JSS 3. TOPIC 10: AIR-MECHANICAL PROPERTIES.

With air all around us, it can be harnessed for the development of technological tools and air transportation. Air content of gases, mainly nitrogen and oxygen eg

                                                           Mechanical properties of air

The mechanical properties of air weight, atmospheric pressure and the relationship between pressure, temperature and speed.

Weight: For the fact that we cannot see air it does not mean that air does not have weight. That air weighs something can be experimented with an empty balloon. If filled with air, the balloons original weight increases.

Atmospheric Pressure: This is the same thing as air pressure. This pressure is defined as the force per unit area, written mathematically as P = F/A. eg siphoning, vacuum pump, vapour pressure (tumbler filled with water) etc. the instrument used in measuring air pressure is called barometer.

Relationship Between Air Pressure and Speed: It has been proven that air flow is generated as a result of difference in pressure. For instance, breeze, wind, hurricane etc can  move objects, depending the direction of flow.

When air flows it produces several effects such lift, drag, sound etc. this results because air pressure increases with the speed of flow. However, it should be noted that air pressure increases twice as speed.ie while speed may be 2kph,  air pressure is already 4kph.

No wonder air pressure us applied to the flying of kites, p1ropelling of airplanes and operation of wind mills etc.

                                                       Effects of air flow on Aerofoil

Streamlined – shaped objects are called airfoils, eg kites, birds, airplanes, rockets etc. Usually streams of air travel longer distance above the surface of the aerofoil because of its shape than the surface below. Thus, air travels faster above than below. The faster air travels, the less the sideways pressure it exerts. For this reason, low pressure is developed at the top of the face of the aerofoil than below.

It is by this principle that airfoils experience a lift, and that’s why airplanes gain weight in the air. eg

                                                           Extremes of Air flow

There are two extremes of air flow, namely:

Laminar air flow: This is slow speed flow of air flow. It is also called streamline flow.

 Turbulent flow: This is the high speed flow of air. Sometimes it is a forced air. Eg see diagram above.

                                                    Pneumatics and Hydraulic Devices

Pneumatics is a device that makes use of compressed air to do useful work. Such devices make use of cylinders to produce force or linear motion at changing speeds. Generally, both pneumatics and hydraulic devices are used for the following purposes.

For pushing

For pulling and

For lifting

                                                                    Pneumatic Devices

Hand Pump: These are of different types, they are used to inflate tyres, balloons, balls etc. the hand pump has a plunger which sucks in and pushes out air at the barrel cylinder.

Compressor Machine: This is used by vulcanizers, while the modified one is used as a spray machine on several products.

 Hydraulic: These are devices that make use of liquids to push, pull and lift materials.

                                                                      Hydraulic Devices

Hydraulic Jack: This jack has two main parts – the handle and the lever which is connected by two pistons which raises the lever that raises the load (car).

Suction and Double acting pumps: These are locally manually operated pumps used for lifting liquids and gases from reservoirs. e.g.

  Garden Sprinkler: The sprinkler is used in water gardens. It has jets which issues out water at a given speed about an axis.e.g.

Water Wheel: This wheel can be used to create mechanical energy in grinding, milling and electric power machines.

Others: (a) Reaction turbine (at dams) and (b) Brakes – used in cars to control motion.

Class Work.

What are pneumatics?

What is hydraulic?

Name 2 devices that use pneumatics

Name 4 devices that make use of hydraulic

Assignment:

Using the sketches shown on your text book sketch the following

Hand pump

Suction and double acting pump

Garden sprinkler

Water wheel

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JSS 3. TOPIC 9: FLOORS AND ROOFS.

Floor may be defined as a continuous horizontal platform constructed between walls to support any load- both human and materials.
                                                            Types of Floors
There are basically three types of floors, namely:
(i). Solid(basement) Floors: This is a type of floor that consists of concrete but may be finished with a smooth surface like cement screed, laid with tiles or terrazo. Eg.

(ii).Suspended Floors: This is a kind of floor that consists of wood, which are nailed over solid lengths of timber. The ends  are usually supported by the main walls of the building. The solid timber that supports this type of floor a re known as joists. Eg.



(iii). Upper Reinforced Floors: These are solid floors containing reinforcements like sand, concrete, cement, water, and steel. These are the type of floors used in decking storey buildings.

Floor may be defined as a continuous horizontal platform constructed between walls to support any load- both human and materials.
                                

