93 Steering linkage ball and socket joints

All steering linkage layouts are comprised of rods and arms joined together by ball joints. The ball joints enable track rods, drag-link rods and relay rods to swivel in both the horizontal and vertical planes relative to the steering arms to which they are attached. Most ball joints are designed to tilt from the perpendicular through an inclined angle of up to 20 for the axle beam type front suspension, and as much as 30 in certain independent front suspension steering systems. 9.3.1...

Trailing arm with progressive quarterelliptic spring

(Fig. 10.101) Each axle is carried on a trailing arm the arms on one side are interconnected by a spring in such a way that the upward reaction at one wheel increases the downward load on the other (Fig. 10.101). The inverted quarter-elliptic spring is clamped to the rear trailing arm. Fig. 10.101 Trailing arm with progressive quarter-elliptic spring Its leading end is shackled to a bracket on the front trailing arm. Both trailing arms are welded fabricated steel members of box-section. The...

10171 Description and application of sensors

A list of sensors which can be used are given below however, a limited combination of these sensors may only be installed depending on the sophistication of the suspension system adopted 3 longitudinal acceleration sensor 9 vehicle speed sensor 10 mode selector Height sensor (Fig. 10.121) The linear variable differential sensor is often used to monitor vertical height movement as there is no contact between moving parts it therefore eliminates any problems likely to occur due to wear. It is...

763 Inter axle with third differential

Description of forward rear drive axle (Fig. 7.27) A third differential is generally incorporated in the forward rear axle of a tandem bogie axle drive layout because in this position it can be conveniently arranged to extend the drive to the rear axle (Fig. 7.27). Fig. 7.26 Relationship of relative speeds of double drive axles and the amount of transmission twist Fig. 7.26 Relationship of relative speeds of double drive axles and the amount of transmission twist Power from the gearbox...

821 The structure and properties of rubber

The outside carcass and tread of a tyre is made from a rubber compound that is a mix of several substances to produce a combination of properties necessary for the tyre to function effectively. Most metallic materials are derived from simple molecules held together by electrostatic bonds which sustain only a limited amount of stretch when subjected to tension (Fig. 8.19). Because of this, the material's elasticity may be restricted to something like 2 of its original length. Rubber itself may...

51 Automatic transmission considerations

Because it is difficult to achieve silent and smooth gear ratio changes with a conventional constant mesh gear train, automatic transmissions commonly adopt some sort of epicyclic gear arrangement, in which different gear ratios are selected by the application of multiplate clutches and band brakes which either hold or couple various members of the gear train to produce the necessary speed variations. The problem of a gradual torque take-up when moving away from a standstill has also been...

33 Gear synchronization and engagement

The gearbox basically consists of an input shaft driven by the engine crankshaft by way of the clutch and an output shaft coupled indirectly either Fig. 3.4 Five speed and reverse single stage synchromesh gearbox with integral final drive (transaxle unit) Fig. 3.4 Five speed and reverse single stage synchromesh gearbox with integral final drive (transaxle unit) through the propellor shaft or intermediate gears to the final drive. Between these two shafts are pairs of gear wheels of different...

Description of differential and viscous coupling

(Figs 7.16 and 7.17) The crownwheel is bolted to the differential bevel gearing and multiplate housing. Speed differentiation is achieved in the normal manner by a pair of bevel sun (side) gears, each splined to a half shaft. Bridging these two bevel sun gears are a pair of bevel planet pinions supported on a cross-pin mounted on the housing cage. A multiplate back assembly is situated around the left hand half shaft slightly outboard from the corresponding sun gear (Fig. 7.16). The viscous...

134 Vapourcompression cycle refrigeration system with reverse cycle defrosting

A practical refrigeration system suitable for road transportation as used for rigid and articulated vehicles must have a means of both cooling and Reverse expansion valve - cold (closed) Fig. 13.15 (a and b) Refrigeration system with reverse cycle defrosting Reverse expansion valve - hot (open) Condenser coil Remote feeler bulb Reverse expansion valve - hot (open) Condenser coil Remote feeler bulb defrosting the cold compartment. The operation of such a system involving additional valves...

1018 Electronic controlled pneumatic air suspension for on and off road use

A pneumatic (air) controlled suspension system provides a variable spring rate so that a constant suspension frequency is obtained between light and heavy load conditions. Additional telescopic dampers are also installed to improve the ride quality and comfort. A driver's height control is also provided to enable the body height to be adjusted for specific purposes such as loading the boot or cargo space, towing a trailer, driving over rough terrain, or muddy ground, or travelling though...

146 Afterbody drag

14.6.1 Squareback drag (Figs 14.41 and 14.42) Any car with a rear end (base) slope surface angle ranging from 90 to 50 is generally described as a squareback style (see Fig. 14.42). Between this angular surface inclination range for a squareback car there is very little change in the air flow pattern High speed Reduced speed low pressure increase in pressure High speed Reduced speed low pressure increase in pressure 14.39(a-c) Effect of rear end spoiler on both lift and drag coefficients...

Differential action when moving straight ahead

(Fig. 7.15) When the vehicle is moving straight ahead power is transferred from the propellor shaft to the bevel pinion and crownwheel. The crownwheel and differential cage therefore revolve as one unit (Fig. 7.15). Power is divided between the left and right hand worm wheel by way of the spur gear pins which are attached to the differential cage. It then flows to the pair of meshing worm gears, where it finally passes to each splined half shaft. Under these conditions, the drive in terms of...

M N

W, WF and WR Total, front and rear weight transfer respectively (N) t Wheel tract (m) 10.3.7 Lateral (side) force distribution The total lateral resisting forces generated at all tyre to ground interfaces must equal the centrifugal Fig. 10.33 Longitudinal weight distributions Fig. 10.33 Longitudinal weight distributions Independent suspension (t> J Higid axle tieam suspension Fig. 10.34(a and b) Comparison of rigid and independent suspension body roll stiffness Independent suspension (t> J...

