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).
Repeated tappet and camshaft trouble on a Phantom III, chassis 3-AX-95, after conversion to solid tappets.
| Identifier | ExFiles\Box 96\1\ scan0400 | |
| Date | 14th August 1939 | |
| 361 SWD2 Mx{John H Maddocks - Chief Proving Officer}/SB.{Mr Bull/Mr Bannister}5/G.14.8.39. Hd.{Mr Hayward/Mr Huddy} o.{Mr Oldham} Ry. o.{Mr Oldham} Rm.{William Robotham - Chief Engineer} c. W/S. (C). e.{Mr Elliott - Chief Engineer} Rm{William Robotham - Chief Engineer}/GWH.{George W. Hancock - Head Chateauroux} File TAPPETS & CAMSHAFT - PHANTOM III. CHASSIS NO. 3-AX-95. PLAYER. We wish to confirm the recommendations made verbally concerning the repeated tappet trouble on this car, the present trouble being the second failure after converting to solid tappets. In the first place it is clear that this last failure is not due to the tappet chambers not having been cleaned out as has been suspected in certain other cases where failure has been premature after a similar conversion, but as we have had more trouble on these conversion jobs than on the original hydraulic tappets, we are bound to conclude that this type of conversion is not satisfactory. We believe this is due to the eccentrics riding away from the solid plungers when the engine is running, thus taking up the tappet clearance and causing base circle loading on the tappets. This riding away is due to excessive friction in the rocker bushes which always occurs in the direction of valve opening, which swings the eccentric arm away from the plunger. We are looking into the possibility of anchoring the eccentric more positively and this may make the conversion more satisfactory. There is also less oil going down to the tappets with the conversion scheme, and this is a disadvantage. In the meantime, we do not consider it advisable to continue with the present conversion scheme, and we recommend reverting to the original hydraulic mechanism which can be made to function satisfactorily provided the following modifications are carried out :- (1). The oil level in the tappet chambers should be raised 2" by fitting copper stand pipes to the two oil drain holes at either end of both sections at the bottom of the Vee (eight pipes in all), the intermediate drain holes being plugged with cork. The ends of the pipes should be tapered so that they are a good tapping fit in the casing. (see sketch herewith). Note. It is most important before finally re-erecting the engine to fill both chambers with oil to the height of the standpipes as it would otherwise be a long while before the oil reached this level. | ||