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).
Reprinted article explaining the design and operation of the D.N. Shock Absorber.
| Identifier | ExFiles\Box 44\5\ Scan108 | |
| Date | 3rd July 1924 | |
| Reprinted from 'THE AUTO MOTOR JOURNAL' of July 3, 1924. THE D.N. SHOCK ABSORBER ONE of the most successful of the shock absorbers and damping devices is the D.N., formerly known as the Derihon, which is now much improved. The principle underlying the D.N. device is that of allowing the compression or extension of the spring to be always free and unrestrained, while the rebound only and in each direction is checked or damped. Our illustrations have been prepared to show the action of the appliance. In the first is shown the exterior view of the damper, which is screwed to the chassis frame. A corrugated collar over a corrugated shoulder on the damper body holds it to the chassis frame, and allows of its angular positioning to suit the position of the operating lever, which is attached at its end to an adjustable link with a right and left-hand lengthening or shortening sleeve and a lignum-vitae ball joint for attachment to suitable anchorage on the car axle—front or rear. Our second drawing shows three sectional views through the appliance from which its operation will be easily gathered. The letters in all three diagrams refer to the same parts of the apparatus. The cylinder G which forms the body of the shock absorber is bored out and ground to the radius of the paddle XY, which, in conjunction with a fixed partition, D, containing a bye-pass valve, E, divides the cylinder into three compartments: A, in which the pressure of the castor oil always remains constant, and B and C, in which the pressure is variable, due to the displacement of the oil in compartments B and C set up by semi-rotary action of the paddle XY which is actuated by the movement of the road springs through the lever and link shown in the exterior view. The semi-rotary action of the paddle XY is set up by the variations in the road surface, which are transmitted to the road spings and in turn transmitted by means of the link affixed to the springs and the lever L to the spindle N which actuates the paddle, the shock absorber being fitted to the chassis frame. The paddle contains ball valves S and T, which permit the oil to flow from the compartment B to C, and vice versa, through an annular space, R, connecting a port, H, which remains closed by the fixed partition D so long as the paddle is in such a position as to allow the volume in each of the compartments B and C to remain constant. The combined volume of compartments B and C is always constant, no matter what the position of the paddle. The front portion of the cylindrical casing is fitted with a gland or stuffing-box, and carries the paddle spindle N, which is in one piece with the paddle XY, on to which is fitted the lever or arm L, which is actuated by a connecting rod and so operates the apparatus. It will be seen that, since the paddle is supported and rotates about the spigot, M, and is in addition carried in a phosphor-bronze bush by the spindle N, the packing or gland which forms the stuffing-box is not in any way subjected to radial stresses, with the result that oil leakage can only take place directly through the high pressures that are set up inside the chambers B and C during the working of the apparatus and which tend to force oil between the spindle N and its phosphor-bronze bush. The possibility of this happening is, however, prevented by the D.N.-recuperator, which consists of an annular space or groove, V, which is connected to the compartments B and C by a duct, Q, in the fixed partition D, and the outlet of which is controlled by two non-return ball valves, W, and K, the outlets of which are either side of the fixed partition. Any further possibility of oil leakage is prevented by two chrome leather washers, which are forced against the point P, which is formed by the journal and bush of the paddle spindle N. When the road spring is compressed, the movement is transmitted to the lever by means of the connecting-rod, and forces the lever L upwards, this causing a movement of the paddle XY, which squeezes the oil in the chamber C, causing it to find free outlet through paddle ball valve T round the annular space R and out of port H to chamber B. The rebound of the spring pulls the lever down with the Image Captions: The D.N. Shock Absorber, showing the arm and the adjustable link connecting it to the road wheel axle. Inset: A view of the paddle which moves against the resistance of the oil flow each side of the central partition. The corrugated collar on the corrugated shoulder of the casing allows for all positions of fitting on the chassis side frame member. Three sectional views of the D.N. Shock Absorber: Centre, the long bearing of the paddle and trunnion, in the box, also the adjustable control valve. Right, a section through the paddle showing the non-return valves. Left, a section through the paddle and trunnion. Diagram Labels: SECTION ON A.B. SECTION ON E.D. SECTION ON E.F. | ||