# Green Mechanic

Knowledge Is Free

### Brakes

A device whose sole purpose is to make any rotating mechanism slow or stop or control it as required is called brake. Brake can generally be divided in to two main parts; one forces applying part and second force transferring part. Force taking part is one which takes force from operator and turns that force into pressure which can be applied to second part. Second part takes pressure from first part and transferring it to rotating mechanism after converting it to torque.
There are two main types of braking mechanism available
1. Drum Brake
2. Disk Brake

### Drum Brake

Drum brakes get their name from the one of their part shape which looks like an empty drum. Drum brake usually consist of three main parts; shoes, shoes pad and drum. Drum is the part which is attached with the rotating part of the mechanism where shoes pads which are attached to shoes are attached to the hydraulic or any other force providing mechanism. When force is provided by the hydraulic or any other force providing mechanism to shoes of the brake then shoes presses the shoes pads with drum of the brake. Force provided to the drum is used against the motion of the mechanism and stop that mechanism as the result of that force.

### Disk Brake

Disk brakes get their name from the one of their part shape which looks like a disk. Disk brake usually consist of three main parts; shoes, shoes pad and rotor (disk). Rotor (disk) is the part which is attached with the rotating part of the mechanism where shoes pads which are attached to shoes are attached to the hydraulic or any other force providing mechanism. When force is provided by the hydraulic or any other force providing mechanism to shoes of the brake then shoes presses the shoes pads with rotor (disk) of the disk brake. Force provided to the rotor (disk) is used against the motion of the mechanism and stop that mechanism as the result of that force.

### Comparison between Disk brake and Drum brake

Disk brake and drum brake both are used to provide resisting power to stop different mechanism but both have same working principles. In order to know which type of brake can be used for some particular work following is the comparison of disk brake with drum brake.

Number of Components
Number of components of a braking system means the total number of components any braking system have which includes working and supporting components. With only three working and one supporting components ( rotor, shoes hydraulic system and pad) the disk brake has the minimum number of components than the drum brake which have total of six components ( drum, shoes, pads, anchor pins, retracting springs, and cam to expand brake shoes)

Installation
Installation of braking system means how much time it takes to install or remove any braking system for maintenance or replacement. Due to its simple design and ability of self adjustment disk brakes takes much less time for installation and removal.

Maintenance
Maintenance of braking system means how much time and money it takes to repair any braking system during maintenance. Due to its simple design and less parts disk brake takes much less time and money for maintenance

Cost
Cost of braking system means how much money it takes to purchase, install and repair any braking system during its life time. Due to its simple design and less parts disk brake is much more cost effective than disk brake.

### V belt Drive

They are used for high power; high toque and short distance transmissions for example power transmission from motor to pumping section of water pump (Dokey pump). V belt get their names from the shape of their cross section as it looks like the English alpha bet “V”. Like their cross section shape, the pulley used in v belt drive is also like English alpha bet V. they can easily cover come the shocks introduce in power transmission system because of greater belt strength and can avoid slipping due to greater belt and pulley friction.

### Flat Belt Drive

They are used for moderate power; moderate toque and moderate distance transmissions for example power transmission from motor to pulley of conveyer belt. Flat belt get their names from the flat geometry and rectangle shape of their cross section. The pulley used in flat belt drive has a simple cylindrical shape. They can easily cover come the small shocks introduce in power transmission system but cannot handle high because of moderate belt and pulley friction.

### Comparison of Flat belt drive with V belt drive

Flat belts and v belt both are used for power transmission for different mechanism but with same working principles. In order to know which type of belt can be used for some particular work following is the comparison of flat belt drive with V belt drive.

Power Rating
Power rating means the amount of power any mechanism can transfer with effective working. Power rating of flat belt drive is little less than the V belt drive main due to type of contact between belt and pulley

Velocity Ratio
Velocity ratio means the amount of velocity that can be increased or decreased by any mechanism with effective working. Velocity ratio of flat belt drive is little less than the V belt drive main due to type of contact between belt and pulley

Performance
Performance of belt drive means how smoothly a belt can transfer power from driver to driven pulley. Shock absorbing ability of flat belt drive is little less than the V belt drive main due to type of contact between belt and pulley

Noise
Noise is the unwanted sound produce by any mechanism during operation. Both types of belt produce noise but noise produce by flat belt drive is little less than the V belt drive main due to type of contact between belt and pulley

Life
Life of belt drive is the working hours a belt can provide with effective working. Life of flat belt drive is much more than the V belt drive main due to type of contact between belt and pulley

Installation
Installation of any belt drive is how easy it is or how much time it require to install or remove any belt from its pulley. Time require to install flat belt drive is little less than the V belt drive main due to type of contact between belt and pulley

Manufacturability
Manufacturability of belt drive is how easy it is to manufacture a belt which can work effectively. Manufacturability of flat belt drive is little easy than the V belt drives main due to design of belt.

