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).
The failure of a scheme to convert Phantom III tappets and camshafts from hydraulic to non-hydraulic.
| Identifier | ExFiles\Box 96\2\ scan0308 | |
| Date | 24th August 1939 | |
| Wd.{Mr Wood/Mr Whitehead} W. Levallois O.{Mr Oldham} Hy{Tom Haldenby - Plant Engineer} O.{Mr Oldham} Lun C. S/S - O C. Ins/GWH{George W. Hancock - Head Chateauroux} (R) PHANTOM III - TAPPETS & CAMSHAFT We have now had sufficient evidence to indicate that the scheme for converting from hydraulic to non-hydraulic tappets does not have the slightest beneficial effect; on the contrary, there have been five or six cases where the tearing up of the cams has been worse after the conversion than it was on the original hydraulic tappets. This conversion should therefore be discontinued. Any failures of the hydraulic type camshaft should be dealt with by replacing the shaft with one of similar type until such time as we are able to issue final instructions regarding the whole trouble. We have now learned enough about the hydraulic mechanism to be able to ensure that it has at least a fair chance. We believe that the chief reasons for the repeated failure of this conversion scheme are:- 1. The solid plungers do not offer any restraint against the eccentrics riding round in the direction of valve opening when the friction on the rocker bushes reaches a certain point. In this respect the scheme is little better than the normal hydraulic arrangement. 2. Due to the oil supply for the hydraulic tappets being cut off, there is much less oil going down to the bottom tappets. 3. After one camshaft failure, there is bound to be a good deal of chromium and steel debris left in the camshaft trough, and this is bound to have a very destructive effect if it is not completely removed. We have stressed the importance of this on several occasions when there has been a repetition failure. Mx{John H Maddocks - Chief Proving Officer}/SB{Mr Bull/Mr Bannister}58 | ||