Front end splitter two speed gearbox power flow

(Fig. 3.23) Input power to the gearbox is supplied to the first motion shaft. When the splitter synchronizing sliding sleeve is in neutral, both the splitter low and high input gear wheels revolve on their needle bearings independently of their supporting first motion shaft and mainshaft respectively. 3.5.4 Twin counter shaft ten speed constant mesh gearbox with synchromesh two speed rear mounted range change (Fig. 3.24) With the quest for larger torque carrying capacity, closer steps between...

Operation of the rotary control valve and power piston

Neutral position (Fig. 9.16(a)) With no steering effort being applied when driving along a straight Fig. 9.16(a-d) Rack and pinion power assisted steering with rotary control valve Fig. 9.16(a-d) Rack and pinion power assisted steering with rotary control valve track, the longitudinal lands formed by the slots milled on the rotor periphery angularly align with the internal sleeve slots so that equal space exists between the edges of adjacent rotor and sleeve slots. Fluid therefore flows from...

1253 Rear axle braking Fig 1242ad

Rear axle foot brake released (Fig. 12.42(a)) When the brake pedal is released the travel sensors within the brake value sensor (BVS) signal the electronic control module (ECM) which in turn informs the axle modulator to release the brake Foot brake Proportional Proportional Pressure Single circuit Speed pedal (FBP) relay valve valve (PV) sensor (PS) (diaphragm) sensor (nS) Four circuit protection valve (4CPV) Foot brake Proportional Proportional Pressure Single circuit Speed pedal (FBP) relay...

L t IJurfKK Z

Fig. 7.23 Outboard epicyclic bevel gear two speed double reduction axle Fig. 7.24 Two speed double reduction helical gear axle Fig. 7.24 Two speed double reduction helical gear axle drive. For example, with a single reduction final drive the gear reduction can be so chosen as to provide a high cruising speed on good roads with a five speed gearbox. Conversely, if the truck is to be used on hilly country or for off-road use then a double reduction axle may provide the necessary gear reduction....

81 Tractive and braking properties of tyres 811 Tyre grip

Tyres are made to grip the road surface when the vehicle is being steered, accelerated, braked and or negotiating a corner and so the ability to control the tyre to ground interaction is of fundamental importance. Road grip or friction is a property which resists the sliding of the tyre over the road surface due to a retardant force generated at the tyre to ground contact area. The grip of different tyres sliding over various road surface finishes may be compared by determining the coefficient...

961 Steering desirability

To meet all the steering requirements the rack and pinion steering must be precise and direct under normal driving conditions, to provide a sense of feel at the steering wheel and for the steering wheel to freely return to the straight ahead position after the steering has been turned to one lock or the other. The conventional power assisted steering does not take into account the effort needed to perform a steering function relative to the vehicle speed, particularly it does not allow for the...

845Cornering stiffness cornering power

When a vehicle travels on a curved path, the centrifugal force (lateral force) tends to push sideways each wheel against the opposing tyre contact patch to ground reaction. As a result, the tyre casing and tread in the region of the contact patch very slightly deform into a semicircle so that the path followed by the tyre at ground level will not be quite the same as the direction of the wheel points. The resistance offered by the tyre crown or belted tread region by the casing preventing it...

29 Spicer twin driven plate angle spring pull type clutch Fig 214

An interesting clutch engagement and release pressure plate mechanism employs three pairs of coil springs which are inclined to the axial direction of the driven plates. These springs are mounted between the pressure plate cover housing, which takes the spring reaction, and the release lever central hub (Fig. 2.14). The axial clamping thrust is conveyed by the springs to the six to one leverage ratio release levers (six of them) spaced evenly around the release hub. These release levers span...

852 Directional stability on a curved track

True rolling of all four wheels can take place when projection lines drawn through the rear axle and each of the front wheel stub axles all meet at a common point somewhere along the rear axle projected line. This steering layout with the front wheels pivoted at the ends of an axle beam is known as the Ackermann principle, but strictly it can only be applied when solid tyres are used and when the vehicle travels at relatively slow speeds. With the advent of pneumatic tyres, the instantaneous...

122 Reasons for flexible mountings

It is the objective of flexible mounting design to cope with the many requirements, some having conflicting constraints on each other. A list of the duties of these mounts is as follows 1 To prevent the fatigue failure of the engine and gearbox support points which would occur if they were rigidly attached to the chassis or body structure. 2 To reduce the amplitude of any engine vibration which is being transmitted to the body structure. 3 To reduce noise amplification which would occur if...

Setting crownwheel and pinion backlash and preloading differential bearings using adjusting nuts

(Figs 7.6 and 7.7) Locate the differential bearing caps on their cones and position the differential assembly in the final drive housing. Refit the bearing caps with the mating marks aligned and replace the bolts so that they just nip the caps in position. Screw in the adjusting nuts whilst rotating the crownwheel until there is just a slight backlash. Bolt the spread gauge to the centre bolt hole of the bearing cap and fit an inverted bearing cap lock tab to the other cap (Fig. 7.7). Ensure...

572Main pressure regulator valve MPRV Fig 514a and b

This valve controls the output pressure which is delivered to the brake band, multiplate brake and clutch servos. Oil pressure from the pump acts on the left hand end of the valve and opposes the return spring. This oil pressure moves the valve to the right, initially permitting oil to pass to the converter pressure valve and its circuit, but with further valve movement oil will be exhausted back to the pump intake passage. The line pressure build-up is also controlled by introducing limited...

