What is Belt Drive?- Types and Material of Belt

What is belt drive?

A belt is a loop of flexible material used to link two or more rotating shafts mechanically, most often parallel. Belts may be used as a source of motion, to transmit power efficiently, or to track relative movement. Belts are looped over pulleys and may have a twist between the pulleys, and the shafts need not be parallel.

In a two-pulley system, the belt can either drive the pulleys normally in one direction (the same if on parallel shafts), or the belt may be crossed, so that the direction of the driven shaft is reversed (the opposite direction to the driver if on parallel shafts).

As a source of motion, a conveyor belt is one application where the belt is adapted to carry a load continuously between two points. The belt drive can also be used to change the speed of rotation, either up or down, by using different sized pulleys.

The amount of power transmitted depends on the following factors:

  • The velocity of the belt.
  • The tension under which the belt is applied to the pulleys.
  • Arc of contact between the belt and small pulley.
  • Conditions under which belts are used.

Types of Belt Drive

There are Seven different types of belt drive that can be found and those are:

  • Open belt drive
  • Closed or crossed belt drive
  • Fast and loose cone pulley
  • Stepped cone pulley
  • Jockey pulley drive
  • Quarter turn belt drive
  • Compound belt drive

1. Open Belt Drive

The open belt drive is used with shafts arranged parallel and rotating in the same direction. In that case, the driver pulls the belt from one side and delivers it to the other side.

Thus, the tension in the lower side belt will be higher than the upper side belt. The lower side belt is known as the tight side belt while the upper side belt is known as the slack side belt.

Open belt Drive

When the shafts are too far apart, the bottom of the belt should be the tight side and the upper side should be the slack side. This is so, when the upper side becomes the dull side, it will relax due to its own weight and thus increase the arc of contact.

2. Closed or Crossed Belt Drive

Cross or twisted belt drives are used with rotating shafts in parallel and opposite directions. In this case, the driver pulls the belt from one side and delivers it to the other side.

Thus, the tension at the Bottom Side of the belt will be higher than at the upper side of the belt. The belt is known as the tight side due to high tension, while the belt due to low tension is known as the slack side.

Cross belt Drive

This type of belt drive employs a belt when two parallel shafts have to rotate in the opposite direction. At the junction where the belt crosses, it rubs against itself and wears off. To avoid excessive wear, the shafts should be kept at maximum distance from each other and operated at very low speeds.

A little consideration will show that at a point where the belt crosses, it rubs against each other and there will be excessive wear and tear. To avoid this, the shaft must be placed at a maximum distance of 20 B, where B is the width of the belt and the belt speed must be less than 15 m/s.

3. Fast and loose cone pulley

This type of belt drives is used when the driven or machine shaft is to be started or stopped whenever desired without interfering with the driving shaft. A pulley which is keyed to the machine shaft is called a fast pulley and run at the same speed as that of the machine shaft.

A loose pulley runs freely over the machine shaft and is incapable of transmitting any power. When the driven shaft is required to be stopped, the belt is pushed on to the loose pulley by means of a sliding bar having belt forks.

4. Stepped cone pulley drive

A step or cone pulley drive is used to change the speed of the driven shaft, while the main or driving shaft moves at a constant speed. This is accomplished by shifting the belt from one part of the steps to another.

A step cone pulley is an integral casting consisting of three or different numbers of different sizes of pulleys adjacent to each other, as shown in fig. A set of driven cone pulleys is placed upside down on the drive shaft. An endless belt will be wrapped around a pair of pulleys.

By shifting the belt from one pair of pulleys to another, the speed of the driven shaft can be varied. The diameter of the pulleys driving and operated is such that the same belt will operate when transferred over pairs of different pulleys.

5. Jockey pulley drive.

In an open belt drive arrangement, if the center distance is small, or if the driven pulley is too small, the arc of the belt’s contact with the driven pulley will be very small, which reduces the tension in the belt, or if the belt requires Stress cannot be achieved by other methods, a sluggish pulley, called a jockey pulley, is placed on the slack side of the belt as shown in fig.

Jockey Pulley belt drive

This increases the arc of contact and thus stress resulting in an increase in power transmission.

6. Quarter turn belt drive

Quarter turn belt drives are also known as right-angle belt drives. It is used with shafts arranged at right angles and rotating in a certain direction. To prevent the belt from leaving the pulley, the width of the face of the pulley must be greater than or equal to 1.4 b, where b is the width of the belt. If the pulley cannot be arranged or when reversible speed is desired, a quarter-turn belt drive with a guide pulley may be used.

