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).
Magazine page discussing ignition components, insulation testing, and motoring in the West Indies.
| Identifier | ExFiles\Box 4\5\ 05-page263 | |
| Date | 8th February 1924 | |
| THE AUTOCAR, February 8th, 1924. 255 Ensuring the Vital Spark. Normal in its design, the rocker type contact breaker exhibits a close attention to detail. The baseplate and the rocker arm are made from materials specially selected to remain immune from deterioration due to vibration. That most important part of the device, the bush, in which the rocker arm spindle takes its bearing is, after machining, impregnated with a non-hydroscopic compound which prevents the absorption of moisture by the bush, and therefore reduces liability to stick. A noticeable feature is that the adjustable screw carrying the contacts is placed well away from the baseplate, the latter being recessed so that a small magneto-adjusting spanner can be got to work easily. Incidentally, the contact points are made of the hardest platinum iridium obtainable. Following usual practice, the contact breaker baseplate is fastened to the armature spindle by taper and key, whilst down the centre of the assembly a taper-threaded locking plug passes. The hollow end of the armature spindle into which the contact breaker taper fits is reinforced by a steel sleeve round the outside of it, to prevent damage by over-screwing the locking plug. Variable ignition is provided for, there being spigoted into the end cover a gun metal sleeve arranged to be rocked by means of a control. This sleeve carries two long steel contact cams, and at the end of one of these is an oil-saturated felt pad held in place by a light spring to make the rocker arm slipper self-lubricating. In the distributer there are also some interesting points, one of them being that the distributer gear wheel is built up with a bakelite centre disc, to which the inner boss and the outer toothed ring are riveted. The object of this disc is to prevent noise and also to provide insulation which precludes deterioration of the ball bearings of the distributer spindle from electrical discharges. The distributer itself is of the wipe type, and carries a carbon brush bearing on segments sunk into the insulating material of the distributer body. The brush holder is of normal design, but is made of a special Para rubber ebonite, and has its metal parts plated and sealed to prevent destruction by the hidden generation of nitrous gases. Of the distributer outer body a point is that the outer face is flat and the contact studs and knobs are sunk below the surface, so that there are no projecting studs or shrouds to be broken easily. MOTORING IN THE WEST INDIES. Testing the Insulation. It is interesting to note that all the ebonite parts used in this machine are tested in an oil bath at a pressure of 40,000 volts, and thereafter are again tested in air at 15,000 volts. Though this results in a fair percentage of rejections, it does, on the other hand, ensure that those parts which actually get into the assembled production magnetos are absolutely reliable. Another point about the construction is that the armature windings undergo a special process of varnish impregnation in vacuum, after which the armature is taken for a period extending to two days. Lastly, a feature is that all the ball bearings, when the instruments are assembled, are packed with a special heat-resisting grease of a nature and quantity sufficient to last for an indefinite period. Further, at the coupling end bearing, an annular well is provided filled with oil-saturated felt, and if this bearing should run hot, owing to misalignment of the drive, it automatically receives extra lubrication from the oiled pad. A correspondent who has done much motoring in Jamaica sends us these illustrations of wayside scenes in the island. Motoring is extremely popular and there are some two thousand miles of main roads. British cars, unfortunately, are few and far between. (Top) On the road between Morant Bay and Kingston. (Bottom) Filling up with petrol in Brown's Town. 15 c 19 | ||