Trailing arms with central longitudinal wishbone and antiroll tube nondrive axle rear suspension

(Fig. 10.47) A rectangular hollow sectioned axle beam spans the two wheels and on either side are mounted a pair of coil springs. A left and right hand trailing arm links the axle beam to the body structure via rubber bushed pivot pins located at both ends of the arms at axle level (Fig. 10.47). To locate the axle beam laterally and to prevent it rotating when braking, an upper longitudinal wishbone arm ('A' arm) is mounted centrally between the axle and body structure. The 'A' arm maintains...

710 Traction control system

With a conventional final drive differential the torque output from each driving wheel is always equal. Thus if one wheel is driven over a slippery patch, that wheel will tend to spin and its adjacent sun (side) gear will not now be able to provide the reaction torque for the other (opposite) sun (side) gear and driving road wheel. Accordingly, the output torque on the other wheel which still has a good tyre to surface grip will be no more than that of the slipping wheel and it doesn't matter...

161 The need for automatic lubrication system

Owing to the heavy loads they carry commercial vehicles still prefer to use metal to metal joints which are externally lubricated. Such joints are kingpins and bushes, shackle pins and bushes, steering ball joints, fifth wheel coupling, parking brake linkage etc. (Fig. 1.29). These joints require lubricating in proportion to the amount ofrelative movement and the loads exerted. If lubrication is to be effective in reducing wear between the moving parts, fresh oil must be pumped between the...

59 The continuously variable belt and pulley transmission

The continuously variable transmission CVT, as used by Ford and Fiat, is based simply on the Selector position Possible fault Table 5.5 Table of symptoms for a faulty one way clutch Fault 0-50 km h above 50 km h Slipping stator Very sluggish Drives normally Seized stator Drives normally Loss of power principle of a belt running between two V-shaped pulleys which is designed so that the effective belt contact diameter settings can be altered to produce a stepless change in the input to output...

521 D drive range first gear

With the selector lever in D range, engine torque is transmitted to the overdrive pinion gears via the out put shaft and pinion carrier. Torque is then split between the overdrive annular gear and the sun gear, both paths merging due to the engaged direct clutch. Therefore the overdrive pinion gears are prevented from rotating on their axes, causing the overdrive gear set to revolve as a whole without any gear ratio reduction at this stage. Torque is then conveyed from the overdrive annular...

Direct and overdrive controlled gear change action

(Fig. 3.29) When direct drive is selected, hydraulic pressure is steadily increased and this gradually releases the double-sided cone clutch member from the cone brake fixed to the casing. The release of the cone clutch frees the sun gear and removes the load from the engine. The engine speed increases immediately until it catches up with the output shaft, at which point the unidirectional clutch rollers climb up their respective ramps and jam. The input shaft's power coming from the engine is...

945 Dual front axle steering

Twin Front Axle Steering Mechanisms

Operating large rigid trucks with heavy payloads makes it necessary in addition to utilizing tandem axles at the rear to have two axles in the front of the vehicle which share out and support the load. Both of the front axles are compelled to be steer axles and therefore need to incorporate steering linkage such as will produce true or near true rolling when the vehicle is driven on a curved track. The advantages gained by using dual front steering axles as opposed to a single steer axle are as...

1012 Variable rate leaf suspension springs

The purpose of the suspension is to protect the body from the shocks caused by the vehicle moving over an uneven road surface. If the axle were bolted directly to the chassis instead of through the media of the springs, the vehicle chassis and body would try to follow a similar road roughness contour and would therefore lift and fall accordingly. With increased speed the wheel passing over a bump would bounce up and leave the road so that the grip between the tyre and ground would be lost....

311 Resistance to vehicle motion

To keep a vehicle moving, the engine has to develop sufficient power to overcome the opposing road resistance power, and to pull away from a standstill or to accelerate a reserve of power in addition to that absorbed by the road resistance must be available when required. Road resistance is expressed as tractive resistance (kN). The propelling thrust at the tyre to road interface needed to overcome this resistance is known as tractive effect (kN) (Fig. 3.1). For matching engine power output...

Brake application with fully worn linings

(Fig. 11.11(d)) When the brakes are operated with fully worn linings the shoes move outwards before they contact the drum. During this outward movement the rear end of the slot contacts the inner edge of the quadrant lever, disengaging it from the pinion. At the same time the quadrant lever rotates until the fingered end of the lever touches the side of the shoe web. Releasing the brakes permits the shoes to retract until the quadrant lever contacts the pinion at its least return position near...

772 Understeer and oversteer characteristics

Tyre Tire Slip Angles

In general, tractive or braking effort will reduce the cornering force (lateral force) that can be generated Fig. 7.30(a and b) The influence of front and rear tyre slip angles on steering characteristics Fig. 7.30(a and b) The influence of front and rear tyre slip angles on steering characteristics for a given slip angle by the tyre. In other words the presence of tractive or braking effort requires larger slip angles to be produced for the same cornering force it reduces the cornering...

1221 Truck air over hydraulic brake system Fig 121

Trailer Air Brake System Diagram

Compressed air supply Air is drawn into the compressor and then discharged into and out of the wet tank where it is semi-dried it then flows to the multi-circuit protection valve, here it divides to feed the two service reservoirs. At the same time, pressurized air from the reservoirs combine through internal passages in the multi-circuit protection valve to supply the remote spring brake actuator via the hand control valve. Service line circuit (Fig. 12.1) There are two service lines feeding...

41 Hydrokinetic fluid couplings

Fluid Flywheel Simple Diagram

The hydrokinetic coupling, sometimes referred to as a fluid flywheel, consists of two saucer-shaped discs, an input impeller (pump) and an output turbine (runner) which are cast with a number of flat radial vanes (blades) for directing the flow path of the fluid (Fig. 4.1). Owing to the inherent principle of the hydro-kinetic coupling, there must be relative slip between the input and output member cells exposed to each other, and the vortex flow path created by pairs of adjacent cells will be...