Cost
Cost of the belt drive is how much a belt cost because they are replaced continuously. Cost of flat belt drive is little less than the V belt drive main due to type of contact between belt and pulley

### Four Different Power Transmission Methods

Power transmission is one of the most comment phenomena which happen in most of the mechanical powered machines. Power transmission is the transfer of power from primary mover to the mechanism which provides the useful output. Power transmission can be done in number of way and they are as follow
1. Gear Drive Power Transmission System
2. Chain Drive Power Transmission System
3. Rope Drive Power Transmission System
4. Belt Drive Power Transmission System

### Gear Drive Power Transmission System

Power transmission using gears is one of most commonly used method in vehicles where power from motor or engine is transfer to the tires using one or more gear sets. Gear drives are mostly used in those applications where length between the primary mover and driving mechanism is very small and power or rpm value requirement at the output is fixed. Gears used in gear drives are as follow
1. Spur Gears
2. Spur Helical Gears
3. Bevel Gears
4. Helical Bevel Gear
5. Worm and worm wheel

### Chain Drive Power Transmission System

Power transmission using chain is one of most commonly used method in vehicles like bicycle and motor bike where power from motor or engine is transfer to the tires using set of chain and sprocket. Chain drives are mostly used in those applications where length between the primary mover and driving mechanism is large and weight of chain drive done not affect the system. The power or rpm value requirement at the output is fixed for chain drive power transmission system.

### Rope Drive Power Transmission System

Power transmission using ropes is one of most commonly used method is machines (in which large power is needed to transfer with light weight mechanism) where power from motor or engine is transfer to the tires using set of rope and pulleys. Rope drives are mostly used in those applications where length between the primary mover and driving mechanism is very large and weight of rope drive done not affect the system. The power or rpm value requirement at the output is not fixed (slip will not affect system) for rope drive power transmission system.

### Belt Drive Power Transmission System

Power transmission using belts is one of most commonly used method in machines like lathe machine water pump where power from motor or engine is transfer to the tires using one or more belts and pulleys sets. Belt drives are mostly used in those applications where length between the primary mover and driving mechanism is very large and power or rpm value requirement at the output is not fixed (slip will not affect system). Belts used in belt drives are as follow
1. Flat Belts
2. V Belts

### Belt Drive Material Selection Procedure

One of the tasks in designing of any mechanical product is the selection of material for it. Material selection for the product is the most important task in designing of the product as the strength and density of the material will decide the dimensions and working parameters of the product. Material selection for any mechanical product consist of follow steps (Kenneth G. 2010)
1. Product Requirements
2. Material Selection Criteria
3. Available Material Analysis
4. Final Material Selection

### Product Requirements

Product requirements are based to the working of the product. They are those mechanical, physical and economical properties which are required for the effective working of the product. For the effective working of the belts following are the mechanical, physical and economical properties which are required (M. F. Ashby 2010).
1. Tensile Strength
2. Elastic Modulus
3. Fatigue Strength
4. Density
5. Cost

Tensile Strength
Tensile strength of belt material will help them to resist against the external load during operation. Higher the tensile strength of the material higher will be its ability to resist the external load George Murray (n.d).

Elastic Modulus
Elastic modulus of the belts material will help them to resist elongation in belt length under stress. Higher the elastic modulus of the belt material higher will be its ability to maintain its shape under stress (B. K. Agrawal 2007).

Fatigue Strength
Fatigue Strength of the belts material will help them to resist fatigue load during work. Fatigue loading is the cycling load which happen lathe machine usually during threading process. Higher the Fatigue Strength of the belt material higher will be its ability to resist Fatigue loading (M. F. Ashby 2010).