Quarter turn

7. Compound belt drive

A compound belt drive is used when power is passed from one shaft to another through multiple shafts.

compound belt drive

Factors to consider before using belt drive:

  • The shaft must be properly lined to ensure uniform tension in the belt section.
  • The pulley should not be too close together so that the arc of contact on the small pulley is as large as possible.
  • The pulley must not be far enough to cause heavyweight on the belt shaft, increasing the friction load on the bearings.
  • A long belt rotates from side to side, causing the belt to exit the pulley, causing crooked spots in the belt.
  • The tight side of the belt should be at the bottom so that whatever sag is present on the loose side will increase the arc of contact on the pulley.
  • To achieve good results with flat belts, the maximum distance between the shafts should not exceed 10 m and the minimum should not be less than 3.5 times the diameter of the larger pulleys.

Classification of Belt Drive

The belt drives are usually classified into the following three groups:

  1. Light drives.
  2. Medium drives.
  3. Heavy drives.

Light drives: They are used as agricultural machines and small machine tools to transmit small forces at belt speeds to about 10 m/s.

Medium drive: They are used to transmit medium forces at belt speeds of more than 10 m/s but up to 22 m/s like machine tools.

Heavy drives: They are used in compressors and generators to transmit large forces at belt speeds above 22 m/s.

Types of Belt

There are four different types of belt:

  • Round belts. Round belts are generally made of rubber.
  • V belts. V belts are arguably the most widely used belts in the industry.
  • Flat belts. Flat belts are also used to transmit power from one shaft to another.
  • Timing/toothed belts.
Types of Belt

There are three basic types of power transmission belting: flat belt, V belt, and synchronous belt. Misalignment is a common cause of premature belt failure. Power transmission belting has been used for more than 200 years. The first belts were flat and ran on flat pulleys.

1. Flat Belt

Flat belts are also used to transfer power from one shaft to another. The flat belt transmits power using the friction output between the belt and the pulley. In a flat belt, the pulleys rotate in the same direction.

They are usually classified as small woven endless belts or high strength flat belts. Woven endless belts are particularly useful, where minimal vibration is required on the driven pulley due to the semi-elastic material used in construction.

High-strength flat belts are often useful because they eliminate the need for high belt tension used to hold the pulleys, which in turn reduces the load on the shaft bearings.

The material used for high strength flat belts is a viscous resistant abrasive compound.

2. V belt

V-belts are mostly used in factories and workshops, where a large amount of power has to be transmitted, from one pulley to another, when two pulleys are very close to each other.

The V belt solved the slippage and alignment problem. It is now the original belt for power transmission. They provide the best combination of traction, movement speed, a load of bearings, and longer service life. They are usually endless, and the size of their normal cross-section is broadly trapezoidal.

3. Circular belt

The round belt is a circular cross-section belt 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 O-ring type belts are used.

V-grooves transmit torque through palpation, which increases friction. Nevertheless, round belts are only for use in relatively low torque situations and can be purchased at various lengths or cut to length and can be connected either by a staple, a metal connector, gluing, or welding. Early sewing machines used a leather belt, either attached to a metal staple or glued, to great effect.

4. Timing belt

Timing belts are a positive transfer belt and can track relative movement. These belts have teeth that fit into a matched toothed pulley. When properly stressed, they have no slippage, move at a constant speed, and are often used to transfer direct motion for the purposes of sequencing or timing.

They are often used instead of chains or gears, so noise is low and a lubrication bath is not necessary. Automobiles’ camshafts, short timing systems, and stepper motors often use these belts. Timing belts need the least tension of all belts and are among the most efficient.

Selection of a belt drive:

The following are the various important factors on which the selection of belt drive depends:

  • Speed ​​of driving and driven shafts,
  • Speed ​​reduction ratio,
  • The power to be transmitted,
  • Center distance between shafts,
  • positive drive requirements,
  • Shaft layout,
  • Location available, and 
  • Service Terms.

Applications of Belt-drive:

Belt-drives are used in various places like:

  • A belt drive is used to power transfer.
  • Drive to the rotor on the rotor spinning machine.
  • The belt drive is used in Conveyor.
  • Drive to drafting rollers and other rolling elements on a single delivery drawing machine.
  • Drives to opening rollers, friction drums, and take-off rollers on friction spinning machine.
  • Main drive on the draw-texturing machine.
  • The belt drive is used in the Mill industry.
  • Drive to creel-rollers of a high-speed drawing machine.