Description of power assisted steering system

External Power Assisted Steering

(Figs 9.12, 9.13 and 9.14) This directly coupled power assisted system is hydraulic in operation. The power assisted steering layout (Fig. 9.14) consists of a moving power cylinder. Inside this cylinder is a double acting piston which is attached to a ramrod anchored to the chassis by either rubber bushes or a ball joint. One end of the power cylinder is joined to a spool control valve which is supported by the steering box drop arm and the other end of the power cylinder slides over the...

1452 Exposed wheel air flow pattern

When a wheel rotates some distance from the ground air due to its viscosity attaches itself to the tread and in turn induces some of the surrounding air to be dragged around with it. Thus this concentric movement of air establishes in effect a weak vortex, see Fig. 14.36(a). If the rotating wheel is in contact with the ground it will roll forwards which makes windtunnel testing under these conditions difficult this problem is overcome by using a supportive wheel and floor rig. The wheel is...

32 Five speed and reverse synchromesh gearboxes

With even wider engine speed ranges (1000 to 6000 rev min) higher car speeds (160km h and more) and high speed motorways, it has become desirable, and in some cases essential, to increase the number of traditional four speed ratios to five, where the fifth gear, and sometimes also the fourth gear, is an overdrive ratio. The advantages of increasing the number of ratio steps are several not only does the extra gear provide better acceleration response, but it enables the maximum engine...

1237 Pressure reducing valve piston type

Various parts of an air brake system may need to operate at lower pressures than the output pressure delivered to the reservoirs. It is therefore the function of the pressure reducing valve to decrease, adjust and maintain the air line pressure within some predetermined tolerance. Fig. 12.13 (a-c) Pressure reducing valve (piston type) Fig. 12.13 (a-c) Pressure reducing valve (piston type) Operation When the vehicle is about to start a journey, the compressor charges the reservoirs and air will...

221 Axial driven plate friction lining cushioning

In its simplest form the driven plate consists of a central splined hub. Mounted on this hub is a thin steel disc which in turn supports, by means of a ring of rivets, both halves of the annular friction linings (Figs 2.2 and 2.3). Axial cushioning between the friction lining faces may be achieved by forming a series of evenly spaced 'T' slots around the outer rim of the disc. This then divides the rim into a number of segments (Arcuate) (Fig. 2.4(a)). A horseshoe shape is further punched out...

92 The need for power assisted steering

With manual steering a reduction in input effort on the steering wheel rim is achieved by lowering the Torque taction at steering wheel tfeell Torque taction at steering wheel tfeell Fig. 9.10 Typical relationship of tyre grip on various road surfaces and the torque reaction on the driver's steering wheel Force at end of steering drop ari*rt (N) Fig. 9.11 Comparison of manual steering with different reduction gear ratio and power assisted steering Force at end of steering drop ari*rt (N) Fig....

Trailing arm rear wheel drive independent suspension

(Fig. 10.53) The independent trailing arm suspension has both left and right hand arms hinged on an axis at right angles to the vehicle centre line (Fig. 10.53). Each arm, which is generally semi-triangular shaped, is attached to two widely spaced pivot points mounted on the car's rear subframe. Thus the trailing arms are able to transfer the drive thrust from the wheel and axle to the body structure, absorb both drive and braking torque reactions and to restrain transverse body movement when...

712Setting pinion depth

Crown Wheel And Pinion Design

Press the inner and outer pinion bearing cups into the differential housing and then lubricate both bearings. Slip the standard pinion head spacer (thick shim washer) and the larger inner bearing over the dummy pinion and align assembly into the pinion housing (Fig. 7.2). Slide the other bearing and centralizing cone handle over the pinion shank, Fig. 7.1 Stretching axle housing to remove differential cage assembly Fig. 7.1 Stretching axle housing to remove differential cage assembly then screw...

6115 Preloading ball and taper roller bearings

An understanding of the significance of bearing preloading may be best visualized by considering a final drive bevel pinion supported between a pair of taper roller bearings (Fig. 6.24). Since the steel of which the rollers, cone and cup are made to obey Hooke's Fig. 6.26 Comparison of bearing load-deflection graph with and without preload law, whereby strain is directly proportional to the stress producing it within the elastic limit of the material, the whole bearing assembly can be given the...

Swing arm rear wheel drive independent suspension

Transverse Swing Arm Design

(Fig. 10.51) This suspension normally takes the form of a pair of triangular transverse ('A' arm) swing arm members hinging on inboard pivot joints situated on either side of the final drive with their axes parallel to the car's centre line (Fig. 10.51). Coil springs are mounted vertically on top of the swing arm members near the outer ends. The wheels are supported on drive hubs mounted on ball or tapered roller bearings located within the swing arm frame. Each drive shaft has only one...

461 Overrun clutch with single diameter rollers

Type Clutch

A roller clutch is comprised of an inner and outer ring member and a series of cylindrical rollers spaced between them (see Fig. 4.13). Incorporated between the inner and outer members is a cage which positions the rollers and guides so that they roll up and down their ramps simultaneously. One of the members has a cylindrical surface concentric with its axis, this is usually made the outer member. The other member (inner one) has a separate wedge ramp formed for each roller to react against....

5105 Description of major hydraulic and electronic components

Hydraulic control unit (Fig. 5.38) The hydraulic control unit is housed in the oil-pan position underneath the transmission gears. A fluid pump operates the hydraulic circuitry it is driven directly from the engine via the torque converter casing, fluid is directed by way of a pressure regulation valve to the interior of the torque converter and to the various clutches and brakes via passages and valves. The hydraulic control circuit which operates the gear shifts are activated by three...

