Mechanical Engineering

Belt drive

What is a belt drive and how does a belt drive work? Learn more in this post. Various types of belt drives, what is a crowning, slip and creep in the belt, as well as the benefits and drawbacks of belt drives?

Belt drives have been utilized in power transmission for almost 200 years. The original belts had flat pulleys and ran on flat belts. To lessen belt stress, cotton or hemp rope was later utilized with V-groove pulleys. In 1917, the vulcanized rubber V-belt was invented as a result of this. The development of synchronous or toothed belts around 1950, as well as the later development of fabric-reinforced elastomer materials, was motivated by the need to eliminate speed variations.

Power transmission systems are still done with flat, V, and synchronous belting methods nowadays. Belts offer a strong mix of flexibility, low cost, easy installation and maintenance, and minimal area requirements when compared to other modes of power transmission.

Components for belt-driven machinery are easily accessible. Local distributors can readily provide replacement components. Downtime and inventory are reduced as a result of its availability. Sheaves ” or “ pulley wheels are generally less costly than chain drive sprockets, and they wear out less over time.

Belt drives

The efficient and cheapest technique of transmitting mechanical power with minimal losses is rotating motion. Transmission systems or drives are systems that allow rotational motion to be transferred from one mechanical unit to another.

These systems are powered by a prime mover or transfer rotational motion to the different components of a machine within the machine. Shafts are commonly used to transfer rotational motion. Before we are ready to learn belt drives we need to understand some concepts to go further. They are:

The one that drives is referred to as the driving system, while the one that is driven is referred to as the driving system.

What Is Belt Drive?

A belt is a flexible material loop that is used to mechanically connect two or more rotating shafts, usually in parallel. Belts can be employed as a source of motion, a means of effectively transmitting power, or a means of tracking relative movement. Belts are wrapped around pulleys with a twist between them, and the shafts do not have to be parallel.

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

A conveyor belt is one use where the belt is fitted to transfer a load constantly between two places as a source of motion. Using different sized pulleys, the belt drive may also be utilized to adjust the rotational speed up or down.

The quantity of energy transferred is determined by the following variables:

• The belt’s velocities.
  
• The amount of tension given to the pulleys by the belt.
  
• The belt and the small pulley form an arc of contact.
  
• The circumstances under which belts are worn.
  

Law of Belting

The law of belting states that when the belt approaches the pulley, its centerline must be in the pulley’s midplane, which should be perpendicular to the pulley’s axis. Otherwise, the belt will slip off the pulley and fall off.

Crowning of pulleys

To prevent the belt from slipping off the pulley owing to centrifugal force, pulleys have a little conical (or) convex form in their rim’s surface. This is referred to as pulley crowning.

The crowning height is usually 1/96 of the pulley face width.

When choosing a belt-drive, there are a few things to think about.

a) The amount of power to be transmitted

b) Peripheral and angular speeds

c) Speed ratio

d) Efficiency

e) The distance between shafts

f) The amount of space available

g) The working environment

Types Of Belt Drive

The following are the seven various types of belt drives that may be found:

• 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

With shafts oriented parallel and rotating in the same direction, the open belt drive is employed. The driver in this scenario pulls the belt from one side and distributes it to the other.

As a result, the lower side belt will have a higher tension than the upper side belt. The upper side belt is referred to as the loose side belt, while the lower side belt is referred to as the tight side belt.

When the shafts are apart from each other, the tight side of the belt should be on the bottom and the loose side on the top. As a result, when the upper side becomes dull, it will relax as a result of its own weight, increasing the arc of contact.

2. Closed Or Crossed Belt Drive

With rotating shafts in parallel and opposing directions, cross or twisted belt drives are employed. The driver in this scenario takes the belt from one side and distributes it to the other.

As a result, the tension on the bottom side of the belt will be higher than on the top side. The high tension in the tight side of the belt is known as the tight side, while the loose side is known as the slack side.

When two parallel shafts must rotate in the opposite direction, this sort of belt drive is used. The belt scrapes against itself at the point where it crosses and wears down. The shafts should be kept at a maximum distance from each other and operated at extremely low speeds to minimize excessive wear.

A little thought will reveal that the belts grind against each other at the area where they cross, causing considerable wear and tear. To avoid this, the shaft should be set at a maximum distance of 20 B, where B is the belt width, and the belt speed should not exceed 15 m/s.

3. Fast And Loose Cone Pulley

When the driven or machine shaft must be started or stopped at any time without interfering with the driving shaft, this form of belt drive is utilized. A fast pulley is a pulley that is keyed to the machine shaft and runs at the same speed as the machine shaft.

