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).
Servo mechanism lubrication issues and modifications, and the analysis of a failing clutch pressure plate.
| Identifier | ExFiles\Box 11\3\ 03-page226 | |
| Date | 20th July 1930 guessed | |
| -4- SERVO DRIVE TO L.O.P. G.76740. SERVO MECHANISM TO L.O.P. G.77669. (1) G.78380 Pull Rod replaces G.77581. (2) Cotton 'A' fabric secured to pressure plates by staples in place of copper tubular rivets. (3) Damper for stopping clank from Servo mechanism.- The servo has been efficient and mechanism fairly satisfactory. There has not been sufficient oil supplied to the bearings and cams, the bijur when tested did not pass any oil. Upon dismantling the servo completely, we found no oil at all had reached the driving shaft of the servo, and with the present arrangement of the oil wick it is limited too much. The copper wire with the wick attached in the recess for the bijur is too tight and completely blocks the oil passage. We tried with a full supply of oil, but 7/8 of it passed through the feed pipe to the cams. It is more important to lubricate the shaft than the cam faces. We have altered the arrangement by enlarging the passage of the oilway feeding the scissors and shaft to .105", placed the copper wire holding the wick in the oilway but keeping the wick out of the oilway, the wick being at the top covering both feeds, i.e. cams and shaft. With this arrangement (bench test), there is an equal supply of oil to either unit. The servo fabrics have spread outwards, and have fouled the drum slightly. We are of the opinion that additional staples would prevent this. There is no sign of the fabrics having any tendency to be dragged in the direction of rotation. The damper for preventing servo clank has acted efficiently in this respect, there being no noise from the servo mechanism when same is released. FLYWHEEL & CLUTCH TO L.O.P. G.78478 INCORPORATING N.S. 2973 AUTOMATIC CLUTCH SPIGOT LUBRICATION FROM GEAR BOX. Complete to above L.O.P., but incorporating the following MODIFICATIONS:- (1) G.78479 Damper Plate produced in C/I. (2) G.78481 Pressure Plate produced in C/I. modified by screwing ferrules into plate, leaving plain facing as shown on drgs: Ex.5090/1. (3) G.78517 Ferrule modified to Drg: Ex.5091. (4) G.78731 Screws modified to Drg: Ex. 5092. (5) G.78483 Friction Plate modified to Drawing Ex. 5094 (extended length of slots) with Ferodo linings cut in 8 segments, rivetted on. 40° chamfer at each end of Ferodo segments as shown on Drawing Ex.5103.- The clutch, for the first part of the mileage, was entirely free from jaggers, the engagement being a very smooth drive. It stopped readily both hot and cold. At a mileage of 4443, it was noticed to jagger slightly, and became hard to disengage as the speed of the engine increased. We carried out various tests to locate the trouble, but none were effective. Upon finishing the tests in hand, the gear box and clutch were dismantled, and we found the cause to be due to the C.I. pressure plate G.78481 having cracked right through one of the recess holes for the pressure springs and the thick portion of the plate. This opened out by the centrifugal force as the engine speed was increased, which caused it to bind in the flywheel, hence the hardness experienced to disengage the clutch. We found cracks had started in two other places. The mileage is held up awaiting a new pressure plate from | ||