Transfer case propler shaft diffrential and axalel

1. CHAPTER 4 : TRANSFER CASE,
PROPELLER SHAFT, DIFFERENTIAL AND
AXLES
Out line
• Transfer case
• Propeller shaft
• Differential and
• Axles

2. A transfer case is the center of the drivetrain of
 Four-wheel drive and
 Some all-wheel drive vehicles.
Mounted to the back of the transmission.
It splits engine power and sends it to the front and rear
axles by means of front and rear drive shafts.
It also synchronizes the difference in rotation of the front
and rear wheels, and
May contain one or more sets of low range gears for off-
road use.
The three basic types of transfer cases are part-time
4WD, full-time 4WD, and active 4WD.
Transfer case

3. Transfer case

4. Transfer case

5. 1. Part-time 4WD
 Is the most common type of transfer case.
 It allows you to operate the vehicle in
 Two-wheel drive,
 Four-wheel drive high-range (4hi), and
 Four-wheel drive low-range (4lo).
 The 4hi operation typically utilizes a differential to
improve drivability.
 Part-time 4wd systems offer smoother operation on
pavement and better fuel economy since the front
driveshaft and axle can be cut off completely from the
power.
 The strongest transfer cases are generally part-time
systems because they are designed for real off-road use,
often in truck and utility vehicle applications.
Transfer case

6. 2. Full-time 4WD
 is the simplest type of transfer case.
 It sends power to the front and rear axles all the time.
 To eliminate, or at least diminish, driveline bind on hard
surfaces, this type of transfer case also uses a differential
in high range.
 Some offer a 4Hi lock position which locks the
differential to improve traction on slippery surfaces, but
will also cause binding when operated on dry pavement
Transfer case

7. 3. Active 4WD
 Is the easiest type of transfer case to use because it does
not require any input from the driver.
 A variety of full-time and part-time systems have been
developed that use electronic, computerized, or
mechanical means to adjust the amount of power
delivered to the axles according to wheel slip. .
 They have a variety of names and levels of performance,
but they provide some of the benefits of a part-time
system without the owner ever having to switch
anything.
 Active 4wd was designed for smooth operation without
any input from the driver and can be found on everything
from trucks to luxury sports cars.
Transfer case

8. PROPELLER SHAFT
Some times called a cardan shaft, transmits power from the
gear box to the differential gearbox.
 Normally the shaft has a tubular section and is made in one
or two piece construction.
 The shaft must be strong to resist the twisting action of the
driving torque
 Should be resilient to absorb the torsional shocks.
 It must resist the natural tendency to sag under its own
weight.
 Whirling may occur at certain critical speed. This produces
bending stresses in the material
 The shaft should be properly balanced to reduce whirl.

9. PROPELLER SHAFT

10. PROPELLER SHAFT

11. PROPELLER SHAFT

12. COMPONENTS OF PROPELLER SHAFT:
 The propeller shaft transfers engine torque to the
rear axle through one or more universal joints.
 The splines on the ends at the propeller shaft fit
perfectly into the splines in the sleeve. This
permits a length variation between the driving and
the driven unit to vary slightly without damaging
the output and input bearings.
 The main bearing support and guide the propeller
shaft.
 The flanges associate the propeller shaft to the
gearbox.

13. CRITICAL SPEED
The speed at which the shaft starts whirling
Varies directly as diameter of the tube and inversely to the square of
the length.
NC = (60 / 2Л).(Л2 / l2).(EI/ρA)1/2 rpm
Where I = moment of inertia = Л(dO
4 – di
4) / 64
A = cross sectional area = Л(do
2 – di
2) / 4
do, di = outside and inside diameter
l = length
E = modulus of elasticity = 196 GPa
ρ = density of steel = 7860 Kg / m3
Thus, Nc = 117659 (do
2 + di
2)1/2 / l2
If Te = engine torque
G = overall gear ratio
Tt = torque to be transmitted
Td = designed torque
PROPELLER SHAFT

