FOR HIGH-EFFICIENCY SPORTS AND RACING-CARS
THE LUCAS CAMSHAFT SPEED VERTICAL MAGNETO
THE efficiency of modern Coil Ignition is such that the Lucas equipment of the modern car will operate up to sixcylinder engine speeds of 5,500 r.p.m. or 7,000 r.p.m. in the case of four-cylinder engine, while the equipment for sports and racing-cars will give regular sparking up to 10,000 r.p.m. For those who prefer magneto ignition Lucas have a special Camshaft Speed Magneto which is arranged for mounting vertically, or at a slight angle, in the same way as a distributor, so that it can be readily fitted to an engine designed for coil ignition. This is the magneto fitted on the famous Austin Seven 0.H.V., which has been bench tested .up to 14,000 r.p.m., besides revving up to 8,000 and 10,000 r.p.m, in its innumerable hillclimbing and racing successes during the past year. Additionally, drivers of such cars as the E.R.A., M.G., Riley and Singer have also used this magneto with outstanding success at Brooklands, Le
Mans, Donington and elsewhere. This success is not, perhaps, surprising when it is known that the Lucas Vertical Magneto has to pass tests at sparking speeds far higher than those attained by the fastest racing engines, while at the other end of the scale it has to spark regularly at speeds as low as 50 engine r.p.m. The magneto is of the rotating magnet design, that is, the magnet system revolves while the less robust parts, such as the windings and condenser, remain station ary. The magnet and pole system is arranged so that the number of sparks produced for each revolution of the magnet rotor is equal to the number of engine cylinders for which the magneto is in tended. The drive for the unit is half engine speed, exactly as for a coil ignition distributor, so that no gearing is required
between the rotor shaft .and the contact breaker and distributor portion of the in achine.
The rotor, which is carried on two large bearings, is built up with a single circular magnet and four or six laminated pole shoes, •according to the type of machine. The magnet is of Nifal, a special nickelaluminium-iron alloy, %villa is particularly resistant to demagnetisation and which has magnetic properties far superior to those of cobalt steel. The magneto is manufactured both with and without an automatic timing .–DISTRIBUTOR MOULDING
control. This is ot the usual centrifuga type but is specially designed to withstand the heavier load of the magneto drive. An auxiliary weight is coupled to the main weight, and is arranged so that at low speeds the auxiliary weight acts with the main weight, and at high speeds against it. By this means the weights can be arranged to give a timing curve of any desired characteristic. The mechanism is designed to be self-locking, so that there is no possibility of rattling
at low speeds, and is housed in the base of the Magneto, between the rotor and the driving shaft. An additional refinement incorporated in some magnetos is a friction brake or damper which is in operation only when the magneto is running slowly. This brake is fitted to magnetos intended for
engines which have been found to develop a slight rattle or period in the timing gear at low speeds due to variations in the driving torque of the magneto and of the engine. The brake consists of felt pads which at low speeds press on to a drum machined
inside the main casing of the magneto. Thus a steady unidirectional load is applied to the drive and chattering is prevented. As the speed increases
centrifugal forces cause the brake pads to move off the surface of the drum and so release the brake. The distributor moulding is held in position on the magneto by means of
two large knurled-headed nuts, secured in the moulding. A metal flange on the body reduces to a minimum the small risk of breakage and cracking of the moulded cap.
There is a very interesting leaflet describing this magneto which Messrs. Joseph Lucas Ltd. will be glad to send to anyone who would like a copy.