DE-503 Assignment.

FRICTION WHEELS:
Kinematically, the motion and power transmitted by gears is equivalent to that transmitted by friction wheels or discs in contact with sufficient friction between them. In order to understand motion transmitted by two toothed wheels, let us consider the two discs placed together.

When one of the discs is rotated, the other disc will be rotate as long as the tangential force exerted by the driving disc does not exceed the maximum frictional resistance between the two discs. But when the tangential force exceeds the frictional resistance, slipping will take place between the two discs. Thus the friction drive is not positive a drive, beyond certain limit.
Gears are machine elements that transmit motion by means of successively engaging teeth. The gear teeth act like small levers. Gears are highly efficient (nearly 95%) due to primarily rolling contact between the teeth, thus the motion transmitted is considered as positive.
Gears essentially allow positive engagement between teeth so high forces can be transmitted while still undergoing essentially rolling contact. Gears do not depend on friction and do best when friction is minimized.

TYPES OF GEARS:
1. Spur Gears:

Spur gears are the most common type of gears. They have straight teeth, and are mounted on parallel shafts. Sometimes, many spur gears are used at once to create very large gear reductions. Each time a gear tooth engages a tooth on the other gear, the teeth collide, and this impact makes a noise. It also increases the stress on the gear teeth. To reduce the noise and stress in the gears, most of the gears in your car are helical.
Spur gears are the most commonly used gear type. They are characterized by teeth, which are perpendicular to the face of the gear. Spur gears are most commonly available, and are generally the least expensive.
Limitations: Spur gears generally cannot be used when a direction change between the two shafts is required.
Advantages: Spur gears are easy to find, inexpensive, and efficient.

2. Parallel Helical Gears:

The teeth on helical gears are cut at an angle to the face of the gear. When two teeth on a helical gear system engage, the contact starts at one end of the tooth and gradually spreads as the gears rotate, until the two teeth are in full engagement.
Helical gears to have the following differences from spur gears of the same size:
• Tooth strength is greater because the teeth are longer,
• Greater surface contact on the teeth allows a helical gear to carry more load than a spur gear
• The longer surface of contact reduces the efficiency of a helical gear relative to a spur gear.

3. Bevel gears:

Bevel gears are useful when the direction of a shaft’s rotation needs to be changed. They are usually mounted on shafts that are 90 degrees apart, but can be designed to work at other angles as well.
The teeth on bevel gears can be straight, spiral or hypoid. Straight bevel gear teeth actually have the same problem as straight spur gear teeth, as each tooth engages; it impacts the corresponding tooth all at once.

4. Worm Gear:

Worm gears are used when large gear reductions are needed. It is common for worm gears to have reductions of 20:1, and even up to 300:1 or greater.
Many worm gears have an interesting property that no other gear set has: the worm can easily turn the gear, but the gear cannot turn the worm. This is because the angle on the worm is so shallow that when the gear tries to spin it, the friction between the gear and the worm holds the worm in place.
This feature is useful for machines such as conveyor systems, in which the locking feature can act as a brake for the conveyor when the motor is not turning. One other very interesting usage of worm gears is in the Torsion differential, which is used on some high-performance cars and trucks.

SPRING:
Spring is an elastic machine element that can deflect under the application of load. When the load is removed, it regains its original position. In other words, spring is a mechanical object made up of material having very high yield strength to restore elastic. It is used in various machines to absorb shocks or it also resist to transfer shocks and vibrations on various critical machine members.
Spring materials:
The material used to made springs are called a spring steel. Spring steels are mostly low-alloy manganese, low carbon steel or high carbon steel with very high yield strength.

TYPES OF SPRING:

1. Helical Spring:
It is the most commonly used Mechanical springs. In this type of spring a coil is wrapped in such a way that it resemble like a thread. This type of springs is used for carrying Compression, Extension, and Torque forces.
According to the loading condition helical springs are classified into following four types:
• Open coil springs (or)
• Compression helical springs
• Closed coil springs (or)
• Tension helical springs
• Torsion spring
• Spiral spring
2. Leaf springs:
Leaf springs are also called as s semi- elliptical spring or Cart spring. It is one of the oldest forms of springs. Leaf springs are long and flat slender arc -shaped. These types of springs are used In Vehicle suspensions. Location for axel is center of the arc. And either end of loop is attached to the vehicle. It spread the load over vehicle chassis.
Advantages:
Leaf springs are easy to construct.
These springs are strong.
No need for separate linkage to hold the axle in position, leaf springs work as a linkage.
Rear axle location helps in reducing the extra weight.
Axle damping is control by leaf springs.
It reduces cost by eliminating the need of trailing arm and pan hard rod.
Applications:
Automobiles Suspension
Used by blacksmiths  (due to its relatively high quality steel.)
3. Belleville spring:
A Belleville springs also known as a coned-disc spring, conical spring washer, disc spring, Belleville washer or cupped spring washer. Belleville washers are mostly coin shape spring with a hole in center. This disc springs are dynamically or statically loaded to its axis. This spring required less space for installation but can bear a very large load. These springs have more advantages compare to other springs.
4. Volute and conical Spring:
These springs are conical shape compression springs. Conical springs are also known as tapered spring. These springs used to provide stability and reduce solid height.
5. Special purpose Spring:
As the name suggest this springs are made for special purpose use. Special purpose springs are made up from different types of material all together such as Air and water.

FLY WHEEL:

A flywheel is a mechanical device specifically designed to efficiently store rotational energy (kinetic energy). Flywheels resist changes in rotational speed by their moment of inertia. The amount of energy stored in a flywheel is proportional to the square of its rotational speed and its mass. The way to change a flywheel's stored energy without changing its mass is by increasing or decreasing its rotational speed. Since flywheels act as mechanical energy storage devices, they are the kinetic-energy-storage analogue to electrical capacitors, for example, which are a type of accumulator. Like other types of accumulators, flywheels smooth the ripple in power output, providing surges of high power output as required, absorbing surges of high power input (system-generated power) as required, and in this way act as low-pass filters on the mechanical velocity (angular, or otherwise) of the system.
Common uses of a flywheel include:
• Smoothing the power output of an energy source. For example, flywheels are used in reciprocating engines because the active torque from the individual pistons is intermittent.
• Energy storage systems
• Delivering energy at rates beyond the ability of an energy source. This is achieved by collecting energy in a flywheel over time and then releasing it quickly, at rates that exceed the abilities of the energy source.
• Controlling the orientation of a mechanical system, gyroscope and reaction wheel