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).
Product specification sheet for the Marelli Magneto Type M.P. Monoblock.
| Identifier | ExFiles\Box 4\5\ 05-page232 | |
| Date | 9th May 1921 guessed | |
| MARELLI MAGNETO TYPE M.P. "MONOBLOCK" .. for 4-cylinder engines of motor-cars, motor-lorries, etc. up to 90 m/m bore General features and special advantages. It embodies in one casting: Base, Pole pieces, Cover (contact breaker side), Cover (coupling side), Upper part and Distributing channels for lubricant. The number of screws is reduced to the minimum: all the principal parts being in one piece only; as a result of this, greater solidity is assured and it is impossible for any part to become detached even after long work and when the engines are very power-ful and subject to continuous vibration. Further, absolute non-variation of the air-gap between the pole pieces and the armature is ensured, and the magnetic efficiency remains unimpaired. The magneto is easily assembled and hermetically closed. There is maximum resistance and, as a consequence, maximum durability. Improvements embodied in the Monoblock " Marelli ,, Magneto: Perfect centralisation of the armature with the pole pieces: an essential condition for high efficiency; the possibility of current loss totally eliminated: absolute uniformity of sparking obtained. Only one lubricating aperture; automatic lubrication by means of centrifugal force generated by the spindle of the gear-wheel. Base: The base is so designed that it may be mounted on flat or spherical supports; this latter arrangement ensures perfect centralisation with the coupling shaft of the engine, which is necessary for smooth running. Single Magnet: Every operation of assembling and dismounting can be effected without any risk of demagnetisation of the magnet, caused by the antagonistic actions which is set up when the magnets are in pairs. There is a further advantage in the fact that the magneto is constructed is such a manner that all the mechanical or electrical parts can be examined or removed without the necessity of displacing the magnet, which, consequently, retains its magnetic properties. Lubricating bearing: This is made of aluminium with an internal bush of special bronze. The lubrication of all parts requiring oil is regular and emanates from an oil distributing chamber. Distributor: This has flat contacts and the leads are carried inside instead of having outside terminals; this results in a better appearance and avoids the breaking of the leads. It is also easier to handle. Cam ring: This is made of hard bronze and is so arranged that there is no play whatever. Contact Breaker: This carries a very powerful spring and a hammer made of special material guaranteed to work regularly at the highest speeds. The Magnetos are tested at 2000 r.p.m. and at high compression, and are guaranteed for normal work under these conditions. Features common to the Monoblock and all other types of " Marelli „ Magnetos. Complete division between the mechanical and electrical part of the Magneto. Gear wheel mounted on the same side as the coupling shaft. This latter is made of special bronze of great resistance, and is cast in one block with the end section of the armature. The cutting of the pinions has been done with special tools in order to obtain perfectly silent running. The armature is perfectly balanced and machined to the 1/100th of a millimetre from the ball bearings. The condenser has been very carefully constructed and specially finished in order to make one block with the armature. Perfect winding. Rotating distributor arm of very simple design with safety spark gap, ventilated by the action of the magneto itself in such a manner as to avoid the deterioration of the points. The " Marelli „ Magnetos are stripped of all superfluous parts, the collector and distributor are easily accessible, the connections are extremely simple, and the advance is adjustable up to 30°. | ||