CHAPTER 3 propellor shaft, diff.ppt
- 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
- 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.
- 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
- 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
- 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?
- 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. Birhanu sintayehu h/eyesus atsede Yomifan Lemi Fkiru