Topics in Basic TechnologyBelt Drives: Types of belt drive Ceramics: Types of Ceramics Advantages and Disadvantages of Chain drives Len Academy Questions for Basic Technology JSS3, 2nd Term, 2020 Len Academy Question for Basic Technology, JSS3, 2nd Term, 2020, Part 2 Belt and Pulley Drives: Types of Belt in Belt Drives Electromechanical Energy: Parts of the Refrigerator and how they operate Chain Drive, Types and Classifications 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 Maintenance, Types of Maintenance Hardwood and Softwood - Characteristics and Examples What are Ceramics? Characteristics of Ceramics
Academic Questions in Basic Technology
With regards to chain drives, the diagram above is a/an _____ chain.
A type of chain drive commonly used in bicycles is the _____ chain.
A chain drive consists of an endless chain running over two _____.
Which is the most economical of all power transmitting drive mechanisms?
A. Pulley drive
B. Gear drive
C. Chain drive
D. Belt drive
E. Thread drive
F. Fabricated drive
Which of the following is false concerning drive mechanisms in machines?
A. Pulley drives do not require a means of power transmission
B. Gear drive is a means of power transmission
C. Chain drive is a means of power transmission
D. Belt drive is a means of power transmission
E. The drive mechanisms of machines accomplishes it's function via a rotational motion
F. Drive mechanisms results into a mechanical movements of machines via power transmission
The lines above are used at the end of dimension lines?
Which of the following is not a type of maintenance?
Which of the following is incorrect concerning preventive maintenance?
A. It is considered to be the best form of maintenance
B. Immunization is a form of preventive maintenance
C. Worn out parts may be discovered when preventive maintenance is carried out
D. Preventive maintenance is defined as the repairs carried out on an equipment or object after a correct prediction of an impending fault
E. A person who services his car monthly practices preventive maintenance (even though the car functions properly)
F. The main goal of preventive maintenance is to stop a device from breaking down suddenly
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Belt drives are frictional drives that transmit mechanical energy on a dry surface from one shaft to another in a pulley like system.
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 shaft 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.
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; while been 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.
Note: The pulley keyed to the machine shaft is referred to as the fast pulley.
The stepped cone pulley (step or cone pulley drive), sometimes called the 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 drive 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.
Understand that the same belt is used in the stepped cone pulley whenever there is a shift in the 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 into 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.
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
The diagram below shows the various types of line in technical drawing, their description and general application:
Preventive maintenance is carried out routinely on a device even though no apparent fault may be present on such device.
The goal of preventive maintenance as the name suggest is to prevent a sudden breakdown on a device or equipment.
As an instance, a person who services his or her car monthly even though the car is still able to function correctly is said to be carrying out preventive maintenance on the car.
In the course of a preventive maintenance, worn out parts may be discovered and replaced as soon as possible. Also, there may be a change of oil while other little adjustments may also be carried out.
We can even carry out preventive maintenance on our body to prevent certain diseases. For this reason, some persons have discovered cancerous cells in their body through regular medical checkup; and were able to kill such cells before they become malignant.
As a matter of fact; immunization is a form of preventive maintenance.
Hardwoods are derived from angiosperms. They show the following characteristics:
They usually have a higher density than softwood. Balsa is an exception.
They are usually more expensive than softwood.
They grow at a slower rate than softwood.
Hardwood trees shed their leaves in certain times of the year.
Hardwood are more fire resistant than softwood.
The leaves of hardwood trees are evergreen.
They are used for making quality furniture (in terms of strength). They are also suitable for decking in buildings.
Hardwood trees always have divided trunks which are sometimes referred to as a dendritic form.
In terms of price, hardwood are usually more expensive than softwood.
Examples of hardwood include iroko, ash, beech, alder, teak, birch, mahogany, maple, oak, balsa and walnut.
Ceramics are refractory. They also require a very high amount of heat and subsquent cooling to be formed.
Being refractory means that they are capable of withstanding a variety of abuses like high temperatures and chemical attacks.
Ceramics are generally made by taking clay from the ground and mixing it with water. It is then shaped into any form and fired inside an oven (called kiln) at a very high temperature. They may then be decorated with a waterproof, paint-like substances called glazes.
Ceramics may have constrasting physical and chemical properties (or characteristics); but in general,
They have high melting points.
They are heat resistant.
They can be very hard with great strength; although a few are brittle or soft; for example, graphite.
They are durable (last for a long time).
Most are electrical insulators (cannot conduct electricity) but; graphite is an electrical conductor.
They are chemically unreactive or inert.
They are not easily oxidized.
Most are non-magnetic.