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).
Modifications to the ignition advance control springs and hydraulic piston return spring.
| Identifier | ExFiles\Box 72\1\ scan0016 | |
| Date | 25th September 1924 | |
| R.R. 493A (50H) (D.B. 175 25-9-24) J.H.D. EXPERIMENTAL REPORT. -2- Expl. No. REF Hs{Lord Ernest Hives - Chair}/Rml/LG21.4. 25. in the pipes or relay on assembly rather than dirt working up from the sump. Neither of the 10,000 miles cars have had the inner piston stick. Control springs. By taking an average of the ignition advance require- ments of the large number of engines, we have somewhat modified the original curves given for this feature. To accommodate this modification we have modified the control springs of the governor. To cater for the considerable amount of advance required by this engine at low speeds, the relay is now given an initial setting which advances the flywheel ignition 2½° as soon as the oil pressure reaches 20 lbs.per sq.in. This does not affect the flick start, but enables full low speed acceler- ation to be obtained, at the same time giving a definite zero setting of the relay for production. Return spring E.72506 for hydraulic piston E.72509. This spring was not quite strong enough to return the controls as initially fitted. Its position, moreover, is such that any back lash in the linkage is emphasized rather than deminished. The main stiffness of the controls was due to the magneto. The specification of this machine calls for a load of 3 or 4 lbs. on the advance lever before the latter moves. This is to obviate vibration and noise. With a stiff magneto we found that the whole ignition linkage would pivot about the magneto when the hand control was advanced, the lever on the exterior of the oil relay chamber rotating and compressing the return spring for the hydraulic piston. contd :- | ||