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).
Damper performance, testing, potential replacements, and comparisons with competitor parts.
| Identifier | ExFiles\Box 152\2\ scan0211 | |
| Date | 1st May 1940 guessed | |
| -4- to give the 2½ to 3 sec. leak was finally found to be .100" wide x .015" deep. The dampers on the Buick Century gave the following leak times: Bump...1½ secs. Rebound...1¼ secs. The valve loading universally used on rationalised cars has been 100 lbs. Rear. The M.R. type are satisfactory except for occasional leaking glands. They are rather expensive, however, and it is proposed to replace them with Gordon Armstrong dampers except on the most expensive models in the range. They have not yet been tried on rationalised cars. The large one functions satisfactorily on the rig but the medium size one for the Junior range exhibited too great a change in leak with change in temperature. This fault was overcome by fitting pistons having a clearance cold of zero to .0005", and a valve holder having an interference fit could in the case of .004". The damper then functioned satisfactorily on the rig. The standard leak on B.V. was Bump 1½ sec. and Rebound 3 secs. obtained by drilling an .039" hole down the valve stem and an .055" hole through the bump piston into the reservoir. This .055" hole made it necessary to have two replenishing valves in the rebound end of the piston to get 100% replenishment. On some of the faster and/or heavier cars it has been found better to delete this .055" hole in order to get adequate damping at high speeds. All new dampers should be thoroughly tested on the indicator rig for reliability and consistency. Particular attention should be paid to temperature effects. It has not so far been found possible to use a constant viscosity oil such as Castrol Shockol because of its poor lubricating properties. The indicator rig can be adjusted to give any desired stroke. The speed generally used is 70 cycles per minute because that is the approximate frequency of our cars on their springs. A frequency of between 500 and 600 would also be informative, but the rig will not function satisfactorily at over 400 in its present form. However, indicator cards can be taken over a short stroke at 400 and should prove helpful. This applies to Front as well as Rear Dampers. Reverting to the standard setting on B.V., the valve loading used is 40 lbs. but this can be altered by the hand control. On Gordon Armstrong dampers this valve loading will have to be much higher - around 100 lbs. probably - because they are not adjustable while the car is in motion. The dampers on the Buick Century give the following leak times: Bump ... 1½ secs. Rebound...3 secs. | ||