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Belt (mechanical)

technology Maturity 7-9 Next article →

A mechanical belt is a loop of flexible material used to connect two or more rotating shafts.

Flachriemen
Flachriemen

Most often, these shafts are parallel to one another. Belts serve several vital roles in machinery. They can act as a source of motion, transmit power efficiently, or track relative movement between parts. One common application is the conveyor belt, which is specifically adapted to carry a load continuously between two points.

HagleyBeltDrive01
HagleyBeltDrive01

By linking rotating parts, belts allow complex machines to function as a single, coordinated system.

The mechanism of a belt drive relies on the interaction between the belt and pulleys. Pulleys are wheels that the belt loops over to transfer motion. In a standard two-pulley system, the belt drives the pulleys in the same direction. However, if the belt is crossed between the pulleys, the direction of the driven shaft is reversed.

Transmissionsriemen
Transmissionsriemen

This setup allows engineers to control the direction of rotation. You can also change the speed of rotation by using different sized pulleys. Using a large pulley to drive a small one increases speed, while the opposite decreases it. The power transmitted depends on the tension on the tight side versus the slack side of the belt.

There are several distinct types of belts designed for different mechanical needs. Flat belts are simple loops that were widely used in 19th-century factories. Because they tend to climb toward the higher side of a pulley, many pulleys feature a convex or "crowned" surface to help the belt self-center.

Wide flat belt
Wide flat belt

V-belts, or vee belts, have a trapezoidal cross-section that solves many slippage and alignment issues. The V-shape allows the belt to wedge into the pulley groove, which improves torque transmission.

V-belt angle
V-belt angle

Other specialized types include round belts for low torque, spring belts made of steel coils for toy engines, and toothed belts that prevent stretching.

Rew3k04-002 spring belt transmission
Rew3k04-002 spring belt transmission

History shows how deeply belts have influenced human industry. The mechanical belt drive was first mentioned in 15 BC by the Han Dynasty philosopher Yang Xiong. He described a quilling machine used to wind silk fibers onto bobbins for weavers.

Riemverbinders (02)
Riemverbinders (02)

The belt drive also became an essential component in the invention of the spinning wheel. By the 1st century AD, belts were being applied to hydraulic-powered bellows. During the 19th and 20th centuries, flat belts were the standard for line shafting in factories, powering everything from sawmills to electrical generators.

The materials used for belts have changed significantly over time. Traditionally, flat belts were made of fabric or leather. This led to surprising historical moments. After World War I, a shortage of shoe leather in Ukraine was so severe that people cut up belt drives to make shoes. This caused flour milling to stop and contributed to famine conditions.

During the Rhodesian Bush War, leather belts were used in a different way, placed on vehicle floors to protect riders from land mines. Today, most modern belts are manufactured from rubber or synthetic polymers.

Engineers choose specific belts based on efficiency and power requirements. Belt drives are highly efficient, usually operating at 90% to 98% efficiency. They are also excellent at absorbing shocks, which protects motors and bearings when power loads change suddenly.

Multiple-V-belt drive 001
Multiple-V-belt drive 001

While they transmit less power than gears or chain drives, they are much cheaper and require no lubrication. For high-power needs, a multiple-V-belt drive can be used. This involves joining two or more V-belts side-by-side to run on matching multi-groove sheaves, allowing for much greater strength.

Belts connect to broader mechanical systems by solving problems of distance and alignment. While flat belts can deliver high power at speeds up to 51 m/s, they are bulky and require high tension. V-belts have largely replaced them for short-distance transmission because they handle smaller distances more effectively. In many modern factories, the use of long belt systems has decreased because individual machines now use their own electric motors. Despite these changes, the fundamental concept of the belt remains a cornerstone of mechanical power transmission.

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🖼️ Images & Media (13)
File:Flachriemen.png
Flachriemen.png
File:HagleyBeltDrive01.jpg
HagleyBeltDrive01.jpg
File:Transmissionsriemen.jpg
Transmissionsriemen.jpg
File:Wide flat belt.JPG
Wide flat belt.JPG
File:Riemverbinders (02).jpg
Riemverbinders (02).jpg
File:Bankschroef-apparaat voor riemverbinders (01).jpg
Bankschroef-apparaat voor riemverbinders (01).jpg
File:Rew3k04-002 spring belt transmission.jpg
Rew3k04-002 spring belt transmission.jpg
File:Yanmar 2GM20.JPG
Yanmar 2GM20.JPG
File:Multiple-V-belt drive 001.jpg
Multiple-V-belt drive 001.jpg
File:Timing belt.jpg
Timing belt.jpg
File:F8hub.jpg
F8hub.jpg
File:BeltProfiles.jpg
BeltProfiles.jpg

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