INDEX
1. INTRODUCTION
2. DIFFERENTIAL
3. HISTORY
4. PRINCIPLE
5. DISCRIPTION
6. NEED OF DIFFERENTIAL
7. DIFFERENTIAL USED AS ACCELERATOR
8. FUTURE SCOPES OF IT
9. COSTING & ESTIMATING
INTRODUCTION
PROJECT:- A project is organized venture to be taken to achieve a desirable objective. It is a more action or an activity, or an attempt towards a particular aim. It is a rather an intregrated efforts including action & activities towards that aim. It is not jumbled mass of activities or action within an intregrated some but organized effort.
A project has four basic elements:-
1. It is a venture.
2. It is an organized ventured.
3. It has a desirable objective.
4. It is an organized venture proposed to be undertaken.
Depending upon the objectives that are desired to be achieved. Project may be of various types namely research, development welfare & industrial.
MEANING OF PROJECT
Before taking a project work for formation, it seems quite relegent to leave in mind the exact meaning of word project. The word has useful meaning which are as follows:-
Ø “P” stands for planning
Ø “R” stands for research
Ø “O” stands for operation
Ø “J” stands for joint effort
Ø “E” stands for engineering function
Ø “C” stands for communication
Ø “T” stands for technique
PURPOSE
What is a Differential?
The differential is a device that splits the engine torque two ways, allowing each output to spin at a different speed.
The differential is found on all modern cars and trucks, and also in many all-wheel-drive (full-time four-wheel-drive) vehicles. These all-wheel-drive vehicles need a differential between each set of drive wheels, and they need one between the front and the back wheels as well, because the front wheels travel a different distance through a turn than the rear wheels.
Part-time four-wheel-drive systems don't have a differential between the front and rear wheels; instead, they are locked together so that the front and rear wheels have to turn at the same average speed. This is why these vehicles are hard to turn on concrete when the four-wheel-drive system is engaged.
Ø Input torque is applied to the ring gear (blue), which turns the entire carrier (blue). The carrier is connected to both the side gears (red and yellow) only through the planet gear (green) (visual appearances in the diagram notwithstanding). Torque is transmitted to the side gears through the planet gear. The planet gear revolves around the axis of the carrier, driving the side gears. If the resistance at both wheels is equal, the planet gear revolves without spinning about its own axis, and both wheels turn at the same rate.
Ø If the left side gear (red) encounters resistance, the planet gear (green) spins as well as revolving, allowing the left side gear to slow down, with an equal speeding up of the right side gear (yellow).
A differential is a device, usually but not necessarily employing gears, capable of transmitting torque and rotation through three shafts, almost always used in one of two ways: in one way, it receives one input and provides two outputs—this is found in most automobiles—and in the other way, it combines two inputs to create an output that is the sum, difference, or average, of the inputs.
In automobiles and other wheeled vehicles, the differential allows each of the driving roadwheels to rotate at different speeds.
History
There are many claims to the invention of the differential gear but it is likely that it was known, at least in some places, in ancient times. Some historical milestones of the differential include:
- 1050 BC–771 BC: The Book of Song (which itself was written between 502 and 557 A.D.) makes the assertion that the South Pointing Chariot, which uses a differential gear, was invented during the Western Zhou Dynasty in China.
- 30 BC - 20 BC: Differential gear systems used in China and on the Greek island of Antikythera
- 227–239 AD: Despite doubts from fellow ministers at court, Ma Jun from the Kingdom of Wei in China invents the first historically verifiable South Pointing Chariot, which provided cardinal direction as a non-magnetic, mechanized compass.
- 658, 666 AD: two Chinese Buddhist monks and engineers create South Pointing Chariots for Emperor Tenji of Japan.
- 1027, 1107 AD: Documented Chinese reproductions of the South Pointing Chariot by Yan Su and then Wu Deren, which described in detail the mechanical functions and gear ratios of the device much more so than earlier Chinese records.
- 1720: Joseph Williamson uses a differential gear in a clock.
- 1810: Rudolph Ackermann of Germany invents a four-wheel steering system for carriages, which some later writers mistakenly report as a differential.
- 1827: modern automotive differential patented by watchmaker Onésiphore Pecqueur (1792–1852) of the Conservatoire des Arts et Métiers in France for use on a steam cart. (Sources: Britannica Online and[1])
- 1832: Richard Roberts of England patents 'gear of compensation', a differential for road locomotives.
