Belt

A belt is a loop of flexible material used to link two or more rotating shafts mechanically. 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 or the belt may be crossed, so that the direction of the driven shaft is reversed. 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.

Material used for belt : Leather, rubber, fabric, synthetic polymers

Properties of a belt material

1. The material from which belt is made of should have high coefficient of friction.
2. To withstand the tensions created, the belt material should have high tensile strength.
3. When belt passes through pulley bending stress is induced, to avoid this material should be flexible and should not be rigid.
4. The material should have water resistance.

 Types of belts

1.   Flat Belt

2.   V-Belt

3.   Round Belt

4.   Timing Belt 

1 Flat belt

Flat belts were widely used in the 19th and early 20th centuries in line shafting to transmit power in factories. They were also used in countless farming, mining, and logging applications, such as bucksaws, sawmills, threshers, silo blowers, conveyors for filling corn cribs or haylofts, balers,  water pumps and electrical generators. Flat belts are still used today, although not nearly as much as in the line-shaft era. The flat belt is a simple system of power transmission that was well suited for its day. It can deliver high power at high speeds (373 kW at 51 m/s), in cases of wide belts and large pulleys. But these wide-belt-large-pulley drives are bulky, consuming much space while requiring high tension, leading to high loads, and are poorly suited to close-centers applications, so V-belts have mainly replaced flat belts for short-distance power transmission.

Advantages of flat belts

1. Flat belt can be used where the distance between pulleys are more.
2. They have high load carrying capacity.
3. They can be employed where high operating speed is required.
4. They produce less noise compared to v-belts.
5. They can absorb shock loads compared to v-belts. 

Disadvantages of flat belts

1. Due to high load the belt may slip over the pulley.
2. In long run the belt gets elongated and may slip
3. High pulley diameter is required. 

2. V-Belt

V belts solved the slippage and alignment problem. It is now the basic belt for power transmission. They provide the best combination of traction, speed of movement, load of the bearings, and long service life. They are generally endless, and their general cross-section shape is roughly trapezoidal (hence the name "V"). The "V" shape of the belt tracks in a mating groove in the pulley (or sheave), with the result that the belt cannot slip off. 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. 

Advantages and Disadvantages of V-belt Drive over Flat Belt Drive:-

 

Following are the advantages and disadvantages of the V-belt drive over flat belt drive :-

 

Advantages:-

1. The V-belt drive gives compactness due to the small distance between centers of pulleys.

2. The drive is positive, because the slip between the belt and the pulley groove is negligible.

3. Since the V-belts are made endless and there is no joint trouble, therefore the drive is smooth.

4. It provides longer life, 3 to 5 years.

5. It can be easily installed and removed.

6. The operation of the belt and pulley is quiet.

7. The belts have the ability to cushion the shock when machines are started.

8. The high velocity ratio (maximum 10) may be obtained.

9. The wedging action of the belt in the groove gives high value of limiting *ratio of tensions. Therefore the power transmitted by V-belts is more than flat belts for the same coefficient of friction, arc of contact and allowable tension in the belts.

10. The V-belt may be operated in either direction, with tight side of the belt at the top or bottom. The center line may be horizontal, vertical or inclined.

 

Disadvantages:-

1. The V-belt drive cannot be used with large center distances, because of larger weight per unit length.

2. The V-belts are not so durable as flat belts.

3. The construction of pulleys for V-belts is more complicated than pulleys of flat belts.

4. Since the V-belts are subjected to certain amount of creep, therefore these are not suitable for constant speed applications such as synchronous machines and timing devices.

5. The belt life is greatly influenced with temperature changes, improper belt tension and mismatching of belt lengths.

6. The centrifugal tension prevents the use of V-belts at speeds below 5 m/s and above 50 m/s.

3. Round belt

Round belts are 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. 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, gluing or welding. Early sewing machines utilized a leather belt, joined either by a metal staple or glued, to great effect.

