MD 2 (Belts and Pulleys, Wire Ropes, & Chain and Sprockets)

a loop of flexible material used to mechanically link two or more rotating shafts, most often parallel.

Belt

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

Is a simple system of power transmission that was well suited for its day.

Flat Belt

What are the flat belt applications?

1. Farming
2. Bucksaws
3. Sawmills
4. Silo Blowers
5. Conveyors
6. Electric Generators
7. Mining

____________ were occasionally used, but _________, ___________, ________________, and ____________ saw the widest use.

Wire ropes, cotton, hemp, manila hemp, flax rope

Over long distances, ______________________ were used to support the "________________," and in the late 19th century, this was considered quite efficient.

Intermediate sheaves, flying rope

What are the rope belt applications?

Connections from stationary engines to the jack shafts and line shafts of mills, and sometimes from line shafts to driven machinery.

Are only suitable for idler pulleys that guide the belt, or when _______________ are used.

Round grooves, (soft) O-ring type belts

_________________ solved the slippage and alignment problem. It is now the basic belt for power transmission.

V-belts

V-belts are generally endless, and their general cross-section shape is _____________?

Trapezoidal

The added _______________ offers an improved ____________, as less energy is wasted in the internal friction of continually bending the belt. In practice, this gain of ______________ causes a reduced heating effect on the belt and a cooler-running belt lasts longer in service.

flexibility, efficiency

Though often grouped with flat belts, they are actually a different kind.

Film Belt

In a two pulley system, depending upon direction the belt drives the pulley, the belt drives are divided into two types

Open belt drive and Crossed belt drive

Higher the ________________ enables more power can be transmitted than an open belt drive. However, ________________ and _______________ of the belt are important concerns.

Value of wrap, bending and wear

What are the advantages of belt drives?

1. They don't require Parallel shafts.
2. Belt Drives are provided with overload and jam protection.
3. Noise and vibration are damped out. Machinery life is increased because load fluctuations are shock-absorbed.
4. They are lubrication-free. They require less maintenance cost.
5. Belt drives are highly efficient in use (up to 98%, usually 95%)
6. They are very economical, when distance between shafts is very large.
7. Wide range of speeds available.
8. Flat belts are best for extremely high speed drives.
9. Single belt drives will accept more misalignment than chain drives.
10. Belt drives cushion shock loads and load fluctuations.

An arc of contact greater than 180 degrees can be obtained three ways:

1. A crossed belt drive.
2. Moving the input and output shafts farther apart.
3. Using an idler or snub pulley.

Put an additional bending stress on the belt, which reduces belt life.

Idlers

The best location for an inside idler is on the __________________ of the drive.

Slack side

This is commonly used to help increase the arc of contact on both pulleys.

Backside Idler

The diameter of the flat idler pulley should be at least _____________ the diameter of the smallest sheave located as close as possible to the small sheave

1.5 times

It reduces the arc of contact but the amount of take-up is unlimited. The smaller arc of contact will decrease the horsepower rating of each belt.

Inside Idler

________________, which is located as close as possible to the driven pulley. The idler helps to increase the arc of contact on the large diameter pulley, which reduces belt slippage problems that may be encountered on the driven side.

Backside Idler

What are Belt tension recommendations?

1. Check the belt tension frequently during the first 24 to 48 hours of run-in operation.
2. Maintain sheave alignment while tensioning the drive.
3. Make V-belt drive inspections periodically checking belt tension.
4. Keep all belts free from foreign material, which can cause slippage.
5. Over-tensioning belts will lead to reduced belt and bearing life.

To tighten a belt drive unit, take up the drive until the belts are _______________ in the grooves.

Snug

Each manufacturer's belt must operate at the ________________________ in the standardized sheave groove

same speed

What are the V-Belt Components?

1. Tensile Member
2. Undercord
3. Overcord
4. Cover
5. Adhesion Resin

What are the undercord materials commonly used?

1. Natural or Synthetic rubber compounds,
2. Fiber-loaded rubber compounds,
3. Woven natural or synthetic cords, or piles.

Light duty V-belts are commonly used singly on?

1. Small pumps
2. Small fans
3. Lawn mowers
4. Garden tractors
5. Home appliances
6. Compressor
7. Other light equipment

_______________ is essential to maintain long V-belt and sheave life.

Proper alignment

The wire ropes are widely used in?

1. Elevators
2. Mine hoists
3. Cranes, conveyors
4. Hauling devices
5. Suspension bridges

The wire ropes run on grooved pulleys but they rest on the _______________ of the grooves and are _____________ between the sides of the grooves.

bottom, not wedged

The wire ropes are made from ______________________ in order to have increase in strength and durability. It may be noted that the ____________ of the wire rope increases as its _____________decreases.

cold drawn wires, strength, size

The various materials used for wire ropes in order of increasing strength are?