Advantages of a belt drive

The advantages of a belt drive include:

  • It is cost-effective and simple to use.
  • New belt-drive efficiency can be up to 95-98 percent.
  • Belt drive requires a low maintenance cost.
  • Belt drives do not require a parallel shaft.
  • They come with overload and jam protection
  • Speeds Difference can be obtained by using a step or tapered pulleys.
  • Belt drives are the most economical option when a large distance of power transmit between shaft.
  • Damp out noise and vibration, Load fluctuations are shock-absorbed, increasing the machinery life
  • Clutch action can be activated by releasing belt tension

Disadvantages of Belt drive

However, belt technology also comes with certain disadvantages of belt drive. These are:

  • Belt drive not suitable for small distances.
  • There is a loss of performance due to high levels of slip and creep.
  • Constant velocity ratio can not achieve between drive and driven pulley.
  • It produces high noice.
  • it has low mechanical efficiency.

The material used for Belts

There are five main materials that conveyor belts are made out of:

  • Leather belts
  • Cotton belts or Fabric belts
  • Rubber belts
  • Balata belts
  • Plastics belts

There are five main materials that conveyor belts are made out of: thermoplastics, metal, rubber, fabric, and leather. Plastics include polyester, polyvinyl chloride, silicone, and polyethylene.

The metals are stainless and carbon steel and the fabric materials are canvas or cotton. The most popular material is a rubber composite because it is flexible, resistant, smooth, and seamless.

1. Leather Belt

The most important material for a flat belt is leather. The best leather belts are made from strips 1.2 m to 1.5 m long, cut from either side of the backbone of the top-grade step hides.

The side of the leather hair is smooth and hard on the flesh side, but the flesh side is strong. The fibers on the hair side are perpendicular to the surface, while the flesh side parts are interconnected and parallel to the surface.

2. Cotton or Fabric Belt

Most fabric belts are made by folding three or more layers of canvas or cotton duck and stitching them together. These belts are also woven into a strip of desired width and thickness.

They are applied like linseed oil with some filler to make the belt waterproof and prevent injury to fibers. Cotton bands are inexpensive and suitable in moist climates, moist environments. Since cotton belts require little attention, these belts are mostly used in farm machinery, belt conveyors, etc.

3. Rubber belt

Rubber belts are made of layers of fabric that are fastened with a rubber structure and have a thin layer of rubber on the face. These belts are very flexible but are quickly destroyed when allowed to come in contact with heat, oil, or grease.

One principal advantage of these belts is that they can be made endlessly easily. These belts are found suitable for sawmills, paper mills where they are exposed to moisture.

4. Balata belt

These belts are similar to rubber belts except that balata glue is used in place of rubber. These belts are acid-proof and waterproof and are not affected by animal oils or alkalis.

The belt should not be at a temperature above 40 ° C because at this temperature the sanding starts to soften and become sticky. Balata belts have a strength of 25 percent higher than rubber belts.

5. Plastic belt

Plastics include polyester, polyvinyl chloride, silicon, and polyethylene.

FAQs.

What is belt drive?

In machinery, Belt drive is a pair of pulleys attached to usually parallel shafts and connected by an encircling flexible belt (band) that can serve to transmit and modify rotary motion from one shaft to the other.

What are the types of belt drives?

There are seven different kinds of belt drive can be found and those are:

  • Open belt drive
  • Closed or crossed belt drive
  • Fast and loose cone pulley
  • Stepped cone pulley
  • Jockey pulley drive
  • Quarter turn belt drive
  • Compound belt drive

What are the types of belts?

There are three types of power transmission belts: flat belt, V belt, and synchronous belt.

  • Round belts. Round belts are generally made of rubber.
  • V belts. V belts are arguably the most widely used belts in the industry.
  • Flat belts. Flat belts are also used to transmit power from one shaft to another.
  • Timing/toothed belts.

Why are belt drives used?

Belt drives are simple, inexpensive, and do not require axially aligned shafts. They help protect machinery from overload and jam, and damp and isolate noise and vibration. Load fluctuations are shock-absorbed (cushioned). They need no lubrication and minimal maintenance.

What is belt drive example?

The treadmill is another great example of a belt driven mechanism. The belt in this drive system is not to be confused with the tread on which the runner directly runs; rather the belt drive system is the toothed, synchronous belt that transfers the rotary motion from the central motor to the drive pulley.

How do belt drives work?

In belt drives, power is transmitted between at least two pulleys by a belt. One pulley drives the belt (driving pulley) and the other pulley is driven by the belt (driven pulley). In belt drives, the speed is often reduced, so that in these cases the smaller of the two pulleys is the driving pulley.

Is belt drive better than chain?

One difference is that chain drives are simply stronger: they can lift more than a belt drive. This makes them the choice for moving heavier doors, so consider them if you’re going with a steel carriage. But this won’t be a factor with lighter door models. Go with a chain drive if you have a 2-car garage door.

What machines use a belt drive?

