Belts are used with pulleys in drives for high-volume products, such as home appliances and automobile engines, as well as machines built in small numbrs, such as heating, ventilating, and air-conditioning systems, and pumps.

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Click Here for the Glossary of Belt Terms

V-Belt Classical V-Belts Single V-Belts Double V-Belts Open-end V-Belts Link-Type V-Belts Narrow V-Belts Cogged, Raw Edged V-Belts Joined Belts V-Ribbed Belts Adjustable-Speed Belts Endless Round Belts V-Belt Pulleys

Synchronous Drives Trapezoidal-Tooth Belt Curvilinear-Tooth Belt Poly Chain Dual-Sided Synchronous Belts Synchronous Pulleys Flat Belt Leather Belts Fabric Belts Rubber Compostion Belting Synthetic Belting Flat Belt Pulleys

Widely available from distributors, V-Belts are often used in industrial and commerial applications because of their low cost and wide range of sizes. These belts are easy to install and they operate quietly and smoothly. Suitable both for transmitting power and conveying materials, V-Belts operate over a wide horse-power range and at speeds up to 6,500 feet per minute (fpm) or more.

• Classical V-Belts: One of the first V-Belts to become an industry standard is the heavy-duty classical multiple V-Belt. The term 'Multiple' originated from the use of several belts to replace a single wide flat belt on a pair of shafts.
  • Single V-Belts: A specail category, called single V-Belts, has evolved for light-duty applications such as fractional-horsepower(fhp-less than 1 hp) motors. Typical applications are appliances and samll machines used in industry and business.
  • Double V-Belts: The drive and driven shafts on most machines rotate in the same direction. But on some equipment, particualarly in the textile industry, driven shafts rotate in a direction opposite to that of the driving shaft. This is accomplished by a double V-Belt, which drives from either its top or bottom surface. Drives of this type with several pulleys are called serpentine drives.
  • Open-end V-Belts: In some situations, and endless V-Belt can't be used. For example, the drive and realted equipment amy be situated such as to prevent a belt from being slipped orver a pulley, or emergency replacement of a V-Belt precludes normal installation.
  • Link-Type V-Belts: Adjustable-link V-Belts consist of removable links that are joined by T-shaped rivets or interlocking tabs. These belts can be installed without dismantling drive components. Other advantages include chemical and abrasion resistance, and reduced inventory.
• Narrow V-Belts: Narrow V-Belts offer higher power ratings than conventional belts for a given width. Hence, they do more work in less space, which translates into low-cost, small pulleys and low 'overhung' load on bearings.
• Cogged, Raw-Edge V-Belts: Belts with notches molded or cut in the underside, are called cogged belts. If the cogs are at an angle other than 90 degrees to the belt, it is known as a helical cog pattern. The notches relieve some of the bending stress induced in belts when they flex, enabling them to operate on smaller pulleys. Helical cogs also serve to quiet the drive by cancelling sidewall noise.
• Joined Belts: Pulsating loads, such as those generated by internal combustion engines driving compressors, produce a whipping acton in conventional V-Belts, which may cause them to turn over in the pulley grooves. To stabilize such drives and prevent turnover, two or more belts are joined at the top by a layer of rubber and fabric.
• V-Ribbed Belts: Another member of the 'V' Family, the V-ribbed belt resembles a flat belt, but with V-Shaped ribs along the inside surface. These ribs operate in grooved pulleys, making the belt more stable than a flat belt.
• Adjustable-Speed Belts: By contrast to conventional drives, an adjustable-speed belt drive (often called variable-speed) has one or more grooved pulleys with flanges that can be adjusted in width so the belt moves radially within the groove. The pitch diameter changes with the belt location in the pulley groove, thereby providing a speed-ratio change.
• Endless Round Belts: Light-duty power transmission and conveying applications often call for endless round belts, which have a cross section like an O-Ring and are available in diameters from 1/4 through 9/16 inches. The elasticity of these belts simplifies design problems and reduces costs. However, they are limited to sub-fhp applications such as recorders, projectors, and business machines.
• V-Belt Pulleys: Pulleys for V-Belts are usually made from cast iron, ductile iron, or steel. Light-duty versions are made of pressed steel or plastic. Standard identification systems for pulleys include the belt cross section, number of grooves, and diameter. Pulleys are either bored to size or they accept tapered bushing. A fixed-bore pulley can be installed only on one size of shaft. A bushed pulley, because it accepts different sized busings, can be mounted on a range of shaft diameters.

Used primarily where the motion of input and output shafts
must be precisely matched, synchronous belts were originally known as timing belts. Synchronous belt drives are used where back-lash of chain or gear drives would be undesirable.

• Trapezoidal-Tooth Belts (Timing): Conventional synchronous belts have trapezoidal-shaped teeth, that engage mating teeth on pulleys to maintain a constand speed ratio between driving and driven shafts. Pitch is the distance between centers of two adjacent teeth as measured along the pitch line.
• Curvilinear-Tooth Belts (HTD): Newer type synchronous betls incorporate curvilinear tooth forms, rather than the conventional trapezoidal tooth profile. These rounded forms offer more uniform load distribution, increased capacity, and smoother, quieter action. They also handle high torque loads.
• Poly Chain: New Poly Chain GT2 is Gates most powerful synchronous belt, ideally sutied for low-speed (below 500 rpm), high torque industrial applications. This Poly Chain performs flawlessly, even under the harshest operating conditions. The aramid fiber tensile cords constitute the belt's muscle. The nylon fabric covering the teeth is highly resistant to oil, chemicals, pollutants, corrosion and abrasion, while providing excellent tooth shear strength and durability.
• Dual-Sided Synchronous Belts: Some synchronous belts, called dual-sided, have teeth on both sides that enable one-belt reversed-motion drives and serpentine drives. Dual-sided belts have similar dimensions to conventional synchronous betls and use the same code except with the prefix 'D'.
• Synchronous Pulleys: Synchronous-belt pulleys are supplied with detachable hubs or are bored-to-size. The detachable hubs are available with a broad range of bore sizes, minimizing the need for a large pulley inventory.

One of the oldest forms of power transmission, flat belts are well suited for high-speed, samll-pulley drives. Early drives used flat belts running on flat-faced wheels. A typical industrial plant powered multiple machines with flat-belt drives running from overhead line shafts, via speed-reduction stages where required.

• Leather Belts: The earliest material used for flat belting was probably leather, a material that exhitbits excellent flexibility and good service life. It also has a high coefficient of friction and good fastener-holding ability. Several manufacturers continue to supply leather belting.
• Fabric Belts: Woven cotton belts, some with multiple plies, are generally used in the textile industry and for light conveyor applications. Woven endless belts made of cotton, nylon, or synthetic material are most often used in low-horsepower applications and at relatively high speeds. Surface grinders typically use this type of belt.
• Rubber Compostion Belting: Rubber is the material most widely used for flat belts. Such belts have a lower coefficient of friction than leather and are run at higher tension. They have less initial stretch, more lateral stiffness, and they track better.
• Synthetic Belting: Flat belts with nylon and polyester tension members offer high strength-to-weight ratios and negligible permanent stretch so that narrow, thin belts transmit high horsepower at high speed.
• Flat Belt Pulleys: Belt pulleys are made of cast iron, steel, wood, plastic, and fiber. Both solid hub and bushed type pulleys are available, the latter having bushings similar to those in V-Belt pullyes.

All information taken from the Power Transmission Handbook.

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