                                                          Roofs
Roof is defined as a covering over buildings that may serve the following purposes:
 (i). protect the occupants from any harsh weather;
(ii). beautify a building;
(iii). to secure buildings.
                                                          Materials used for making Roof
(i). Clay tiles (ceramics).
(ii). Corrugated iron sheets.
(iii). Asbestos sheets
(iv). Aluminum span sheets
(v). Plastic sheets (usually for light)
(vi). Palm fronds.

                                               Types of Roofs
(i). Shed roof or Lean-to roof: These are small-sized roofs used for kiosks, shops and boys quarters. Some are  constructed resting on walls, hence they are referred to as lean-to. Eg.

(ii). Gable or Collar roof: This is a type of roof that contains two sloping faces with the walls rising into the r oof at two opposite ends. It is the commonest type of roof in Nigeria. Eg.

(iii).Hipped roof: This type of roof slopes down all four sides. The walls also rises into the roof on all four sides. This roof is steeper than the gable roofs. Eg.

(iv). Butterfly roof: This type of roof is used for buildings with large spans. It is sometimes called double shed ro9of, since it looks almost like one, but only bigger.eg.

(v). Combination roof: These are asymmetrical roofs used for most school buildings where one face slopes steeper than the other. The greater slope covers the rooms while the shorter slope covers the walkway. Eg.

(vi). Monitor roof: This is a type of roof used for factories and warehouses. It usually contains two surfaces at different levels, where light is let into the building.eg.

(vii). Half-monitor roof: This roof looks like the monitor roof. The only difference is that in this  type of roof, one surface is lowered than the other. Openings are fixed where light is also let into the building in this type of roof. Eg.

(viii). Arched roof: This type of roof has a rounded or curved  shape like an arc. It is also used for buildings with large spans, such as for filling stations, warehouses, etc. eg.

(ix). Flat roof: These are roofs made of concrete castings (like slabs). Drainages are provided through plastic pipes from the roof.

(x). Mansard roof: These are roofs that contain double slopes on all four sides. This type of roof is gradually being outdated.  

Examples of Roofs:

Arc Roof.

Class Work.
(i). define a roof.
(ii). list four materials used for making roofs.
(iii). list five types of roofs.


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JSS 3. TOPIC 8:BUILDING CONSTRUCTION-Windows, doors. Types and uses

Definition:
Door can be defined as openings into buildings. They serve the following purposes:
(i). doors provide security against burglary.
(II). it provides a means of access into the building.
(iii). It facilitates ventilation.
(iv). It also admits a measure of light into the building.
                                                                   Types of Doors
Doors are generally classified into two groups, namely exterior and interior doors.
(i). Exterior doors:  These are doors that are put on the outer part of a building. Some are the doors at the entrances of buildings or at the outer part of the kitchen or garage. They are usually stronger.
(ii). Interior doors:  As the name implies, these are the types of doors that are placed inside the building. They include the bathroom door, bedroom doors and kitchen doors.
For these classes of doors mentioned, they may be one of the  following types:

1. Casement door: These doors may be used for both exterior and interior purpose, depending on the taste of the builder. It contains different casement designs. e.g.

2. Louvered door: This is door made of louvers. It is for internal use only.

3. Sliding glass door: These doors are used in offices, shopping  complexes and shops. It slides side ways to allow for passage. It is an exterior door.

4. Flush door: These are internal doors used in toilets, bedrooms and in the kitchen. It is made of flush and plywood.

5. French doors: These are sophisticated, hardened doors, finished with French polish, used for external purpose only.

6. Revolving door: These are doors used in most public buildings like stadia, supermarkets and banks. It is often a glass door.

7. Roller shutter: This is a metal, wide door used in big shops and warehouses or garages. It can be rolled up and down.

8.  Panel door: This door can serve both interior and exterior purpose. The number of panels in this type of door gives it its complete and appropriate name. For instance, some are 5-panelled door, 6 or 7-panelled door.

9. Ledged braced and battened door:  These doors do open both sides at the opening of buildings. They are used on wider openings at garages, shops and stores.

10. Headed doors: These are doors mostly used on worship buildings. They may be semi-circle at the top, tudor, gothic or segmental in shape.

NOTE. To see an image of these types of doors, kindly google them.

                                                                                 Windows.