4.Timing belt

Timing belts also known as toothed, notch, cog, or synchronous belts are a positive transfer belt and can track relative movement. These belts have teeth that fit into a matching toothed pulley. When correctly tension, they have no slippage, run at constant speed, and are often used to transfer direct motion for indexing or timing purposes. They are often used instead 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 at speeds of 16,000 ft/min (4,900 m/min).

Advantages of Timing belt

1.   Precision registration and timing with no loss of high torque carrying capability.

2.   Minimal vibration.

3.   Positive slip proof engagement.

4.   Wide speed range, especially important when the entire speed range is developed from a single source.

5.   Virtually no elongation (stretching) due to wear.

6.   High mechanical efficiency, as much as 98% when properly maintained. By contrast, chain drives are in the 91-98% efficiency range, while V-Belts average in the 93-98% range.

7.   Power transmission efficiency is not lost with use.

8.   Clean operation, no need for lubrication.

9.   Reduced noise.

10.                Long, dependable trouble-free service.

11.                Excellent abrasion resistance.

12.                Rust resistant.

13.                Resists chemicals and contaminants.

14.                Increased drive design options.

15.                Weight savings.

16.                Safety issues.

17.                Economical operations.

Disadvantages of Timing belt

1.   Relatively high purchase cost

2.   Need for specially fabricated toothed pulleys.

3.   Less protection from overloading, jamming, and vibration due to their continuous tension cords.

4.   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.

Bearing and Types

BEARING

A bearing is a machine element that constrains relative motion to the desired motion, and reduces friction between moving parts. The design of the bearing may, provide for free linear movement of the moving part or for free rotation around a fixed axis or, it may prevent a motion by controlling the vectors of normal forces that bear on the moving parts. Most bearings facilitate the desired motion by minimizing friction.

Types of Bearing

Bearings are classified broadly according to the type of operation, the motions allowed, or to the directions of the loads applied to the parts.

1. ROLLING BEARING

A rolling bearing is a bearing which carries a load by placing rolling elements such as balls or rollers between two bearing rings called races. The relative motion of the races (Outer race and inner race) causes the rolling elements to roll with very little rolling resistance and with little sliding.

Rolling-element bearings have the advantage of a good trade-off between cost, size, weight, carrying capacity, durability, accuracy, friction, and so on.

There are two types of Rolling bearing

(I) Ball Bearing

(II) Roller Bearing

(I) BALL BEARING

A ball bearing is a type of rolling-element bearing that uses balls to maintain the separation between the bearing races.

The purpose of a ball bearing is to reduce rotational friction and support radial and axial loads. It achieves this by using at least two races to contain the balls and transmit the loads through the balls. In most applications, one race is stationary and the other is attached to the rotating assembly like a hub or shaft. As one of the bearing races rotates it causes the balls to rotate as well. Because the balls are rolling they have a much lower coefficient of friction than if two flat surfaces were sliding against each other.

Ball bearings tend to have lower load capacity for their size than other kinds of rolling-element bearings due to the smaller contact area between the balls and races. However, they can tolerate some misalignment of the inner and outer races.

There are FOUR types of ball Bearing

a. Angular contact Ball bearing

An angular contact ball bearing uses axially asymmetric races. An axial load passes in a straight line through the bearing, whereas a radial load takes an oblique path that acts to separate the races axially. So the angle of contact on the inner race is the same as that on the outer race. Angular contact bearings better support combined loads (loading in both the radial and axial directions) and the contact angle of the bearing should be matched to the relative proportions of each. The larger the contact angle (typically in the range 10 to 45 degrees), the higher the axial load supported, but the lower the radial load. In high speed applications, such as turbines, jet engines, and dentistry equipment, the centrifugal forces generated by the balls changes the contact angle at the inner and outer race.

 

b. Deep groove ball bearing

Deep groove ball bearings are the most widely used bearing type and are particularly versatile. They have low friction and are optimized for low noise and low vibration which enables high rotational speeds. They accommodate radial and axial loads in both directions, are easy to mount, and require less maintenance than other bearing types. 

