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).
Design principles, performance issues, and testing of hydraulic dampers.
| Identifier | ExFiles\Box 16\4\ Scan078 | |
| Date | 19th April 1929 | |
| 47520. DA.{Bernard Day - Chassis Design} Hs.{Lord Ernest Hives - Chair} BY.{R.W. Bailey - Chief Engineer} from R.{Sir Henry Royce} c. to SG.{Arthur F. Sidgreaves - MD} Wor.{Arthur Wormald - General Works Manager} PN.{Mr Northey} c. to E.{Mr Elliott - Chief Engineer} OY. HYDRAULIC DAMPERS. X. 235 X. 7520 I hope it is agreed that restricted passages for the oil are undesirable and dangerous, because we must allow the axle to move very quickly (especially upwards) without causing excessive stresses in the damper mechanism. Personally, I, and perhaps others, did not realise this quick movement of the axle, apart from the slower movement of the body. Naturally both need damping (probably equally). Also we should agree that by-pass holes are treacherous because they may easily spoil the action of the dampers as experience has shewn us, though if made of an exact size as a round hole of very small size they are permissible, but as the body movement is only about 60 per min. they must not be large enough to reduce the damping at this slow speed. It was here that we got wrong. So that we want the damping to slow movements to be as effective as to quick movements, though we may desire the big movements to be more damped than the small ones, but we must leave this for later. If we need to soften the ends we must do so by opposed springs in the conn. rods, as we do in the steering tube. If no disadvantages occurred such practice would have the double advantage of softening any knock, and keeping the ball joints tight and free from rattles. Regarding the breakage of the front damper at Chateauroux I am inclined to think this may be due to the brakes, or in some way the axle control. The sudden braking I have experienced puts enormous strains on the parts affected: study it from this aspect. In conclusion, I believe we want more damping than has been our practice in the past, and this must be effective at slow periodicity. I suggest trying 150/75 for Phantoms, and 100/50Ø for Goshawks. The difference between 60 periods and 600 should be as small as possible (i.e. very free oil passages). Road spring friction has probably obscured the results of tests. SS.{S. Smith} has less than Phantom, and also latest oiling has again reduced it. Our best design of damper is the older one with L.P. (upwards) valve in piston. R.{Sir Henry Royce} | ||