What belt should I choose for my application

This is a very common question among designers when choosing a belt and I also a question that users ask when having continuous problems with the equipment even since new. There is no question about the advantages of the belt over other types of power transmission mechanisms like gears:

  • belt drives are simple and very jam
  • Damps and isolates noise and vibration
  • Load fluctuations are shock absorbed
  • They don’t need lubrication and the maintenance they need is minimum
  • They have an efficiency of 90-98%
  • They have a low cost if the shaft are apart
  • Clutch action can be achieved by reducing belt tension

Here are the specifics of some of the different types of belts on the market and the advantages and applications of each one of them:

Flat belts:

They can deliver high power at high speeds (500 hp at 10,000 ft/min or 373 kW at 51 m/s), where wide belts and large pulleys are required. But consume too much space and require high tension leading to high loads, and are not suited to close-centers applications, V-belts have replaced flat-belts for short-distance power transmission; and longer-distance power transmission is typically no longer done with belts at all.

 

Round belts

round-belt

 

Are a circular cross section belts designed to run in a pulley with a 60 degree V-groove. Round grooves are only suitable for idler pulleys that guide the belt, or when (soft) O-ring type belts are used. The V-groove transmits torque through a wedging action, thus increasing friction. Nevertheless, round belts are for use in relatively low torque situations only and may be purchased in various lengths or cut to length and joined, either by a staple, a metallic connector (in the case of hollow plastic), gluing or welding (in the case of polyurethane

V belts

v-beltsV belts prevent  the slippage and minimize alignment problems which makes them  the basic belt for power transmission. They provide the best combination of traction, speed of movement, load of the bearings, and long service life.

The “V” shape of the belt tracks in a mating groove in the pulley or sheave The belt also tends to wedge into the groove as the load increases—the greater the load, the greater the wedging action—improving torque transmission and making the V-belt an effective solution, needing less width and tension than flat belts. V-belts trump flat belts with their small center distances and high reduction ratios. The preferred center distance is larger than the largest pulley diameter, but less than three times the sum of both pulleys. Optimal speed range is 1,000–7,000 ft/min (300–2,130 m/min). V-belts need larger pulleys for their thicker cross-section than flat belts.v-belt-pulley

For high-power applications, two or more V-belts can be used side-by-side (multi-V), running on matching multi-groove sheaves. This is known as a multiple-V-belt drive (or sometimes a “classical V-belt drive”).

 

Multi-groove belts

A multi-groove or polygroove belt  is made up of usually 5 or 6 “V” shapes alongside each other making it thinner and more flexible. More flexibility means improved efficiency, as less energy is wasted in the internal friction of continually bending the belt. In practice this gain of efficiency causes a reduced heating effect on the belt and a cooler-running belt lasts longer in service.multi-groove-belt

A further advantage of the polygroove belt that makes them popular is that they can run over pulleys on the ungrooved back of the belt. Though this is sometimes done with Vee belts with a single idler pulley for tensioning, a polygroove belt may be wrapped around a pulley on its back tightly enough to change its direction, or even to provide a light driving force.

Ribbed belt

banded-belt

 

 

Is a power transmission belt featuring lengthwise grooves. It operates from contact between the ribs of the belt and the grooves in the pulley. Its single-piece structure is reported to offer an even distribution of tension across the width of the pulley where the belt is in contact, a power range up to 600 kW, a high speed ratio, serpentine drives (possibility to drive off the back of the belt), long life, stability and homogeneity of the drive tension, and reduced vibration. The ribbed belt may be fitted on various applications : compressors, fitness bikes, agricultural machinery, food mixers, washing machines, lawn mowers, etc.

 

Film belts

Though often grouped with flat belts, they are actually a different kind. They consist of a very thin belt (0.5-15 millimeters or 100-4000 micrometres) strip of film-beltsplastic and occasionally rubber. They are generally intended for l ow-power (less than 10 Watts), high-speed uses, allowing high efficiency (up to 98%) and long life. These are seen in business machines, printers, tape recorders, and other light-duty operations.

 

Timing belts

These belts have teeth that fit into a matching toothed pulley. When correctly tensioned, they have no slippage, run at constant speed, and are often used to transfer direct motion for indexing or timing-beltstiming purposes (hence their name). They are often used in lieu of chains or gears, so there is less noise and a lubrication bath is not necessary. Camshafts of automobiles, miniature timing systems, and stepper motors often utilize these belts. Timing belts need the least tension of all belts, and are among the most efficient. They can bear up to 200 hp (150 kW) at speeds of 16,000 ft/min (4,900 m/min).

Disadvantages include a relatively high purchase cost, the need for specially fabricated toothed pulleys, less protection from overloading, jamming, and vibration due to their continuous tension cords, the lack of clutch action (only possible with friction-drive belts), and the fixed lengths which do not allow length adjustment (unlike link V-belts or chains).