I was never a faithful listener. I’d catch them when I remembered. One time there was the puzzler that I wanted to know the answer, but missed the next week.
It asked: in the old days, gas trucks had chains hanging from the axles, dragging on the ground. What were they for? And why don’t gas trucks have them anymore?
I think I know the answer to the first, but not the second. Does anyone remember this puzzler, or know the answer?
to prevent the buildup of static electricity
They’re intended to ground the chassis so a static electric potential doesn’t build up between the chassis and the Earth ground.
As to why not now, I don’t know the for-sure answer. My bet is different procedures are now used when loading & unloading the tanker. And these procedures include a different way to zero the static potential before connecting the hoses. E.g. a dedicated ground wire and bonding point at the station.
I do sometimes see grounding chains dragging under / behind modern paramedic or fire vehicles. So I doubt the answer is that truck tires are conductive enough to eliminate the need for direct ground bonding.
I believe I remember hearing it years ago. The answer to the second was that tires are conductive nowadays, IIRC.
I don’t know about truck tires, but tires in general are LESS conductive now than they used to be, which creates more of an issue for static buildup.
If tires were conductive, cars and trucks could (and often would) be struck by lightning.
I’m assuming from the following link that the static buildup occurs during the filling process, not while the truck is driving down the road. The chain provided protection during filling, and the fact that it was still in place dragging on the ground did no harm, so it was just left in place. In later years, the pumps at the bulk plants were more carefully monitored and controlled by safety standards, so there was no need anymore to rig the trucks to defend them against irresponsible filling.
BZZZT!
Wrong!
A lightning bolt isn’t going to be stopped by an inch of rubber after travling through a mile of air…
Cars and trucks are sometimes struck by lightning: https://www.youtube.com/watch?v=k4WL0s09Z9c
From someone who had chains on his 55 International – most of that probably and it just looked/felt cool.
In aircraft filling, there is a grounding connection that must be attached to the aircraft fuselage before fueling (the truck is also grounded similarly). Maybe they started doing that at gasoline depots as well. That makes sense if so.
Yeah, it was a ground. The drivers probably didn’t notice that the chain bouncing on concrete at freeway speeds probably made a lot of sparks which isn’t a wonderful thing. There’s probably a built in ground with all the hooking up stuff a driver needs to do to make a delivery, but to fill his tanker, there’s got to be something specific.
I think this was the answer. These days, there’s a grounding procedure that prevents static discharges.
That is extremely rare – so rare that when I saw your link, I new it was going to be in Alberta. It is the rarity that makes that video viral. For every car that is struck by lightning, there a thousand people standing out in the open who are. But the number of people standing outdoors at any given time (especially when there is a storm) is a tiny fraction of the number of cars sitting outside. Explain why so many people and so few cars are struck by lightning, given the numbers of them that are out in the rain…
Because they are short.
How many lightning strikes actually hit the ground? Most hit the tallest object nearby - a pole, tree, or building.
We used to see a lot of cars with a strap hanging down at the back. This was a grounding strap that was supposed to prevent car sickness. Many people swore by them. Hardly ever see them these days.
I don’t remember seeing those straps, but I do remember those curb feelers that looked like whiskers sticking out of the side of your car.
maybe
KABOOM
Wrong!
and a number of miles.
a bolt most often splits and hits multiple things including the earth.
Too Soon! 