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Live spark plug lead


PB1980
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8 hours ago, section swept said:

The higher amperage in the case of electric shock will cook the muscles and anything else it passes through. It’s bloody nasty being electrocuted, entry point just hides the damage going on inside, the exit point will be awful and it usually involves a surgeon having to cut away dead and dying body tissue and that which has been electrically cooked. It isn’t funny and it certainly needs to be avoided, goodness knows what those poor *******s who were sent to the electric chair thought ....scarred sh**less I would imagine. Electric shock affects the brain first by sending it into an electrical storm, that produces the heart stopping symptom and if not corrected death follows very quickly. A shock can have lasting effects upon the nervous system which can also be very debilitating. Hybrid cars are now at the stage where the batteries can deliver a fatal current if incorrectly worked on. Not sure about the electric Osset’s but four 12 volt batteries hooked up to supply 48 volts more if fully charged is boarder line to having a nasty effect upon the human body. ⚡️⚡️⚡️⚡️?‍♂️

Much depends on the path of the current and the dc current of a high voltage battery is a very different beast than the pulsed current of an ignition system or even 50/60Hz ac. Edison used an electric chair as an example of the dangers of dc when he was selling his ac distribution system in competition to Westinghouse's dc systems. Edison was kind of a jerk. Current directly through the chest can stop the heart with as little as 100mA dc. That's why they tell you to only touch things with one hand while doing electrical work. Watch the Formula1 garages and they are all wearing insulating gloves and being very carful anywhere near the battery packs. You'll also see a couple guys with insulating hooks standing aside to pull someone free if they get frozen by a shock. dc tends to hold you in place once it gets into the muscle. At least with ac you have a chance of pulling off as long as the frequency is low enough. At high frequency like a revving engine... Again from experience I can tell you that you're not going anywhere until the thing winds down and stops.

The purpose of the resistance in the plug/plug cap/wire is indeed to reduce radio interference. It does this by slowing the rise time of the spark current after the gap has been ionized. The spark gap is basically a "negative resistance" device. It has incredibly high resistance until the voltage across the gap can form an ionized path. Once that path is established the resistance across the gap goes to milliohms and a huge surge of current jumps the gap while dropping the voltage across the gap. The resistors slow down the current rise time across the gap reducing the peak current as well as the radio frequency energy generated by the current. Originally this was just for radio interference but as engine control systems got more remote sensors it became necessary as the EMF noise from an unregulated spark tends to leak into everything.

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6 hours ago, dan williams said:

Much depends on the path of the current and the dc current of a high voltage battery is a very different beast than the pulsed current of an ignition system or even 50/60Hz ac. Edison used an electric chair as an example of the dangers of dc when he was selling his ac distribution system in competition to Westinghouse's dc systems. Edison was kind of a jerk. Current directly through the chest can stop the heart with as little as 100mA dc. That's why they tell you to only touch things with one hand while doing electrical work. Watch the Formula1 garages and they are all wearing insulating gloves and being very carful anywhere near the battery packs. You'll also see a couple guys with insulating hooks standing aside to pull someone free if they get frozen by a shock. dc tends to hold you in place once it gets into the muscle. At least with ac you have a chance of pulling off as long as the frequency is low enough. At high frequency like a revving engine... Again from experience I can tell you that you're not going anywhere until the thing winds down and stops.

The purpose of the resistance in the plug/plug cap/wire is indeed to reduce radio interference. It does this by slowing the rise time of the spark current after the gap has been ionized. The spark gap is basically a "negative resistance" device. It has incredibly high resistance until the voltage across the gap can form an ionized path. Once that path is established the resistance across the gap goes to milliohms and a huge surge of current jumps the gap while dropping the voltage across the gap. The resistors slow down the current rise time across the gap reducing the peak current as well as the radio frequency energy generated by the current. Originally this was just for radio interference but as engine control systems got more remote sensors it became necessary as the EMF noise from an unregulated spark tends to leak into everything.

Totally agree and on multi- cylinder petrol engines the HT leads can suffer a fault called cross firing. This is where the electro magnetic field develops around the HT lead and can cause the next nearest HT lead to receive a signal which robs power from the first lead and also causes a weak spark at the plug of each lead affected. Cured by simply having the lead pass across one another at least once, this cancels out the effect when the leads are all nicely routed they do look good but if there is a weakness anywhere in one lead this phenomenon takes place. I last had to perform this magic on a Solicitors car who was not happy that his car would give a small hiccup when turning into his driveway. Working for Mercedes Benz gives you access to all kinds of information, some you think not possible until you try it. You should have been a Lecturer like me.??‍?I used to deliver a case study on electric shock whereby  four members of a group where asked to wait outside while the remaining members had to set up an electric shock incident. This would involve a volunteer laying on the ground with an electric drill at their side and the power lead across their chest. There were a number of items that tend to be available in most workshops close to hand. There was also a pool of water next to the volunteer electrocutionee. One of the four outside the workshop had to enter and deal with this scenario whilst the rest of the group were the audience. First one in was a time served fully qualified electrician with their own business, immediate fail as he lifted the drill off of the volunteer without switching the power off. Result, two electrocuted people, and before any smart Alec starts off about reducing class sizes, this was a totally isolated circuit being employed.This was a none RCD scenario I hasten to add as too much reliance is placed on an often abused safety device. Just goes to show how complacent we all get with something we use everyday. ??‍??

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10 hours ago, PB1980 said:

By the sounds of things I got off lightly just felt like a 240v shock . But I did do the classic and touch it again just to make sure ?

I find licking both terminals of a PP9 battery reminds just how effective electricity can be at grabbing your attention?

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I’ve done a lot of gigs as a freelance sound engineer. It’s amazing how many college electricians will blithely connect the power distro up with ground tied to the neutral bar. “It’s the same thing.” 

No Chucko, it’s not. I’ve learned to inspect it myself to protect band and crew.

I did get to watch one guy drop a big screwdriver into the live power panel of a hockey rink once. That was impressive!

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