LV12 drive shafts issue 1

LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 aLV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 aLV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 aLV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 aLV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 aLV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 aLV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 aLV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1

kap all covers 6/9/03 9:49 am Page 23 Student Workbook LV12 Drive Shafts (1) LV12/SWB Student Workbook for Technical Certificates in Light Vehicle Maintenance and Repair MODULE LV12 Drive Shafts (1) Contents Page Drive Train Layouts: Front engine rear wheel drive Power transfer Front engine front wheel drive Mid engine rear wheel drive Four wheel drive (full-time 4WD) Non-permanent four wheel drive Operational requirements of drive shafts and propeller shafts Steering condition Wheel rebounding Disadvantages of the simple universal joint Angular velocity Fitting Propeller Shafts: Propeller shaft alignment ……… Page 3 4 5 Drive Shaft Joints: Construction of the Hooke’s joint Construction of a rubber coupling Drive shaft joints Tripod joint Constant velocity joints Drive shaft assemblies 11 11 11 12 13 13 14 7 Drive Shaft Construction: Propeller shaft Two piece propeller shafts Front propeller shaft (intermediate shaft) Drive shaft layout 15 15 15 16 16 Drive Shaft Operation: Progress check 17 18 10 10 -1Copyright © Automotive Skills Limited 2003 ‘All Rights Reserved Module LV12: Drive Shafts (1) Issue -2Copyright © Automotive Skills Limited 2003 ‘All Rights Reserved Module LV12: Drive Shafts (1) Issue Drive Train Layouts In this unit we consider the means by which power is transmitted between the power source and the driven wheel Front engine rear wheel drive Power produced by the engine must be transferred to the driving wheels of the vehicle This is achieved by a series of shafts and specialised joints Front engine rear wheel drive The power produced by the engine in this illustration must be transferred from the front to the rear of the vehicle This is achieved by using a propeller shaft At the rear, the differential and half shafts transfer the power to the rear wheels within a rigid axle casing -3Copyright © Automotive Skills Limited 2003 ‘All Rights Reserved Module LV12: Drive Shafts (1) Issue Power transfer In this example the power is also transferred from the front to the rear of the vehicle, but the differential transmits the power to smaller shafts, generally referred to as drive shafts, before driving the rear wheels This allows each drive shaft to move independently of each other, rather than together in the rigid casing of a conventional rear axle Front engine front wheel drive The position of the engine and transaxle close to the driving wheels of this front engine front wheel drive example means that a propeller shaft is not required Engine power is transferred directly to the differential and from there to the driving wheels by two drive shafts -4Copyright © Automotive Skills Limited 2003 ‘All Rights Reserved Module LV12: Drive Shafts (1) Issue Mid engine rear wheel drive In the same manner this mid engine rear wheel drive vehicle has an almost identical layout Four wheel drive (full-time 4WD) This permanent four wheel drive layout is a combination of the front wheel drive and rear wheel drive systems previously explained -5Copyright © Automotive Skills Limited 2003 ‘All Rights Reserved Module LV12: Drive Shafts (1) Issue Non-permanent four wheel drive In this example of a non permanent four wheel drive vehicle engine power is transferred to the rear wheels by a propeller shaft However before leaving the transmission the power is also transferred, via a transfer unit, to a front differential and then to the front wheels In this layout there is a means by which the front differential can be disconnected leaving the vehicle in two wheel drive mode Engine power can be transferred from the differential units to the wheels by either a rigid axle or, in independent suspension systems, by separate drive shafts -6Copyright © Automotive Skills Limited 2003 ‘All Rights Reserved Module LV12: Drive Shafts (1) Issue Operational requirements of drive shafts and propeller shafts The transmission is normally fixed to the vehicle chassis by flexible rubber mountings The rear differential and rear axle are usually supported by the rear suspension Therefore suspension travel, due to vehicle loading and bumps in the road, causes the rear axle and differential to change position in relation to the transmission The propeller shaft must therefore be designed to constantly change length and transmit