Service station robbery - not an urban myth

sparrks said:
Car tyres are not good conductors of electricity.

On seeing that ludicrous statement I just went out in the drizzle and "Meggered" my van tyre - Probes 10mm apart at 1000V the reading was in excess of 2000M Ohm, which is I guess why they sell conductive straps.
Click to expand...

A word to the wise Wints.

You may be able to get away with that sort of behaviour in rural France, but try to get out of the habit before you return to these more refined climes.

Dezi :cheers:
 
i used to work in an industry that used black rubber componants , the marketing geniuses decided black was boring so got the carbon black taken out and substituted a silicon compound to give green mouldings..... usefull life went from years to weeks apparently the carbon black stopped the uv in daylight from degrading the rubber. which i would guess is probably why its used in car tyres.


oh and we used copper cored ignition leads on performance engines cos the new fangled carbon filled things were crap.
 
As an expert in what? Yes I can use an insulation tester and understand the results. It is my understanding that the straps are to discharge any build up of static in the vehicle. Of course they wear out, but when new are several inches longer than needed. When the vehicle is at speed then the straps hardly touch, if at all, the ground and unlikely to wear very quickly.


What causes static electricity build up?

Why does it not happen with your cars? Pass.

During the last 10 years or so, working with static sensative devices I now wear anti-static boots for work and no longer get shocks whilst wearing them.
 
Anti -Static Straps

When correctly fitted the anti-static strap should just touch the ground, if fitted correctly the strap then lifts from the ground with forward motion and does not wear when stopped it then touches the ground to discharge. these of course are the English instructions only. My neighbour has a French contraption for his push push its a 10kg weight on a chain when stopped they drop it out of the door before getting out

Alf
 
I only remember getting static shocks from vehicles when it's really hot and really dry,so hot and dry you don't sweat
 
I know nothing about static in cars but in operating theatres it was very dangerous back in the days of Ether. The Ether was very heavy compared to air so if ventilation did not get rid of it, a spark in the area where the air joined the ether vapour would be a disaster. To prevent this they would attach chains to the metalwork of trollies which dragged on the floor. In practise they failed to work. Wheels where impregnated with conductive material (Carbon based) which was finely mixed with the rubber to provide some resistance so that the static would slowly leak to earth and not cause a spark. As time progressed the floors where also fitted with a conductive grid to make sure there was a good earth. The staff would have a small plug of conductive material in their footwear to earth them and we where not supposed to wear man made fibres. To this day scrubs are made from cotton or linen and air is vented from theatre at ground level.

Richard
 
Tyre Conductivity

It seems you need a ohm meter that reads in the excess of one million ohms according the continental tyre website


sparrks said:
Car tyres are not good conductors of electricity.

On seeing that ludicrous statement I just went out in the drizzle and "Meggered" my van tyre - Probes 10mm apart at 1000V the reading was in excess of 2000M Ohm, which is I guess why they sell conductive straps.
Click to expand...
 
I have answered it in my earlier post. When a car tyre is subjected to very high electrical energy (lightning) it is considered to be a conductor.When it is subjected to relatively weak electrical energy eg static build up as generated in a car it is considered as an insulator. It's all a relative thing or a question of degree. Apply to many materials a high enough charge and they become conductors but at low levels they resist sufficient enough to be considered insulators.
Car tyres these days have less carbon black, (substituted with silica: the black pigmentation can be provided by synthetics). But this has resulted in greater electrical resistance, counteracted by some manufacturers by incorporating carbon strips.
 
Last edited:
Carbon Black

I know it's from Wikipedia but...........

Surface chemistry

All carbon blacks have chemisorbed oxygen complexes (i.e., carboxylic, quinonic, lactonic, phenolic groups and others) on their surfaces to varying degrees depending on the conditions of manufacture. These surface oxygen groups are collectively referred to as volatile content. It is also known to be a non-conductive material due to its volatile content. Maybe that's your answer

The coatings and inks industries prefer grades of carbon black that are acid oxidized. Acid is sprayed in high temperature dryers during the manufacturing process to change the inherent surface chemistry of the black. The amount of chemically-bonded oxygen on the surface area of the black is increased to enhance performance characteristics.
 
Alf 1 said:
It seems you need a ohm meter that reads in the excess of one million ohms according the continental tyre website
Click to expand...

2000M Ohms exceeds one million ohms. 2000M Ohms is 2000 million Ohms or 2 billion Ohms
 
sparrks said:
Have you actually seen these strips? Just curious because I would have thought for them to be effective they would go from rim to tread, so they would earth the car via the wheel hub and the ground. If the strip was around the circumference then it would never be in contact with the metal parts of the car.
Click to expand...

Have seen them on motorbike tyres, some time ago, the line was visible on the circumference but there was no visible line to the rim, but then of course this section wouldn't need to be in contact with the road and could be buried in the tyre wall. I made casual enquiries and was told that some car tyres had this same feature for the reasons I gave in my previous post ie reduced carbon black.
Should have added that hubs (all that grease) can insulate the car body from road earth, sometimes a thin metal tab contact was fixed on the axle thrust washer/nut anywhere to form a bridge mainly to attenuate radio static interference I think.
 
Last edited:
Byronic said:
Have seen them on motorbike tyres, some time ago, the line was visible on the circumference but there was no visible line to the rim, but then of course this section wouldn't need to be in contact with the road and could be buried in the tyre wall. I made casual enquiries and was told that some car tyres had this same feature for the reasons I gave in my previous post ie reduced carbon black.
Click to expand...

I guess they could also be using the steel brading/bands inside the tyres. One thing I am certain of, is that the tread on my tyres are great insulators - at least at 1000volt and at whatever miniscule current it uses.
 
You must log in or register to reply here.

Users who viewed this discussion (Total:0)

Back
Top