Windows may be defined as openings in the wall of buildings that serves the following purposes:
(i).allows adequate flow of air into the building (ventilation).
(ii). allows light into the building.
(iii). gives additional beauty to the building.
(iv). It is also a means of viewing the outside world.
Windows are both for interior and exterior purposes.

                                                                    Types of Windows
(i). Casement window: This is a wooden window built just like the casement door.

(ii). Louvered window: As the name implies, this window is made of glass, either transparent or translucent.

(iii).Sliding glass window: This is the most common type of window in Nigeria in recent times. It allows for much ventilation and light, as a part of it can slide sideways.

(iv). Bull’s eye window: This type of window is used for viewing the environment and outside world from a vessel. It is made of a circular  glass.

(v).Dormer window: This is a window attached to a chimney so that smoke can escape from the roof of colonial buildings in the past. It is often made of wood.

(vi). Semi circular or segmental window: These are windows used in religious buildings. The upper part forms an arc. It is usually constructed with wood or glass.

It should be noted that the first three types of windows are commonly used in Nigeria while the other three are special-purpose windows.

Class Work

(i). state 3 purpose of a window in a building.
(ii). list 4 types of windows and their uses.
                                            ASSIGNMENT
Sketch the following types of windows:
Bull’s eye window, dormer window, casement window, sliding door window, louvered window and semi-circular headed window.

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JSS 3. After Mid-Term.TOPIC7: MOTION IN ENGINEERING SYSTEMS.

Definition:
Motion can be defined as the movement of a body (object) from one point to another with the application of force.

                                                                 Types of Motion

At this level, the two types of motion to be considered are Linear Motion and Rotary Motion.

Linear Motion: This is the motion of a body moving in a straight line. For instance, a push-pull link mechanism is a simple machine that operates with linear motion. E.g.

 Rotary Motion: This is motion of a body moving in a circular form. Examples of circular motion is the rotation of a fan, vehicle tyres, the handle of the clock, etc. e.g.

                                                             Transmission of Motion

For any engine to function, motion must be transmitted from one part of the engine to other parts. For instance, in a car, motion is often transmitted from the car engine to the wheels. This is possible because of the motion transmission system in the car.
The transmission system in a car includes the gearbox and the clutch.

Function of the Clutch: The function of the clutch is to disconnect two shafts running at different speeds, that is, the engine crankshaft and the gearbox shaft.

                                                             Types of Car Engines

1.Front- Engine Rear-Wheel Drive: This is an engine that consists of a clutch, a gear box, a propeller shaft and a rear axle. Most cars in Nigeria operate on this type of engine.

2. Front-Engine Front Wheel Drive: In this type of engine, every other parts mentioned in 1 above is present except for the propeller shaft. Transmission is directly from the gearbox to the rotating wheels.

3. Rear-Engine Rear-Wheel Drive: In this type of engine, there is no propeller shaft also. The clutch, engine, gearbox are all engineered at the back of the car. Example is Volkswagen cars.

4. Front-Engine 4-Wheel Drive: This is a more recent technological advancement in the engineering of cars. There is no propeller shaft and most times no mechanical gearbox. The gear system is a hydraulic system. This car contains of the brake and the accelerator only, with all 4 wheels connected to the gear box.

e.g. Mechanical Gear System and Hydraulic Gear System.

                                             Control of Rotary Motion-Brakes
Brakes are meant to bring bicycles and cars in motion to a stop. Kinetic energy in a moving object is absorbed by the brake. This produces heat on the brake as kinetic energy is converted into potential energy. As the brake absorbs heat, the vehicle slows down until it finally comes to a stop.

                                                      How Brakes Work
There are different types of brakes. However, the principle of how the brake works is the use of friction. If the brake in a car or bicycle is pressed against the rotating drum or disc or wheel, the resulting friction between the pad and the drum or wheel slows down the rotating wheels, until they eventually come to a stop. E.g.

A Bicycle Brake.

A Disc Brake.

  

                                   Conversion of Rotary Motion to Linear Motion

In some machines, it is necessary for a change from one form of motion to another along it’s line of operation. For instance, a sewing machine will need to convert linear motion from the moving pedal to rotary motion at the wheel and finally to linear motion again at the needle.

The piston-crank mechanism of a car engine is another example of converting rotary motion at one point of an engine to rotary motion at another point of the same engine. (teacher will explain more). E.g.

