A THIEF SHOCKER.
Page 27
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Our Driver and Mechanic Readers Talk Upon Matters Pertaining to Ignition.
THE FOLLOWING iather.ingenious wheeze is communicated in a letter. from ."G.M.," of Pontyclun. The sender has been awarded the 15s. prize this week. "Trailing unobtrusively," he says, "from the lowest part of my lorry, a 3-ton Albion, is a small piece of cheap brass watch chain, by virtue of which, whenever the engine is working, any person who dares to touch the radiator, wings, body, or, indeed, any part of the vehicle in metallic connection with the chassis, suddenly evinces a most remarkable haste to get away from the machine. If the contact has been made by hand, the 'backing off' action is generally accompanied by energetic search—from a safe distanee—for the cause of the trouble. Since the fitting of this little gadget there has been a notable absence of hangers-on to the tack of the lorry, a result which was the main object intended to be achieved by its fitting.r As it is a useful device, quite simply made and as easily attached, the following instructions may be of interest.
" Connect a length of insulated wire -to any one of the distributor terminals, and carry it, through a switch, to the lowest point of the chas*; in fact, the insulation should extend almost to Mb road surface. On the open end' of the wire fasten a short length of cheap brass chain, which must he arranged so that it traits along the ground.
" What happens is this. The earth in the vicinity of the vehicle is charged with current at high potential, which is delivered by the trailing chain, and is constantly trying to return to the magneto via the chassis, in which object it is frustrated by the intervention of the rubber tyres, which act as insulators. So soon, however, as anyone standing on The earth touches any part which is in metallic contact with the chassis; he completes the circuit, becoming, too, a most reluctant ' shock absorber.'
" The switch to this device is, of course, located so that I can switch the special circuit off while I get on or off the vehicle, and so that I can leave it in operation while I am away from it, or when I am actually on the driver's seat. So soon as I am off the ground I am, of course, immune from shock. No ignition trouble whatever has resulted from the adoption of this little device : the engine pulls as well as ever, and does 20 equally whether the special switch be
on or off. With an all-steel body, there is -no part of the vehicle which may safely be touched by an intruder ; wooden body offers sanctuary as to some
part of it. In the latter -case, to pre vent hangers-on, connect the tailboard fitting to the chassis by a piece of insulated wire.
"My lorry is fitted with an Eagle steel tipping body, and I have to confess to using it as a source of amusement many a time, switching on and off when various workmates are about and in contact with it.
"The sceptic may easily hang a piece of high-tension cable on the distributor, with a nut at its free end in contact with the ground, and then invite some friend to take" off the radiator cap. The result will be electrical."
A Few Magneto Repairs.
"S.F.," of Colchester, finding the ball eace had worked loose in the arm tore end plate, so that it was throwr out of line with the half-timewheel pnt the and plate in the lathe chuck and bored the hole out to 3-16 in. over
size. He then turned up a phosphorbronze bush to fit, and made the mag• neto as good as new again.
" H.H.," of Leeds, had unusual magneto trouble recently. An engine stoppage was traced to ignition trouble, and eventually befoul-id that a short-circuit was occurring through the high-tension collector brush holder. Apparently, the
insulating material, which was moulded round the brass core, was rather thin at one point, and there it was the current leaked. (See sketch.) The remedy was simple. The burnt, hole in the insulation was carefully • cleaned out with a drill, and filled up -with a thick paste of plaster of Paris and. water, being subsequently allowed to dry. On assembling, the magneto sparked at once, and is doing so to-day.
A similar trouble was encountered by "E.A.," of Southall. He, however, fOund that the insulation was actually cracked. He filed a V groove, 1-16 in. deep and itin, wide, along the crack, and filled the groove in with a strip of patching rubber. The rubber being slightly thicker than the insulation, it was compressed tightly into place as the brush holder was pushed home.