1. Wrought iron
2. Plough steel
3. Cast steel
4. Extra strong cast steel
5. Alloy steel

What are the advantages of the wire ropes as compared to fibre ropes?

1. These are lighter in weight
2. These offer silent operation
3. These can withstand shock loads
4. These are more reliable
5. These are more durable
6. They do not fail suddenly
7. The efficiency is high
8. The cost is low

In these type of ropes, the direction of twist of the wires in the strands is same as that of strands in the rope.

Parallel or lang lay ropes

These ropes have better bearing surface but is harder to splice and twists more easily when loaded. These ropes are more flexible and resists wear more effectively. Since such ropes have the tendency to spin, therefore these are used in lifts and hoists with guide ways and also as haulage ropes.

Parallel or lang lay ropes

For light and medium service, the sheaves are made of _________________, but for heavy crane service they are often made of _______________.

cast iron, steel castings

The pitch ( p ) of the grooves must be ____________________ than the rope diameter to avoid friction and wear between the coils.

made slightly larger

It is the distance between the hinge centre of a link and the corresponding hinge centre of the adjacent link.

Pitch of chain

These chains are used for hoisting and hauling purposes and operate at a maximum velocity of 0.25 m/s.

Hoisting and Hauling Chains

The links of this type of chain are of oval shape. The joint of each link is welded.

Chain with oval links

The conveyor chains are usually made of?

malleable cast iron

These chains do not have smooth running qualities.

Conveyor Chains

The conveyor chains run at slow speeds of about?

0.8 to 3 m/s

Under the European standards, chains manufactured to the above standards are covered by _____________ and _____________. These standards cover 3 versions:

ISO606 and DIN 8187, SIMPLEX, DUPLEX, TRIPLEX

The range of pitch sizes can vary between 4mm, (0.158 inch) to 114.3mm, (4.500 inch). They are characterized by a large pin diameter, especially for the larger pitch sizes. This results in better wear resistance due to the greater bearing area.

EUROPEAN STANDARD

What are the types of belts?

1. Flat belts
2. Rope
3. Round
4. V-belt
5. Multi-groove
6. Ribbed
7. Film
8. Timing

It can deliver high power at high speeds (500 hp at 10,000 ft/min or 373 kW at 51 m/s).

Flat Belt

Unlike leather belts, however, _______________ were sometimes used to transmit power over relatively long distances.

Rope drives

Are a circular cross section belt designed to run in a pulley with a 60 degree V-groove.

Round belts

What are the round belt applications?

Round belts are for use in relatively low torque situations.

V-belts are also called?

Style V-belts, Vee belts, (less commonly) Wedge rope

They provide the best combination of _____________, ______________, ________________, and _________________.

Traction, speed of movement, load of the bearings, and long service life

The belt also tends to wedge into the groove as the load increases—___________________, _________________________—improving torque transmission and making the V-belt an effective solution, needing less width and tension than flat belts.

The greater the load, the greater the wedging action

What are the V-belt applications?

General Applications from low to high transmission system.

Multi-groove belts is also called as

Polygroove belt

is made up of usually 5 or 6 "V" shapes alongside each other. This gives a thinner belt for the same drive surface, thus it is more flexible, although often wider.

Multi-groove

What are the multi-groove belt applications?

1. ATM vending machinery
2. Electric utilities equipment
3. Hand tools
4. Machine tools
5. Conveyors
6. HVAC equipment
7. Textile equipment

Is a power transmission belt featuring lengthwise grooves.

Ribbed belt

It operates from contact between the ribs of the belt and the grooves in the pulley

Ribbed belt

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

Ribbed belt

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.

Ribbed belt

What are the ribbed belt applications?

Mass Consumer Goods:
1. Snow blowers
2. Home power tools
3. Clothes dryers

The ribbed belt may be fitted on various applications.

1. Compressors
2. Agricultural machinery
3. Washing machines
4. Lawn mowers
5. Food mixers
6. Fitness bikes

They consist of a very thin belt (0.5-15 millimeters or 100-4000 micrometres) strip of plastic and occasionally rubber.

Film Belt

They are generally intended for low-power (less than 10 Watts), high-speed uses, allowing high efficiency (up to 98%) and long life.

Film Belt

What are the film belt applications?

1. Business machines
2. Printers
3. Tape recorders
4. Other light-duty operations

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.

Timing Belts

They are often used in lieu of chains or gears, so there is less noise and a lubrication bath is not necessary. They need the least tension of all belts, and are among the most efficient.

