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Auto repair is actually a very skilled and dangerous type of work. Many people do not know that there are some restricted areas near car tires, especially truck tires, in which many auto mechanics are killed. Today let's take a look at the "dirty stuff" of tires.

▲ Picture Source: wikipedia

I don't know if you have ever seen such a magic operation when you are browsing a short video: people spray a car tire with something and then light a fire, and the originally flat tire duang bulges.

▲ is a dead operation, do not imitate it. Photo Source: funny hill

The videos have been circulating online for years and have received a staggering number of hits. But what is the principle of this? The principle of this "technology" is not complicated, but this operation involves fatal risks.

The principle of this method should start with the structure of modern tires.

In the past, most of the tires had an inner tube, that is, the structure of a large sleeve and a second tire. Inside the outer tire, there is an inner tube made of different rubber.

However, such a tire has been relatively rare, now most of the tyres are tubeless tires. You probably didn't expect the inside of the tire to look like this:

▲ tubeless tire. Photo Source: wikimedia

As can be seen from the figure, the tubeless tire is not completely closed and is separate from the hub (also known as steel ring).

The inside of the tire has a rim (also known as the heel), which is similar to the sealing ring at the mouth of the bottle and can be stuck with the slot on the hub.

▲ tire cross section: the tire (blue) and the hub (gray) fit by the rim (structure with red dots). Photo Source: wikimedia

However, the rim does not always fit perfectly with the hub.

Sometimes, in order to increase the grip of the tire, the driver will deliberately inflate the tire, and the rim may roll out of the hub slot. In addition, a sharp turn or a hit by a kerb may derail the rim of the tire.

The rim (white spot) and hub (gray) of ▲ tire (black) fit and derailment. Image source: see watermark

Obviously, once the rim is derailed, the tire will leak quickly. At this time, it is very troublesome to pump the tire normally, because the valve is usually on the hub, if the hub and the rim do not fit, the pump can only make people angry.

The valve of the ▲ is usually on the hub. Photo Source: funny hill

In such a situation, some veteran drivers will use the "trick" in the video: spray combustibles on the wheels and the liquid will seep into the tires. At this time, the combustible material is ignited, the combustible material burns and explodes, and the tire that expands instantly will drive the tire rim back to position.

However, this "skill" actually hides risks.

The Occupational Safety and Health Administration (OSHA) prohibits this operation. The bureau pointed out that never use any gasoline, start-up fluid or other combustible material to lubricate the tire rim, as this may lead to the separation of the tire and the wheel hub, resulting in casualties.

▲ Photo Source: BlondinrikardFr ö berg / flickr

In fact, just inflating tires or repairing tires (especially truck tires) is a very dangerous job, even without ignition. Many people have died as a result, and the relevant regulations of many countries, such as the Occupational Safety and Health Administration of the United States, are based on individual lives.

▲ is a dead operation, do not imitate it. Photo Source: funny hill

For example, the Labor Safety Agency of British Columbia (Worksafebc) has reported three deaths caused by repairing / changing tires.

The first worker died while unloading the tire.

The tire involved has several layers of wheels, and dozens of bolts are used to connect the outer tire to the inner hub. At that time, the worker removed the bolts without completely deflating the tire, resulting in an accident.

▲ caused the accident with tires and wheels. Photo Source: Worksafebc

The bolt failed to withstand the 6.1 standard atmospheric pressure inside the tire, and the tire flew out and hit the worker. Under the great impact, the worker bounced into the rear car and shattered the hard car.

▲ smashed the car. Photo Source: Worksafebc

In the second accident, the worker was welding a crack in the hub.

He did deflate the tire in advance, but during the operation, the tire didn't come off, it was still in the car. After welding the cracks in the wheels, the worker re-inflated the tires while the tires were still on the car.

That's when the accident happened. The heat during welding partially melts the tire, producing combustible gas. During the pump, the combustible gas began to burn, causing the tire to explode and split into four pieces. One of them hit the worker and caused him to die on the spot.

▲ cracked the tire that caused the accident. Photo Source: Worksafebc

You may have found that the worker's operation is actually very similar to the "skill" mentioned in the article, so now you can see why the Occupational Safety and Health Administration forbids that kind of tire "right" way.

In the third accident, the hapless worker did not make the mistake of the second worker, who unloaded the tire before pumping air.

At that time, the tire was flat on the ground, above the front tire of the worker. However, the rim of the tire did not get stuck in the hub. In order to make the rim fit with the hub, the workers continued to inflate the tire. as a result, the tire inflated too much, the rim exploded, and both the worker and the tire ejected into the air.

This is the dent left by the tire on the roof at the scene of the accident:

▲ Picture Source: Worksafebc

According to the Occupational Safety and Health Administration, most accidents occur during the inflation phase after tire assembly.

Because of these countless lessons of blood and tears, you need to follow a set of fixed operating rules when inflating tires, especially truck tires, such as deflating before bolting, and putting tires in a safe inflatable cage (safety cage) when inflating tires, never in the same position as a third worker.

A safety cage used when tires are inflated.

Of course, different tires have different degrees of danger. There has been a tyre nicknamed "widow maker" in history. Until now, it has not been completely off the stage, and some trucks still use this rolling machine.

This "widow maker" is Firestone's RH5 tire (Firestone RH5).

▲ RH5 tires. Photo Source: jalopyjournal.com

According to the Occupational Safety and Health Administration, as of 1973, RH5 tires had caused 81 accidents and 13% of deaths in 10 states in the United States alone.

The RH5 tire is actually a groundbreaking tire because it uses a new design: multi-piece wheels, that is, there are many wheels, and multi-piece wheels rely on the air pressure of the tire to press the parts without screws. Before that, the hub was one-piece.

▲ multi-piece wheel tyre. Photo Source: OSHA

However, after the advent of multiple wheels, accidents occur frequently. In 1980, the Occupational Safety and Health Administration listed four types of multi-piece wheels as designs that pose safety risks to people, including RH5 tires. The bureau pointed out that although these designs are more economical, they add to the damage caused by the explosion of the tire, the most dangerous of which is the RH5 tire.

This is the power of a multi-piece hub tire when inflated:

▲ Picture Source: OSHA

So in 1980, the National Highway Traffic Safety Administration (NHTSA) considered banning multi-piece wheels, but the matter came to an end, and many of the tires on the market are still multi-piece. RH5 tires were introduced in 1946. Between 1946 and 1973, 15 million RH5 tires were made, some of which are still on the market.

The risks mentioned above are high for auto mechanics, but ordinary people should not be taken lightly near tires. The Occupational Safety and Health Administration has announced the following dangerous areas near tires. It is best to stay away from these silent dangerous areas, especially to teach children to pay attention to safety.

Hazardous area of ▲ multi-piece hub (gray). Photo Source: OSHA 1910.177 Appendix A

Who would have thought that not only are running cars dangerous, but unloaded wheels are also potential bombs?

Some of them are so cute, some of them are so cute.

Reference:

Https://docs.qq.com/doc/DVGRYRG1Lc25OU01N

This article comes from the official Wechat account: take Science Home (ID:steamforkids), author: Qijun

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