Arcing

[21121956]

Hello everybody:

A friend ask me about a curious situation he is suffering these days. The story is as follows: Ever since one month or so, he has been experiencing a sort of electrical shock at the moment when he gets down of his car.

Sometimes (not always) when his hand is close enough to the metal of the door, he says that he can feel (see and hear) the electrical arc.

He has been driving for more than twenty years (three of them with the present car) and this is the first time he is bothered for that situation.

I have told him that it probably is a case of static electricity developed by him while driving by the action of rubbing the steering wheel.

I know that this type of problem can be solved by strengthen the earth connection between the chassis and the motor frame of the car. He made so but, the annoying arcing is still going on.

I would like to be adviced on this subject in order to give a hand to a worried friend.

Thanks in advance

 

[GregLocock]

more likely static between him and the seat. See if it still happens when he dresses all in cotton.

Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[patprimmer]

I'm with Greg

Static generated between clothing and seat.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[MiketheEngineer]

It's static. You can buy a commercial spray that will get rid of it or take a dryer towel and rub it on you pants.

 

[Peter7307]

There is an alternative to sprays etc which do work but need to be replaced when they run out.

The sequence is this:

Open the car door and touch a bare part of the body to a metal part of the car BEFORE putting the feet on the ground.

The panel immediately behind the driver's door is a convenient place.

Pete.

 

[21121956]

Hello everybody:

Thanks a lot for your comments.

Greglocock and patprimmer: my friend says that for the last five years he has been using the same clothes, at work and on weekends; he usually dresses with not too different clothes.

MiketheEngineer and Peter7307: thanks for your helpful suggestions. I will feed back the results.

At this moment I wonder, is it possible that someone driving the same car by three years, dressed with the same type of clothes can be, suddenly, on the last two months, develop a reaction to static? Can this reaction to this phenomenon disappears in the same way that it appears?

Thanks.

 

[patprimmer]

Dry weather.

Wear on the seat fabric so the natural or cellulosic fibres wear more exposing the synthetics more.

I don't believe he never changes his cloths. They might look similar but the might have a different composition re fibre type.

He might also have installed seat covers.

The seat may have had an earth that has been disturbed by something as simple as greasing the adjustment mechanism.

He may have been earthed but has since changed shoes.

It didn't happen, it now does. Something changed, unless of course you want think it is supernatural.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[mcgyvr]

Not sure where you are located but its probably due to humidity levels. That happens to me all the time in the winter (low humidity) but never in the summer (higher humidity).

To me this is normal. It happens with every car I've ever had and with any car I've ever rode in (in the winter)

 

[ewh]

Has he replaced the tires recently?

Believe it if you need it or leave it if you dare. - [small]Robert Hunter[/small]

 

[ivymike]

yeah, different tire compounds will affect this behavior. I've never noticed my clothes making any difference - but ambient humidity is a huge player. I usually just tap the door frame with the butt of my hand while getting out (strongly reinforced habit at this point). Alternatively, one could install a ground strap that drags under the car (auto supply stores carry them).

see also:

http://www.cartalk.com/content/columns/Archive/1994/November/11.html

 

[21121956]

Hello everybody:

mcgyvr: my friend lives in a zone with an average air dry bulb temperature of 30º C, an average wet bulb temperature of 24º C and an average Relative Humidity of 70%.

He is telling me that, for example, these days the ambient temperature is around 37º C and a RH of 43 %.

ewh: the last replacement of tires was on August 2007.

Thanks.

 

[ivymike]

new shoes?

 

[thruthefence]

I've seen people attach a small chain ( attached to a good ground )under the car that drags along grounding the chassis. A former employer used to operate a bunch of Helicopters on "fixed floats" & they build up quite a static charge in flight. They were all equipped with a dangling cable. When doing external load work, the load is always 'touched' to earth before the ground crew positions it.Overly Enthusiastic ground crew have been zapped quite handily when this is not accomplished.

 

[IRstuff]

Has he had this same car all this time? Did he get it new? Some new cars come with antistatic coatings on the seats. It's possible that they've been worn down to the point where they're not doing what they did when the car was new.

TTFN

FAQ731-376

 

[21121956]

Hello everybody:

Thanks again for all the comments.

patprimmer and ivymike: Surprisingly he is using new shoes but, he is suffering the same thing even though he is wearing the old ones.

The car always has had the seats wrapped with covers. There is no any change with this.

IRstuff: He has had this same car all this time and he got it new.

ivymike and thruthefence: in your opinion, where is the more convenient place to install that ground strap?

 

[ivymike]

back end of the vehicle, to just about any exposed bolt

 

[patprimmer]

I was of the opinion that all modern tyres had enough conductivity built in to ground static build up.

It will be the cloths and the seat cover or upholstery. Whether he knows it or not, something in that combination has changed.

If the seat covers are removable, treat them with an antistatic.

Different fibre types have different potentials to gain or lose electrons to each other. Different surface treatments and finishing treatments also influence that. Different residual chemicals also influence it. It could be as simple as a change in laundry products.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[IRstuff]

I think he simply wore off the original ScotchGard on the seat.

TTFN

FAQ731-376

 

[KENAT]

Probably a second order effect but has humidity changed?

We had some packaging at my last place that had been around for years with no problem. It started getting used in a desert area and there where static problems.

As best anyone can tell it was due to the humidity, or lack there of, not allowing the charge to leach off as fast as normal.

KENAT, probably the least qualified checker you'll ever meet...

 

[Bribyk]

I started getting shocked when getting out of my truck right after installing a 1-farad cap for my amplifier. After double-checking my wiring, I wrote the timing off as a coincidence (start of winter) but I'm curious as to whether the capacitor could have had a role...