- 1876: James Starley of Coventry invents chain-drive differential for use on bicycles; invention later used on automobiles by Karl Benz.
- 1897: first use of differential on an Australian steam car by David Shearer.
- 1913: Packard introduces the spiral-gear differential, which cuts gear noise.
- 1926: Packard introduces the hypoid differential, which enables the propeller shaft and its hump in the interior of the car to be lowered.
- 1958: Vernon Gleasman patents the Torsen dual-drive differential, a type of limited slip differential that relies solely on the action of gearing instead of a combination of clutches and gears.
Principal
When the vehicle is going straight the cage and the inner gears rotate as a single unit and the two half shafts revolve at the same speed. In this situation, there is no relative movement among the various differential gears. To understand what happens when the vehicle is taking a turn, assume that the cage is stationary. Then turning one sun gear will cause the other to rotate in the opposite direction. That means that if left sun gear rotates “n” times in a particular time, the right sun gear will also rotate n times in the same period but, of course in the opposite direction. This rotation is super-imposed on the normal wheel speed when the vehicle is taking a turn. Thus, for example, consider a vehicle with wheel speed N r.p.m going straight, when it takes a turn toward right. At this time there will be a resistance to the motion of the right wheel and as a result of differential action if the right wheel rotates back at “n” r.p.m then the left wheel will rotate forward at “n” r.p.m. This will give the resultant speed of the left wheel as (N+n) and that of the right wheel as (N-n) r.p.m.
The torque from the final drive is also divided between the two half-shafts. As the planet pinions are free to rotate on the cross-pin or the spider arm, they cannot apply different torque to the teeth on one side from the one on the other. Therefore, they act as a balance and divide the torque equally between the two wheels on the axle, even when their speeds are different.
Due to this reason if one wheel is on a slippery surface where it can simply skid and any torque that is transmitted to it will simply cause it to rotate idly, then no tractive force could be obtained from the other wheel. In this situation the slipping wheel will spin at twice the crown wheel speed, while the opposite wheel will remain stationary. This equality of torques is true only if there is no friction present anywhere in the differential system. However, because this is not possible in practice, some inequality of torques is always there. The larger the amount of friction present in the differential, the larger is the inequality of torques and hence if one wheel of the vehicle with friction in the differential gets on to a slippery surface e.g., ice, mud or if the wheel gets lifted off the ground while turning at high speeds as in racing cars, for example then a larger torque may be transmitted to the other wheel, which has a good grip on the road than to the slipping wheel. Thus the grip of that is utilized; this would not be possible in the absence of friction.
Functional description
A cutaway drawing of a car's rear axle, showing the crown wheel and pinion of the final drive, and the smaller differential gears
The following description of a differential applies to a "traditional" rear-wheel-drive car or truck with an "open" or limited slip differential combined with a reduction gearset: Torque is supplied from the engine, via the transmission, to a drive shaft (British term: 'propeller shaft', commonly and informally abbreviated to 'prop-shaft'), which runs to the final drive unit that contains the differential. A spiral bevel pinion gear takes its drive from the end of the propeller shaft, and is encased within the housing of the final drive unit. This meshes with the large spiral bevel ring gear, known as the crown wheel. The crown wheel and pinion may mesh in hypoid orientation, not shown. The crown wheel gear is attached to the differential carrier or cage, which contains the 'sun' and 'planet' wheels or gears, which are a cluster of four opposed bevel gears in perpendicular plane, so each bevel gear meshes with two neighbours, and rotates counter to the third, that it faces and does not mesh with. The two sun wheel gears are aligned on the same axis as the crown wheel gear, and drive the axle half shafts connected to the vehicle's driven wheels. The other two planet gears are aligned on a perpendicular axis which changes orientation with the ring gear's rotation. In the two figures shown above, only one planet gear (green) is illustrated, however, most automotive applications contain two opposing planet gears. Other differential designs employ different numbers of planet gears, depending on durability requirements. As the differential carrier rotates, the changing axis orientation of the planet gears imparts the motion of the ring gear to the motion of the sun gears by pushing on them rather than turning against them (that is, the same teeth stay in the same mesh or contact position), but because the planet gears are not restricted from turning against each other, within that motion, the sun gears can counter-rotate relative to the ring gear and to each other under the same force (in which case the same teeth do not stay in contact).
