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).
The development, issues, and proposed modifications for front shock dampers.
| Identifier | ExFiles\Box 152\2\ scan0210 | |
| Date | 1st May 1940 guessed | |
| -3- 2. Shock Dampers. Front. The front shock dampers on B.V. are not very reliable. Originally the leak was obtained by drilling a hole through the replenishing valve. The sizes were .046" dia. on bump and .031" dia. on rebound. These holes gave leak times on the rig of 1 sec. bump and 2 secs. rebound. These figures were arrived at during the winter and in the summer there was insufficient damping. The hole through the rivet being fairly large it was unduly sensitive to changes in temperature, and was also liable to get blocked up. It was, therefore, decided to delete the hole and substitute a groove across the rim of the replenishing valve. The alternative was a hole through the replenishing valve which had been tried previously and found unsatisfactory because the replenishing valve was free to move about slightly on the piston so that sometimes the hole in the replenishing valve was over the hole in the piston and sometimes completely masked. This caused a much larger variation in leak than the groove so the groove was adopted. At the same time it was found that a leak of 2½ to 3 secs. gave a more satisfactory control of wheel movement without undue harshness. The leak is measured on a rig which applies a constant torque of 20 lbs.ft. and the time to move the damper arm through an arc of 22½ deg. is noted. The main valve was liable to seizure on account of the small area and the light poundage of its spring. Being of the pressure compensated type the actual pressure area was much smaller than the area of the orifice in which it worked. A new damper was in process of manufacture for the Ripplet with two single acting valves having a much higher spring load and no close fits. When 10.B.V. was on the bumper drums it was proved that end play between the rocking lever and the case could cause a considerable noise, and it wasdecided that end play must be kept below .002". This item requires serious consideration, and a form of threaded bush may be necessary. On the other hand it has not been definitely proved that end play causes a noticeable noise on the road. The oil seals which are used as oil retaining glands are not satisfactory andshould be replaced by rubber glands with a lining of canvas on the inside dia. to prevent wear due to slip. They appear to be satisfactory on the rig and some have been ordered for fitting to the new dampers on Ripplet. While lp{Mr Lappin}'s car was being converted from holes through the rivets to grooved leaks it was discovered that thereplenishing valves did not seat on the pistons due to distortion of the pistons when assembling the gudgeon pin. Instructions were issued for the replenishing valves to be lapped in, and the size of the groove | ||