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).
Page from a journal detailing Splitdorf and Scintilla double magnetos for aircraft engines.
| Identifier | ExFiles\Box 37\1\ scan 165 | |
| Date | 1st July 1927 | |
| Vol. XXI July, 1927 No. 1 34 THE JOURNAL OF THE SOCIETY OF AUTOMOTIVE ENGINEERS FIG. 7—SPLITDORF MODEL-VA DOUBLE MAGNETO DESIGNED ESPECIALLY FOR AIRCRAFT ENGINES This Provides Two Electrically Independent Sources of Spark from One Unit That Weighs Less Than a Conventional Single Magneto. Has a Single Shaft with Flange Mounting That Allows Direct Gear or Splined-Shaft Drive; Preserves Constant Angular Relation between the Two Sets of Sparks, whether Synchronized or Staggered, with One Spark-Advance Control-Rod: Allows the Distributors To Be Driven from the Camshaft without Special Gear-Reduction; and This Single Type of Magneto Can Be Used for Engines Having Any Number of Cylinders FIG. 8—SCINTILLA MODEL-SC DOUBLE MAGNETO Some Distinctive Features of This Are a Weight of 12.50 Lb., a Cobalt-Steel Four-Pole Rotating Magnet Weighing 3.62 Lb., a Condenser That Is an Integral Part of the High-Tension Coil-Assembly between the Primary and Secondary Windings, Sliding Metal Brush-Connections, Very Low Hysteresis and Eddy-Current Losses, Bearings Supported in Insulated Cages, and Easily Removable Breaker sparks could be obtained from either one or both the secondary windings when either one or both the primary circuits were interrupted, the spark apparently following the path of the lowest resistance. These troubles and the unsatisfactory performance of the breaker caused the abandonment of this type, but the attempt was very much worthwhile, as it showed the inherent advantages of the double-vertical type of magneto and led to the development of a true double-magneto. At the request of the Materiel Division, the Splitdorf Electrical Co., through its chief engineer, E.{Mr Elliott - Chief Engineer} B. Nowosielski, developed the Splitdorf Model-VA vertical double-magneto, as shown in Fig. 7. It is interesting to note that the first experimental model was made by splitting two Dixie-100 hand-starting magnetos horizontally through the center line and bolting the two halves together with a common inductor-rotor. This type of magneto is of a very simple, compact and rugged design and is probably the first type specially designed for aircraft engines. Following are the important features of the double type: (1) Two electrically independent sources of spark from one unit weighing less than one conventional single-magneto (2) Single shaft with flange-mounting allowing direct splined shaft or gear-drive and eliminating the necessity for special drive-shafts and mounting-brackets (3) Constant angular relation between two sparks either synchronized or staggered; one spark-advance control-rod (4) Distributors driven from the camshaft without special gear-reduction (5) A single type of magneto for engines having any number of cylinders (6) Rugged, compact, waterproof, and fireproof construction The Splitdorf Model-VA vertical double-magneto, shown in Fig. 7, has the following distinctive characteristics: (1) Weight, 15.5 lb. (2) Two sets of magnets (3) A single inductor-rotor, weighing only 1.5 lb. and having a very low moment of inertia (4) Breaker mechanism and condensers accessible from the top of the magneto (5) Breakers synchronized by shifting the split breaker mounting-plate about the cam The Scintilla Magneto Co. has recently developed a double magneto known as the Model SC, having the same general characteristics as the Splitdorf Model-VA. The following are the distinctive features of this model, which is shown in Figs. 8 and 9: (1) Weight, 12.5 lb. (2) Four-pole rotating magnet of cobalt steel, weighing 3.62 lb. (3) Condenser, an integral part of the high-tension coil-assembly lying between the primary and the secondary windings (4) All primary and secondary conductors molded into a single terminal-block for each coil (5) Sliding metal brush-connections to the breakers instead of stranded pig-tail connections (6) Very low hysteresis and eddy-current losses (7) One double-row self-aligning bearing on the driving end and one annular bearing on the cam end | ||