Double inclined rectangular sandwich mounting

(Fig. 1.18(h)) A pair of rectangular sandwich rubber blocks are supported on the slopes of a triangular pedestal. A bridging plate merges the resilience of the inclined rubber blocks so that they provide a combined shear and compressive distortion within the rubber. Under small deflection conditions the shear and compression is almost equal, but as the load and thus deflection increases, the proportion of compression over the shear loading predominates. These mounts provide very good lateral...

97 Rack and pinion electric power assisted steering

Basics Rack And Pinion Steering

The traditional hydraulic actuated power assisted steering requires weighty high pressure equipment, which incorporates an engine driven high pressure pump, fluid reservoir and filter, reaction valve, high pressure hoses, servo cylinder, piston, ram and a suitable fluid. There is a tendency for fluid to leak due to severe overloading of the steering linkage when driving against and over stone kerbs and when manoeuvring the car during parking in confined spaces. The electric power assisted...

1129 Properties of friction lining and pad materials

Friction level (Fig. 11.6) The average coefficient of friction with modern friction materials is between 0.3 and 0.5. The coefficient of friction should be sufficiently high to limit brake pedal effort and to reduce the expander leverage on commercial vehicles, but not so high as to produce grab, and in the extreme case cause lock or sprag so that rotation of the drum becomes impossible. The most suitable grade of friction material must be used to match the degree of self-energization created...

Unequal weight distribution levelling control

(Fig 10.124(a and b)) Uneven weight distribution is automatically compensated for by the levelling control (a) Heavy load without height level control (b) Heavy load with height level control (a) Heavy load without height level control (b) Heavy load with height level control (c) Cornering without anti-roll control (c) Cornering without anti-roll control (d) Cornering with anti-roll control (d) Cornering with anti-roll control Fig. 10.124(a-g) Active self-levelling hydraulic coil spring...

5102 Gear train power flow for individual gear ratios

D drive range first gear (Fig. 5.31) With the position selector lever in D drive range, the one way clutch (OWC) holds the front planet carrier while multiplate clutch (B) and the multiplate brake (G) are applied. Power flows from the engine to the torque converter pump wheel, via the fluid media to the output turbine wheel. It is then directed by way of the input shaft and the applied multiplate clutch (B) to the front planetary large sun gear (SL). With the front planet carrier (CF) held...

95 Variableratio rack and pinion

Variable-ratio rack and pinion can be made to improve both manual and power assisted steering operating characteristics. For a manual rack and pinion steering system it is desirable to have a moderately high steering ratio to provide an almost direct steering response while the steering wheel is in the normally 'central position' for straight ahead driving and for very small steering wheel angular correction movement. Conversely for parking manoeuvres requiring a greater force to turn the...

45 Torque converter performance terminology

Vehicle Performance Characteristics

To understand the performance characteristics of a fluid drive (both coupling and converter), it is essential to identify and relate the following terms used in describing various relationships and conditions. 4.5.1 Fluid drive efficiency (Figs 4.11 and 4.12) A very convenient method of expressing the energy losses, due mainly to fluid circulation within a fluid drive at some given output speed or speed ratio, is Fig. 4.11 Characteristic performance curves for a three element converted coupling...

1016 Lift axle tandem or triaxle suspension

Tandem Suspension

Vehicles with tandem or tri-axles which carry a variety of loads ranging from compact and heavy to bulky but light may under-utilize the load carrying capacity of each axle, particularly an empty return journey over a relatively large proportion of the vehicle's operating time. When a vehicle carries a full load, a multi-axle suspension is essential to meet the safety regulations, but the other aspects are improved road vibration isolation from the chassis, better road holding and adequate ride...

1015 Air suspensions for commercial vehicles

A rigid six wheel truck equipped with pairs of air springs per axle is shown in Fig. 10.106. The front suspension has an air spring mounted between the underside of each chassis side-member and the transverse axle beam, and the rear tandem suspension has the air springs mounted between each trailing arm and the underside of the chassis (Figs 10.107 and 10.108). Air from the engine compressor passes through both the unloader valve and the pressure regulator valve to the reservoir tank. Air is...

123 Air operated power brake equipment

12.3.1 Air dryer (Bendix) (Fig. 12.7(a and b)) Generally, atmospheric air contains water vapour which will precipitate if the temperature falls low enough. The amount of water vapour content of the air is measured in terms of relative humidity. A relative humidity of 100 implies that the air is saturated so that there will be a tendency for the air to condensate. The air temperature and pressure Fig. 12.7(a and b) Air dryer (Bendix) Fig. 12.7(a and b) Air dryer (Bendix) determines the...

731 Salisbury Powr Lok limited slip differential

Multiclush Plate For Tractors Pictures

This type of limited slip differential is produced under licence from the American Thornton Axle Co. The Powr-Lok limited slip differential essentially consists of an ordinary bevel gear differential arranged so that the torque from the engine engages friction clutches locking the half shafts to the differential cage. The larger the torque, the greater the locking effect (Fig. 7.11). Fig. 7.11 Multiclutch limited slip differential Fig. 7.11 Multiclutch limited slip differential There are three...

Operation of exhaust compression brake

How Work Retarder

Retarder operating (Fig. 12.31(a)) When the foot control (on off) valve is depressed by the driver's left foot heel, compressed air from the brake system's reservoir is delivered to both the brake butterfly valve slave cylinder and the fuel cut-off slave cylinder via the pressure regulator valve, causing both slave pistons to move outwards simultaneously. The outward movement of the butterfly slave piston causes the butterfly operating lever to rotate about its spindle to close the exhaust...