14. Dimensions of propeller shaft
fs = the safe shear stress
J = polar moment of inertia = Л(dO
4 – di
4) / 32
Then, Tt = Te. G
Td = Tt . Factor of safety
And Td / J = fs / y
Where y = d / 2
Practice question
An automobile engine develops 28 kW at 1500 rpm and its
bottom gear ratio is 3.06. If a propeller shaft of 70 mm outside
diameter is to ber used, determine the inside diameter of mild
steel tube to be used, assuming a safe shear stress of 55000
kPa for the MS.
PROPELLER SHAFT

15. DOUBLE HOOKES TYPE CV JOINT

16. UNIVERSAL JOINTS
Universal joints are capable of transmitting torque and
rotational motion from one shaft to another shaft when their
axis are inclined to each other by some angle, which may
constantly vary under working conditions.
These are incorporated to perform the following:
Propeller shaft end joints between longitudinally front
mounted gear box and rear final drive axles
Rear axle drive shaft end joints between the sprung final
drive and the unsprung rear wheel stub axle
Front axle drive shaft end joints.
Basic types of universal joints
 Cross type joints: also called as hook joints
 Rubber joints
 Moulten joint: rubber trunion type joint
 Layrub joint: uses a number of moulded rubber blocks
 Doughnut joint

17. TYPES OF DRIVE
Hotch kiss drive
Four link (semi hotchkiss)
Torque tube
De – dion
Hotch kiss drive.
This drive incorporates an open propeller shaft with two
universal joints and a slip joint.
Commonly used for passenger cars and heavy trucks
Torque tube drive
A tubular member called torque tube encloses the
propeller shaft and is bolted rigidly to the axle casing.
Torque reaction and drive thrusts are taken up by torque
tube. A universal joint is installed in the center of the ball
joint to allow for angular deflection of the drive.

18. HOTCHKISS DRIVE

19. TORQUE TUBE DRIVE

20. DIFFERENTIAL
Purpose
To transmit the drive from propeller shaft to the wheels
through final drive
Turn the drive at 900 angle.
To rotate the wheels at different speeds during
cornering.
Components
A crown wheel is bolted on to a differential cage
The differential cage carries the sun pinions on plane
bearings and transmits drive to the cross pinion.

21. DIFFERENTIAL

22. DIFFERENTIAL GEAR

23. PRACTICE QUESTION
The previous figure shows a differential gear as applied to a
motor vehicle. The pinion a on the propelller shaft has 12 teeth
and crown wheel got 60 teeth, shaft r and s form the rear axle
to which the road wheels are connected.
 Show that the speed of the casing is the mean of the speed
of the two rear wheels, when the vehicle is taking a turn
 If the propeller shaft has a speed of 1000 rpm and the road
wheel which is driven by c has a speed of 210 rpm, what is
the speed of the road wheel driven by d?

24. DIFFERENTIAL UNIT (SIMPLIFIED)

25. TORQUE TRANSMISSION
 When torque TR is applied to the crown wheel, it is applied to the
housing and transmitted to the planet pinions of the differential.
 Each planet pinion may be regarded as a lever between the sun
pinion, which divides the input torque evenly at all times between
the two sun pinions and half shafts.
 Taking moments about a, 2b x=TR x or b = TR / 2
 This proves that the torque is equally divided between the two sun
pinions Let Nc = revolution of crown wheel
Ni = revolution of inner wheel
No = revolution of outer wheel
Then,Nc = (Ni + No) / 2
Ni = 2Nc – No
No = 2Nc – Ni
 Power developed at a single road wheel pr
Pr = TR. 2лn / (2x60) = trлni / 60
 If TE = engine torque DR = final drive ratio then TR = TEDR
 IF PE = ENGINE POWER AND ηt = transmission efficiency then
PR = PRηt

26. PRACTICE QUESTION
TORQUE DEVELOPED BY AN ENGINE IS 82 nm
AT 2000 RPM. The final drive ratio is 4.73:1. In top
gear the inside road wheel makes 60 rpm. Calculate
the torque and power at the inner and outer driving
road wheels.
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