FORD VAN POINTERS.
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By R. T. Nicholson (Author of "The Book of the Ford ").
Wthe kindness of the Runbaken Magneto Co.; Ltd., I have lately had an opportunity of seeing and testing their latest timer. (They call it a commutator because so many other people call it that, but they are too good electricians not. to know that the timer is no sort Of commutator—which is a device for changing alternating current into continuous or direct current.) 380.—Of Timers in General, and of the Runbaken in Particular.
The Runbaken comma—timer' I should say—is a beautiful piece of work. So well is it finished, and made of such excellent material, that it would serve as a draWing-room ornament. But "good to look at" is not by any means the last word about an electrical. fitnient.
Take, first of all, the cover. It has what is known as a continuous track. All the time the brush is turning inside the cover, and rubbing its way round, it is rubbing on an unbroken metal track, or, rather, to be.. absalutely accurate, the track is not quite unbroken,for very narrow insulators separate the contact segments of the track. (You must have these insulators, you know, in order that the current may be conducted to the right wires in turn.) For practical purposes, however, the track may. be considered to be unbroken.
Do you see that this means that the wear of the track will be even, whatever the wear. may be ? You will no longer get those hills and valleys that in the long run must form inside a timer cover which has alternate metal and fibre insets. And the Runbaken people use no fibre for insulation : a very much harder material is inbuilt.
Now we come to the brush—the contact piece that turns inside the cover and rubs against the track. E is not a roller, as in the case of the standard brush, but a pressed block of copper gauze. Such wire gauze brushes are, of course, largely used in big dynamos and motors. Indeed, it was this kind of wiper, looking and being more or less like any brush used for other purposes, that first suggested the name " brush" for such a part.
Do you see that this construction means that there is no roller to wear loose on its centre—that whatever wear takes place occurs evenly all over the contact surface of the brush? There can, therefore, 'be
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no jumpy eccentricaction in the brush—particularly as steps have been taken to • prevent uneven wear of thetrack as we haVe already seen). True, wear does take -plaCe,• and the brush; in the very long run, shortens; but while it is wearing down a spring continues to push the brush out -against the track (as in the case of the standard tinier). • This brush.is meant to run4ry:--ethat is to say, without lubrication of.-any sort -Whatever: That is, of course, a decided help to easy starting, particularly in cold weather, whenoil gums-up things badly. While liquid oil will not prevent electrical contact, gummed oil will certainly do so ; and even liquid oil partly prevents contact, so that starting with oil in the timer is never Aseasy-as it ought to be. As a matter of fact, some oil will Work into the timer from the engine,' but the Runbaken company. intend their timer to work without 'oil; and.Would take it kindly if you would occasionally wash out the engine oil with petrol. The Runbaken conitinier, I should say—is Made, first, with the idea of reducing wear to a minimum, secondly, of making it so that what. wear takes place makes no difference, and, thirdly, of making electrical contact certain and immediate.
A further improvement has recently been intro
duced into the Runbaken timer brush. A" " or flex connection (shown at A 'inthe_drawing) is used to conduct the current from the brush (B) to " earth.'! Between brush and " earth," 'therefore, there are no loose contact points, and there can be no doubt that any such looseness-means uncertainty of circuit.
There is no strain on this ".pigtail." It is always slack, with beth ends tightlyanchored. No matter, • therefore, what wear takes place, the brush is always hard up against the contacts, one end of the "pigtail " is always fast to the brush, and the other end of the " pigtail" is securely fastened to that part of the timer metal which is rigidly 'attached to the engine.
The Runbaken Theory.
The Runbaken people are working OD a. theory which, though nearly as old as electrical science, does. not seem to have been hitherto applied to the Ford timer. They hold that the chief cause of the wear of Ford timer parts lies in the arcing—sparkingwhich takes place every tie a contact is broken. By intention, contact is broken four times in every revolution of the timer brush, and by accident it is broken any number of other times if parts fit loosely through wear. The Runba.ken company have set to work to do away with all such looseness., eliminating arcing, and thus reducing wear and tear on the one hand and improving the firing an the other: I am giving the Runbaken timer a long test, knowing that time tries timers but I have every reason to foresee that it. will stand up to its job well. I will report further later. I already know that it gives. easy starting and beautifully balanced firing.
381.—Voltage and Candle-power. ,
You are told that you must use 6-8 'volt 17 c.p. bulbs for your bright lights on the modern Ford, and 6-8 volt 2 clp. for your dim lights. Did you ever stop to think exactly what that statement means?
You should know that, theoretically (though there are practical limits), you can get any desired candlepower from a given voltage. The longer and thinner you make the filament, the more light you will get from the voltage. You know why? The longer and thinner the filament, the greater the resistance t( the electricity ; the greater the resistance the greater the heat ; the greater the heat the greater the light. The limit to the candle-power you can get from a given voltage is the degree of fineness which can hegiven to the material of which the filament is made: Apart from that, however, it does not pay to have the filament anything like as fine as you can get it ; it breaks too easily ; and for the same reason it does not do to have it as long as you can get it; the longer, . the weaker.
When you put a low-voltage bulb in a relatively high-voltage circuit (say a 3. volt lamp in a 6 volt circuit), you get much more than the proper candlepower out of that lamp while it lasts ; but it will not last any time: it cannot stand the racket of that extra voltage, its makers having put in a filament calculated to stand -only 3 volts.
When your bulbs glow too well, suspectione of two things—either that your filaments are of insufficient voltage or that your current voltage is too high.