 

c. Self aligning ball bearing

Self-aligning ball bearings are constructed with the inner ring and ball assembly contained within an outer ring that has a spherical raceway. This construction allows the bearing to tolerate a small angular misalignment resulting from shaft or housing deflections or improper mounting. The bearing was used mainly in bearing arrangements with very long shafts, such as transmission shafts in textile factories. One drawback of the self-aligning ball bearings is a limited load rating, as the outer raceway has very low osculation.

d. Thrust bearing

Thrust ball bearings, composed of bearing balls supported in a ring, can be used in low thrust applications where there is little axial load.

Thrust bearings absorb axial loads from rotating shafts into the stationary housings or mounts in which they are turning. Axial loads are those transmitted linearly along the shaft. Good examples of axial loads are the forward thrust on boats or prop-driven airplanes as a result of their propeller's rapid rotation.

 

(II) ROLLER BEARING

Common roller bearings use cylinders of slightly greater length than diameter. Roller bearings typically have higher radial load capacity than ball bearings, but a lower capacity and higher friction under axial loads. If the inner and outer races are misaligned, the bearing capacity often drops quickly compared to either a ball bearing or a spherical roller bearing.

As in all radial bearings, the outer load is continuously re-distributed among the rollers. Often fewer than half of the total number of rollers carry a significant portion of the load. 

There are FOUR types of roller bearing

a. Taper roller bearing

Tapered roller bearings use conical rollers that run on conical races. Most roller bearings only take radial or axial loads, but tapered roller bearings support both radial and axial loads, and generally can carry higher loads than ball bearings due to greater contact area. Tapered roller bearings are used, for example, as the wheel bearings of most wheeled land vehicles. The downsides to this bearing is that due to manufacturing complexities, tapered roller bearings are usually more expensive than ball bearings; and additionally under heavy loads the tapered roller is like a wedge and bearing loads tend to try to eject the roller; the force from the collar which keeps the roller in the bearing adds to bearing friction compared to ball bearings.

b. Spherical roller bearing

Spherical roller bearings have an outer ring with an internal spherical shape. The rollers are thicker in the middle and thinner at the ends. Spherical roller bearings can thus accommodate both static and dynamic misalignment. However, spherical rollers are difficult to produce and thus expensive, and the bearings have higher friction than an ideal cylindrical or tapered roller bearing since there will be a certain amount of sliding between rolling elements and rings.

c. Cylindrical roller bearing

Cylindrical rollers are in linear contact with the raceways. They have a high radial load capacity and are suitable for high speeds.

Some cylindrical roller bearings have no ribs on either the inner or outer ring, so the rings can move axially relative to each other. These can be used as free-end bearings. Cylindrical roller bearings, in which either the inner or outer rings has two ribs and the other ring has one, are capable of taking some axial load in one direction Double-row cylindrical roller bearings have high radial rigidity and are used primarily for precision machine tools.

d. Needle roller bearing

Needle roller bearings use very long and thin cylinders. Often the ends of the rollers taper to points and these are used to keep the rollers captive, or they may be hemispherical and not captive but held by the shaft itself or a similar arrangement. Since the rollers are thin, the outside diameter of the bearing is only slightly larger than the hole in the middle. However, the small-diameter rollers must bend sharply where they contact the races, and thus the bearing fatigues relatively quickly.

 

2. FLUID BEARING

Fluid bearings are bearings in which the load is supported by a thin layer of rapidly moving pressurized liquid or gas between the bearing surfaces. Since there is no contact between the moving parts, there is no sliding friction, allowing fluid bearings to have lower friction, wear and vibration than many other types of bearings. Thus, it is possible for some fluid bearings to have near-zero wear if operated correctly.

 Fluid bearings are frequently used in high load, high speed or high precision applications where ordinary ball bearings would have short life or cause high noise and vibration. They are also used increasingly to reduce cost. For example, hard disk drive motor fluid bearings are both quieter and cheaper than the ball bearings they replace. Applications are very versatile and may even be used in complex geometries such as lead screw.

They can be broadly classified into two types: hydrostatic bearings and hydrodynamic bearings.

