INTRODUCTION ABOUT SiMPLE MACHINE (GEARS)
INTRODUTION ABOUT SIMPlE MACHINE (GEARS).
We have learnt about simple machine.
Machine makes work easier and convenient.In this page we shall learn about a wheel fixed in machine
Called gear. It is mainly found in cars,
bicycles, motorcycles,clocks, crane,
winding engine and other machines at homes and industries at homes and
industries. We shall be concerned with
the description and uses of gear.
WHAT IS A GEAR.
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gear is a wheel fixed in machines to make different speed be in different
direction. When two gear wheels are
fitted into each other it is referred to
as meshing. For meshing to occur, the
edges of both gear must be cut uniformly all round the edge of the gears are in mesh, they are called gear train.
You can make gear on your own.there are many methods of making a gear depending on what the gear is going to
be used for, the materials used can be steel, cast iron, plastic or bronze.
ACTIVITY:
Get a cardboard paper, your teacher will show you the necessary steps to be
followed in drawing and cutting out the
cardboard. You can use a bottle cap in
cutting your own cardboard paper.
TYPES OF GEAR.
There are different types of gear.some are big while others are small. The smallest type of gear is called pinion.
Gears are classified according to the
Position of their shaft and teeth .
Each gear has teeth, shaft, gear drive
Worm wheel etc.
SPUR GEARS:
The shaft run parallel with the teeth.
The teeth are straight.
HELiCAl GEARS:
Run more silent, since the tooth engagement takes place in a gradual
way.however,an axial pressure develops
Which must be absorbed by thrust bearing.
HERRING BONE GEARS:
THIS IS applied for heavier transmission. The axial pressure is
Compensated.
BEVEL GEAR:
This shafts meets in one point. The gears
Have a bevelled basic form. There are bevel gear with straight, helical and spiral teeth. It is mainly used in rear axle.
NOTE:
(A). Bevel gear (a) is gear with straight teeth.
(B). Bevel gear (b) is gear with spiral teeth.
SPIRAL GEAR:
Spiral gears are spiral toothed gears.
The gear drive consists of worm and
Worm wheel and is suitable for heavy
Loads. It runs smoothly and is compact.
The worm gear is always driven by the
worm.
USES OF GEAR:
(1) Gears are used principally in gear drives to transmit motion between two
parallel or inclined shaft.
(2) Gears are used to transmit power from the point where such power is being developed to a point where it is
Used to do work.
(3) Gear is used to transmit the power being developed by the engine to the road wheels.
(4) Nowadays some bicycles have gears to help make pedaling as relaxing as possible thereby saving energy.
(5) Gear is used in changing speed of a car.
(6).It can also be used in changing the direction of rotations of machine.
(7).Gear is used in connecting two machines together.
(8). Gears are used in making our clocks.
(9). Gears transmit rotary action from one moving shaft to another and also
to change the direction of rotation.
(10) Gears are used to harness efficient
engine speeds for slow speed tasks such as in car pulling through sand or mud, climbing a steep hill, or starting from
and rest. E.g. gears are used in motor
vehicles and bicycles to ensure their
Bicycles to ensure their smooth running
Under the varying speed and road conditions.
GEAR SPEED AND RATIO:
When two gears mesh with one another,one usually drive the other, hence one is called driving gear. When
The other is called driver gear. If the driven gear has fever teeth than the driving gear, the driven gear will turn
more slowly than the smaller gear driving it. On the other hand if the driving gear has more teeth than the
Driven gear, the driven gear will turn
More rapidly than the driving gear.
In other way if a gear wheel A has 60 teeth and gear B has 30 teeth. B will turn twice to everyone rotation.
This property of gear,gear ratio is made
up of in clocks.
Clocks have different sized gear wheels.
So that the hands move at different speeds. Gear wheel A and B are connected to the driving shaft and therefore move at gear ratio.
{Rotation per second of wheel A).
( rotation per second of wheel B).
( no of teeth on wheel B).
( no of teeth on wheel A).
The same speed as the shaft even through they have different numbers
of teeth. The smaller driven wheel C meshes with bigger wheel B.
ACTIVITY:
You can do this using two bottle of caps.
Arrange them in such a way that each others space. If you do it you have arranged a simple gear.
