Text/Meite polymer only milan
I don't know if you've noticed that regular sized or even larger passenger planes like Airbus A330 only have over ten tires, even smaller than a truck, and tire size isn't very large. So how to withstand hundreds of tons of quality? Do aircraft tires have any special design? What pressure and what gas is charged?
Actually, not all aircraft tires are solid. Only some light aircraft such as fighter jets or Cessnas are solid tires. Solid tires cannot withstand impact of a heavy aircraft during landing and will immediately burst.
Aircraft tires are divided into two types: internal and tubeless, and depending on pressure they are divided into low pressure and high pressure tires, all of which are filled with nitrogen. The more pressure, more weight tire can support, which is why high pressure tubeless tires are commonly used in large aircraft or high speed aircraft. Tubed low pressure tires are commonly used on small propeller-driven aircraft.
Let's take Boeing 777 as an example:
The total weight of Boeing 777 aircraft is about 300 tons in preparation for international flights, and this weight mainly rests on main landing gear of two wings. The Boeing 777 has six wheels on one side of main landing gear. In other words, 12 wheels carry a weight of almost 300 tons, an average weight of 25 tons per wheel. Secondly, when aircraft takes off and lands, tires also experience strong impact in vertical direction and friction when braking in horizontal direction. The takeoff speed of aircraft is 300-350 kilometers per hour, and landing speed exceeds 200 kilometers per hour, which indicates a lot of pressure on tires.
If you calculate by number of flights, then one tire is enough for about 250 flights. After 250 consecutive flights, tires must be serviced. For example, to retread a worn tread, this type of retreading can typically be repeated 5-6 times, meaning a tire can be used for about 1500 flights.
Inside tread rubber of aircraft tires, two layers of a special layer, commonly known as "reinforced layer", are added. With cord layer as boundary, tread rubber is divided into an outer tread rubber and an inner tread rubber. When a tire wears out to point where second curtain layer opens, it will be scrapped.
The rubber coating of aircraft tires is made of wear-resistant and heat-resistant special materials glued with steel wire, has a thickness of about 20 mm and has high strength. Aircraft tires do not have inner tubes, mainly to facilitate disassembly and maintenance. Air can be injected directly into tires during flight.
At same time, aviation material manufacturers all over world use high-strength magnesium and zinc alloys to make hub and moving rim, and use O-rings to seal joint between hub and moving rim, and between valve and hub, which can guarantee that number of tires inside tire. Gas at atmospheric pressure does not leak, its performance is unmatched compared to conventional tires, and its cost is also quite high.
An aircraft weighing from tens to hundreds of tons lands at a speed of several hundred kilometers. In addition to weight and load, it must overcome sudden temperature changes. At high altitude, temperature is about 50-60 degrees below zero, and when decelerating and braking, about 150 degrees. You can't do without one of these tires.
For example, tire pressure of a Boeing 737 is 1.378 MPa, six times that of a car tire. The air in airplane tires is actually nitrogen. Why is it filled with nitrogen?
1. Improve stability and driving comfort on tires.
Nitrogen is an almost inert diatomic gas with extremely inactive chemical properties. Gas molecules are larger than oxygen molecules. It is not easy to expand when heated and contract when cold. Convenience; sound conductivity of nitrogen is low, which is equivalent to 1/5 of ordinary air. The use of nitrogen can effectively reduce tire noise and improve driving peace.
2. Prevent emissions and lack of air.
Blowing a tire is number one cause of traffic accidents. When car is running, temperature of tire rises due to friction against ground. Especially when driving at high speed and emergency braking, temperature of gas inside tire will quickly rise, and tire pressure will rise sharply. So there is a possibility of blowout. High temperatures lead to aging of tire rubber, reduced fatigue strength and severe tread wear, which is an important factor that can lead to tire failure. Compared with ordinary high pressure air, high purity nitrogen has a low thermal expansion coefficient, low thermal conductivity, and slow temperature rise because it contains no oxygen and contains almost no water or oil. blow out.
3. Extend tire life.
After using nitrogen, tire pressure is stable and volume change is small, which greatly reduces possibility of uneven tire friction such as crown wear, tire shoulder wear, partial wear, and increases tire life; air affects aging of rubber. Due to oxidation of oxygen molecules in tire after aging, its strength and elasticity will decrease, cracks will appear, which is one of reasons for shortening of tire life.
The nitrogen separation device can remove oxygen, sulfur, oil, water and other impurities from air to greatest extent, effectively reducing oxidation of tire inner shell and rubber corrosion phenomenon, and will not corrode metal hub, prolonging service life of tire. not only prolong tire life, but also greatly reduce rim rust.