A loose pulley is incapable of delivering any power since it travels freely over the machine shaft. The belt is forced onto the loose pulley by a sliding bar with belt forks when the driven shaft has to be halted.

4. Stepped Cone Pulley Drive

The driven shaft’s speed is changed using a step or cone pulley drive, while the main or driving shaft remains constant. This is performed by moving the belt from one step to the next.

As seen in fig., a step cone pulley is an integrated casting that consists of three or more distinct sizes of pulleys adjacent to one another. The driving shaft is upside down with a series of driven cone pulleys. A pair of pulleys will be encircled by an infinite belt.

The speed of the driven shaft may be changed by transferring the belt from one set of pulleys to another. When the same belt is moved through pairs of different pulleys, the diameter of the pulleys driving and operated is such that the same belt will work.

5. Jockey Pulley Drive.

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 is very small, which reduces the tension in the belt, or if the belt requires Stress that 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.

This increases the contact arc and, as a result, the stress, resulting in increased power transfer.

6. Quarter Turn Belt Drive

Right-angle belt drives are sometimes known as quarter-turn belt drives. It is utilized with shafts that are at right angles to one other and rotate in a certain direction. The width of the pulley’s face must be more than or equal to 1.4 b, where b is the belt’s width, to prevent the belt from leaving the pulley. A quarter-turn belt drive with a guide pulley can be used if the pulley cannot be set or when reversible speed is necessary.

7. Compound Belt Drive

When power is transferred from one shaft to another through multiple shafts, a compound belt drive is employed.

Factors to Consider Before Using Belt Drive:

• To achieve uniform tension in the belt section, the shaft must be accurately lined.
  
• The pulleys should not be too close together in order to maximize the arc of contact on the little pulley.
  
• The pulley must not be set too far back on the belt shaft, since this will increase the friction strain on the bearings.
  
• A lengthy belt moves from side to side, generating crooked patches in the belt as it exits the pulley.
  
• The tight side of the belt should be near the bottom so that any sag on the loose side will increase the pulley’s arc of contact.
  
• The greatest distance between the shafts should not exceed 10 m, and the minimum should not be less than 3.5 times the diameter of the bigger pulleys to produce satisfactory results with flat belts.
  

Classification Of Belt Drive

The three types of belt drives are often categorized as follows:

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

Light Drives: Light drives are used to transfer tiny forces at belt speeds of up to 10 m/s in agricultural equipment and small machine tools.

Medium drive: They’re utilized in machine tools to transfer medium forces at belt speeds of more than 10 m/s but up to 22 m/s.

Heavy Drives: Compressors and generators employ heavy drives to convey enormous forces at belt speeds over 22 m/s.

Types Of Belts

There are four different types of belts:

• Round belts. Rubber is commonly used for round belts. The grooved pulleys are used with this sort of belt, which has a circular cross-section.
  
• V belts. V belts are, without a doubt, the most popular belts in the industry. V-belts, which have a trapezoidal cross-section, are also utilized with grooved pulleys. These belts can convey more power and have a greater speed ratio. It is possible to have many drives.
  
• Flat belts. Power is also transferred from one shaft to another using flat belts. The cross-section of this belt is rectangular. Power may be transmitted across extended distances between pulley centers using these belts. This drive has a 98 percent efficiency and produces very little noise.
  
• Timing/toothed belts.
  

Flat belts, V belts, and synchronous belts are the three fundamental forms of power transmission belts. Premature belt failure is frequently caused by misalignment. Belting has been utilized in power transmission for almost 200 years. The original belts had flat pulleys and ran on flat belts.

1. Flat Belt

Power is also transferred from one shaft to another using flat belts. The friction output between the belt and the pulley is used to convey power via the flat belt. The pulleys on a flat belt all rotate in the same direction.

Small woven unending belts or high-strength flat belts are the most common classifications. Because of the semi-elastic material used in production, woven endless belts are particularly suitable where little vibration on the driven pulley is required.

Flat belts with high strength are frequently employed because they avoid the requirement for high belt tension to retain the pulleys, reducing the stress on the shaft bearings.

A viscous resistant abrasive compound is utilized for high-strength flat belts.

2. V Belt

V-belts are commonly used in factories and workshops to carry a considerable amount of power from one pulley to another when two pulleys are close together.

