Vehicle Power transmission
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Transcript of Vehicle Power transmission
Power transmission
Power transmission
Power transmissionis the movement ofenergyfrom its place of generation to a location where it is applied to performing usefulwork.
What is power transmission ?
Fly wheel and clutch
Bell housing and input shaft
Drive shaft
Gear box
Differential
axle
Basic component of power transmission in a vehicle.
Power transmission assembely
The first link in the drive line or power transmission is the flywheel.
Fly wheel
Aflywheelis a rotating mechanical device that is used to storerotational energy. Flywheels have a significantmoment of inertiaand thus resist changes in rotational speed
what Is a fly wheel ?
First problem is the high mass of the fly wheel.
Second problem is the rotational inertia of the fly wheel.
Problems with the fly wheel.
for reducing the rotational inertia of the fly wheel we run the minimum diameter flywheel.
Choose a suitable material for increasing the efficiency of flywheel.
So the solutions.
Material selecting chart.
Chart shows that aluminum is best for making the fly wheel because
it has low mass maximum strength.
Clutches is a mechanical device that are useful in devices that have two rotating shafts. In these devices, one of the shafts is typically driven by a motor or pulley, and the other shaft drives another device. In a drill, for instance, one shaft is driven by a motor and the other drives a drill chuck. The clutch connects the two shafts so that they can either be locked together and spin at the same speed, or be decoupled and spin at different speeds.
Clutch .
Clutch
In a car, you need a clutch because theenginespins all the time, but the car's wheels do not. In order for a car to stop without killing the engine, the wheels need to be disconnected from the engine somehow. The clutch allows us to smoothly engage a spinning engine to a non-spinning transmission by controlling the slippage between them.
why we need a clutch ?
Clutch working.
Bell housing.
Front and rear faces of the bell housing are not both true and parallel.
The pilot diameter at the rear of the bell housing into which the gearbox or transaxle spigots is not concentric with the crankshaft.
Misalignment in bell housing assembely.
a notable bending load is put into the input shaft to the detriment of the bearings involved and of the gear itself
It waste the power of the engine
This will result in a lost oil seal, oil on the clutch
Effect on the transmission
Adrive shaft is a mechanical component for transmittingtorqueand rotation, usually used to connect other components of adrive trainthat cannot be connected directly because of distance or the need to allow for relative movement between them.
Drive shaft.
Twisted driveshaft tube
Broken yoke shaft, slip yoke, tube yoke, flange yoke, end yoke
Broken journal cross
Universal Joint Operating Angles
Critical speed.
Causes of driveshaft vibrations.
Driveshaft critical speed measuring calculator.
3.Universal joint angle
improper universal joint causes many problems.
Vibrations
Reduced universal joint life
Problems with other drivetrain components that may include:
Transmission gear failures
Differential problems
Universal joint angle.
How we measure U-joint Angle
Place vehicle on level ground
No load on vehicle
Measure with an inclinometer
Transmission output shaft angle
Driveshaft tube angle
Pinion angle
Difference between output shaft and driveshaft tube is the front joint operating angle
Difference between pinion angle and driveshaft tube is rear joint operating angle
Measure u-joint angle
Drive shaft phasing.
When both of the u-joint in drive shaft are not in the same phase then this causes the vibration of drive shaft
Anaxleis a central shaft forarotating wheel
orgear. In the former case bearings or bushings are provided at the mountings points where the axle is supported
Axle .
Material.
mechanical design.
Heat treat.
Three things are very important
for any part of a machine.
Use 4340 steel-it has better through heat treating properties.
The only thing to avoid in the design of an axle is the stress raiser. Stress raisers are normally caused by rapid section changes and by sharp corners.
Natural places for these are at the end of splines.
Material and Design.
Axle break.
The spline i.D. and the i.D. of any snap grooves must be greater than the actual shaft O.D. and all radius must be as gentle as
Solution for design.