10135 Alternative tandem axle bogie arrangements

Balance Beam Vehicle Technology

Leading and trailing arms with inverted semi-elliptic spring suspension (Fig. 10.97) An interesting tandem axle arrangement which has been used for recovery vehicles and tractor units where the laden to unladen ratio is high is the inverted semi-elliptic spring with leading and trailing arm (Fig. 10.97). The spring and arms pivot on a central chassis member the arm forms a right angle with its horizontal portion providing the swing arm, while the vertical upper portion is shaped to form a...

104 Antiroll bars and roll stiffness Fig 1035

A torsion anti-roll bar is incorporated into the suspension of a vehicle to enable low rate soft springs to be used which provides a more comfortable ride under normal driving conditions. The torsion bar does not contribute to the suspension spring stiffness (the suspension's resistance to vertical deflection) as its unsprung weight is increased or when the driven vehicle is subjected to dynamic shock loads caused possibly by gaps or ridges where concrete sections of the road are joined...

148 Commercial vehicle drag reducing devices

Civil Engineering Truck Turning Diagrams

14.8.1 Cab roof deflectors (Figs 14.54(a and b), 14.55(a and b) and 14.56(a-c)) To partially overcome the large amount of extra drag experienced with a cab to trailer height mismatch a cab roof deflector is commonly used. This device prevents the air movement over the cab roof impinging on the upper front of the trailer body and then flowing between the cab and trailer gap, see Fig. 14.54(a). Instead the air flow is diverted by the uptilted deflector surface to pass directly between the cab to...

332 Positive baulk ring synchromesh unit

Constant Load Synchro Hub Engagement

The gearbox mainshaft rotates at propellor shaft speed and, with the clutch disengaged, the first motion shaft gear, layshaft cluster gears, and mainshaft gears rotate freely. Drive torque will be transmitted when a gear wheel is positively locked to the mainshaft. This is achieved by means of the outer synchromesh hub internal teeth which slide over the inner synchro-mesh hub splines (Fig. 3.6(a)) until they engage with dog teeth formed on the constant mesh gear wheel being selected. When...

912 Screw and nut steering gear mechanism

Square Cut Screw From Steering Gear Box

To introduce the principles of the steering gearbox, the screw and nut type mechanism will be examined as this is the foundation for all the other types of steering box gear reduction mechanisms. A screw is made by cutting an external spiral groove around and along a cylindrical shaft, whereas a nut is produced by cutting a similar spiral groove on the internal surface of a hole made in a solid block. The thread profile produced by the external and internal spiral grooves may take the form of a...

1124 Drum shoe arrangements Fig 113ac

Drum Brakes Due Sevo

Leading and trailing shoe brakes (Fig. 11.3(a)) If a single cylinder twin piston expander (double acting) is mounted between two shoe tips and the opposite shoe tips react against a fixed abutment, then the leading shoe is forced against the drum in the forward rotation direction, whilst the trailing shoe works against the rotation direction producing Fig. 11.3 (a-d) Various brake shoe arrangements Fig. 11.3 (a-d) Various brake shoe arrangements much less frictional drag. Such an arrangement...

Double diaphragm chamber type actuator

Diaphragm Civil Engg

(Fig. 12.28(b)) The double diaphragm chamber actuators are designed to be used when there are two separate air delivery circuits, known as the service line (foot) and the secondary (hand) line, systems operating on each foundation brake. Service line application When the service (foot) brake is applied compressed air enters the service chamber via the intake ring. As the air pressure rises, the service diaphragm and push rod are forced outwards, applying the leverage to the slack adjuster....

823 Natural and synthetic rubbers

Synthetic materials which have been developed as substitutes for natural rubber and have been utilized for tyre construction are listed with natural rubber as follows b) Chloroprene (Neoprene) rubber (CR) c) Styrene-butadiene rubber (SBR) e) Ethylene propylene rubber (EPR) g) Isobutene-isoprene (Butyl) rubber (IIR) Natural rubber (NR) Natural rubber has good wear resistance and excellent tear resistance. It offers good road holding on dry roads but retains only a moderately good grip on wet...

Automatic adjuster operation

Quadrant Brake Adjustment

Brake application with new linings (Fig. 11.10(b)) When the foot brake is applied, hydraulic pressure forces the twin plungers apart so that the shoes are expanded against the drum. If the linings are new and there is very little lining to shoe clearance, then the outward movement of the leading and trailing shoes will not be sufficient for the clearance between the rectangular slot in the sector lever and the strut inner edge to be taken up. Therefore the shoes will return to their original...

814 Braking characteristics on wet roads

Maximum friction is developed between a rubber tyre tread and the road surface under conditions of slow movement or creep. A tyre's braking response on a smooth wet road with the vehicle travelling at a speed, say 100 km h, will show the following characteristics (Fig. 8.9). When the brakes are in the first instance steadily applied, the retardation rate measured as a fraction of the gravitational acceleration (g m s2) will rise rapidly in a short time interval up to about 0.5 g. This phase of...

10143 Willetts velvet ride leading and trailing arm torsional rubber spring suspension Fig 10105a and b

The tandem suspension consists of leading and trailing swing arms. These arms are mounted back to back with their outer ends attached to the first and second drive axles whereas the swivel ends are supported on central trunnion pivot tubes which are mounted on a frame cross-member on either side of the chassis (Fig. 10.105(a)). Torque arms attached to the suspension cross-member and to brackets in the centres of each axle casing assist the swing arms to transfer driving and braking torque...

102 Suspension roll centres

Roll centres (Fig. 10.29) The roll centre of a suspension system refers to that centre relative to the ground about which the body will instantaneously rotate. The actual position of the roll centre varies with the geometry of the suspension and the angle of roll. Roll axis (Fig. 10.29) The roll axis is the line joining the roll centres of the front and the rear suspension. Roll centre height for the front and rear suspension will be quite different usually the front suspension has a lower roll...

