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).
Feasibility, cost, and implications of modifying Phantom III tappets and washers.
| Identifier | ExFiles\Box 96\2\ scan0293 | |
| Date | 20th July 1938 | |
| To BY.{R.W. Bailey - Chief Engineer} & Rm.{William Robotham - Chief Engineer} From RHC.{R. H. Coverley - Production Engineer} c. to Da.{Bernard Day - Chassis Design}, LA.{L. A. Archer}, Mx.{John H Maddocks - Chief Proving Officer} SWDL{Len H. Swindell} 6/Les RHC.{R. H. Coverley - Production Engineer}12/MJ.20.7.38. PHANTOM 111 TAPPETS. 354 With reference to By.1/G.6.7.38, the modifications shown on ECD.782 would not be so easy or economical to introduce as appears at first sight. The large diameter bore of tappet guide, E.88546 shown on the scheme will not increase the cost of future pieces, but there are already 1860 tappet guides in operation which could only be converted by grinding out the bores. This would be a very difficult operation due to the fact that these guides have already been gashed for the tappets, and the cost of grinding would be 10d. per guide, or £78.0.0d. for the full quantity involved. It will be necessary to produce the new tappet washers from square bar which will involve removal of burrs on the flat side by hand, whilst in addition, existing stock of 2600 circular washers E.85360 value £11.0.0d., will be rendered scrap. The new type washers incidentally will increase the Factory Cost of each Chassis by 9d. The existing tappet washer which has .025 - .045 diametral clearance in the guide appears to offer ample area for oil to escape, and it seems unlikely that sufficient hydraulic pressure could be set up to destroy the tappet surface. It will be recalled that the trouble in question was formerly attributed to excessive loading from the hydraulic tappet mechanism, but the trouble has recurred since this unit was abolished and appears simply due to the tappet being of inadequate area. If it is decided to introduce these washers, however, they will only be fitted to 90 engines since 110 on 'D' Series are already completed. The question of retrospective action will also no doubt arise, since only a small number of engines will be initially assembled with square washers, and in considering such action it is necessary to take into account all Ph.lll Chassis manufactured to date. The Cost of fitting squared washers to existing Chassis would be £8.0.0d. each, due to the necessary dismantling etc., and the following figures indicate the total charges involved - 110 Chassis 'D' Series at £8 per Chassis ...... £880. 0. 0d. Ph.lll Chassis A.{Mr Adams} B. & C. Series ........... £4800. 0. 0d. Total (All Ph.lll Chassis to date) ...... £5680. 0. 0d. Since the solid type tappet was introduced, 48 tappets have failed from a total of 2640 tappets (1 3/4%), but the trouble is expected to disappear completely when the flat bottomed tappet is standardised, and the question is therefore raised as to whether these failures are sufficient to warrant any action at present. In view of the Cost of incorporating the mods. shown on ECD.782, and and having regard to the fact that Wraith type barrel tappets are proposed for 'E' Series, it is considered that the possibility of improvement provided by altering existing design is so slight as not to justify proceeding. RHC.{R. H. Coverley - Production Engineer} | ||