Half shaft-
the obvious necessity for the half shaft to be articulated they must have some provision to acommodate the axial plunge associated With the four bar independent suspension system If there is any notable resistance to this axial plunge, or change In half shaft length, the effect will be the same as a bind in the suspension and power application will be accompanied by a Jerky and unpredictable oversteer.
History of half shaft-
What is axial plunge
The classic solution was to use a splined two piece half shaft and let the splines accommodate the plunge Naturally the splines always bound up to some extent under torque loadings and this didn't work out very well.
first solution
Then Lotus came out with the fixed length half shaft which was also the upper link of the suspension system. This arrangement has
been perpetuated in the Corvette and the E Type Jaguar but the geometry is limited for race car use and the half shaft feeds some unnecessary loads into the final drive unit.
Second solution
Next came the rubber doughnut-which worked just fine so long as it was properly located and piloted but was limited in its ability to transmit torque. In its ultimate form (Brabham, Formula One) the drive shaft had two standard universals and a rubber doughnut
Third solution
Rzeppa type constant velocity joint half shaft which has been around forever
today
Maximum torsion bar length
Minimum weight and moment of inertia
Minimum package dimensions-which leaves more room for such things as exhaust systems and suspension links
Virtually frictionless axial plunge
Increased angular capacity and true constant velocity
Simplicity, reliability and cost
Adavantages of Rzeppa type half shaft
The differential is a device that splits the enginetorquetwo ways, allowing each output to spin at a different speed.
differential
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.)
The differential has three jobs:
Why we need a differential
Open differential.
Spool differential
Detroit differential
Locked differential
Limited slip differential
Types of differential which are commonly used.
Working of open differential
It sends equal amount of torque to the both of the wheels which is not good in some situations. It is good for an on road vehicle.
Limitations of open differential.
Spool differential
The spool simply ties the two wheels together eliminating all differential action. The housing itself is internally splined to receive the drive axles. The driving torque, taken from the ring gear drives the axles directly. Both wheels turn at the same speed regardless of traction levels, or direction of travel. This means that when equipped with a spool, the car naturally wants to go straight, regardless of steering input
Drawbacks of spool differential
handling suffers greatly when using a spool, because the tied-together wheels cause massive steer.
Another very significant downside to the spool is that when you are leaving the track with hot tires, the torque generated in turns can easily be enough to break axles. Remember that on the track, the inside wheel is unweighted, reducing its traction; so that the torque required to force the inside wheel to slip in the turns is reduced. When leaving the track, the weight is equal on both hot tires, the maximum grip possible on both tires will be achieved with the inside tire fighting the outside tire.
Detroit differential.
The operating principal of the Detroit Locker is much like that of a bicycle rear wheel sprocket. It was originally built for drag racing to allow the turnoff at the end of a run with less stress induced in the axles. When turning off, the faster wheel will unlock allowing it to coast through the corner. This is a great setup for drag racing and off-road use. However, in a road racing application only the inside wheel will drive creating massive mid turn understeer. Only when the inside tire slips and catches up with the outside tire will the outside tire begin to drive.At this point, the Detroit Locker becomes a spool,
The basic rule of road racing with a Detroit Locker is the same
as a spool. DO
NOT USE IT unless it is required by the rules
A locking differential may provide increasedtractioncompared to a standard, or "open" differential by restricting each of the two wheels on an axle to the same rotational speedwithout regard to available traction or differences in resistance seen at each wheel.
Locked differential
Some off road situation in which the locked differential is suitable. in these situations the torques in the both tires are limited by the function of the locked differential
Because they do not operate as smoothly as standard differentials, automatic locking differentials are often responsible for increased tire wear
Some locking differentials are known for making a clicking or banging noise when locking and unlocking as the vehicle negotiates turns.
some locking differentials can affect the ability of a vehicle to steer in some situations,
Disadavantages
They are also capable of subjecting the axle shafts to much higher torque loads than would be possible with an open differential because they allow 100% of the available torque to carried by a single axle shaft as opposed to being divided up between the two. Under extreme conditions, this can cause an axle shaft failure.
