On topic: Serious static problem

At 11:12 12/04/98 -0800, Aaron C. Finney wrote: -- snip -- Yes. It's not the car but it's the tires. I've had the same problems with a couple of Toyota Camrys I've leased over the past years. Extreme and rather painful shocks are generated especially in this part of the country when it is very cold and low humidity. Finally getting tired of the fireworks, I asked a few tire dealers and auto dealers about this and they told me that modern tires nowadays have somewhat less carbon black, which is conductive, in their rubber compounds. Something about reduced wear, etc. Static charges built up from the motion of the tires over the road don't drain off as fast. Hence, when you step out of the car you get nailed. This is because the resistivity of the tire rubber is higher because of less carbon black content. Carbon black, incidentally started to be put into tire rubber back around 1910-1912, IIRC, when it was found that it drastically reduced the damage to the natural rubber caused by the sun's UV rays. Tires up until then were as white as the original rubber tree sap was when harvested and did not last very long. You can see examples of reproduction white tires on correctly-restored antique cars from around the early teens and earlier at an antique car show or auto museum. I found a solution by holding my fingers on the unpainted door jamb hardware as I turn and step out of the car (if I'm wearing normal rubber-soled shoes). This keeps my body and the car at equal potentials as the static continues to drain off through the less resistive tires. Minimal or no zaps anymore. I worry a bit about those shocks at the gasoline station if somebody is fueling their car and there is a significant concentration of fuel vapors and no wind about. It takes at least a 14:1 air to vapor ratio for ignition to occur which is not too likely at the gas bar. I have a pair of ESD-type work shoes which I wore at work and still wear around the house. There is a high amount of carbon in the heels and soles which allows them to be used as an anti-static device for electronics workers. I never get nailed in the house on a carpet nor from my car whenever I wear them. They're great! Made by Titan Safety Shoe Company. Needed them in the cleanroom at work and when repairing electronic controls around the plant or working up in the R&D lab. Additionally, I recall that I had very little problem when I wore leather-soled shoes back in the days when I had them. Seems the leather was a bit conductive especially when damp. Incidentally, do some of you remember the automobile accessory fad from back in the 70's which was an anti-static strap that hung from the bottom of the car? If it was conductive it would serve a good purpose for you today Aaron. You've probably seen fuel tanker trucks with a metal chain dragging. It too was used as a static drain for obvious reasons ;) Happy zapping! --Chris -- -- Christian Fandt, Electronic/Electrical Historian Jamestown, NY USA cfandt(a)netsync.net Member of Antique Wireless Association URL: http://www.ggw.org/freenet/a/awa/