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).
Vehicle suspension conditions, including vibration, chatter, pitching, and bouncing, with corresponding shock absorber settings.
| Identifier | ExFiles\Box 28\1\ Scan127 | |
| Date | 28th June 1928 guessed | |
| - 2 - Rm.{William Robotham - Chief Engineer} has tested at : - LOW SPEED 3.7" stroke 200 cycles/min. 7" " 200 " " and 11" " 200 " " We consider that there are four "typical" conditions :- (1) "Criss-Cross" vibration of front axle:- 550-600 cycles/min. Approx. 1" max. allowable stroke. (Frequency determined from marks on road during H.S. wobble.) (2) "Chatter" of rear axle on corduroy:- 450-500 cycles/min. Approx. 1" max. allowable stroke. (NOTE: Tire deflection is 1" so that this stroke just assures contact of tire and road) (3) "Pitching" of car. 120 cycles/min. Approx. 2" max. allowable stroke front and rear. (4) "Bouncing" of car (or "rear spring action") 70 cycles/min. 4" max. allowable stroke (chiefly at rear.) If our guesses are anything like the truth the maximum piston velocity in cases 3 and 4 is about half the condition of cases 1 and 2, so that if pressure increases with velocity to the extent shown in the diagrams, there should be little difficulty in controlling the axle movements of cases 1 and 2, if the car movements of cases 3 and 4 are properly controlled. (7) This reasoning agrees with the results so far obtained with leaking valves i.e. we can restrain rear axle chatter and still have the "soft rear spring action" after passing over a large, slow bump. Also if the front shock absorbers are just "tight" enough to prevent pitching, though we get a little tramping at about 60 m.p.h. this will not build up into a real shimmy. The settings particularly referred to are :- Front 80 up 100 down Oil pressure 143 lbs/in² and 180 lbs/in² Valve A-12293 Rear 60 up 100 down Oil pressure 186 lbs/in² and 310 lbs/in² Valve A-12306 (Continued) | ||