Tires bias-belted

Other polyamides having higher moduli and T than nylon-6 and nylon-6,6 have been evaluated in an effort to reduce wrinkle resistance and eliminate flat-spotting of bias and bias-belted tires (Table 3). Nylons have also been tested extensively over the years for apparel and carpets (Table 4). 

In the category of industrial appHcations, nylon is the predominant fiber used in the carcass of bias tmck, racing car, and airplane tires because of its exceUent strength, adhesion to mbber, and fatigue resistance. Nylon is used less in the carcass of radial tires for automobiles and in replacement bias and bias-belted tires because of the development of temporary flat spots. For this reason, nylon has lost most of this market to polyester. 

Introduced successfully for tires in 1967, glass fibers had properties that made them very attractive for use in tires (5,8). The britdeness of glass fibers, however, imposed some limitations on the final tine cord properties because of the requirement that each fiber be individually coated with a mbbery adhesive to avoid interfilament damage during fabrication and use. This additional treatment step is introduced at the fiber manufacturing stage. For several years fiber glass was used extensively in bias-belted and radial tires, but was ultimately replaced by steel belts in radial tires. 

The tire building is carried out on a flat drum, which is rotated at a controlled speed. The plies of rubber-coated cord fabric are placed in position, one over the other, and rolled down as the drum rotates, the inner lining being placed next to the drum and the ends of the drum being flanged to suit the bead configuration of the tire. The plies of rubber-coated textile are assembled in three basic constructions— bias (diagonal), radial, and bias belted. 

The bias-belted tire, on the other hand, has much of the tread wear and traction advantage of the radial tire, but the shift from bias to bias-belted tires requires less radical change in vehicle suspension systems and in tire building machines. These features make the bias-belted tire attractive to both automobile and tire manufacturers. 

Up to the advent of World War II, practically all of the rubber consumed was of the natural variety, mostly derived from Hevea brasiliensis plantations in the Far East. With the entrance of Japan into the war, both the United States and western Europe were cut off from the main source. At this point one of the most massive organic chemistry research and development efforts in history was launched, which ultimately resulted in the development of synthetic elastomers such as Buna N, Neoprene, Thiokol, and styrene-butadiene. While these were not equivalent to the natural product in some respects, product improvement continued so that by 1970 worldwide synthetic rubber production was 3.8 million metric tons compared to 2.7 million of the natural product. Styrene-butadiene rubber sold for about the same price as natural rubber. Although national defense interest dictated a policy of independence from foreign raw materials, conventional bias-belted tires still required 15% natural rubber for optimum performance. 

Tire Construction The geometry of the various layers of tire fabric in the final tire. Three constructions are commonly used. Bias Tire— In this construction, tire fabric is laid alternately at bias angles of 25—400° to the tread direction. An even number of layers (or piles) is used. Radial Tire- In a radial tire, tire fabric traverses the body of the tire at 90° to the tread direction. Atop the tire fabric are laid alternating narrow layers of fabric at low angles of 10-300° to the tread direction the belt that is formed around the tire body restricts the movement of the body. Bias/Belted Tire-This tire construction combines features of the preceding two. The first layers of fabric are identical to the bias tire. The belt is added in alternating layers at 20° to the tread direction. 

The carcass ply/pHes coat compouad fuactioas are basically the same as the steel breaker compouad. Normally ia the steel belted PCT the ply is textile cord of polyester or rayoa fabrics which are soft and flexible. The tmck radial steel tire normally uses a steel cord ply. Earthmover tires are of two basic constmctions, ie, radial usiag steel and bias usiag textiles (see Tire cords). 

The effect can be seen in Figure 26.75 which shows the results obtained with the two-wheeled trailer discussed above. Tire group A was a re-treaded bias tire group B a commercial steel-belted radial ply tire. When one tire of each group was mounted on the axle of the trailer for equal set slip angles, the direction of the tow bar adjusted itself in such a way that the tires run under the same... 

The most important single trend in the U.S. tire market is the switch from cross-ply and belted bias-ply to radial-ply tires. Radials held only 8% of the... 

Although the majority of truck tires are steel-belted radials, there are still a number of bias ply truck tires, which contain either nylon or polyester belt material... 

In the radial-ply tire, one or two plies are set at an angle of 90° from the center line and a breaker or belt or rubber-coated wire or textile is added under the tread. This construction gives a different tread-road interaction, resulting in a decreased rate of wear. The sidewall is thin and very flexible. The riding and steering qualities are noticeably different from those of a bias-ply tire and require different suspension systems. 

The increase in natural rubber usage translates into approximately 21 kg per tire for a radial construction compared with approximately 9 kg found in a bias buck tire. Natural rubber compounds also tend to And use in covers of high-performance conveyor belts where a similar set of performance parameters such as those of a buck tire bead compound are found. Low hysterebc properties, high tensile sbength, and good abrasion resistance are required for both products. 

The selection of cord materials for belts and plies in a tire and the associated physical locations lend themselves to further FEA analysis. If one takes an inflated nonbelted tire, the ply cords, whether they are in a single-ply casing or multiple-bias-ply construction, will assume a configuration that minimizes strain within the composite. The resulting cord path is termed the neutral contour. Belted tires introduce a restriction to the inflated diameter of the tire, and the neutral contour or plyline of such systems is consequently altered. 

In the 1940s rayon was used almost exclusively in tires. It was difficult to adhere rayon to rubber mechanically because of the smooth surface of the rayon filaments. Fortunately, two Dupont Co. chemists, W. H. Charch and D. B. Maney found that incorporating a resorcinol-formaldehyde thermosetting resin into a rubber latex made a cord adhesive which gave excellent adhesion of rayon to rubber carcass compounds. The same RFL cord adhesive was also used when nylon was introduced as a tire reinforcing material in 1947 and when glass fiber was introduced as belt material in belted bias and radial tires. 

Some glass tire cord is still being used in the belts of belted-bias and radial passenger tires. However, the use of glass in belts has been limited because of the preference of steel wire in radial tires. Still, there has been some research work done in order to improve the dynamic performance of glass belts in tires. 

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