Other examples of machines involved in converting one form of energy to another are;
Screw jack, Rack and piston steering system, Crankshaft and cylinder, Metalwork table vice, Woodworker’s vice, Pipe vice, G-clamp, etc. 

Class Work.

(i) define motion
ii. list the two types of motions
iii. explain how to convert one form of motion to another
iv. explain machines that make use of motions.

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JSS 1. TOPIC 9. PROCESSING OF MATERIALS- metals

 Metal is processed from a natural solid mineral found beneath the earth called iron-ore. In its natural state iron-ore contains a lot of impurities which is removed through smelting.

Blast furnace: The blast furnace is a smelting (heating or burning) plant used for changing iron – ore into pig –iron. To smelt iron – ore in the blast furnace, other chemicals like coke (which serves as fuel) and limestone (which removes impurities) are added to the iron – ore so that most of the impurities may be removed. Eg.

Pig – iron:  Pig –iron is derived from iro n- ore. It is the product,  derived from the blast furnace. Further processing of pig – iron gives birth to steel. The furnace used for this purpose is called “Bessemer Converter”.eg.

Bessemer Converter: This is the furnace used for smelting pig – iron into steel by further burning off of impurities in the right percentage. Since steel are categorized into three categories, the Bessemer converter is used for this purpose. Eg.

Other Methods: Other furnaces used for smelting iron – ore into steel are:

The basic oxygen furnace:

The electric furnace :  for producing cast iron products

The open-hearth furnace:  is one of a number of kinds of furnace where excess carbon and other impurities are burnt out of pig iron to produce steel

This three methods listed above make use of iron oxide at high temperature (1600⁰   C)  to remove impurity.

Bessemer Converter

Electric Arc Furnace

                                                               Classification of Steel

Steel is produced from pig – iron. However  pig – iron contains 3 to 5% of carbon. This percentage of carbon is too high for any steel since the metal will be too weak for any engineering work.

The three basic elements of steel are ferrite (pure iron), cementite and pearlite.

                                                       Classes of steel

Low Carbon Steel: The content of  carbon In a low carbon steel is about 0.05% - 0.3%. it contains mostly ferrite. It has low tensile strength and is used for car bodies and light structures.

Medium Carbon Steel: This class of steel mainly contains cementite. This property makes medium carbon steel hard and ad of great strength. It is mainly used in making lighter springs and power transmission devices. The carbon con tent is about 0.3% - 0.6%.

High Carbon Steel: This is the steel that contains mostly pearlite. It is usually very hard and it is used for making cutting tools like files, punches, chisels, dyes, etc.

Class Work

What is iron – ore?

How is pig – iron produces from iron – ore

What is the bessemer converter used for?

ASSIGNMENT

Draw the following, fully labeled

Blast furnace

Bessemer converter

Open – hearth furnace 

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JSS 1. TOPIC 8: Veneers and Boards

Veneer: A veneer is a thin sheet of wood used in the manufacture of boards. It is usually sliced from log.

                                          Methods of producing veneers

(i).Slicing Method: The method of using slicing blade to cut off thin leaves from a particular log. Eg

(ii). Reeling method: This is the method of peeling log in a continuous rotary fashion mounted on a machine. The log is usually soften through steaming first. Eg

(iii).Eccentric or Sawing Method: In this method the log is cut into quarters. It is this quarter that is then sliced to veneer. Eg

                                                    Manufactured Boards
Manufactured boards are man- made boards made from multiple veneers, using adhesives, sawdust, etc. In Nigeria, the size of common boards is 2440 by 1220mm.

                                            Types of Manufactured Boards
(i). Plywood: These are boards made from multiple veneers glued together with adhesives. The veneers are usually arranged so that the grains criss-cross each other. Eg.

(ii). Block boards: This board looks like a flush door. The inner part of this board contains a strip of timbers forming the core and covered with two layers of veneers. Eg

(iii). Laminated boards: These are boards used for high class veneer furniture. It contains a thinner strip of timber forming the core and glued together. The surface is glossy. Eg

(iv). Particle boards: These are boards made from wood chippings glued together and compressed under heat. It is used for paneling and kitchen furniture work.eg

(v). Hard boards: These boards are made from the combination of wood waste (sawdust in Nigeria) and bonded together under high temperature and compression.

                                         Advantages of Manufactured Boards
(i). Using a manufactured board produces various large flat sheets of timber.
(ii). Manufactured boards do not check nor warp.
(iii). Manufactured boards can be worked on easily.

