The right timing belt

Which timing belt: AT, HTD or GT? With customers we regularly discuss which type of toothed belt is most suited to their application, not an easy task because of the many dimensions and different tooth profiles. We can also now supply pre-machined pulleys to suit the new PL series of compact planetary gearheads. The supply of toothed belts is getting ever closer to our product range and therefore we think that it is time to put all the possibilities in one overview.

Timing belts are available in two sizes: in metric (millimetres) and imperial (inches) dimensions. The profile of the inner teeth of the belt which goes over the outer teeth of the pulley is the second most important factor. The most common forms are the trapezoidal and round tooth shape. What makes it complex are the different types of tooth shapes. Therefore, we are going to discuss the variety of different tooth types available and to help you one step further, we also provide a number of common applications in each case.

TIMING BELT: METRIC DIMENSIONS

The metric dimension belts commonly feature both trapezoidal and round tooth profiles. For metric timing belts the number in the description refers to the spacing or “pitch” of the teeth in mm. (For example, AT05 and HTD 5M are 5 mm pitches, and 8YU has 8 mm).

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V belt selection it’s a veritable cinch

The most common systems for transmitting power from a drive to a driven shaft are V belt, gear, and chain drives. But V belt drive systems, also called friction drives (because power is transmitted as a result of the V belt’s adherence to the pulley) are an economical option for industrial, automotive, commercial, agricultural, and home appliance applications.

The most common systems for transmitting power from a drive to a driven shaft are V belt, gear, and chain drives. But V belt drive systems, also called friction drives (because power is transmitted as a result of the V belt’s adherence to the pulley) are an economical option for industrial, automotive, commercial, agricultural, and home appliance applications. V belt drives are also easy to install, require no lubrication, and dampen shock load.

Pulleys with more tracks pull more load

Here’s the catch: Standard friction drives can both slip and creep, resulting in inexact velocity ratios or degraded timing precision between input and output shafts. For this reason, it is important to select a V belt appropriate for the application at hand.

V belt makeup

V belt drives are one of the earliest power transmission systems and were widely used during the Industrial Revolution. Then, flat belts conveyed power over large distances and were made from leather. Later, demands for more powerful machinery, and the growth of large markets such as the automobile industry spurred new belt designs. V belts, with a trapezoidal or V shape, made of rubber, neoprene, and urethane synthetic materials, replaced flat belts. Now, the increased overall surface material of modern V belts adheres to pulley grooves through friction force, to reduce the tension required to transmit torque. The top part of the V belt, called the tension or insulation section, contains fiber cords for increased strength as it carries the load of traction force. It helps hold tension members in place and acts as a binder for greater adhesion between cords and other sections. In this manner, heat build-up is reduced, extending V belt life. Prestretched tension-member cords (polyester, aramide, steel, fiberglass) also minimize stretch.

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Replace V Belts with Cogged or Synchronous Belt Drives

About one-third of the electric motors in the industrial and commercial sectors use belt drives. Belt drives provide flexibility in the positioning of the motor relative to the load. Pulleys (sheaves) of varying diameters allow the speed of the driven equipment to be increased or decreased. A properly designed belt transmission system provides high efficiency, low noise, does not require lubrication, and presents low maintenance requirements. However, certain types of belts are more efficient than others, offering potential energy cost savings.

The majority of belt drives use V belts. V belts use a trapezoidal cross section to create a wedging action on the pulleys to increase friction and the belt’s power transfer capability. Joined or multiple belts are specified for heavy loads. V belt drives can have a peak efficiency of 95% to 98% at the time of installation. Efficiency is also dependent on pulley size, driven torque, under or over-belting, and V belt design and construction. Efficiency deteriorates by as much as 5% (to a nominal efficiency of 93%) over time if slippage occurs because the belt is not periodically re-tensioned.

Cogged belts have slots that run perpendicular to the belt’s length. The slots reduce the belt’s bending resistance. Cogged belts can be used with the same pulleys as equivalently rated Vbelts. They run cooler, last longer, and have an efficiency that is about 2% higher than that of standard V belts.

Synchronous belts (also called timing, positive-drive, or hightorque drive belts) are toothed and require the installation of mating toothed-drive sprockets. Synchronous belts offer an efficiency of about 98% and maintain that efficiency over a wide load range. In contrast, V belts have a sharp reduction in efficiency at high torque due to increasing slippage. Synchronous belts require less maintenance and retensioning, operate in wet and oily environments, and run slip-free. But, synchronous belts are noisy, unsuitable for shock loads, and transfer vibrations.

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What is a Conveyor Belt?

One of the basic tools in material handling industry, conveyor belts are most commonly used in transportation of bulk materials (grain, salt, coal, ore, sand, etc.).

Belt conveyor systems consist of two or more pulleys (a.k.a. drums). An endless loop of carrying medium—the conveyor belt— rotates about them. To move the conveyor belt and the material it carries forward, one or both pulleys are powered. The powered pulley is called “drive pulley,” the unpowered one is known as “idler pulley.” Belt conveyors in general material handling such as those moving boxes along inside a facility form a different class of conveyor belt from those that are used to transport large volumes of resources and agricultural materials.

Based on the proposed use, conveyor belts are manufactured using either PVC or rubber.

The conveyor belt consists of one or more layers of material. Most belts in general material handling consist of two layers. Carcass is the name of the under layer that provides linear strength and shape, while cover is the name of the over layer. Polyester, nylon and cotton are used most often to create the carcass, while a variety of rubber or plastic compounds specified by use of the conveyor belt are used to create the cover.

