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Mechanical Drives- Belt, Chain, Gear | Advantages and Disadvantages

Mechanical Drives- Belt, Chain, Gear | Advantages and Disadvantages 

INTRODUCTION :
Energy is required to drive the machines and equipments for variety of applications. Available energy/power is required to be transmitted to get desired motion and work. When the power is transmitted from input to output using mechanical elements is known as mechanical power transmission. Mechanical elements like friction disc, various type of belts, rope, chain, gears, couplings etc. are used for power transmission. 

BELT DRIVE : 
To transmit power from one shaft to another, pulleys are mounted on the two shafts. The pulleys are then connected by an endless belt passing over the pulleys. The connecting belt is kept in tension so that motion of one pulley is transferred to the other without slip. The speed of the driven shaft can be varied by varying the diameter of the two pulleys.

Belt Drive
Belt Drive 
Advantages and Disadvantages of belt drives :
  1. Made from flexible material, it can be used for the shafts whose axes are note parallel. 
  2. Initial cost is low.
  3. Lubricant is not required. 
  4. Noise is relatively less.
  5. It is flexible member, it slips or break during overload and safeguards the machine. 
Disadvantages Of Belt Drive;
  1. Drive is not positive as the belt slip over the pulleys.  
  2. Oqupies relatively more space. 
  3. Speed ration can not be maintained because of slipping of belt.
  4. Adjust the tension in the belt is require time to time.
  5. Life is relatively low
ROPE DRIVE : 
When the center distance between the driver and driven shaft is very large and higher power is required to be transmitted, rope drives are used. Here instead of belt, wire rope is used. Appropriate size and number of grooves are provided on the pulley rim. e.g elevator/lift, overhead crane, hoist, rope way etc.
Rope Drive Example
Rope Drive Example
Advantages Of Rope Drive:
  1. Large power can be transmitted by using no. of ropes.
  2. Easy and simple maintenance.
  3. More than one drive can be accommodated from single pulley.
  4. Silent drive.
  5. Because of wedging action due to groove, the higher coefficient of friction compared to flat belt drive.
  6. Due to flexibility in the rope little misalignment in the drive is permissible.
Disadvantages of Rope Drive:
  • Power loss due to slip. 
  • Oqupies larger space.
  • Constant speed ratio can not be maintained.
  • Adjustment in center distance is always necessary. 
  • Wear rates for the wire rope pulleys is higher
  • Initial cost is relatively higher.
CHAIN DRIVE :
The chain drive consist of three elements – driving sprocket, driven sprocket and endless chain wrapped around the sprocket as shown in fig. Pin joint contains, pin, bush and roller to minimize the friction and such chains are known as roller bush chain. The chain drive is positive drive where there is no slip & constant velocity ratio can be maintained. Chain drive used in bicycle, motorbike, printing machine, textile machine etc.
Chain Drive Mechanical drives
Chain Drive Mechanical drives 
Advantages of Chain drive;
  1. Positive drive as there is no slip, hence constant velocity ratio. 
  2. Oqupies less space compared to belt drive.
  3. Life is more compared to belt drive.
  4. Used for large center distance.
  5. Transmission efficiency is larger than belt drive.
Disadvantages Of Chain Drive:
  1. Noisy compared to belt drive.
  2. Initial cost is higher compared to belt drive
  3. Initial cost is higher compared to belt drive
  4. Adjustment in the center distance is necessary.
  5. Maintenance cost is higher & complex compared to belt drive.
GEAR DRIVE :
 In gear drive no. of teeth are cut on both the blanks of the gear wheel which mesh with each other. The projections on one disc and recesses on other disc are made to mesh with each other to avoid slipping.

See also: Types Of Gears, Material Used For Gears,Design Specification and Application

Gear Drives :
Gear Drives :
Advantages and  disadvantages of gear drive :

Advantages Of Gear Drive:
  • Positive drive and has more efficiency than belt and rope drive. 
  • Operation of drive is simple and effective.
  • Life is more compared to other drives.
  • With one input speed, no. of output speeds can be obtained by using suitable gear drive. 
  • Safe and compact.
  • Constant velocity ration is obtained.
  • Using different type of gears, power can be transmitted between shafts whose axes are parallel, inclined or intersecting to each other.
Disadvantages of Gear Drive:
  1. If the tooth geometry of the gear is not properly maintained, the drive may get locked.
  2. Not preferred when very high speed transmission is required.
  3. If lubrication arrangement is not provided, it may produce noise.  

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