Timing Belts

What are the timing belt applications?

1. Camshafts of automobiles
2. Miniature timing systems
3. Stepper motors often utilize these belts

Offers smooth transmission of power between shafts at considerable distance.

Belt Drive

Belt drives are used as ____________________, _______________________, or ____________________.

1. Source of motion
2. To efficiently transmit power
3. To track relative movement

Is used to rotate the driven pulley in the same direction of driving pulley.

Open Belt Drive

Is used to rotate driven pulley in the opposite direction of driving pulley.

Crossed Belt Drive

What are the disadvantages of belt drives?

1. In Belt drives, angular velocity ratio is not necessarily constant or equal to the ratio of pulley diameters, because of slipping and stretching.
2. Heat buildup occurs. Speed is limited to usually 35 meters per second. Power transmission is limited to 370 kilowatts.
3. Operating temperatures are usually restricted to -35 to 85°C.
4. Some adjustment of center distance or use of an idler pulley is necessary for wearing and stretching of belt drive compensation.
5. Belts are easily damaged by oil, grease, abrasives, some chemicals, and heat.
6. Belts can be noisy; also loose or worn belts can be a major cause of machinery vibration

To obtain the best service from any particular belt application, remember:

1. Select the correct belt for the job.
2. Ensure that the belt is installed correctly and used properly.

It is one of the belt selection considerations, in which the belt will operate, such as: exposure to oil and grease, range of operating temperatures, abrasive dust and chemical conditions, sunlight, and other weather conditions.

Environmental conditions

What are the Belt Selection Considerations?

1. Type of drive required
2. Driver/Driven Revolutions Per Minute (RPM)
3. Horsepower requirements
4. Pulley diameters and center distance
5. Take-up allowances and take-up design
6. Space limitation for operation
7. Pulsating or shock load conditions
8. Static dissipation problems
9. Belt availability and inventory considerations
10. Belt construction and service lif

Three major factors determine the potential of the grip are?

1. Area of contact
2. Belt tension
3. Friction between the belt and pulley or sheave surface (coefficient of friction)

Is determined by width and the arc of contact.

Area of contact

The arc of contact with pulleys of equal diameters is ______________ on each pulley

180 degrees

For maximum power transfer on the belts and pulleys, the pulley ratio should be ________ or ____________?

3 to 1 or less

Where a high ratio is required, a ______________________ can be used to avoid excessive single-step ratios or undersize pulleys

Two-step drive (counter-shaft)

the ______________ the idler pulley, the greater ____________ in belt life.

smaller, reduction

If an accurate tension is required, a ________________________ for determining and setting belt tension can be used.

Numerical Method

The drive powers the driven pulley by the pull, which results in increased tension and stretch on the tight side of the unit as it overcomes the load resistance. The slack side has no tension increase, it simply returns to the driven pulley.

Establishing Belt Tension

If one or more belts are too loose or too tight, one of the following problems exists:

1. Worn sheaves
2. Improper belt tension
3. Damaged belts
4. Improperly matched belts
5. Angular sheave misalignment

If a body of weight (W) rests on a horizontal plane surface and a force (P) parallel to the surface is sufficient to cause the body to be at a point of slipping, then the ratio of P to W is the ___________________________ between the two surfaces.

Coefficient of friction (F)

Friction between sliding surfaces, as in belt and pulley surfaces, is _______________ by the area of surface.

Not influenced

The friction is solely dependent on the ________________ and _____________ of the faces, and the _______________ normal to the faces.

Character and Condition, Total pressure

Belt manufacturers meet the standards and tolerances as set by the _________________________________________________.

Rubber Manufacturers Association (RMA)

Its purpose is to withstand the tension or pull that is imposed to transmit the desired power.

Tensile member or Pitch line

The tensile member materials commonly used are?

1. Rayon
2. Nylon
3. Polyester
4. Steel
5. Fiberglass
6. Kevlar

_________________________ locates the tensile member correctly in relation to other belt components, and it also assists in preventing the tensile member from sagging in the center under load.

Overcord

_____________________________ protects the internal belt components from weather and environmental conditions. It also provides the ____________________ for the belt.

Cover, Wearing surface

The cover must remain _____________________, and may be __________________________. The cover material meets RMA standards for static conductivity, and most belt covers are _____________________; they do not catch fire from heat build-up if the belt is subjected to severe slippage.

flexible, oil and heat resistant, flame-resistant

__________________________ act as a cushion to prevent tensile members from rubbing together as well as fully bonding all of the belt components together.

Adhesion resins or Gums

Through ____________________________, both the adhesion gums and tensile members are joined in a chemical bond, which is flexible and permanent.

hot vulcanizing process