Conveyor belts with regularly spaced partitions are known as elevator belts. They are used to transport loose materials up steep inclines. Conveyor belts are also used in self-unloading bulk freighters and in live-bottom trucks.

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Types of Drive Belt and How They Improve Efficiency

In the industrial and commercial sectors, one in three electric motors use drive belt. However, some customers fail to take advantage of the potential energy cost savings of certain industrial drive belts, which are readily available and cost -efficient. While pulleys control the speed of the equipment, industrial drive belts are designed to position the motor relative to the load. High efficiency and low maintenance are key components to top performing drive belt transmission systems.

Types of Drive Belt

V-belts

These are the most commonly used types of drive belt. Using a trapezoidal cross section V-belts create a wedge action on pulleys to increase friction and improve the drive belt’s power transfer capability.

Heavy loads often require joined or multiple belts. At the time of installation, V-belts have 95% to 98% peak efficiency. Pulley size, driven torque, under or over-belting, and V-belt design and construction impact efficiency. V-belts have a nominal efficiency of 93%, a reduction of 5%, over time if slippage occurs because the belt is not periodically re-tensioned.

Cogged belts

These types of drive belt have slots that run perpendicular to the belt’s length, helping to reduce the bending resistance of the belt. While using the same pulleys as v-belts, cogged belts manage to run cooler, last longer, and increase efficiency by 2% from standard v-belts.

Synchronous belts

This type of drive belt, often referred to as timing belts, boast a 98% efficiency, which is maintained over a wide load range. These toothed belts require the installation of mating tooth-drive sprockets. Synchronous belts require less maintenance and re-tensioning, operate in wet and oily environments and run slip-free. While synchronous belts are the most efficient, they can be noisy, transfer vibrations, and are unsuitable for shock loads. In such applications, cogged belts are the better choice.

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V Belt Pulleys Information

V belt pulleys (also called vee belt sheaves) are devices which transmit power between axles by the use of a v belt, a mechanical linkage with a trapezoidal cross-section. Together these devices offer a high-speed power transmission solution that is resistant to slipping and misalignment.

V belt pulleys are solely used for transmitting power between two parallel axels. The most notable difference between a v belt pulley and other types of pulleys (round belt, flat, etc.) would be the geometry of the groove or grooves located around the circumference of the pulley; these grooves guide and gain traction on a v belt. The accompanying video offers a comprehensive overview of some v belt basics, as well as their advantages and variations.

A v belt is a unique mechanical linkage with a cross-section that resembles an isosceles trapezoid. The v belt and its complementing pulley create the most efficient belt drive known (sometimes achieving 98% transmission efficiency). V belts were developed in the early days of automobile innovation to improve belt reliability and torque transmission from the crankshaft to rotating assemblies. V belts remain a common type of serpentine belt today.

V belt transmissions are a notable upgrade from round or flat belt transmissions; v belts provide excellent traction, speed, and load capabilities, while enjoying an extended service life with simple replacement. Heavy loads actually increase transmission efficiency since they wedge the belt further into the pulley’s groove, thereby improving friction. Typically, v belt drives operate between 1,500 to 6,000 ft/min, with 4,500 ft/min the ideal capacity for standard belts. Some narrow v belts can operate at speeds of up to 10,000 ft/min, but these pulleys must be dynamically stabilized. V belt pulleys may be placed in a side-by-side configuration or a single pulley may feature multiple grooves around the circumference in order to accommodate a multiple-belt drive. This type of drive distributes torque across several belts and provides a mechanical redundancy.

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V Belt Construction and Material

Each component has a vital role to play in how well V belts perform and how long they last. Different materials and configurations can influence belt performance characteristics in specific applications.

The tensile cord is the load-carrying component of a V belt. Most V belts are made with polyester cords, although some belts are constructed with aramid or Kevlar? cords, which offer higher tensile strength, limit stretch, and can handle heavier shock loads. In a well-engineered V belt, the tensile cords and rubber body of the belt are chemically bonded to form one unit, allowing for equal load distribution and longer belt life.

Tensile cords are supported by rubber stocks, both above (over cord) and beneath (under cord). Various synthetic rubber stocks are used by different manufacturers to provide heat resistance and reduce wear. Some high-performance synthetic rubber compounds, such as ethylene, significantly extend a belt’s operating temperature range and resist hardening, cracking, and premature failure.

A well-engineered V belt will have transverse rigidity, which means a high level of rigidity across its width so that the tensile cords will transfer the load equally. At the same time, the belt must be highly flexible along its length to reduce heat and bending stresses, which in a superior belt is accomplished by parallel alignment of fibers in the rubber compound.

Adhesion gum is the element that forms a strong chemical bond between the tensile cord and the rubber stock. It bonds the belt together so that it acts as a single unit. The gum also absorbs cord stresses and avoids cord pullout.

To protect the core of the belt from destructive environmental forces such as oil, grime and heat, as well as from general wear and tear, some V belts have a fabric cover, or band ply. In a well-engineered belt, this flexible fabric is treated to form a chemical bond with the belt core materials, allowing it to withstand the stress of constant bending over time and prolonging cover life.

As described earlier, the notches in a notched V belt are designed to increase belt flexibility and reduce bending stresses, especially on small sheaves.

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