Disadavantages
Four wheel drive vehicles that drive off-road often use locking differentials to prevent from getting stuck when driving on loose, muddy, or rocky terrain. Locking differentials are considered essential equipment for serious off-road driving.
Some utility vehicles such as tow trucks, forklifts, tractors, and heavy equipment use locking differentials to maintain traction, especially when driving on soft, muddy, or uneven surfaces. Lockers are common in agricultural equipment and military trucks.
application
A limited slip differential is a device found in the driveaxleof an automobile or truck that the axles and ring gear are mounted to. Used to engage both sides of the axle in the event of needed traction, the limited slip differential causes both drive tires to receive power, resulting in added traction. Unlike a locked, welded or spooled differential that has both sides of the axle meshed together constantly, the limited slip differential is made so that thedrive axle will disengage one side while turning a corner. This prevents the wheels from binding and the tires from chirping as the outside tire fights to turn faster than the inside tire while the vehicle negotiates a sharp turn.
Limited slip differentials
Comparison b/w lock and lsd
Lock differential
Limited slip differential
it is better for only off road vehicle not good in general on road vehicle.
It causes the wear of tires when turn on a smooth road .
It locks the tires 100%.
it is better for both off road and on road
on the smooth road or pavements it behaves just like a open differential and on the off road like a lock differential.
It does not lock 100%
Manual transmission
Automatic transmission
Cvt(continuously variable transmission)
Types of transmission.
manual transmission gear box.
Hewland gear box
Baulk ring gear box
Types of manual transmission gear box but these are generally used for formula cars.
there are two big differences between an automatic transmission and amanual transmission:
There is no clutch pedal in an automatic transmission car.
There is no gear shift in an automatic transmission car. Once you put the transmission intodrive, everything else is automatic.
Automatic transmission.
Automatic transmission gear box.
inputoutputstationarycalculationGear ratio
first gearsunPlanet carrierRing gear1+r/s3.4:1
Third gearPlanet carrierringsun1/(1+s/r).71:1
Reverse gearsunringPlanet carrier-r/s-2.4:1
Automatic transmission working by simple one planet gear
Ring=72teethSun=30teeth
Comparison b/w manual and automatic transmission.
manual
automatic
Manual gearshifts are more fuel efficient as compared to their automaticcounterpart
It provides better control over vehicle.
It is very simple and little costly
Torque convertor used to engage and disengage automatic gears may lose power and reduce acceleration as well as fuel economy.
It provides less control
An automatic transmission is made up of several components and a breakdown of even a single component can stall the car completely.
Comparison b/w manual and automatic
manual
automatic
A manual is better because you have lower gearing in 1st which means more for climbing.
An automatic provides some higher first gear ratio than a manual
Unlike traditional automatic transmissions, continuously variable transmissions don't have a gearbox with a set number of gears, which means they don't have interlocking toothed wheels. The most common type of CVT operates on an ingeniouspulley systemthat allows an infinite variability between highest and lowest gears with no discrete steps or shifts.
Cvt transmission.
Pulley-belt cvt
Torodial cvt
Hydrostatic cvt
Types of cvt
feature benefit
Constant, stepless acceleration from a complete stop to cruising speed
Eliminates "shift shock" -- makes for a smoother ride
Works to keep the car in its optimum power range regardless of how fast the car is traveling
Improvedfuel efficiency
Responds better to changing conditions, such as changes in throttle and speed
Eliminates gear hunting as a car decelerates, especially going up a hill
Responds better to changing conditions, such as changes in throttle and speed
Better acceleration
Adavantages of cvt
Cvt is better than manual and automatic transmission but requires some experience for handling vehicle
Conclusion-
By-Chetan badsar
2015/11/3
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