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 effect of pull off spring strength on brake thumping for the New Phantom 4-wheel brakes.
| Identifier | ExFiles\Box 66\5\ scan0033 | |
| Date | 4th November 1925 | |
| R.R. 498A (50 H) (D.D. 31, 12-6-25) J.H.D. Expl. No. +8420 REF: Hs {Lord Ernest Hives - Chair} /An2/LG4.11.25. EXPERIMENTAL REPORT. To DA. {Bernard Day - Chassis Design} from Hs {Lord Ernest Hives - Chair} /Rm. {William Robotham - Chief Engineer} NEW PHANTOMCodename for PHANTOM I - 4-WHEEL BRAKES. With reference to DA {Bernard Day - Chassis Design} 3/M22.10.25. We find that increasing the strength of the pull off springs on the Phantom beyond the present standard does not have a beneficial effect on thumping. With no friction on the swinging arm, increasing the strength of the pull off springs does not increase the intensity of the thump but increases [handwritten note 'extends' above] the road speed period at which it occurs. More friction, if anything, is required to eliminate thumps under these circumstances than when the car is in standard condition. Hs {Lord Ernest Hives - Chair} /Rm. {William Robotham - Chief Engineer} | ||