Self-starting

Sir,

The letter of Mr. B. W. Rivett and your comment in the July Vintage Postbag on “Self-starting” arc of course absolutely correct. If anyone doubts the method was in use well before there were Silver Ghosts, they could be referred to “Motor Ignition Appliances” by “I’. W. Hawley, dated 1905, which on pages 132 and 133, goes into detail and says it is equally applicable to four and six-cylinder four-stroke engines.

I have a far more difficult problem. My 1909 Cooper is fitted with a Bosch S4 magneto the Simms HT. magneto was virtually the same and on the dashboard is a device which proclaims itself as a “Simms Magneto Switch Starter”. It is a round brass instrument with a lever at the bottom with On and Off positions and in the centre has a push button with the instruction “Tap Quickly”. At the back are three terminals marked “M” and “E” and “A”. In the Off position the lever connects the terminals “M” and “E” which are effective as “Magneto” and “Earth”. When the switch is in the On position, if you “Tap Quickly”, you connect the magneto to the “A” terminal.

I am utterly mystified as to how a car equipped with a magneto, but without a coil, could start on a switch. Conventionally the whole of the electricity on the Cooper is conveyed by six wires to serve the dash switch and four sparking plugs even if two crankshafts and twelve pistons are hardly conventional with four sparking plugs. I cannot believe the switch is a special production of Simms for Coopers because Tom Cooper only made six of his own cars. Previously he had built the initial batch of coil-equipped Lucas Valveless two-stroke cars that is before the chassis layout became conventional and David Brown took on production. From the aspect of starting or torque, a four cylinder two-stroke is, of course, the equivalent of an eight cylinder four-stroke.

Can you or any of your readers tell me what the “A” terminal stands for automatic, armature? -and to what should I connect it? My only idea is that the “A” terminal is for “Accumulator”, to provide an electric supply to the L.T. side of the magneto armature and that by tapping quickly the button on the “Magneto Starter Switch”, a current is induced in the I-1.T. side and thence to a sparking plug? I am no electrician and would like to know if this is possible as a method or would it’ damage the magneto windings or the permanent magnet?

Stoke Poges JOHN BRISCOE