HOW DOES IT WORK:
Get a bicycle that has gears.turn it upside down.try locate the gear wheels
Which are Attached to the pedals.note how the small gear on the back works.
It is driven by a chain drive.turn the pedals with your hands now and watch the back road wheel move.take note of
the engaged gear. change gear , turn the
pedals again and watch the back wheel
move. continue this way until all the gears are used in turn.you will notice that greater effort is required to move
at speed with bigger gear. They can move down from hills at speed.they rider selects higher gear which provide
a higher speed in return for slower pedaling. For climbing hills the rider change to a slower gear which makes pedaling easier in return for a lower speed.this situation is less tasking as it
requires less effort to turn the pedals,
thereby enabling the rider to climb through the hill without getting tired
soon.
The principal described about is the same when changing gears in motor
vehicles.
CHANGING GEAR:
All cars and lorries have gear box containing sets of gear wheels which
can be combined in various ways.the
arrangement of these gear is controlled by the gear lever when the car or lorry
is in bottom gear, the gear wheels are
arranged in such a way that the velocity
ratio of the whole vehicle is high even the mechanical advantage is also high,
The force supplied through the train gears to the tyres is relatively large.
Low or bottom gear is used in starting
From rest or in climbing step hill.this is
gear 1 in most car.this is because large
force is required on the vehicle.
But when the car or lorry is on top gear
the gear wheels give a low velocity ratio
and low mechanical advantage so that the force supplied through the train gears to the back wheels is relatively small. Top gear 3 or 4 is used for cruising at high speed on a level road,for gentle acceleration and climbing gentle hills. Most cars and lorries have two intermediate gears,
Between gear 1 and 3 or 4 for use when
The vehicle is gradually gathering speed. This is gear 2 . Three speed gears
are common on bicycles and motorcycles.
The bigger driven wheel D meshes with the smaller driving wheel A and turns the hour hand. Since the gear wheel A and B moves at the same (speed of the
Driving shaft) the smaller driven wheel
C moves faster than the bigger driven wheel D. The number of teeth on the various gears are arranged in such a way that the minute hand travels round
The clock once an hour while the small
Hand goes round the clock face in twelve hours.
ACTIVITY:
Draw a gear system that will operate a clock that has second hand, as well as the minute and hour hands .
The overall velocity ratio of a complex
Machine is found by multiplying the gear ratios together, and then multiplying them by the velocity ratio
Provided by all the other parts of the machine.
Reducing frictional effect between meshing gear.
When two surfaces move relative to one
Another, friction comes into play when two gear teeth mesh they rub against one another such that frictional effect generates heat, this causes machine to
Wear away easily and also leads to loss
Power of transmission.
In order to reduce wear and loss of power of transmission, friction between
The meshing teeth must be reduced. This is achieved by lubricating the gears
With a suitable oil called " gear oil".
This is why most motorists check their
Gear oil levels regularly.
It is important to use the proper lubricants.
Remember lubricants is that which is done to reduce the effect of friction. It could be substances whether in the form
Of oil or grease. It helps to overcome friction, prevent excessive wear between moving parts, protect surface
From rust and also fill the space between metal parts thereby acting as a cushion.
COLLUSION:
Gear is a wheel fixed in machine to make different parts move at different speed in different direction.
(1). When two gears are fitted into each other, it is referred to as meshing.
(2). For meshing to occur,the edges of both gears must be cut uniformly all
Round the edges.
(3). When two gears are in mesh they are referred to as gear train.
(4). Pinion is always the smallest gear .
(5) Spur gear, helical gear, bevel gear,
and spiral gears are different types of gears.
(6). Friction comes into play when two
gear teeth mesh this causes heats, leading to wear away of machine and
Wear away of machine and loss of power of transmission in gears.
(7). Lubricants like oil or grease can be used in reducing frictional force in gear.
(8). We have many uses of gear_ gear is a drive mechanism.
REFERENCE:
Definition of GEAR www.merriam-webster.com. Retrieved 20 September 2018.
"Transmission Basic HowStuffWorks.
Derek J. de Solla Price, On the Origin of Clockwork, Perpetual Motion Devices, and the Compass, p.84
The Antikythera Mechanism Research Project: Why is it so important? Archived from the original on 4 May 2012. Retrieved 10 January 2011. The Mechanism is thought to date from between 150 and 100 BC
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