Airless tires, or non-pneumatic tires (NPT), are tires that are not supported by air pressure. They are used on some small vehicles such as riding lawn mowers and motorized golf carts. They are also used on heavy equipment such as backhoes, which are required to operate on sites such as building demolition, where risk of tire punctures is high. Tires composed of closed-cell polyurethane foam are also made for bicycles and wheelchairs.
Airless tires are tires that do not house compressed air to provide structural support. They are currently used in small vehicles such as lawn mowers and motorized golf carts. They are also used in heavy equipment such as backhoes, which operate in places such as demolitions of buildings, where pricks are likely to occur. These tires are made of closed-cell polyurethane foam, and are also used on bicycles and wheelchairs. The main advantage of airless tires is that they can not be punctured and deflated, but they are much less popular than air tires.
Airless tires usually have a higher rolling resistance and provide much less suspension than air tires of similar sizes and shapes. Other problems of airless tires are that they get hot when they are used, due to internal friction processes in the material from which they are built. Airless tires are often filled with polymers (plastic).
Michelin is developing an integrated tire and wheel, a concept called ” Tweel “, which works without air. Michelin states that compared to traditional tires “Tweel” has a bearing capacity, cushioning, and handling characteristics that are comparable. The engineering group of the automotive engineering department of the University of Clemsony is developing an airless tire with low energy dissipation capacity together with Michelin in the NIST ATP project.
Resilient Technologies and the Polymer Engineering Center at the University of Wisconsin-Madison are working on creating an “airless tire”, which basically consists of a circular polymer honeycomb wrapped with a thick tread. The initial version of the tire is for a Humvee. Airless tire Resilient Technologies have been tested and used by the US Army.
History and Vehicles
Thomas Hancock discovered the 1,843 hard rubber – curing and took on the manufacture of various articles, for which he created forms. In 1845 he produced the first solid rubber tire for horse-drawn carriages. The product could not prevail in the automotive sector first. Furthermore, wooden wheels with shrunk-on iron band were used as tires for carriages, as in the case of the draisine.
Bicycle and Motorcycle
The first pedal bicycles, the Michaulinen (1863-69), were also made with wooden spoked wheels and shrunk-on iron band. The Hanlon Brothers were granted a patent on a solid rubber tire on February 9, 1869, and Eugène Meyer in Paris on 4 August 1869 patented a Michauline with solid rubber tires (4-mm wire spokes and iron rim). However, only with the Ariel Hochrad of 1871 solid rubber tires were in larger numbers for high-wheelers produced. were usual red or gray rubber tires, between 3 / 4, and 7 / 8 -inch thick. With the rediscovery of the pneumatic tire by John Boyd Dunlop (1888), the solid rubber tire on the lower wheel was replaced by pneumatic tires until 1894. The first series motorcycle, the Hildebrand and Wolfmüller (1894), and all the following motorcycles have pneumatic tires.
Car
In the car sector, the solid rubber tire was used longer. First passenger car models were always delivered with solid rubber tires. Michelin produced the first pneumatic tire for the car L’Eclair in 1895, and in 1898 the first pneumatic tires for production automobiles appeared, but their durability was limited to 500 km. In 1902, the average durability of pneumatic tires was 2200 miles. With the introduction of the cord fabric (1920) took the life of the tire to more than 20,000 km away. With the balloon tires (1924), this led to the end of the solid tire for passenger cars. The last car with solid rubber tires delivered Trojan Limited 1929..
Truck and bus
For trucks, the problem of durability of pneumatic tires was even greater. As late as 1922, 80 percent of all trucks in Germany were using solid rubber tires. The Ordinance on Motor Vehicle Traffic of 5 December 1925 restricted the use of solid rubber tires in trucks. Three-axle vehicles over 9 tons in total had to be fitted with pneumatic tires, and over 5.5 tons total weight for cars with solid rubber tires had a top speed of 25 km / h within the city. At speeds exceeding 25 km / h, solid rubber tires overheat and destroy the fact itself. Due to the Road Traffic Safety Standardof 13 November 1937, the solid rubber tire was banned for all vehicles over 25 km / h top speed. This ban is still valid today.
Military
Gusmatik is a rubber shell, the internal volume of which is filled with a special elastic mass, which is based, as a rule, glycerin and gelatin – the so-called gusmatic composition . Subsequently, as a filler, sponge rubber was actually used, made in the form of a separate product inserted into the serial tire instead of the camera, while retaining the name “gusmatic”.
The main advantage of airless tire is invulnerability for punctures, as well as bullet, shrapnel and other similar injuries.
In the final documents of the Soviet command, it was noted that…
3. Gunfire and machine-gun fire for airless tire does not harm. Hitting a whole 37-mm projectile does not put airless tire out of action, but makes a neat hole and the machine continues to work…
– Armored cars in battles, Chapter III. The history of the Soviet armored car 1925 – 1945.