Anticlockwise rotation of the steering wheel turning left low speed Figs 938b and 939b Rotating

Valve sleeve Inner check valve Outer check valve Inner reaction chamber Reaction piston (RP) Fig. 9.38(a-d) Speed sensitive rack and pinion power assisted steering with rotary reaction control valve the steering wheel in an anticlockwise direction twists the control valve rotor against the resistance of the torsion bar until the corresponding leading edges of the elongated groove in the valve rotor and sleeve align. At this point the return path to the exit port '4' is blocked by control edges...

108 Suspension design consideration

Rubber bush type joints act as the intermediates between pivoting suspension members and the body to reduce the transmission of road noise from the tyres to the body. The size, shape and rubber hardness are selected to minimize noise vibration and ride hardness by operating in a state of com-pressive or torsional distortion. If the rubber joints are subjected to any abnormal loads, particularly when the suspension pivots are being articulated, the theoretical geometry of the swing members may...

253 Flywheel friction face and rim face runout

Twin Disc Pull Type Clutch Assembly

When the flywheel is centred by the crankshaft axis, it is essential that the flywheel friction face and rim rotate perpendicularly to the crankshaft axis. Mount the dial gauge magnetic base to the engine flywheel housing. First set the indicator pointer against the friction face of the flywheel near the outer edge (Fig. 2.10(a and b)) and set gauge to zero. Turn the flywheel one revolution and observe the amount of variation. Secondly reset indicator pointer against the flywheel rim and repeat...

5111 Description of transmission system

The system being described is broadly based on the ZF Man Tip Matic ZF AS Tronic 12 speed twin countershaft three speed constant mesh gearbox with a front mounted two speed 'splitter' gear change and a rear positioned single stage two speed epicyclic gear 'range' change however, the basic concept has been modified and considerably simplified in this text. Gear changes are achieved by four pneumatically operated power cylinders and pistons which are attached to the ends of the three selector...

147 Commercial vehicle aerodynamic fundamentals

14.7.1 The effects of rounding sharp front cab body edges (Fig. 14.50(a-d)) A reduction in the drag coefficient of large vehicles such as buses, coaches and trucks can be made by rounding the front leading edges of the vehicle. - Flow almost remains attached (b) Coach with rounded leading edges Flow remains attached (c) Coach with rounded edges and backsloping front 1.0 (d) Effect of rounding vehicle leading edges upon the aerodynamic drag eg (d) Effect of rounding vehicle leading edges upon...

1082 Suspension roll steer

Rolle Lenkbar

When a vehicle is cornering the body tilts and therefore produces a change in its ground height between the inside and outside wheels. By careful design, the suspension geometry can be made to alter the tracking direction of the vehicle. This self-steer effect is not usually adopted on the front suspension as this may interfere with steering geometry but it is commonly used for the rear suspension to increase or decrease the vehicle's turning ability in proportion to the centrifugal side force...

105 Rubber spring bump or limiting stops

Double Rubbers Triple Springs

10.5.1 Bump stop function (Figs 10.40 and 10.42) Suspension bump and body roll control depends upon the stiffness of both the springs and anti-roll bar over the normal operating conditions, but if the suspension deflection approaches maximum bump or roll the bump stop (Fig. 10.40(a, b, c and d)) becomes active and either suddenly or progressively provides additional resistance to the full deflection of the wheel and axle relative to the body (Fig. 10.42). The bump stop considerably stiffens the...

1335 Suction pressure valve throttling valve

This valve is incorporated in the compressor output suction line to limit the maximum suction Outlet vapour to compressor suction valves Fig. 13.10 Suction pressure regulating valve (throttling valve) Outlet vapour to compressor suction valves Fig. 13.10 Suction pressure regulating valve (throttling valve) pressure generated by the compressor thereby safeguarding the compressor and drive engine motor from overload. If the maximum suction pressure is exceeded when the refrigeration system is...

141 Viscous air flow fundamentals

Pressure Distribution Over Vehicle

14.1.1 Boundary layer (Fig. 14.2) Air has viscosity, that is, there is internal friction between adjacent layers of air, whenever there is relative air movement, consequently when there is sliding between adjacent layers of air, energy is dissipated. When air flows over a solid surface a thin boundary layer is formed between the main airstream and the surface. Any relative movement between the main airstream flow and the surface of Fig. 14.1 Comparison of low and high aerodynamic drag forces...

335 Split ring synchromesh unit

Remote Control Gearshift System

In the neutral position the sliding sleeve sits centrally over the drive hub (Fig. 3.9(a)). This permits the synchronizing ring expander band and thrust block to float within the constraints of the recess machine in the side of the gear facing the drive hub (Fig. 3.9(b)). For gear engagement to take place, the sliding sleeve is moved towards the gear wheel selected (to the left) until the inside chamfer of the sliding sleeve contacts the bevelled portion of the synchronizing ring. As a result,...

Summary and forward and reverse efficiency

Worm And Wheel Steering

Efficiency of a screw and nut mechanism is relatively high in the forward direction since the input shaft screw thread inclined plane angle is small. Therefore a very large wedge action takes place in the forward direction. In the reverse direction, taking the input to be at the steering box drop arm end, the nut threads are made to push against the steering shaft screw threads, which in this sense makes the inclined plane angle very large, thus reducing the wedge advantage. Considerable axial...

1251 Introduction to electronicpneumatic brakes Fig 1240

The electronic-pneumatic brake (EPB) system controls the entire braking process this includes ABS TCS braking when conditions demand, and the layout consists of a single electronic-pneumatic brake circuit with an additional dual pneumatic circuit. The electronic-pneumatic part of the braking system is controlled via various electronic sensors (1) brake pedal travel (2) brake air pressure (3) individual wheel speed and (4) individual lining pad wear. Electronic-pneumatic circuit braking does not...

