This is the difference between the American way of handling electricity and the Japanese way.
Electricity wants to work, indeed, it has to have some on the way to ground or there is a dead short.
So, since the work "Potential" is AFTER the switch, the current does not move to ground as they touch, it jumps across the gap as they approach closure, thus providing a pit, burn, eroding, of the contacts.
The japanese have all these things powered 24/7 and the switch or points provide the path to ground. This way, there is no "Potential" since the current has already gone thru the work and just gets ground to complete the circuit.
You almost never have to replace any electrical switch or point type contact on a Japanese car. Of course, they still use relays to move large amounts of current, such as horns and headlights. which are still powered 24/7.
All you engineers have fun with that.
Ray
On Feb 18, 2012, at 12:48 PM, Bill Huff wrote:
How about wiring a capacitor across the points to absorb the inductive kick?
Bill Huff
At 2/18/201201:17 PM, Eastern Sierra Adjustment Svc wrote:
> This pic is captioned:
>
> Here you can see that one side of the upper point is completely
> worn away. You can also see where the lower point actually started
> wearing away the armature after eating through the side of the point.
>
> The unused side of the point is in very good condition. (It should
> be, since it wasn't used.
>
> The points must be realigned to get the clock running again, no matter what. That's the hard part to do properly. You cannot just "bend" the armature. But if we do realign the point, and if we then filed them down, the clock would be operable again. The problem is that then you have about half the point surface area you should have, so the points will wear themselves down again prematurely. That solution would be perfectly ok if you did not want a 24/7 365 operation.
>
> The challenge here is 1) to realign the points without doing any other damage to the clock, and 2) then protect the points to minimize the effects of future wear.
>
> And:
>
> Your friend's point is well taken, but the reason it won't work in our case is that the clock coils represent a highly inductive load, which generates a very high back EMF voltage across the points when the points open. The coils in these clocks would typically be about 10 mH, which results in an arcing EMF of about 3000 volts. That's why the points here are not made of copper in the first place. The better clocks, like Borg, used tungsten points so they could stand up to the inductive load. Even if we could resurface the points with copper I'm afraid they would fail in a matter of only a few weeks. The difference in the central office, of course, and the reason copper points worked there was the absence of inductive loading on the voice circuits.
>
>
> Ron Water's idea about installing an on-off switch might be good, but, I've already got a lot of wiring going on under the dash, with the auxiliary starter, the rear speaker fader switch, and the FM converter's wiring.
>
>
>
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