Hydrostatic bearing

Hydrostatic bearings are externally pressurized fluid bearings, where the fluid is usually oil, water or air, and the pressurization is done by a pump.

Hydrodynamic bearing

Hydrodynamic bearings rely on the high speed of the journal (the part of the shaft resting on the fluid) to pressurize the fluid in a wedge between the faces.

 

3. PLAIN BEARING

A plain bearing, or more commonly sliding bearing and slide bearing in railroading sometimes called a solid bearing, journal bearing, or friction bearing, is the simplest type of bearing, comprising just a bearing surface and no rolling elements. Therefore, the journal (i.e., the part of the shaft in contact with the bearing) slides over the bearing surface. The simplest example of a plain bearing is a shaft rotating in a hole. A simple linear bearing can be a pair of flat surfaces designed to allow motion; e.g., a drawer and the slides it rests on or the ways on the bed of a lathe.

Plain bearings, in general, are the least expensive type of bearing. They are also compact and lightweight, and they have a high load-carrying capacity.

 

4. MAGNETIC BEARING

A magnetic bearing is a type of bearing that supports a load using magnetic levitation. Magnetic bearings support moving parts without physical contact. For instance, they are able to levitate a rotating shaft and permit relative motion with very low friction and no mechanical wear. Magnetic bearings support the highest speeds of any kind of bearing and have no maximum relative speed.

Active magnetic bearings have several advantages: they do not suffer from wear, have low friction, and can often accommodate irregularities in the mass distribution automatically, allowing rotors to spin around their center of mass with very low vibration.

Passive magnetic bearings use permanent magnets and, therefore, do not require any input power but are difficult to design due to the limitations.

An active magnetic bearing works on the principle of electromagnetic suspension based on the induction of eddy currents in a rotating conductor. When an electrically conducting material is moving in a magnetic field, a current will be generated in the material that counters the change in the magnetic field (known as Lenz's Law). This generates a current that will result in a magnetic field that is oriented opposite to the one from the magnet. The electrically conducting material is thus acting as a magnetic mirror.

The hardware consists of an electromagnet assembly, a set of power amplifiers which supply current to the electromagnets, a controller, and gap sensors with associated electronics to provide the feedback required to control the position of the rotor within the gap. The power amplifier supplies equal bias current to two pairs of electromagnets on opposite sides of a rotor. This constant tug-of-war is mediated by the controller, which offsets the bias current by equal and opposite perturbations of current as the rotor deviates from its center position.

 

5. JEWEL BEARING

A jewel bearing is a plain bearing in which a metal spindle turns in a jewel-lined pivot hole. The hole is typically shaped like a torus and is slightly larger than the shaft diameter. The jewels are typically made from the mineral corundum, usually either synthetic sapphire or synthetic ruby. Jewel bearings are used in precision instruments where low friction, long life, and dimensional accuracy are important. Their largest use is in mechanical watches.

The advantages of jewel bearings include high accuracy, very small size and weight, low and predictable friction, good temperature stability, and the ability to operate without lubrication and in corrosive environments. They are known for their low kinetic friction and highly consistent static friction.

6. FLEXURE BEARING

A flexure bearing is a category of flexure which is engineered to be compliant in one or more angular degrees of freedom. Flexure bearings are often part of compliant mechanisms. Flexure bearings serve much of the same function as conventional bearings or hinges in applications which require angular compliance. However, flexures require no lubrication and exhibit very low or no friction.

Many flexure bearings are made of a single part: two rigid structures joined by a thin "hinge" area. A hinged door can be created by implementing a flexible element between a door and the door frame, such that the flexible element bends allowing the door to pivot open.

Flexure bearings have the advantage over most other bearings that they are simple and thus inexpensive. They are also often compact, lightweight, have very low friction, and are easier to repair without specialized equipment. Flexure bearings have the disadvantages that the range of motion is limited, and often very limited for bearings that support high loads.

 

 

Types of Bolt

What is a Bolt.. ?