Belt systems are used in grain belt conveyors, sawmills, printing presses, punch presses, and more. They’re even used in exhaust fan systems and laundry machinery. They’re most commonly used when the two shafts (driving and driven) are very far apart, as in a grain belt conveyor.

What is a belt and pulley?

In a belt and pulley system, a cable or a belt runs along this groove and connects one pulley to the next. Use a pulley and belt system to transmit rotational motion, or, if the pulleys are of a different diameter, to increase or decrease the moment along a rotational motion axis.

What are the 2 types of drive belts?

There are three types of drive belts:

  • Serpentine Belt. A serpentine belt is located under the hood of a car, and it “snakes” its way between various pulleys and accessories.
  • V-Belt. A V-belt runs off a crank and pulley and typically travels between one or two engine accessories.
  • Timing Belt.

Can you drive a car with no belt?

Without the serpentine belt, you’ll lose power steering, the engine might overheat and the battery will eventually die as the alternator stops charging it. While you can drive without some of these things for a bit, you can cause extra damage – and make the repair so much more expensive.

What is slip in belt drive?

Slip: When the frictional grip becomes insufficient. This may cause some forward motion of the driver without carrying the belt with it. This may also cause some forward motion of the belt without carrying the driven pulley with it. This is called slip of the belt and is generally expressed as a percentage.

Are belt drive bikes worth it?

Belt drives are superior to chain drives in many aspects. They are easier to clean and maintain, last longer, and are quieter and smoother as well. However, they are also more expensive, which raises the overall price of the bikes who have them integrated.

Are belt drive bikes slower?

Belts are less efficient at low power inputs- If you’re just cycling casually, you’ll burn more energy while riding a belt drive bike vs a chain drive. Belt drives may cause the bottom bracket and rear hub to wear out faster- This happens because belts run at a much higher tension than chains.

Why do Harleys use belt drives?

There are good reasons to adopt belt drive: It requires no lubrication, lacks the sound of a roller chain, and cannot stretch because it doesn’t have a chain’s 100 or more joints to wear.

What are belts used for?

A belt is a fashion accessory that is traditionally used to secure the waist of a pair of pants or bottoms. They can be used to keep pants up that may be tight, or to tighten the waist of pants that are slightly loose.

How many belts does a car have?

There are two belts you need to be familiar with when talking about car maintenance — the serpentine belt and the timing belt. The serpentine belt winds through your engine and carries power to several key components, including the alternator, air conditioning, and power steering pump.

What is the difference between a belt and B belt?

V-belt cross sections can be identified by their top width and depth dimensions. For example, a v-belt with a top width of 21/32” and a depth of 7/16” is a “B” belt. You can also use our Browning Belt Rule that includes a gauge to help easily identify belt type. If the belt you have is “notched” add an “X” to the type.

What is a drive pulley?

In short, a drive pulley is one which is attached to a power source. When in use, a force is placed upon the belt around the pulley, which is also connected to an object being driven. In most cases, the applied force causes the object to spin.

How much does it cost to replace a drive belt?

Of course, it depends on your make and model as well as labor costs, but in general a replacement serpentine belt costs around $70-$200 (plus taxes and fees), including around $50 for the belt and around $150 for the labor.

What happens to your car if the belt breaks?

If a serpentine belt breaks, a car won’t be drivable and will have to be towed. If the engine runs without a serpentine belt, it might overheat as the water pump will no longer work. A broken belt can also damage other parts.

How do I know if my car needs a new belt?

Common Signs of Drive Belt Replacement

  • Strange Noises. One of the biggest signs that you probably need to take your vehicle to the dealership for a check is when you start hearing strange noises coming from your engine.
  • Visual Signs of Wear
  • Mileage Indicators.
  • Breakage is Bad.

What is the difference between rope and belt drive?

A rope drive is a form of belt drive, used for mechanical power transmission. Rope drives use a number of circular section ropes, rather than a single flat or vee belt.

What is difference between belt slip and creep?

Slip is the difference between the linear velocities of pulley (driver/driven) and belt. Creep: Uneven extensions and contractions of the belt when it passes from tight side to slack side. There is relative motion between belt and pulley surface, this phenomenon is called creep of belt.

Which belt drive transmit more power?

Power transmission capacity of flat belt is comparatively lower due to higher chance of slip. V-belt can transmit more power without slip due to increased friction. It is recommended for long distance power and motion transmission. It is preferred for short to medium distance power and motion transmission.

Can you put a belt drive on any bike?

Belt drives are compatible with the majority of bikes subject to frame modification. Chains make more sense for those on long treks with a conventional chain much simpler to replace while somewhere remote.

Are belts stronger than chains?

Tensioning a chain is harder than a belt. A typical belt is tensioned with a spring – being light this is easy enough.

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