Belt and Chain Drive: Uses, Advantages and Disadvantages – JSS2 Basic Technology Lesson Note (Third Term)

Belt drives and chain drives are methods of transferring power from one shaft to another within a machine. A belt drive uses a loop of belt, usually made of rubber or other polymers. A chain drive uses a loop of metal chain, usually made of steel alloys.

Behavioural objectives

By the end of the lesson, students should be able to:

1. state the advantages and disadvantages of belt drives;
2. state the advantages and disadvantages of chain drives;
3. list the uses of belt drives and chain drives;
4. state the differences and the similarity between belt drives and chain drives.

What is a belt drive?

A belt drive is a power transmission system in which a belt loops round two or more pulleys to carry motion from one shaft to another.

What are the main parts of a belt drive?

• Driver pulley: the wheel fixed to the shaft that supplies the power, such as an engine or motor shaft.
• Driven pulley: the wheel fixed to the shaft that receives the power and does the work.
• Belt: the flexible loop that joins the two pulleys and carries the power.
• Idler pulley: an extra pulley used to adjust belt tightness.

What is a chain drive?

A chain drive is a power transmission system in which a metal chain loops round toothed wheels called sprockets to carry motion from one shaft to another.

What are the main parts of a chain drive?

• Driver sprocket: the toothed wheel on the shaft that supplies the power.
• Driven sprocket: the toothed wheel on the shaft that receives the power.
• Chain: a loop of linked metal parts whose links fit into the sprocket teeth.

• Example: the chain and sprockets on a bicycle or a motorcycle.

What are the advantages and disadvantages of belt drives?

Belt drives are cheap, quiet and need no oil, but they can slip and stretch.

What are the advantages of belt drives?

• Simple and economical: they are cheap to make, fit and replace.
• No parallel shafts needed: the shafts do not have to lie side by side.
• Quiet running: noise and vibration are damped out by the belt.
• No lubrication: they do not need oil or grease.
• Overload and jam protection: the belt slips if the load becomes too great, which protects the machine.
• High efficiency: up to 98% in use, and usually about 95%.

What are the disadvantages of belt drives?

• Slip and stretch: the speed ratio between the shafts may not stay constant.
• Heat build-up: the belt becomes warm as it works.
• Limited temperature range: operating temperatures are usually restricted to -35 °C to 85 °C.
• Adjustment needed: the centre distance must be adjusted, or an idler pulley used, to make up for wear and stretching of the belt.

What are the advantages and disadvantages of chain drives?

Chain drives do not slip and work well in tough conditions, but they cost more, need oil and are noisy.

What are the advantages of chain drives?

• No slip or creep: they are therefore more efficient than belt drives.
• Compact: they take up less space than belt drives.
• Easy to install: they are often easier to fit than belt drives.
• Long-lasting material: they do not deteriorate because of oil, grease, sunlight or age.
• High temperatures: they operate effectively where it is very hot.
• Abrasive conditions: they can withstand dust and grit.
• Wet conditions: they can operate in moist places.
• Reversing drives: they can be used where the direction of motion changes.

What are the disadvantages of chain drives?

• High cost: the production cost of chains is relatively high.
• Precise alignment: the sprockets must line up more exactly than belt pulleys.
• Frequent lubrication: they typically need oiling often.
• Noise and vibration: they are noisy and can cause vibrations.
• No slipping: they cannot be used where the drive must slip.
• Lower capacity than gears: they do not have the load capacity or service life of gear drives.

What are the uses of belt drives and chain drives?

Belt drives are used where smooth, quiet power transfer is needed, and chain drives are used where heavy loads must be moved.

What are the uses of belt drives?

• Power over a distance: they give smooth transmission of power between shafts that are far apart.
• Timed movement: synchronous timing belts keep the movement of two shafts in step.
• Sewing machine: it makes efficient use of synchronous timing belts.
• Automobile: the engine uses a timing belt (cam belt) system.
• Treadmill: it is a good example of a belt-driven mechanism.

What are the uses of chain drives?

• Rigging: they are used in rigging and moving heavy materials.
• Hydraulic lift trucks: they are used in lift truck operation.
• Speed change: using sprockets of different sizes increases or decreases the output speed of the driver.
• Overhead hoists: they lift heavy loads from above.
• Conveyors: they are used in operating conveyor belts.
• Bicycles and motorcycles: they carry power from the pedals or engine to the rear wheel.

What are the differences between belt drives and chain drives?

A belt drive carries power with a flexible belt on smooth pulleys. A chain drive carries power with a metal chain on toothed sprockets.

What do belt drives and chain drives have in common?

Both belt drives and chain drives transfer power from one shaft to another using a loop that runs round two or more wheels.

Evaluation

1. State five advantages and four disadvantages of belt drives.
2. Mention five advantages and six disadvantages of chain drives.
3. State five uses of belt drives.
4. Mention five uses of chain drives.
5. State three differences between belt drives and chain drives.

Assignment

Draw a table with two columns headed “Belt drive” and “Chain drive”. Write three advantages and two disadvantages of each, and name one use of each.