Density
Density of belt material means how much weight belt will have I a given dimensions of the belts. Lower the density of belt material lower will be the weight of the belt and higher the density of the belt material higher will be weight of the belt George Murray (n.d).

Cost
Cost of the belt material will show now much the belt power transmission will cost. . Lower the cost of belt material lower will be the cost of the power transmission and higher the cost of the belt material higher will be cost of power transmission (M. F. Ashby 2010).

### Material Selection Criteria

Material selection criteria for belts will involve giving priority to the material mechanical, physical and economical properties based on their requirements. For giving priority to material mechanical, physical and economical properties number out of 5 will be awarded to them for highest being 5 and lowest being zero. Following is the priorities giving to the material mechanical, physical and economical properties based on their requirements

1. Tensile Strength
Tensile strength of the belt material is the most important mechanical property required for effective performance of the belt. As it will define the maximum Tension a belt can take so this property will have 4.5 marks out of 5

2. Elastic Modulus
Elastic modulus is also very important as it high value will unsure that belt will not extend when load is applied on it. It also effect the maximum tension that can be applied on belt so it will have 4 marks out of 5

3. Fatigue Strength
Fatigue strength is also very important as it high value will unsure that belt will have long life under calculated loading condition. It also effect the working parameters that can be applied on belt so it will have 4 marks out of 5

4. Density
Density is also very important as its low value will unsure that belt will be light weight. It also effect the performance of belt so it will have 3 marks out of 5

5. Cost
Cost is also very important as its low value will unsure that belt will be cost effective. It also effect the overall cost of belt drive so it will have 3.5 marks out of 5

### Available Material Analysis

There are a lot of material that can be used for manufacturing of belts but out of those material following are the material which are mostly used worldwide.

 Material Tensile Strength Elongation % Fatigue Strength Density Cost Natural Rubber 27 600 Poor 0.93 Medium Styrene Buadiene Rubber 25 500 Satisfactory 0.94 Medium Polyamide 6 85 300 Satisfactory 113 Medium Polyamide 12 65 300 Satisfactory 102 Medium Kevlar 49 4100 2.8 Good 144 High Polyurethane 80 6 Good 105 High

### Final Material Selection

Final material selection will be done by giving material number between zero to five based on the availability of property present on that material. Those numbers when multiply with the number that material property got in selection criteria will get the total number for that property. Material that will have maximum number when total is made that material will be selected.

Table 7 Material Selection
 Material Tensile Strength Elongation % Fatigue Strength Density Cost Total Natural Rubber 13.5 12 12 9 10.5 57 Styrene Buadiene Rubber 11.25 14 14 10.5 12.25 62 Polyamide 6 15.75 14 14 10.5 12.25 66.5 Polyamide 12 13.5 12 12 6 10.5 54 Kevlar 49 20.25 18 18 6 15.75 78 Polyurethane 15.75 14 14 9 12.25 65

From the material selection process Kevlar 49 is
selected as the material for belt manufacturing.

### Belt Drive Designing Criteria

There are certain design criteria and standards on which the selections of the belt derive depends. Following is the four point criteria in which selection of belt depends IS: 2494-2017
1. Belt velocity
2. Belt contact arc
3. Belt tension
4. Belt working conditions

### Belt Velocity

Velocity with which belt moves, has a great effect on its selection because when belts moves over pulley it bears wear and tear. So greater the velocity with belts moves over the pulley, grater will be the wear and tear. Along with this there is certain some certain limit of velocity up to which belt can transfer power effectively and after the system does not work effectively.

### Belt Contact Arc

Belt contact arm with the smaller pulley has great influence on its selection because more the contact arc of the belt more of its area will face friction effects. Greater the contact arc of belt more effectively it can transmit power from one pulley to another

### Belt Tension

Tension in belt produce stresses in belts and stress produce in belts directly influence the belt life. So greater the tension in belt more will be stresses and less will be the life of the belt.

### Working Condition

Belt working condition means the atmosphere in which the belts operated. Temperature and humidity or moisture content is the main factor which influences belt selection. At elevated temperature the belt show some elongation due to which its grip on pulley decrease and a result the effectiveness of the system decreases.

### Belt and Pulley Dimensions

According to the IS 2494-1974 following are the dimensions of the belt and pulley for V belts based on the power they needed to transfer.

