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).
Analysis of damper efficiency, air vent restriction, and front axle control systems for 20 HP and Phantom II models.
| Identifier | WestWitteringFiles\V\December1930-February1931\ Scan085 | |
| Date | 3rd January 1931 guessed | |
| - 2 - efficiency slightly but in the case of the 20 HP. damper the drop is not more than 5% and rather justifies the Americans' view that it does no harm. If it softens the riding it appears that the axle must be moving more than 1.0" when the discomfort is experienced. On the score that it appears to make the damper easier to silence it would seem to be justifiable. The .055 hole seems to be the limit to which drilling valves is practicable unless the static loads on the dampers are largely increased, as at large movements the efficiency of the damper is very seriously impaired with a larger hole, in fact it would not be much use where it is most needed over level crossings etc. It is surprising that the .055 hole causes no loss of efficiency over small movements. Confirmed on Sheets I & V.{VIENNA} - 40/50 & 25 H.P. RESTRICTING THE AIR VENT. Partially obstructing the air vent has this advantage, that it silences the damper with the minimum loss of efficiency over large movements, the reason being that it drops the damper loading most at small movements where the knock occurs. (See Sheet I, Col.III) On the other hand these small movements dictate the road holding qualities of the car and therefore it is difficult to recommend such a procedure to cure noises except on highly sensitive cars where frequent complaints have been made. REAR LEVER & CONNECTIONS. 20 HP. We attach a print (Sheet 3) showing the measured deflections for a given ball pin load. It will be noted that these are slightly greater than those of the 40/50. P.II. FRONT AXLE CONTROL DAMPERS. A typical diagram of a front damper is shown on Sheet 2 Fig.2. The most noticeable features are:- (1) That the R.P. or downward stroke of the piston is more than twice as efficient as the L.P. stroke. We attribute this to the fact that we believe the R.P. side of the piston automatically vents itself into the L.P. side and that the excess air on the R.P. side causes the trouble. This is rather confirmed by the fact that we can progressively increase the efficiency of the L.P. stroke by enlarging the air vent up to .156" dia. Figs. 5, 6 & 7.) Also if we change the air vent over to the R.P. side the L.P. suffers (Fig.3). It is possible that the absence of a replenishing valve on the L.P. side may be a contributory factor to its deficiencies. We are making some tests to establish this point. contd. | ||