A bolt is a form of threaded fastener with an external male thread requiring a matching pre-formed female thread such as a nut. A Nut bolt provides us a temporary joint

 Types of Bolts

There are variety of bolts available as per our application, lets discuss some of them.

 

1. Hex bolt

Hex bolts from ITA Fasteners are mostly used in repair and construction work. As the name implies, they have a hexagonal head and come with machine threads for a firm and rough handling. They come in a wide range of different hex bolt sizes for custom applications depending on its dimensional requirements. These Hex Bolts come in the anti-corrosion stainless steel, alloy steel and carbon steel materials which ensures that the structure doesn’t weaken because of rust. Depending on the length of the bolt, it can come with standard threading or full threading. 

2. Anchor bolt

 

 

Anchor bolts are used to connect structural and non-structural elements to concrete.  The Anchor bolt consists of anchor fasteners, steel plates, or stiffeners, an inside pin and a nut. Anchor bolts transfer different types of force like tension forces and shear forces.

3. Carriage bolt

A carriage bolt also called coach bolt and round-head square-neck bolt is a form of bolt used to fasten metal to metal or metal to wood.

It is distinguished from other bolts by its shallow mushroom head and the fact that the cross-section of the shank, though circular for most of its length is square immediately beneath the head. This makes the bolt self-locking when it is placed through a square hole in a metal strap. This allows the fastener to be installed with only one tool, a spanner or wrench, working from one side. The head of a carriage bolt usually is a shallow dome. The shank has no threads; and its diameter equals the side of the square cross-section.

4. Sex bolt

 

A sex bolt, also known as a barrel nut, barrel bolt, binding barrel, Chicago screw, post and screw or connector bolt is a type of fastener that has a barrel-shaped flange and protruding boss that is internally threaded. The boss sits within the components being fastened, the flange provides the bearing surface. The sex bolt and accompanying machine screw sit flush on either side of the surfaces being fastened. It is normally chosen because of its low profile compared to other nuts. The sex bolt often has a built-in feature, such as a slot, to aid in tightening the fastener

5. Elevator bolt

Elevator bolts are often used with canvas or other soft, pliable materials. The large diameter, flat countersunk head keeps them from pulling through the material. Also known as belt bolts, elevator bolts are also known for a shallow, conical bearing surface, an integrally-formed square neck under the head and a unified thread pitch.

A common application for elevator bolts is industrial or agricultural belting systems or conveyor systems, where head clearances must be minimal and where a wide thin bearing surface is desired. Similar to the carriage bolt, the elevator bolt's square shoulder under head prevents turning when nut is applied.

 

 

6. Flange bolt

 

Flange bolts have a circular flange under the head that acts like a washer to distribute the load. Flange bolts that are non-serrated are sometimes called frame bolts.

7. Allen bolt

 A bolt with a hexagonal socket in its head that is designed to be used with an Allen keys are called Allen bolt. The allen bolts comes with different sizes based on the requirement, Usually it has matrix thread. Allen bolt can be full threaded or half threaded based on the purpose.

8. Countersunk bolt

A countersunk bolt is a bolt that is “sunk” into a piece of lumber. The head will sit below the surface of the material and it can easily be filled with a wood plug or filler. The countersunk bolts are used where the projection of bolt head is unacceptable.

9. Hanger bolt

Hanger bolts are studs used to suspend objects from or attach items to wood. Like a typical stud, they are headless, double-ended bolts that have threads at each end. The hanger bolts generally have lag threads to screw into wood but, at the other end, machine screw threads to accept a nut or thread into an internally threaded (tapped) hole. Coupling nuts and threaded rod are often used with hanger bolts to suspend electrical conduits, junction/pull boxes, fixtures and sheet metal. The furniture industry uses them with corner brackets, clinch nut plates, tee nuts and whenever wood and machine screw threads are needed in a single fastener. Hanger bolts are also known as: couch bolts, headless hanger bolts, hanger screws.

