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Things Mom never taught Ya! (SAFETY)

PTSideshow

New member
Welding on rims/wheels with the tire on. Now it is a long video 10 minutes as it explains what happens and answers some other questions that people have brought up.

A degradation process called pyrolysis that causes the tire to decompose and to generate heat. In the confined space of the tire it doesn't take much additional gas to over-pressurize the tire.

Would never have thought to do it, with the tire on the rim. Also for those that don't watch the complete video. Removing the valve stem and air pressure doesn't matter, as it is strictly gas generated from the tire that generates the pressure so fast. That even with one side of the tire loose it has reseated it self and gone boom.

 

OTTO-Sawyer

Subscriber
Re: Things Mom never taught Ya!

Just by the description given, That's one video I'm going to have to go use a friends computer to watch !

While not Totally Related to that, one of the rockets that were privately built to compete for that X-Prize for the first privately built and funded rocket into space was using a mixture of ground up rubber and nitrous oxide as their rocket fuel. There's a lot of gas and heat (expansion for thrust) generated from burning rubber!
 

PTSideshow

New member
Re: Things Mom never taught Ya!

process called pyrolysis that causes the tire to decompose and to generate heat.That occurs spontaneously at high enough temperatures.
and will continue once started with out the additional heat or continuing addition of flame.

This is what can happen to truck tires that blow apart from high heat on the highway. Instead of burning by combustion, that is way not every tire comes apart in a violent fashion doing extreme damage. some do and some have a weak spot that lets go before the pressure can build up.

And for those that don't watch all the way through the video. I should mention that includes heating the lug nuts with a torch to loosen them as with the earth moving equipment with the rim and tire still on the machine!

I guess that is were we get the expression the "TIRE BLEW" and sometimes they do a lot of damage and other times they don't.:eek:
 

oldtractors

Subscriber
Re: Things Mom never taught Ya!

Scares me to think about last summer when I was using a weedburner torch to heat up the hub on a set of L case wheels so they would pop off of the tapered spline axle. I had let the air out of the tires, but the video mentions that once the process starts, the pressure builds up so rapidly that it will blow the tire even with the valve core removed. There were documented cases of that happening with the core removed. I guess I would hope that the air whistling out the valve stem would give me some warning to start running.

Those weedburner torches put out a lot of heat, but you can't really direct the flame very well. I know I had the rim warm before I was done.
 

OTTO-Sawyer

Subscriber
Re: Things Mom never taught Ya!

...This is what can happen to truck tires that blow apart from high heat on the highway. Instead of burning by combustion, that is way not every tire comes apart in a violent fashion doing extreme damage. some do and some have a weak spot that lets go before the pressure can build up.

I guess that is were we get the expression the "TIRE BLEW" and sometimes they do a lot of damage and other times they don't.:eek:
Even though I never heard anyone confirm it, I still strongly feel that is actually what blew apart the space shuttle that disintigrated over several states. Yes they they had other problems working against them with a hole burning through the wing, but one of the last voice recording messages refered to a tire pressure sensor warning from the sudden rise in tire pressure in the landing gear. They were coming in fast and hot, but still had things somewhat under control UNTIL the tire blew and blew off the wing and the rest of the heat shield tiles, sending it into a barrel roll causing it to break up. If they would have had some way to bleed off the tire pressure, they may have had a chance of landing even if they were one wheel short.

I have suspected the tire pressure buildup being the cause of the explosion ever since the day it happened, and that was just figuring normal pressure build up from the amount of heat they were dealing with. Reading here about how rapidly that 'gas pressure' builds up in a tire, just makes my theory that much more plausible.
 

Tony Kautza

New member
Re: Things Mom never taught Ya!

Reminds me a little of what happens in a propane tank when one lets loose it is called a bleve( Boiling liquid expanding vapor explosion) the gas in the tank starts boiling and the pressure keep multiplying so fast that the vessel can't contain it we referred to it as a Big Loud Extremely Violent Explosion lots of scary stuff in the world be safe Tony K
 

oildipper1062

New member
I just stumbled across this thread. Watched the video and scares me to death that I have used heat several times to loosen stuck lug nuts.
 

OTTO-Sawyer

Subscriber
It's been a while since I watched that video (with my slow dial up I had to watch it at the library) but I believe it is more from the electric current than from the heat. The rapid heat & pressure buildup comes from the reaction within the rubber.

There's a public service announcement comercial playing quite a bit lately (at least on the Rockford Illinois TV stations) about a farmer that was killed crawling out of the cab of his terregator (probably spelled wrong) after one of the arms dropped down and touched a power line. The farmer was electrocuted, but they also mention the tires blowing out on it.

Same thing happens when vehicles are struck by lightning (also high voltage).

Still makes a person want to think twice about using heat on lug nuts, but you'd probably have to heat the wheel rim right next to the tire to get the same results as arc welding anywhere on the wheel (or hitting power lines or getting struck by lightning)

I don't know how long ago this was first documented, whether it can happen with old bias ply tires with fiberglass strands in them or if it's a newer phenomenom since the steel belted radials came out and started being used more and more.
 

dalmatiangirl61

Subscriber
There's a public service announcement comercial playing quite a bit lately (at least on the Rockford Illinois TV stations) about a farmer that was killed crawling out of the cab of his terregator (probably spelled wrong) after one of the arms dropped down and touched a power line. The farmer was electrocuted, but they also mention the tires blowing out on it.
I was taught that if you ever tangle with powerlines to just sit tight, the tires keep the cab from ground, when you get out you complete the circuit to ground:uhoh:, even heard of people trying to jump from cab getting fried because they become the carbon rod between two air gaps. Have not hit them yet, have found myself closer than I cared to be.
 

oildipper1062

New member
I was wondering about that too. I do use propane on my torch because I do more cutting than anything else. It does not take a whole lot of heat to loosen a nut. So I don't know, something to think about.
 
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