The V belt solves the problem of slippage and misalignment. It is currently the standard power transmission belt. They offer the optimum balance of traction, movement speed, bearing load, and extended service life. They are normally infinite, and their standard cross-section is broadly trapezoidal.

3. Circular Belt

The round belt is a circular cross-section belt with a 60-degree V-groove designed to run in a pulley. Round grooves are only appropriate for idler pulleys that guide the belt or for belts with O-rings.

V-grooves use palpation to transmit torque, which increases friction. Round belts, on the other hand, are only suitable for low-torque applications and can be purchased in various lengths or cut to length, with connections made with a staple, a metal connector, gluing, or welding. To great effect, early sewing machines employed a leather belt, either linked to a metal staple or bonded.

4. Timing Belt

Timing belts may measure relative movement and are a positive transfer belt. These belts have teeth that fit into a toothed pulley with the same number of teeth. They have no slippage, travel at a steady pace, and are frequently used to transfer direct motion for the purposes of sequencing or timing when suitably strained.

They are frequently used instead of chains or gears since they are quiet and do not require lubrication. These belts are frequently used in automobiles as camshafts, short timing systems, and stepper motors. Timing belts require the least amount of strain and are one of the most efficient.

Selection Of A Belt Drive:

The following are some of the key considerations when choosing a belt drive:

• The power to be conveyed,
  
• the speed of the driving and driven shafts, and
  
• the speed reduction ratio
  
• Positive driving needs,
  
• shaft arrangement,
  
• suitable locations, and
  
• service terms are all factors to consider.
  

Failures in Belt drive

Alignment

One of the most prevalent reasons for early belt failure is misalignment. By increasing wear and fatigue, the condition eventually diminishes belt performance. Misalignment may damage a belt in a matter of hours, depending on its severity. On V-belt drives, sheave misalignment should not exceed 1/2 degree or 1/10 inch of center distance. It should not exceed 1/4 deg. or 1/16-in. of center distance for synchronous belts.

Individual V-belts suffer from rapid belt/sheave-groove wear and consequent stability issues due to angular misalignment. Uneven belt and cord loading, a similar issue, causes unequal load sharing with many belt drives, resulting in premature failure.

Synchronous belt drives are severely harmed by angular misalignment. Excessive belt tracking forces, uneven tooth/land wear, edge wear, high noise levels, and probable failure owing to unequal cable loading are all symptoms that might occur. Angular misalignment is more sensitive in wide belts than in narrow belts.

In addition to faster belt/sheave wear, parallel misalignment might cause individual belt stability issues. Angular misalignment is more important than an uneven belt and cord loads.

V-belts are more prone to parallel misalignment. They run in set grooves and can only float to a limited extent between flanges, unlike synchronous belts. As long as the belt is not jammed or squeezed between opposite sprocket flanges and tracks entirely on both sprockets, parallel misalignment is usually not a major issue with synchronous belts.

Belt Tension and Slack

When the driving pulley pulls the belt, it is subjected to tension. In addition to the static belt tension, this belt tension is responsible for mechanical force transmission. Because there is minimal to no relative motion between the belt and the pulleys, high belt tension reduces heat buildup, slippage, and alignment issues.

The driving pulley, on the other hand, pulls the belt away from the driven pulley. The belt begins to sag as a result of this. As a result, a belt drive creates varying loads in the belt. Premature belt failure can occur if these loads are not taken into account during the design phase. More belt failures are caused by fatigue than by any other factor.

It’s simple to tell which side is loose and which is under stress. The tension is applied to the side of the belt that reaches the drive pulley. The slack side is the opposite.

Applications Of Belt-Drive:

Belt drives are used in a variety of applications, including:

• A belt drive is used to convey power.
  
• On a rotor spinning machine, drive to the rotor.
  
• The conveyor uses a belt driving system.
  
• On a single delivery drawing machine, drive to the drafting rollers and other rolling parts.
  
• On friction spinning machine, drives open rollers, friction drums, and take-off rollers.
  
• The draw-texturing machine’s main drive.
  
• In the milling sector, a belt drive is employed.
  
• A high-speed drawing machine’s drive to creel-rollers.
  

Advantages Of A Belt Drive

• The benefits of a belt drive are cost-effectiveness and ease of usage.
  
• The efficiency of a new belt-drive system can reach 95-98 percent.
  
• Low-cost maintenance is required for belt drives.
  
• A parallel shaft is not required for belt drives.
  
• Overload and jam protection are included.
  
• A step or tapered pulleys can be used to create different speeds.
  
