Way back in the 1970’s, I recall seeing quite a few cars with a pair of black strips dangling from the rear bumper, all the way to the pavement. What did these things do? I’ve been told that they were purely decorative, but I can’t help thinking there was some specious purpose, for example, like using tail fins for stabilizing the car. Can I get some help me on this one?
I’ve seen big rigs that have strips of thin metal that drags along the road. I think it had something to do with grounding the truck in case it was struck by lightning.
They were for electrical grounding. Here in the UK, at least, people fitted them to prevent shocks from static buildup, rather than lightning protectors. It’s hard to see how any of them can have done any good, as they usually don’t touch the ground (or if they do they are soon abraded, and don’t).
Fire engines here have chains dragging on the road under the trailer which does the job rather better, at the expense of a lot of noise.
Russell
At one time there it was believed by many that the straps could prevent police radar from getting an accurate reading. It doesn’t have any effect however.
Another old time common UL was that tinfoil placed in the hubcaps would screw up radar. That one probably came from the chaff (shredded aluminum)that was dropped from aircraft to provide a radar reflection that could hopefully confuse the enemy.
Nandan, you referred to cars with those dangling strips. Could you have been referring to trucks? Specifically fuel and gas trucks?
That would answer the grounding/static rule.
I’m really thinking cars here. There were always a pair of strips that dragged on the pavement and appeared to be made of black rubber.
Definitely cars, and almost always with white chevrons on a black background so that they look dynamic.
Russell
Static buildup is not so much of a problem in humid climates but if you live in a very dry climate the shock you get when you get out of the car can be painful. To avoid shock I, 1- get out of the car without touching any metal parts, 2- close the door by pushing on the glass window and 3- hold the key in my hand and lock the door. Thios way the spark jumps from my key to the car with no effect to me. I do this every time without thinking even if I am in a humid place with little danger of static.
Before there were those grounding strips you would just hang a sort length of chain from the underbody. Then the automotive accessory industry discovered they could improve on that unsightly chain and make a fashion statement and the grounding strip was born. it is silent, it only touches the ground when the vehicle is stopped as it is pushed up by the air when in movement.
I have seen some buses with an ingenious system where a length of chain is connected to the bus door mechanism in such way that the chain touches the ground only when the door is open and is retracted when the door closes.
Vehicles that transport fuel and aircraft need to have safer protection against static and have to be positively grounded before fueling begins.
Anyway, believe me, those jolts from static can be painful.