The V-belt Solution

V-belts came into common use in the automobile industry in 1917. The endless V-belt was invented by John Gates of the Gates Rubber Company. However, the multiple V-belt drive was developed a few years later by Walter Geist of the Allis-Chalmers corporation who patented it in 1928.

The purpose of belts is to transmit and distribute the rotation from a drive shaft to other shafts attached to moving parts of a machine or engine. The belts are often more practical than gears or other modes of connection when the shafts are far apart or are oriented in different directions. Drive belts can be twisted and even turned to reverse the rotation of the motion. Often large engines are engineered around diverse groupings of belts that govern complex actions. Belts are the most economical utility for power transmission between shafts that may or may not be aligned.

The torque that belts can exert on shafts depends the tightness of the belts and an important element of friction grip with which the belt makes contact with the connected pulley or shaft. The power transmitted by the belt is a function of the difference between tensions on the connected pulleys and the velocity of the powered pulley.

Flat Belts

The first drive belts were flat strips, usually of leather, that began appearing in factories, mines, forestry operations and farms during the 19th century, connecting steam-driven engines or water power to utility equipment. The flat belt was well suited for its day. It could deliver high-speed power transmission. The pulleys could be comparatively far apart and needn't be aligned well. The belts themselves needed no lubrication. The belts isolated noise and vibration because they were usually not held absolutely taught. Clutch action was achieved by simply lifting the belt off the pulley and speeds could be governed by switching pulley diameters (large drive pulley to small action pulley turned the action pulley faster).

The problem was that stretch and slippage of the flat belts over the pulleys caused speed fluctuations and loss of torque when loads were high. The distances between drive and load pulleys had to be regularly adjusted to compensate for stretch in the belts.

In order to deliver sufficient torque flat belts had to be very wide, increasing adhesive friction along a wide surface. That means that the pulley drives had to be very large and cumbersome. They also require very high tensions and high power output to make up for energy loss from friction. These systems are not suited to close-centers applications, like care engines or washing machines. Flat belts have been all but phased out of regular use. Factory machines are usually not belt driven, each machine generally has its own electric motor.

V-belts

V-belts (also called "vee belts," or "wedge rope") have mainly replaced flat belts for short-distance power transmission. The "V" shape tracks in a mated grove built into the pulley. This provides stability and maximizes the surface area between the pulley (or sheave) and the belt, increasing adhesive friction, reducing slippage and heat-producing friction. The V-belt is engineered with a trapezoidal cross-section. The belt cannot slip off the pulley. The greater the load, the more the belt wedges into the grove further increasing the drive power.

For high-power requirements, two or more v-belts can be joined side-by-side in a multi-v arrangement. These belts run along matching multi-grooves in the sheave. Typical multi-groove or polygroove belts are made of 5 or 6 V-belts side-by-side.

Composition of Modern V-Belts

V-belts may be homogeneous, made of rubber or polymer throughout. Many V-belts are made with embedded in the rubber or polymer for added strength and reinforcement. The reinforcing fibers can be made of nylon or polyester. The strongest belts are steel reinforced or employ tough fibers such as Kevlar.

The Big Bearing Store offers a full range of V-belts and multi-V belts. Please contact us and take a look at our catalog.