Thus, for example, if the car is making a turn to the right, the main crown wheel may make 10 full rotations. During that time, the left wheel will make more rotations because it has further to travel, and the right wheel will make fewer rotations as it has less distance to travel. The sun gears (which drive the axle half-shafts) will rotate in opposite directions relative to the ring gear by, say, 2 full turns each (4 full turns relative to each other), resulting in the left wheel making 12 rotations, and the right wheel making 8 rotations.
The rotation of the crown wheel gear is always the average of the rotations of the side sun gears. This is why, if the driven roadwheels are lifted clear of the ground with the engine off, and the drive shaft is held (say leaving the transmission 'in gear', preventing the ring gear from turning inside the differential), manually rotating one driven roadwheel causes the opposite roadwheel to rotate in the opposite direction by the same amount.
When the vehicle is traveling in a straight line, there will be no differential movement of the planetary system of gears other than the minute movements necessary to compensate for slight differences in wheel diameter, undulations in the road (which make for a longer or shorter wheel path), etc.
When a car makes a turn, the wheels must spin at different speeds.
In the figure above, you can see that the pinions in the cage start to spin as the car begins to turn, allowing the wheels to move at different speeds. The inside wheel spins slower than the cage, while the outside wheel spins faster.
The differential has three jobs:-
· To aim the engine power at the wheels
· To act as the final gear reduction in the vehicle, slowing the rotational speed of the transmission one final time before it hits the wheels
· To transmit the power to the wheels while allowing them to rotate at different speeds (This is the one that earned the differential its name.)
Why You Need a Differential:-
Car wheels spin at different speeds, especially when turning. You can see from the animation that each wheel travels a different distance through the turn, and that the inside wheels travel a shorter distance than the outside wheels. Since speed is equal to the distance traveled divided by the time it takes to go that distance, the wheels that travel a shorter distance travel at a lower speed. Also note that the front wheels travel a different distance than the rear wheels.
Car wheels spin at different speeds, especially when turning. You can see from the animation that each wheel travels a different distance through the turn, and that the inside wheels travel a shorter distance than the outside wheels. Since speed is equal to the distance traveled divided by the time it takes to go that distance, the wheels that travel a shorter distance travel at a lower speed. Also note that the front wheels travel a different distance than the rear wheels.
For the non-driven wheels on your car -- the front wheels on a rear-wheel drive car, the back wheels on a front-wheel drive car -- this is not an issue. There is no connection between them, so they spin independently. But the driven wheels are linked together so that a single engine and transmission can turn both wheels. If your car did not have a differential, the wheels would have to be locked together, forced to spin at the same speed. This would make turning difficult and hard on your car: For the car to be able to turn, one tire would have to slip. With modern tires and concrete roads, a great deal of force is required to make a tire slip. That force would have to be transmitted through the axle from one wheel to another, putting a heavy strain on the axle components.
HOW CAN WE USE A DIFFERENTIAL AS AN ACCELATOR OR RPM ADDER
According to the upper description when a vehicle bends in a bend then the inner tyre of the bend rotates in (N-n)rpm and the outer tyre rotates in (N+n)rpm.
So if we rotates the inner tyre to k rpm in the opposite direction of outer tyre then we get (N+k)rpm. Therefore we can add the N rpm and k rpm(any other rpm which we want to add in main rpm) to get desirable rpm.
FUTURE SCOPE
The future scope of this accelerator is vary large. It can be used in all those fields where we have to increase the rpm.
The various advantage of this accelerator are as follows:-
1. Turbine can be rotates in high speed by giving small amount of power.
2. This accelerator can be used in fans to increase its rpm of motor.
3. It is used in vehicles to increase their rpm through less input.
4. In the field of machines it can bring revolution. From low power we can get high power.
COSTING AND ESTIMATION
Cost of model:-
Raw materials used cost
1. plywood sheet Rs 150
2. spokes Rs 20
3. wooden cylinder Rs 60
4. wooden support Rs 100
5. steel rod Rs 175
6. tyres Rs 140
7. chain Rs 10
8. paint Rs 40
9. sprocket Rs 60
Total cost Rs 755
Cost of rpm adder or Accelerator:-
Raw materials used cost
1. differential Rs 350
2. axle shaft Rs 50
3. wood Rs 25
Total cost:- Rs 425
Desirable profit= 12%
So market cost=425 + 12(425)/100
=425 + 51
=Rs 476 ≈ Rs 480 only
date- 11 may 2011
i think it is a invantion....
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