### Disk and Drum Brake

In most of mechanically moving item there is a mechanism installed whose main purpose in to stop the motion of that item when required. This mechanism is called braking mechanism. They are design to stop the motion of vehicle (type of motion of the vehicle does not matter) and it does so by producing friction between its components. Friction produce by the braking system uses the energy present in moving body resulting in decrease in speed of vehicle and finally stop of motion of body. Kinetic energy of vehicle which is utilized by the friction of brake is converted into heat and that heat is them move to the surrounding atmosphere.

### Types of Brake

There are two basic types of braking system
1. Disk Brake
2. Drum Brake

### Disk Brake

Disk brake system consists of two main parts, one is called rotor and other is called pad. Working of disk is starts when operator applies pressure on hydraulic pad of which transfer pressure to the pad of the brake. Pad of the braking system convert that pressure into force applied on the rotor. Rotor is attached to the moving part or part responsible to providing motion to the system. Force applied on rotor force it to stop resulting in the decrease or stoppage of the body (R.S. Khurmi & J.K. Gupta 2005).

### Advantages of Disk Brake

1. Simple design of disk brake means easy to install and removal

2. Less no of parts of disk brake means it is easy to manufacture and so it is cost effective

3. Less parts and simple design means easy inspection

4. Less weight and parts make it an effective system

5. Disk brake is completely self-adjusting system.

### Drum Brake

Drum brake consist of two main components one is the drum and other is the set of shoes. Working of the drum brake system starts when the operator apply load on the pair of shoes through hydraulic or wire system. Force provided to the shoes is used by them against the walls of the drum which is attached to the moving part or part responsible to providing motion to the system. Force applied on drum force it to stop resulting in the decrease or stoppage of the body (R.S. Khurmi & J.K. Gupta 2005).

### Belt Drive Power Transmission

Power transfer from primary mover to any mechanism which gives some useful outcome is one of the most common works done in mechanically engineered products. In order to transfer power form primary mover to any mechanism products like gears, belts, rope and chains are used. These products transfer power from one place to another and also can provide mechanical advantages in terms of increase speed or torque at output.

From the above mention products belts are one which can be used to transfer power from primary mover to mechanism when primary mover and mechanism is far apart and light weight power transfer mechanism is required. Belts have the ability to effectively transfer power even when primary power and mechanism are even meters away from each other.

### Belt Power Transfer System

Belt power transfer mechanism consists of at least two pulleys (from which one is attached to shaft of primary mover and second is attached to input shaft of mechanism) and one belt (which stretches between two pulleys).  In belt power transfer system there are three types of belts which are used, one is flat belt drive, second is V-belt drive and third is round belt drive (R.S. Khurmi & J.K. Gupta 2005).

### V-Belt Drive

As their name says v belts has cross section shape like the English alpha bat V and they are mostly used in those application where the centre to centre distance between primary mover and pulley is small. V belt drives has special pulley system on which they are installed for operations and shape of these belts are the same as that of the v belt. The angle made by the v shape is always between 30 to 40 degrees. Operation range in terms of speed of v belts is in between 300 to 1200 meter per min. The pulley of the v belts is also shaped like English alpha bat V and this special shape helps the system to grip the belt properly and increase the friction between belt and pulley (R.S. Khurmi & J.K. Gupta 2005).

### Advantages of V Belt Drive

1. V belts derives are compact in size as they are designed to transfer high power in small distances.

2. The slip between the pulley and belt is almost zero due to which the belt drive for this type is positive

3. There is joint problem in v belts as they are manufactures in special way to make them endless and this make v belt drive smooth

4. V belts has very good life which is usually three to five years

5. V belts are easy to operate and maintain as they can removed and reinstalled easily

6. V belts provide power transfer at very low noise

7. V belts has the ability to absorb the shock of primary mover when machine is initially started

8. V belts can provide very high velocity ratio which is up to 10

9. V belts can be operated in any direction means in it does not matter where is the tight side of the belt.

## Disadvantages of V belt Drive

1. As they are design for compactness so they can never be used for long distance power transfer

2. These belts are not as durable as flat belts are

3. Pulley cost is more as compared to others types as they need a special grove for belt placement

4. There low ability to resist the creep limit their use from constant speed application and in timing devices

5. V belt life depends on the temperature under which it operates.

6. V belts has lower speed limit of  5 m/s and upper speed limit of 50 m/s

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