Question from Car Talk (but not ABOUT Car Talk)

[GreasyJack]

It must have been an old one since it doesn’t seem to be in their online puzzler archive.

I wonder if the second part of the question could have something to do with the switch from above ground to underground tanks.

[Isilder]

@beowulff

Because they are short.

Believe it or not the SHAPE also comes into it.

Turns out that that if there is a flat part (say a the flat roof of a large building) here, and the top of a pole there, (eg the top of a church spire) just next door, it hits the sharp one.

So height isn’t the only reason…

function choose_target (height1, shape1, height2, shape2)

[busterpickle]

Back in the day, tires were made out of polyester. So, to be accurate, we would need to know the timeframe for the puzzler.

Polyester would in fact build up more static electricity and the truck could/would build up a potential. I’m guessing, as the operator is bringing the hose from the tanker truck to the opening in the ground for the refilling, and probably some fumes out of the tank being in the air. And, if conditions were correct, a spark could occur and could ignite the fuel vapor assuming the vapor/air ratio was correct.

So, a lot of variables to consider but it could occur. If having chains on the truck chassis alleviated this potential then it’s worth it due to the relative low cost.

Also, another option is for traction. I forgot the name of it, but there is a “spinning device with chains” that is actuated and the pulley is pushed onto the sidewall of the tires causing the chains to spin underneath the tire to aid in traction. Some emergency vehicles have this.

[Spiderman]

@LSLGuy

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.

@electronbee

Also, another option is for traction. I forgot the name of it, but there is a “spinning device with chains” that is actuated and the pulley is pushed onto the sidewall of the tires causing the chains to spin underneath the tire to aid in traction. Some emergency vehicles have this.

They are automatic snow chains. Once installed, they are activated in seconds with the push of a button. Even pulling an emergency vehicle out of service for 10 minutes to install chains before a storm could be catastrophic if that’s when a call comes in. They don’t need to be installed/removed before/after every storm, they are instantly available, & they really do work (I’ve used them on the ambulance). The older ambulance didn’t have them so we’d put chains on in advance of a storm. Gawd, that sucked driving that thing with the chains on before the snow fell &/or after the roads were cleared!

[engineer_comp_geek]

They put automatic snow chains on the school buses around here too.

[LSLGuy]

@Spiderman

They are automatic snow chains. Once installed, they are activated in seconds with the push of a button. Even pulling an emergency vehicle out of service for 10 minutes to install chains before a storm could be catastrophic if that’s when a call comes in. They don’t need to be installed/removed before/after every storm, they are instantly available, & they really do work (I’ve used them on the ambulance). The older ambulance didn’t have them so we’d put chains on in advance of a storm. Gawd, that sucked driving that thing with the chains on before the snow fell &/or after the roads were cleared!

The device I was talking about is not that. It’s a conventional grounding chain. As in a 2’ length of 3/4" galvanized hardware store chain hanging down near the rear differential.

Which were universal on gasoline tankers in the 50s & 60s and are still occasionally seen on some emergency vehicles. Here in Miami, where nobody ever needs snow chains, automatic or otherwise.

[AskNott]

@Morgenstern

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.

For those who are younger than Morgenstern and I, curb feelers, usually one at each corner of the car, would give the driver an audible SCRINCH when a car being parked got near a curb or another car. It’s cheaper than the other kind of “parking by ear.”

Curb feeler

[johnpost]

@AskNott

For those who are younger than Morgenstern and I, curb feelers, usually one at each corner of the car, would give the driver an audible SCRINCH when a car being parked got near a curb or another car. It’s cheaper than the other kind of “parking by ear.”

i also saw a type where two in a V were at each corner, close to the wheels to protect the hubcaps and whitewalls.

[Ruken]

@jtur88

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…

It’s common enough for me to have learned about it in elementary school. We were told the car was a safe place to go because the current would just pass along the exterior of the car.

[Just_Asking_Questions]

The puzzler was I believe from sometime between 1995 and 1998.

[Enola_Straight]

@CurtC

I believe I remember hearing it years ago. The answer to the second was that tires are conductive nowadays, IIRC.

Wouldn’t this create a greater potential for the battery to drain away charge to the ground? A few times recharging a dead battery would suck…especially needing a passing car driver to attempt to jump one (or two) massive 18 wheeler battery.

[Really_Not_All_That_Bright]

@jtur88

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.

Nonsense. Cars are struck by lightning constantly. It doesn’t make the news because hardly anybody dies that way.

[bob_2]

@Enola_Straight

Wouldn’t this create a greater potential for the battery to drain away charge to the ground? A few times recharging a dead battery would suck…especially needing a passing car driver to attempt to jump one (or two) massive 18 wheeler battery.

I can’t see why this would be a concern. All vehicles have negative earths these days, that is the negative pole of the battery is connected to the chassis. If the chassis has a connection to the ground, it would have no effect. (UK earth = USA ground)

Using a car battery to start a heavy truck would not be possible. Cars are 12 volt and trucks 24 volt. This is aside from the considerable effort turning a truck engine takes. Additionally, modern trucks are very sophisticated and the on board computers do not take kindly to their being jump started. Most have a big sign in the cab or by the battery(s) saying not to. Of course a mechanic would know the correct procedure but it is not for the amateur.

[Enola_Straight]

@bob_2

Using a car battery to start a heavy truck would not be possible.

I’ve done it.

Took a my car AND a jump-pack

Auto Repair, Service, Maintenance & Tires | Pep Boys

simultaneously, but it worked.