Topics in Basic Technology
Definitions of technology and their explanations Examples of technology Forms of technology explained with their differences Types of chain drive Types of belt drive Types of Ceramics Advantages and Disadvantages of Chain Drives Len Academy Questions for Basic Technology JSS3, 2nd Term Len Academy Basic Technology Questions, JSS3 Belt and Pulley Drives: Types of belt in belt drives Refrigerator as an electromechanical device, its parts and operations What is chain drive? Classification of chain drive What are Belt Drives? Advantages and Disadvantages of Belt Drives Type of Lines in Technical Drawings Len Academy questions for Basic Technology, JSS2, 2nd Term Len Academy questions for Basic Technology JSS2, 2nd Term, Part 2 What is Maintenance? Types of Maintenance Hardwood and Softwood - Characteristics and Examples What are Ceramics? Characteristics of CeramicsAcademic Questions in Basic Technology
The _____ functions to remove excess heat from the refrigerator.
A. Evaporator
B. Compressor
C. Condenser
D. Expansion Valve
E. Thermostat
F. Defrost System
A fluid or gas that runs through the compartments of a refrigerator is termed _____.
A. Water vapor
B. Liquid vapor
C. Frost
D. Refrigerant
E. Compressed water
F. Evaporated water
Current flows through a path called _____.
A. Electricity
B. Electric Route
C. Electrolysis
D. Transformer
E. High Tension
F. Electric Circuit
Googles are safety wears.
A. True
B. False
Which of the following is false concerning advanced ceramics?
A. They can be made from metallic oxides
B. They are very hard and durable
C. They are corrosion resistant
D. They are fired in the presence of oxygen
E. They are fired at a very high temperature of about 1700oC
F. They can be made from non-oxides such as carbides and borides
A thin continuous line is used for representing the followings except _____.
A. Intersections
B. Hatching lines
C. Long breaks
D. Diagonal line used to state plane surfaces
E. Leader lines
F. Back section lines
With regards to chain drives, the diagram above is a/an _____ chain.
A. Roller
B. Silent
C. Leaf
D. Flat-top
E. Detachable
F. Acceleration
A type of chain drive commonly used in bicycles is the _____ chain.
A. Roller
B. Silent
C. Leaf
D. Flat-top
E. Detachable
F. Acceleration
Belt drives are frictional drives that transmit mechanical energy on a dry surface from one shaft to another in a pulley like system.
Please read on the concept of belt and pulley drives here.
Below are the various type of belt drives that are used alongside a pulley system:
The open belt drive is used when two parallel shaft are needed to rotate in the same direction.
When the open belt drive is in used on a widely separated shaft, the upper side of the belt must be the slack side while the lower side becomes the tight side.
If we made the upper side the slack side (in a separated shaft), sagging will occur and the contact arc will be increased.
The cross belt drive is used when two parallel shafts are needed to rotate in the opposite direction.
However, due to the crossing nature of this belt, the belts rub against itself at a specific junction, resulting to its wearing off and eventual damage.
Please read on maintenance here.
In order to reduce the excessive wear caused from the meeting point of the crossed belts, the shafts should be placed at an optimum distance from each other, and should be operated at low speeds.
A fast and loose pulley drive is often used when the driven pulley is required to be started or stopped without creating an interference with the driving pulley. Meanwhile, understand that the pulley keyed to the machine shaft is referred to as the fast pulley.
You can attempt Len Academy examination questions for JSS2 here.
The stepped cone pulley, (step or cone pulley drive), or speed cone pulley drive is a belt drive known for its speed. It consists of pulleys with different diameters located adjacent one another.
The step cone pulley drive aid in changing the speed of the driven shaft, with the driving shaft moving at a constant speed. It is able to do this by shifting the belt from one part of the steps to another.
The speed cone pulley drives are often utilized in instances where the gear or speed of the driven shaft changes frequently. For this reason, they are utilized in lathe and milling machines.
You can read on chain drives here.
Understand that the same belt is used in the stepped cone pulley whenever there is a shift in various adjacent pulleys. This is achieved because the pulleys are of different diameters.
In its mechanism of action, a set of speed cone pulley is reversely mounted on the driven shaft. Also, the belt is appropriately wrapped around one of its pulleys pair. It is this shifting of belts from one pair of pulley to another that results in varying speeds of the driven shaft.
The jockey pulleys, sometimes referred to as the idler pulleys are present in an open belt drive. They are typically seen in the steering section of a machine. You can imagine them be idle pulleys that functions to increase the angle of contact.
Note: When the angle of contact is increased in the steering, there is a subsequent increase in the transmission power of the drive.
You can read on ceramics and types of ceramics here.
The idle pulley is always mounted on the slack side of the belt (with a smaller pulley). This is so because the arc of contact of the belt with the driven pulley is very small which inturn results into reduced tensions of the belt.
Functionally, the jockey pulley aid in creating more angles of contact around the belt such that the belt's tension is consequently increased. This automatically provides an output of a high-velocity ratio by the belt drive.
The quarter turn belt drives are popularly known as the right-angle belt drives.
As the name implies, they are used with shafts arranged at right angles, rotating in a specific direction.
It is worthy of note that the face width of the pulley must be greater than or equal to 1.4 b in order to prevent a misalignment of the belt on the pulley.
In some instances where a reversible speed is needed or the pulley cannot be properly arranged, then a right-angle belt drive with a guide pulley may prove useful.
A compound belt drive is utilized when multiple shafts are present in the pulley system. As a result, they are typically used to transfer power from one shaft to another through multiple shafts.
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Amazing facts in Basic Technology
Rubber bands last longer when refrigerated
Lighter was invented before matches
Johann Wolfgang Dobereiner was credited with the invention of lighter in 1826 while the match was made 3 years later
Volkswagen group of companies own some of the top cars of the world. These are Audi, Bentley, Bugatti, Ducati, Lamborghini and Porsche
Notable points in Basic Technology
Arrowhead lines are lines with pointed edges at one or both ends. The pointed edges are in the form of an arrow.
Arrowhead lines are used:
At the end of dimensional lines.
As measurement lines.
A thin continuous line could be a straight or curved line. However, the main point to remember is this: 'it is a tiny line with no dot or dashes within it'.
_______________________
A thin continuous line is used for representing the followings:
Projection lines
Hatching lines
Construction lines
Short center lines
Measurement lines
Diagonal lines used to state plane surfaces
Intersections
Leader lines
Backside section lines
Any action that involves the servicing, checking, replacing and repairing of an equipment, object or device is termed maintenance.
Maintenance has two main goals. These are:
To prevent a breakdown
To repair the breakdown
Below are the types of maintenance:
Preventive maintenance
Corrective maintenance
Predictive maintenance
Periodic maintenance
Reinforcement
Overhaul
Softwoods are often derived from coniferous trees, that is: trees with needle-like leaves, and whose seeds are covered in cones.
Below are some characteristics of softwood:
Most softwood have lower densities than hardwood (weighs lower).
In terms of price, they are often less expensive than hardwood.
Their growth rate is faster than hardwood.
Most softwood do not shed their needle-like leaves during the year. However, the softwood 'larch' and 'cypress' are exceptions.
They are less fire resistant.
The diagram below shows the various types of line in technical drawing, their description and general application:
Please read more on the types of line in technical drawing here
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