A sample of Veneer

Different Types of Boards.

Class Work.

 (i) What is a veneer?

(ii) Explain 3 methods used for producing  veneers.

(iii).Write short notes on how to produce 3 types of manufactured boards.

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JSS 2.After Mid Term.TOPIC 7: UNDERSTANDING BUILDING TERMINOLOGIES.

Most terminologies used in building construction vary with different meaning and application. Below are some of these terminologies.

(i).Foundation: This is the lower part of the building that transfers the load of the building to the soil below without cracking.
(ii).Architect: This is the professional that draws the building plan(blueprint).
(iii). Quantity surveyor: This is a professional that quantifies the amount of money, material, labour and workmanship that could finish a particular project or building.
(iv). Builder: This is the engineer that erects the building according to   plan of the building.
(v). Statutory personnel: This is a government official who makes sure that any building meets local, state or national standard. If it does not meet the standard, such buildings are usually demolished.
(vi). Structural engineers: This is a professional that determines and specifies the strength and types of building materials like cement ratio, number of steel, etc, for any construction.  
(vii). Landscaping: This is the process of making the surrounding of a building more beautiful by planting trees and flowers and the general topography of the land.
(viii). Timbering: This is the practice of using timber to support the vertical  sides of a trench,  so as to avoid collapse.
(ix). Foundation footing: This is the wide base that carries the walls, pillars or columns of any building.

(xi).Excavation: This is the digging up of earth to a required dept, width and length. This can be done both manually and mechanically. 
(xii). Soil: Soil can be defined as any loose material deposit, such as gravel, sand, clay or the mixture of all these other materials listed. There are two types of soil namely, cohesive and non-cohesive.
(a). Cohesive soil: This is the type of soil that is sticky and closely bonded together. Example of such soil is mud and clay soil.
(b).Non-cohesive soil: This type of soil is loose in nature. It includes sharp sand or loamy soil.
(xiii).DPC: The acronym DPC means damp proof course. This is the layer that prevents the penetration of moisture or water into the building from underground. Materials that can be used for DPC include waterproof, polythene and mackintosh.
 (xiv).Lintel: This is the material put over an opening in a wall to enable the wall to continue above  the opening.
(xv).Rendering: This is the method of spraying mortar or concrete on the surface of wall, such that the wall then looks coarse (rough).
 (xvi).Bonding: This is the  type of arrangement used when laying blocks to ensure that no vertical joints occurs.
(xvii).Slab: This is a horizontal part of a building, made from concrete and supported by columns or walls.
(xviii).Batching: This is the process of measuring concrete either by volume or mass.
(xix). Curing: This is the process of maintaining a satisfactory moisture condition for a freshly placed concrete.

Class Work

State the difference between the following professionals:
1.architect
2.quantity surveyor
3.statutory personnel and
4.structural engineer.

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JSS 1..After Mid Term:TOPIC 7: WOOD DEFECTS AND PRESERVATION

DEFINITION

Wood preservation is the process of adding chemical to wood so as to prevent termites, insects, weevils and fungi from attacking the wood. These chemicals are called preservatives. It can be applied to wood through spraying or brushing.

Examples of wood preservatives are creosote, coal- tar,  solignum, chlorinatephenol, paints, etc.

                                                Defects in Wood

Defects are faults or irregularities in wood caused either naturally or during processing of the wood which reduces the value or quality of the timber.
(1). Natural defects: These are defects which occur during the growth of a tree.
They include the following:

(a).Knots: A knot is a defect that occurs at the branch of a tree. If a branch falls from a tree it may leave a knot hole on the tree eg

(b).Cross grain: This is the condition which occurs when the wood fibre is not aligned parallel t o the axis of the piece of wood. it is caused by the manner the tree grew. It gives plants low strength.

(c).Shakes: This is the complete separation of parts of a stem in a living tree. it occurs because of stress variation in the stem. There is the ring shake and the heart shake. Eg

(2) Artificial defects: This is also referred to as processing defects. It includes checks and warps.

(a) Checks: This is a defect which creates a separation of wood grain along the grain board. Eg

(b) Warps: Twists in timber are called warps.  They may be caused by improper seasoning procedure.

Examples on Images:

Class Work

What is wood preservation?

Explain 4 types of wood defects.



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