Lesson Notes By Weeks and Term - Junior Secondary School 2

SUBJECT:  BASIC TECHNOLOGY       

CLASS:  JSS2

DATE:

TERM: 3RD TERM

REFERENCE MATERIALS 

• MELROSE, Basic Science and Technology Book 2
• NERDC, Basic Technology for JSS, Book 2

WEEK THREE

TOPIC: BELT AND CHAIN DRIVES (CONTD.)

CONTENT

• Advantages and Disadvantages of Belt and Chain drives
• Uses of Belt and Chain Drives

ADVANTAGES OF BELT DRIVES

1. Belt drives are simple and economical
2. They don’t need parallel shafts
3. Noise and vibration are damped out
4. They are lubrication-free
5. They are provided with overload and Jam protection
6. They are highly efficient in use (up to 98%, usually 95%)

DISADVANTAGES

1. They can slip or stretch which makes the angular velocity ratio not necessarily constant
2. Heat buildup occurs
3. Operating temperatures are usually restricted to -35 t0 85oc
4. Adjustment of center distance or use of an idler pulley is necessary for wearing and stretching of belt drive compensation

ADVANTAGES OF CHAIN DRIVES

1. Chain drives do not slip or creep, and so are more efficient than belt drives
2. They are more compact than belt drives
3. They are often easier to install than belt drives
4. They do not deteriorate due to oil, grease, sunlight, or age
5. Operate effectively at high temperatures
6. Can withstand abrasive conditions
7. Can operate in wet conditions
8. Can be used on reversing drives

DISADVANTAGES

1. The production cost of chains is relatively high
2. Require more precise alignment than belt drives
3. Typically require frequent lubrication
4. Are noisy and can cause vibrations
5. Cannot be used in applications where the drive must slip
6. Do not have the load capacity or service life of gear drives

EVALUATION QUESTION

1    State five advantages and four disadvantages of Belt drives

2. Mention five advantages and six disadvantages of Chain drives

USES OF BELT DRIVES

1. Belt drives are used for smooth transmission of power between shafts at a considerable distance
2. They are used to track relative movement
3. The sewing machine makes efficient use of synchronous timing belts
4. Automobiles also make use of the timing belt/ cam belt system
5. The treadmill is also a great example of a belt driven mechanism

USES OF CHAIN DRIVES

1. Chain drives are used inrigging and moving heavy materials
2. They are used in hydraulic lift truck operation
3. They are used in increasing or decreasing a driver’s output speed by altering gear ratios between the driver and the sprocket being driven
4. They also used as overhead hoists
5. They are also used in operating conveyer belts

Differences between Belt Drives and Chain Drives

Belt Drives                    Chain Drives

1. Belt drives are made up of polymers        Chain drives are made of alloys 
2. They can operate under high speed         Chain drives can operate under high load conditions
3. They do not need lubrication            They need lubrication 
4. They need dry condition to work properly    They can work in high temperature and

                moist condition 

1. They make nonoise                                       They make noise
2. They are powered by a belt                           They are powered by a chain loop

Similarities

Both belt drives and chain drives are methods to transfer power and objects within a machine

EVALUATION QUESTION

1    State five (5) uses of Belt drives

2. Mention five (5) uses of Chain drives

GENERAL EVALUATION

1. State five(5) advantages of belt drives and five(5) disadvantages of chain drives

1. Mention five (5) uses each of belt and chain drives

READING ASSIGNMENT

Read about Gears (NERDC Basic Tech. for JSS3 page 154-156)

WEEKEND ASSIGNMENT

1. ………. can be used as overhead hoist (a) Belt drives (b) Chain drives (c) Magnetic drives (d) Electrical drives
2. The sewing machine makes efficient use of ……. (a) The flat belt (b) synchronous timing belts (c) cog belts (d) V-belt
3. …………. are used for smooth transmission of power between shafts at a considerable distance (a) Belt drives (b) Chain drives (c) Magnetic drives

(d) Electrical drives 

4.     Which of the following require frequent lubrication?  (a) Series drives (b) Parallel drives   (c) Belt drives    (d) Chain drives
5. Automobiles also make use of the (a) timing belt/cam belt system (b)   Series/parallel system (c) current/potential system (d) hydraulic/lift system

THEORY

1. State five (5) uses/applications of (a) Belt drives (b) Chain drives
2.     (a) Mention two (2) differences between belt and chain drives (b) State two(2)

Similarities between belt and chain drives