• When there is a wide distance of power transmission between shafts, belt drives are the most cost-effective alternative.
  
• Noise and vibration are reduced, and load variations are absorbed, extending the life of the machinery.
  
• When the belt tension is released, the clutch action is triggered.
  

Disadvantages Of Belt Drive

Belt technology, on the other hand, has several drawbacks. These are the following:

• The belt drive is ineffective over short distances.
  
• Because of the high levels of slip and creep, there is a loss of performance.
  
• Between the drive and driven pulleys, a constant velocity ratio cannot be achieved.
  
• It makes a lot of noise.
  
• Mechanically, it is inefficient.
  

The Material Used For Belts

Conveyor belts are constructed of five different types of materials:

• Belts made of leather
  
• Cotton belts or Belts made of fabric
  
• Belts made of rubber
  
• Belts made of balata
  
• Belts made of plastic
  

• Conveyor belts are constructed of five different materials: thermoplastics, metal, rubber, fabric, and leather. Polyester, polyvinyl chloride, silicone, and polyethylene are examples of plastics.
  
• Stainless steel and carbon steel are used for the metals, while canvas or cotton is used for the cloth. Rubber composites are the most preferred material since they are flexible, resistant, smooth, and seamless.
  

1. Leather Belt

Leather is the most significant material for a flat belt. Strips 1.2 m to 1.5 m long, cut from each side of the backbone of top-grade step hides, are used to make the greatest leather belts. The leather might be oak-tanned or mineral salt-tanned, such as Chrome. Two or more strips are bonded together when the desired belt thickness is more than. Leather belts must be cleaned regularly.

The leather hair is smooth and firm on the flesh side, yet the flesh side is powerful. The fibers on the hair side are perpendicular to the surface, but the portions on the flesh side are interwoven and parallel.

2. Cotton Or Fabric Belt

The majority of fabric belts are constructed by sewing three or more layers of canvas or cotton duck together. These belts are also woven into a strip with the width and thickness that you choose.

To make the belt waterproof and avoid fiber harm, they are coated like linseed oil with some filler. Cotton bands are low-cost and ideal for humid climates and settings. Cotton belts are commonly used in farm machinery, belt conveyors, and other similar applications since they require little maintenance.

3. Rubber Belt

Rubber belts contain a thin coating of rubber on the face and are composed of layers of cloth that are attached to a rubber framework. These belts are extremely flexible, but they quickly degrade when exposed to heat, oil, or grease.

One of the most appealing features of these belts is that they may be produced indefinitely. These belts are useful for sawmills and paper mills when moisture is present.

4. Balata Belt

These belts are similar to rubber belts, however, instead of rubber, balata adhesive is employed. Acid-proof and waterproof, these belts are unaffected by animal oils or alkalis.

The belt should not be heated over 40 degrees Celsius since the sanding begins to soften and get sticky at this temperature. Balata belts have a 25% better strength than rubber belts.

5. Plastic Belt

Polyester, polyvinyl chloride, silicon, and polyethylene are examples of plastics.

FAQs.

What Is a Belt Drive System?

Belt drive refers to a pair of pulleys connected by an encircling flexible belt (band) that can be used to transfer and alter rotational motion from one shaft to the other in equipment.

What Are The Different Types Of Belt Drives?

There are seven main types of belt drives that may be found:

• 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 Different Belt Types?

Flat belts, V belts, and synchronous belts are the three types of power transmission belts.

• Round belts. Rubber is commonly used for round belts.
  
• V belts. V belts are, without a doubt, the most popular belts in the industry.
  
• Flat belts. Power is also transferred from one shaft to another using flat belts.
  
• Timing/toothed belts.
  

What Are the Benefits of Using Belt Drives?

Belt drives are simple, low-cost, and do not require shafts to be axially aligned. They dampen and isolate noise and vibration while also protecting machinery from overload and jamming. Variations in load are absorbed (cushioned). They don’t require any lubrication and just require minor maintenance.

What Is An Example Of A Belt Drive?

Another fantastic example of a belt-driven system is the treadmill. The belt in this drive system is not the tread on which the runner runs directly; rather, the belt drive system is the toothed, synchronous belt that conveys rotational motion from the central motor to the driving pulley.

What Is the Process of Using Belt Drives?

A belt transmits power between at least two pulleys in a belt drive. One pulley (driving pulley) drives the belt, while the other pulley is driven by the belt (driven pulley). Because the speed of belt drives is typically lowered, the smaller of the two pulleys is used as the driving pulley.