The main disadvantage of tires of this type is lower elasticity compared to traditional pneumatic tires, which significantly limits the allowable speeds of the vehicle and, as a result, the scope of tires – tires GK (with a sponge chamber) for large speeds quickly heat up, and inside the tire begins the emission of gases, which can cause spontaneous combustion of tires or even their rupture.
Modern analogues
Currently, new, more efficient analogues of airless tire are being developed, in the construction of which a similar principle has been applied. They are used for damping instead of elastic mass using highly elastic cellular structures located between a more rigid and durable solid tire and a wheel disk .
Situation in the 21st Century
Currently, almost all industrial trucks, forklifts and pallet trucks are equipped with solid rubber tires, which can last three times longer than pneumatic tires. Solid rubber tires such as pneumatic tires consist of almost half of natural rubber and synthetic rubber, a quarter of carbon black, a fifth of steel, as well as fabrics, zinc oxide, sulfur and other substances.
According to the road traffic licensing regulations, vehicles with speeds of not more than 25 km / h (for motor vehicles without a suspension axle but only at maximum speeds of not more than 16 km / h) are allowed full tires. This regulation should protect the roads.
In 2017, the Asian bicycle manufacturer Obike established several rental bikes in the center of Berlin without fixed stations. These wheels are equipped with solid rubber tires and have an easily adjustable saddle. A Finnish rental system also resorts to solid rubber tires due to the puncture resistance.
Advantages
The main advantage of airless tires is that they cannot go flat. Other advantages are that airless tires will need to be replaced less often resulting in a savings. Heavy equipment outfitted with airless tires will be able to carry more weight and engage in more rugged activities. Airless bicycle tires can be easy to install. Airless lawn mower tires come in several varieties.
Disadvantages
Airless tires generally have higher rolling resistance and provide somewhat less suspension than similarly shaped and sized pneumatic tires. Other problems for airless heavy equipment tires include dissipating the heat buildup that occurs when they are driven. Airless tires are often filled with compressed polymers (plastic), rather than air or can be a solid molded product.
Airless tires are attractive to cyclists, as bicycle tires are much more vulnerable to punctures than motor vehicle tires. The drawbacks to airless tires depend on the use. Heavy equipment operators who use machinery with solid tires will complain of fatigue whereas lawn mowers that use solid or airless tires have no drawbacks. Bicycle riders who use airless tires may complain that the tire is harder than a comparable pneumatic tire. Only anecdotal evidence exists that airless tires may cause broken spokes on a bicycle wheel. Any airless tire will be heavier than the rubber tire it is meant to replace; however, many rubber pneumatic tires are also heavy. Rubber tires vary in rolling resistance and an airless tire or solid insert may only marginally increase rolling resistance if at all.
Installation of airless tires depends on the use. Heavy equipment will need special equipment to mount but an airless bicycle tire can be mounted with little or no effort. Solid airless lawnmower tires come pre-installed on the wheel allowing quick installation.
Examples
Many bicycle-sharing systems use these tires to reduce maintenance.
In 2005, Michelin started developing an integrated tire and wheel combination, the “Tweel” (derived from “tire” and “wheel,” which, as the name “Tweel” suggests, are combined into one new, fused part), which operates entirely without air. Michelin claims its “Tweel” has load carrying, shock absorbing, and handling characteristics that compare favorably to conventional pneumatic tires. However, the tire has a lot of vibration when driving over 80 km/h (50 mph). A market roll out is therefore not planned in the near future. The automotive engineering group of the mechanical engineering department at Clemson University is developing a low energy loss airless tire with Michelin through the NIST ATP project.
Crocodile Tyres developed and sells a robust version that bolts to standard mining equipment.
Resilient Technologies and the University of Wisconsin–Madison’s Polymer Engineering Center are creating a “non-pneumatic tire”, which is basically a round polymeric honeycomb wrapped with a thick, black tread. The initial version of the tire is for the Humvee and is expected to be available in 2012. Resilient Technologies airless tires have been tested and are used by the U.S. Army. and is also the first group to make a commercially available mass-produced airless tire after their acquisition by Polaris, albeit, only as coupled with their vehicle. The tire trade mark is “Terrainarmor”
Bridgestone is developing the Bridgestone Air-Free Concept Tire, which is similar to the Tweel, and can hold 150 kg (330 lb) per tire.
The Energy return wheel has the outer edge of the tire connected to the inner rim by a system of springs. The springs can have their tension changed to vary the handling characteristics.
Big Tyre Pty Ltd in Australia is developing a “non-pneumatic, non-solid wheel”, which is designed to handle high working loads, such as those found in underground mines. The wheel utilizes multiple arrays of concentric leaf springs to distribute force evenly across the wheel. A prototype of the wheel was built in 2011, and has been tested on an Eimco 936 underground loader.
In 1938, J. V. Martin in the United States invented a safety tire with hoops of hickory encased in rubber and fitted with crisscross spokes of ribbed rubber. It could drive over 100 mm (4 inches) blocks when tested in a springless test car.
Hankook Tire is developing the iFlex airless tire.
Source from Wikipedia