power through a variety of angles To allow changes in length the propeller shaft is usually connected to the transmission by a sliding splined shaft Each end of the propeller shaft is fitted with a universal joint to enable it to absorb changes in drive angle Steering condition Similarly in the above illustration of a front engine front wheel drive arrangement the engine and transaxle are connected to the chassis The front hubs and wheels are supported by the suspension and move in relation to the transaxle Therefore drive shaft operational requirements, to change length and drive through varying angles, are the same as for the propeller shaft arrangement The situation is further complicated because the front wheels are also the steering wheels The turning radius of the vehicle is affected by the ability of the outboard drive shaft joint to deliver power smoothly through an angle of at least 40 degrees, indicated by symbol Ø in the illustration -7Copyright © Automotive Skills Limited 2003 ‘All Rights Reserved Module LV12: Drive Shafts (1) Issue Wheel rebounding The angle (usually in the order of 20 degrees) through which the inboard joint needs to transmit power is considerably less The effects of suspension movement require the drive shaft to change length and in this illustration the inboard joint can slide in an axial direction The distance is usually 25 – 50mm Disadvantages of the simple universal joint In this illustration a simple universal joint, often referred to as a Hooke’s or Spider joint, can be seen to have a major draw back Rotating at an angle of 30 degrees the speed of shaft B varies in relation to shaft A This is often referred to as changing angular velocity If action was not taken to overcome this problem vibration and surge at the wheels would be produced -8Copyright © Automotive Skills Limited 2003 ‘All Rights Reserved Module LV12: Drive Shafts (1) Issue Angular velocity Variations in angular velocity are cancelled out by fitting a similar joint to the other end of the shaft The drive and driven shafts are also fitted parallel to each other to smooth out variations in rotating speeds and torque -9Copyright © Automotive Skills Limited 2003 ‘All Rights Reserved Module LV12: Drive Shafts (1) Issue Fitting Propeller Shafts Correct fitting Incorrect fitting It is vital that propeller shafts are fitted correctly Propeller shaft ends must be marked so that they can be refitted in exactly the same location If this is ignored vibration and noise will be the result In the above illustration the top shaft assembly is fitted correctly and the lower assembly is incorrect Propeller shaft alignment Alignment marks as illustrated should be added before disassembly - 10 Copyright © Automotive Skills Limited 2003 ‘All Rights Reserved Module LV12: Drive Shafts (1) Issue Drive Shaft Joints Construction of the Hooke’s joint The Hooke’s joint illustrated has the advantage of simple construction One of the yokes is welded to the propeller shaft and the other yoke is an integral part of a splined joint, which when inserted into the transmission output housing provides a sliding joint A forged spider is installed between the yokes and needle roller bearings are installed in bearing cups press-fitted into the yoke mountings The cups are located in some instances by circlips or snap rings and can be dismantled and serviced Other versions use shell type bearings instead The cups are crimped in position and this version cannot be dismantled Construction of a rubber coupling An example of a rubber based flexible propeller shaft joint - 11 Copyright © Automotive Skills Limited 2003 ‘All Rights Reserved Module LV12: Drive Shafts (1) Issue Drive shaft joints A Birfield joint, sometimes known as a Rzeppa joint, has an inner race fitted into an outer race between which steel balls are held in position by a steel cage Simple construction and the ability to transmit large torque through a considerable angle means this joint is a common feature of drive shafts fitted to front wheel drive vehicles Because the intersecting point (0 in the illustration) of the driving and driven shafts and the centre (P in the illustration) of each ball bearing is constant this is a constant velocity joint The rotational speeds of the drive and driven shafts are identical The expression constant velocity is commonly abbreviated as C.V and a joint of this type often referred to as a C.V joint The joint is encased in a flexible boot to retain the appropriate lubricating grease - 12 Copyright © Automotive Skills Limited 2003 ‘All Rights Reserved Module LV12: Drive Shafts (1) Issue Tripod joint The Tripod joint has three trunnion shafts on which three rollers, which have roller bearings, run The outer