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).
Secret memo discussing drawings for an automatic advance system for battery and magneto ignitions.
| Identifier | ExFiles\Box 37\1\ scan 293 | |
| Date | 13th September 1924 | |
| X3949 S E C R E T. To EY. from E.{Mr Elliott - Chief Engineer} c. to CJ. c. to HS.{Lord Ernest Hives - Chair} E1/M13.9.24. E.A.C. II. AUTOMATIC ADVANCE FOR BATTERY AND MAGNETO IGNITIONS. X.3949. X.8680, X.8685 We send herewith drawings Lec.1916/17/19/21., dealing with the above. Lec.1917 shews the ignition settings and the curve of advance which the governor should follow. We should be glad if you would calculate the necessary strength of springs for the governor at Derby to give the required curve. Mr. Royce would like the pictorial illustration of timing shewing the advance lever on the steering column given in the instruction book for EAC, when this latter is prepared. Referring to Lec.1916, this drawing gives the details of most of the control mechanism, and the design has been so arranged that no alteration is required to the crank-case pattern for controls. Referring to Lec.1919., this drawing shews the inter-connection of the hand controls of the two ignitions worked out graphically. It shews how the magneto is made to retard quickly at first by hand and then to remain station-ary while the battery ignition goes on to a greater degree of retard for the purpose of obtaining the "flick start" on the switch. Lec.1921 gives the details of the ignition governor and the hydraulic mechanism for doing the work. This latter is single acting, that is to say, the oil pressure of the engine is utilised for advancing the ignitions, and spring pressure is utilised for returning the ignition timing to zero. Half this spring pressure is shewn on the hydraulic cylinder itself. This spring we think should exert about 12 to 15 lbs. Another spring of about 10 lbs. will be placed somewhere near the magneto to assist the first spring. The former has not yet been shewn, but particulars will be sent later. The object in distributing the spring pressure is to avoid having to transmit the force through a long range of control mechanism which would result in loss by friction. Lec.1921 gives particulars of the alteration to the crankcase for carrying the new unit. As discussed with you during your visit to WW. it is desired that the existing ignition shall be modified to suit this same flange so that either type of ignition is interchangeable on the engine. There are one or two small points to be cleared up before this design can be considered absolutely | ||