Is it true that belt drive is superior to chain drive?

One distinction is that chain drives are simply stronger than belt drives, allowing them to move the greater weight. If you’re opting for a steel carriage, this makes them the best option for moving heavy doors. With lighter door versions, however, this won’t be an issue. If you have a two-car garage door, go for a chain drive.

What are some examples of machines that use a belt drive?

Grain belt conveyors, sawmills, printing presses, punch presses, and other machines employ belt systems. They’re even found in exhaust fans and washing equipment. When the two shafts (driving and driven) are quite far apart, such as in a grain belt conveyor, they’re most usually utilized.

What is the difference between a belt and a pulley?

A cable or a belt passes down this groove in a belt and pulley system, connecting one pulley to the next. Use a pulley and belt system to convey rotational motion or to enhance or reduce the moment along a rotational motion axis if the pulleys are of various diameters.

Can You Drive A Car With No Belt?

You’ll lose power steering without the serpentine belt, the engine may overheat, and the battery may finally die as the alternator quits charging it. While you can drive without some of these items for a short time, you risk causing more damage and increasing the cost of repair.

What Is Belt Drive Slip?

Slip: When the frictional grip is no longer enough. This may cause some forward motion of the driver without carrying the belt with it. This may cause the belt to go ahead without carrying the driven pulley with it. This is known as belt slip and is usually represented as a percentage.

Belt-Drive Bikes: Are They Worth It?

In many ways, belt drives outperform chain drives. They are less difficult to clean and maintain, last longer and are also quieter and smoother. They are, however, more costly, which enhances the entire price of the bikes that have them.

Is it true that belt-driven bikes are slower?

Belts are less efficient at low power inputs- If you’re just pedaling for fun, a belt-drive bike will burn more energy than a chain drive bike. Because belts operate at a considerably higher tension than chains, they may cause the bottom bracket and rear hub to wear out faster.

Why do Harley-Davidson motorcycles have belt drives?

There are several compelling reasons to use belt drive: It doesn’t need to be lubricated, doesn’t make the same noise as a roller chain, and can’t stretch because it doesn’t have the 100 or more joints that a chain has.

What Is the Average Number of Belts in a Car?

When it comes to car maintenance, there are two belts to be aware of: the serpentine belt and the timing belt. The serpentine belt runs the length of your engine, supplying power to key components such as the alternator, air conditioning, and power steering pump.

What Is The Distinction Between An A Belt And An B Belt?

The top width and depth measurements of V-belt cross-sections can be used to identify them. A “B” belt, for example, is a v-belt with a top width of 21/32″ and a depth of 7/16″. You may also use our Browning Belt Rule, which comes with a gauge to assist you to determine the belt type quickly. Add an “X” to the type if your belt is “notched.”

What Happens If The Belt Breaks In Your Car?

When a serpentine belt breaks, a car becomes undrivable and must be towed. If the engine is operated without a serpentine belt, the water pump will stop working, causing the engine to overheat. Other parts can be harmed by a damaged belt.

How can I know whether my car’s belt needs to be replaced?

Drive Belt Replacement Warning Signs

• Strange Noises. When you start hearing weird noises coming from your engine, it’s one of the most obvious signals that you should take your car to the dealership for a checkup.
  
• Wear Marks on the Surface.
  
• Indicators of mileage.
  
• Breakage is a bad thing.
  

What is the difference between a rope and a belt drive system?

Rope drives are a type of belt drive that is used to transmit mechanical power. Instead of a single flat or vee belt, rope drives employ several circular section ropes.

What Is The Distinction Between Belt Slip And Belt Creep?

The difference between the linear velocities of the pulley (driver/driven) and the belt is known as slip. Creep refers to the belt’s uneven extensions and contractions as it moves from tight to loose. Belt creep occurs when the surface of the belt moves relative to the surface of the pulley.

Which Belt Drive Delivers the Most Power?

Because flat belts have a larger probability of slipping, their power transmission capacity is reduced. Because of the higher friction, a V-belt can convey more power without slipping. It’s ideal for transmitting electricity and motion across vast distances. It’s best for power and motion transfer across short to medium distances.

Is It Possible To Install A Belt Drive On Any Bike?

The majority of bikes may be fitted with belt drives provided the frame is modified. Chains make more sense for extended hikes, as a traditional chain is much easier to replace when out in the wilderness.

Is it true that belts are more durable than chains?

Tensioning a chain is more difficult than tensioning a belt. A standard belt is tensioned using a spring – this is simple enough because it is light.