casing has a groove in which each of the rollers is located It is a relatively inexpensive joint which usually has axial movement The joint is encased in a flexible boot to retain the appropriate lubricating grease Failure of drive shaft joints are usually preceded by failure of the flexible boot allowing the loss of lubricant and the ingress of road dirt Constant velocity joints In this constant velocity joint an inner race and an outer race have between them a ball cage As can be seen from the illustration the outer race has a series of grooves in which the ball bearings run, providing axial movement The joint is encased in a flexible boot to retain the appropriate lubricating grease Failure of drive shaft joints are usually preceded by failure of the flexible boot allowing the loss of lubricant and the ingress of road dirt - 13 Copyright © Automotive Skills Limited 2003 ‘All Rights Reserved Module LV12: Drive Shafts (1) Issue Similar constant velocity joint, the major difference being that, as can be seen in the illustration, the grooves of the outer race are set at an angle to those of the inner race The joint is produced in two versions one with axial movement and one without The joint is encased in a flexible boot to retain the appropriate lubricating grease Failure of drive shaft joints are usually preceded by failure of the flexible boot allowing the loss of lubricant and the ingress of road dirt Drive shaft assemblies A drive shaft assembly will usually have a combination of two types of joint as illustrated - 14 Copyright © Automotive Skills Limited 2003 ‘All Rights Reserved Module LV12: Drive Shafts (1) Issue Drive Shaft Construction Propeller shaft Propeller shafts are usually made from a high carbon steel tube to prevent torsional and bending forces Despite a careful balance process, and the addition of balance weights, a single shaft having a joint at each end can suffer from imbalance and vibration at higher rotational speeds because of its greater length Two piece propeller shafts A two-piece shaft having three joints and a centre bearing has the advantage of shorter shafts Bending and high speed vibration is therefore reduced The longer shaft is often two piece with rubber insulators fitted in between Because of these advantages this propeller shaft arrangement is more commonly used - 15 Copyright © Automotive Skills Limited 2003 ‘All Rights Reserved Module LV12: Drive Shafts (1) Issue Front propeller shaft (intermediate shaft) To reduce vibration and noise even further the centre propeller shaft bearing is mounted in rubber Drive shaft layout Whilst most shorter drive shafts are solid, longer drive shafts are often made from a tube This increases stiffness to match the rigidity of shorter shafts - 16 Copyright © Automotive Skills Limited 2003 ‘All Rights Reserved Module LV12: Drive Shafts (1) Issue Drive Shaft Operation During sudden acceleration the front of a vehicle tends to rise up If drive shafts of significantly different length are fitted, as in the top illustration, joint angle Ø1 will be much greater than Ø2 This will cause the wheel attached to the shortest drive shaft to attempt to ‘track or toe in’ further than the wheel attached to the longer drive shaft This will cause the vehicle to veer toward the side with the longest drive shaft This can be prevented from occurring, by keeping joint angles and drive shaft length the same An intermediate shaft is often fitted, as shown in the bottom illustration An illustration of an intermediate drive shaft fitted to maintain straight-line stability during acceleration - 17 Copyright © Automotive Skills Limited 2003 ‘All Rights Reserved Module LV12: Drive Shafts (1) Issue Progress check Answer the following questions: What is the purpose of a sliding joint on a propshaft? What is cyclic variation? When removing a propshaft it is good practice to mark a line across the sliding joint Why is this? If a vehicle is fitted with a two-piece propeller shaft, what advantages would this have over a single piece shaft? - 18 Copyright © Automotive Skills Limited 2003 ‘All Rights Reserved Module LV12: Drive Shafts (1) Issue ... 5 Drive Shaft Joints: Construction of the Hooke’s joint Construction of a rubber coupling Drive shaft joints Tripod joint Constant velocity joints Drive shaft assemblies 11 11 11 12 13 13 14 ... Drive Shaft Construction: Propeller shaft Two piece propeller shafts Front propeller shaft (intermediate shaft) Drive shaft layout 15 15 15 16 16 Drive Shaft Operation: Progress check 17 18 10 ... 10 -1Copyright © Automotive Skills Limited 2003 ‘All Rights Reserved Module LV12: Drive Shafts (1) Issue -2Copyright © Automotive Skills Limited 2003 ‘All Rights Reserved Module LV12: Drive Shafts