet valve spring to replace a double spring, detailing changes in poundage and stress.
| Identifier | ExFiles\Box 124\2\ scan0314 | |
| Date | 20th May 1941 | |
| Handwritten top: Rm{William Robotham - Chief Engineer}/CTS.{C. Trot Salt - Carburation} 1044 OR 18th We should get these springs made in straight carbonwire Rm{William Robotham - Chief Engineer} We Typed: To Rm.{William Robotham - Chief Engineer} c. to Rm{William Robotham - Chief Engineer}/HH. [Rm{William Robotham - Chief Engineer}/HH is crossed out] SECRET. Jnr.{Charles L. Jenner}7/JH.20.5.41. SINGLE INLET VALVE SPRING B.60 & B.80. Herewith PL.673 shewing a taper single spring of the closed ended type to replace the double P.III springs which have been used for some time on B.60 & 80. The design also shews the deletion of the grummet and a top washer with an oil seal. The poundage on the seat is kept the same 58 1/2 lbs. but the valve open position is reduced from 153 to 142 lbs. It is only by this means can the stress in the wire be kept reasonable. Our record of failure of this type of spring is not good, it appears to be due to fat springs of a short length and too few coils which results in a large stress range coupled with a fairly high max. stress. The closed end of the spring causes the large range. Such large ranges should have a low maximum stress to make one confident of success, this seems to be one explanation of the difficulty of substituting a single for a double spring in a given height. Jnr.{Charles L. Jenner} [Signature] Original PL.673 to RmHH. Prints to Jnr.{Charles L. Jenner} & Ashby. | ||