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).
Conclusions and recommendations on the design and performance of hydraulic dampers.
| Identifier | WestWitteringFiles\T\March1929-December1929\ Scan116 | |
| Date | 3rd May 1929 | |
| HS.{Lord Ernest Hives - Chair} BY.{R.W. Bailey - Chief Engineer} ) FROM R.{Sir Henry Royce} DA.{Bernard Day - Chassis Design} ) C. to SG.{Arthur F. Sidgreaves - MD} WOR.{Arthur Wormald - General Works Manager} OY Mr. Fuller re. HYDRAULIC DAMPERS. X235 X5520 My conclusions at present are as follows:- (1) That the restriction passage, and our desire that the dampers should be more effective at quick oscillations than slow, are errors, and should be definitely abandoned. (2) The idea that the upward resistance shall be much greater than the downward resistance is subject to some doubt, and until proved should only be used in moderate proportions, such as two up, three down, instead of one up and two down. (3) That the leak past the valves has always existed to a small degree in the air vent hole on the low pressure side. I believe it is possible that this leak if kept very small, such as a round 1/32nd. hole, may be of benefit in both directions, the reason for this being that after the damper has been made to act in one direction it may hold the road springs compressed for an undesirably long period, so that a small hole through the high pressure valve may have the benefit of allowing the car to recover its normal position between the road shocks. Such a small hole would help to get rid of air, and would have no effect at the speed at which the body would nominally oscillate. I therefore agree with such a by-pass passage and wish for its adoption unless some experimental test shews it to render the dampers ineffective. (4) In experimenting with the 20HP. in France I increased the damping of the rear and the front at the same time with marked improvement to the riding on those roads. Since returning home circumstances have made me reduce the damping on the front of the 20HP. experimentally, and I now incline to believe that for riding qualities and steadiness of the front of the radiator it would be better to have the front damping less than the rear. Naturally one would suppose that the damping bore some percentage to the weight or inertia of the parts carried by the axle, and from the short experience I find this reasoning to be supported, and I recommend for test considerably more damping on the rear of the car than the front, and considerably more on a heavy car than a light car at the same speed, and therefore considerably more on the Phantom than on the 20HP. In conclusion we are again sending you a design of the valve in the piston arranged so that the short movements are nearly free from damping, and the ends of the strokes are softened by the free movement of this piston valve carried in the piston. This arrangement should make the small movements and the road springs act at low speed over small inequalities of the road in the way desired. It should also act in the same way as theory suggests, that the longer strokes have proportionately more damping than the short strokes, but should have no difference in effect between a quick axle movement and a slow body movement. We believe this will carry us as far as we know at the present. Naturally we have always wished for increased damping with increased car speeds, but we do not know how to do this in a simple practical manner and it was this idea that led to the dynamic passage etc. But this does not achieve the object, and has other faults. R.{Sir Henry Royce} | ||