 

10. Huck bolt

Huck bolts are a pin and collar combo that are swaged together. In the initial stages of the installation process, the Huck gun engages and pulls on the pin, whilst the nose assembly is forced down the collar. Progressively the tool swages the collar which is softer steel than pin into the grooves of the harder steel pin.

The squeezing action reduces the diameter of the collar whilst increases its length. This in turn stretches the pin generating a clamp force over the joint.

11. J Bolt

J-bolts are J-shaped fasteners, threaded on the flat side. They are often used in structural applications like securing walls to concrete foundations. The bent end hooks around rebar for support, and may be cast in concrete for use as an anchor bolt.

12. Lag bolt

The name lag screw derives from their original use in securing barrel staves, also known as lags. A lag screw requires a hole drilled at the same diameter as the shaft of the screw, a gimlet point helps pull the screw into the hole and tap its thread.

lag screws are some of the toughest fasteners. These extremely sturdy fasteners are usually used to connect heavy lumber or other heavy materials that are bearing an intense load.

13. Machine bolt

A machine bolts are metal rod with a usually square or hexagonal wrench head at one end and threads at the other that is commonly available in a size range from ¹/₄ inch to 3 inches in diameter.

14. Plow bolt

A plow bolt is a type of fastener that is used for making mechanical connections that require a smooth, or flush, surface at the location where the bolt head protrudes. These were so named because of their early use in the manufacture of plows. Today plow bolts are used on many types of heavy construction equipment, such as snowplows, road graders, and scoop shovels. Plow bolts are normally exposed to high forces and wear, and it is important to select the right bolt for each individual application.

15. Square head bolt

The bolt with the square shape head is called square head bolt. Square bolts are now most commonly used for aesthetic purposes to provide a rustic look in a new structure or to match existing fasteners in an older structure.

16. Stud

A straight rod having complete thread or thread in both end is called stud. They are designed to be used in tension. Threaded rod in bar stock form is often called all-thread.

17. T Head bolt

T-Head Bolts, otherwise known as Hammer-Head Bolts, are used in a range of applications – such as the fastening of lift guide rails. They are able to be placed flexibly in required positions within anchor channels.

18. Timber bolt

Timber bolts, also known as mushroom head bolts or dome head bolts, can be used in both marine and wood applications. The underside of the oversized, rounded bolt head has nubs or fins which prevent the bolt from turning in the timber (usually between two and four nubs). The oversized head of the timber bolt eliminates the needs of washer on the bolt head end.

19. Toggle bolt

A toggle bolt, also known as a butterfly anchor, is a fastener for hanging objects on hollow walls such as drywall. Toggle bolts have wings that open inside a hollow wall, bracing against it to hold the fastener securely.

The wings, once fully opened, greatly expand the surface area making contact with the back of the hollow wall. This ultimately spreads out the weight of the secured item, increasing the weight that can be secured compared to a regular bolt.

20. U bolt

A U-bolt is a bolt in the shape of the letter U with screw threads on both ends. U-bolts have primarily been used to support pipework, pipes through which fluids and gasses pass.

21. Shoulder bolt

Shoulder screws, also known as shoulder bolts and stripper bolts, are machine screws with an integral shoulder or journal between the head and thread. Although they are not readily available in local hardware stores, shoulder screws are used extensively in industries from aerospace to consumer products because of their versatility and unique attributes when installed.

Shoulder screws have three main sections: head, shoulder, and thread. The head has the largest diameter, the shoulder is described by its diameter and length, and the thread has a major diameter slightly smaller than the shoulder diameter.

When the thread of the shoulder screw is fully installed, the un threaded shoulder extends beyond the surface into which the thread embeds. The shoulders give the screws their versatility by acting as shafts or dowels for rotating items such as bearings and bushings, axles for rolling parts, guides for sliding elements, and pivot points or mounting pins.

22. Foundation bolt

Foundation bolts are mainly used in pre-engineered buildings manufacturing, fastening heavy machines to foundations, and construction. They are also used in process-based businesses like petrochemical, sugar, and FMCG manufacturing.

The base of the bolt use to be covered with concrete and the threaded part used to install the structure