Description of third differential and viscous coupling

Front Wheel Drive Fig

(Fig. 7.36) The gearbox mainshaft provides the input of power to the third differential (sometimes referred to as the central differential). This shaft is splined to the planet pinion carrier (Fig. 7.36). The four planet pinions are supported on the carrier mesh on the outside with the internal teeth of the annulus ring gear, while on the inside the teeth of the planet pinions mesh with the sun gear teeth. A hollow shaft supports the sun gear. This gear transfers power to the front wheels via...

Rotary vane type vacuum pump rotary exhauster

(Fig. 11.47(c)) When the rotor revolves, the cell spaces formed between the drum blades on the inlet port side of the casing increase and the spaces between the blades on the discharge port side decrease, because of the eccentric mounting of the rotor drum in its casing. As a result, a depression is created in the enlarging cell spaces on the inlet side, causing air to be exhausted (drawn out) directly from the brake vacuum servo chamber or from a separate vacuum reservoir. However on the...

Dual front axle alignment checks using Dunlop optical measurement equipment Fig 932a d

Check the toe-in or -out of both pairs of front steering wheels and adjust track rods if necessary (Fig. 9.32(a)). Assemble mirror gauge stand with the mirror positioned at right angles to the tubular stand. Position the mirror gauge against a rear axle wheel (preferably the nearest axle to the front) with the mirror facing towards the front of the vehicle (Fig. 9.32(b)). Place the view box gauge stand on the floor in a transverse position at least one metre in front of...

6113 Structural rigidity and bearing preloading

The universal practice of preloading bearing assembly supporting a shaft or hub (Fig. 6.24) raises the rigidity of the bearing assembly so that its deflection under operating conditions is minimized. Insufficient structural rigidity of a shaft or hub assembly may be due to a number of factors which can largely be overcome by preloading the bearings. Bearing Fig. 6.24 Final drive pinion bearing spring preload analogy Fig. 6.24 Final drive pinion bearing spring preload analogy preload goes a long...

44Hydrokinetic three element torque converter

Fig Torque Converter

A three element torque converter coupling is comprised of an input impeller casing enclosing the Fig. 4.7 Relationship of torque carrying capacity, efficiency and output speed for a fluid coupling Fig. 4.7 Relationship of torque carrying capacity, efficiency and output speed for a fluid coupling output turbine wheel. There are about 26 and 23 blades for the impeller and turbine elements respectively. Both of these elements and their blades are fabricated from low carbon steel pressings. The...

215 Composite flywheel and integral single plate diaphragm clutch Fig 224

Diaphragm Clutch

This is a compact diaphragm clutch unit built as an integral part of the two piece flywheel. It is designed for transaxle transmission application where space is at a premium and maximum torque transmitting capacity is essential. The flywheel and clutch drive pressing acts as a support for the annular flywheel mass and functions as the clutch pressure plate drive member. The advantage of having the flywheel as a two piece assembly is that its mass can be concentrated more effectively at its...

1246 Hydraulic type retarder Voith

Electric Retard

The design of a hydraulic retarder is similar to that of a fluid coupling. Basically, the retarder consists of two saucer-shaped discs, a revolving rotor (or impel-lor) and a stationary stator (or reaction member) which are cast with a number of flat radial vanes or blades for directing the flowpath of the fluid. The rotor is bolted to the flange of the internally splined drive shaft hub, which is itself mounted over the external splines formed on both the gearbox mainshaft and the flanged...

Where do Distance between track di Ball diameter de Diametric clearance

Fig. 6.5 Internal bearing diametric clearance taper roller bearings do have clearance slackness or tightness under operating conditions but this cannot be measured until the whole bearing assembly has been installed in its housing. A radial ball bearing working at operating temperature should have little or no diametric clearance, whereas roller radial bearings generally operate more efficiently with a small diametric clearance. Radial ball and roller bearings have a much larger initial...

1154 Compensating port type tandem master cylinder Fig 1126ad

Tandem Master Cylinder Compensated Port

Tandem master cylinders are employed to operate dual-line hydraulic braking systems. The master cylinder is composed of a pair of pistons functioning within a single cylinder. This enables two independent hydraulic cylinder chambers to operate. Consequently, if one of these cylinder chambers or part of its hydraulic circuit develops a fault, the other cylinder chamber and circuit will still continue to effectively operate. Brakes off (Fig. 11.26(a)) With brakes in the 'off' position, both...

1171 Hydromechanical antilock brake system ABS suitable for cars SCS Lucas Girling

Lucas Girling Brake System

This hydro-mechanical antilock braking system has two modular units, each consisting of an integrated flywheel decelerating sensor, cam operated piston type pump and the brake pressure modulator itself (Fig. 11.38). Each modulator controls the adjacent wheel brake and the diagonally opposite rear wheel via an apportioning valve. The modular flywheel sensor is driven by a toothed belt at 2.8 times the wheel speed. The flywheel sensor deter- Fig. 11.38 Stop control braking system (SCS) layout...

56 Three speed and reverse transaxle automatic transmission mechanical power flow

(Gear train as adopted by some Austin-Rover, VW and Audi 1.6 litre cars) The operating principle of the mechanical power or torque flow through a transaxle three speed automatic transmission in each gear ratio will now be considered in some depth, see Fig. 5.12. The planetary gear train consists of two sun gears, two sets of pinion gears (three in each set), two sets of annular (internal) gears and pinion carriers which support the pinion gears on pins. Helical teeth are used throughout. For...

1146 Combined foot and hand brake caliper with automatic screw adjustment Bendix

This unit provides automatic adjustment for the freeplay in the caliper's hand brake mechanism caused by pad wear. It therefore keeps the hand brake travel constant during the service life of the pads. The adjustment mechanism consists of a shouldered nut which is screwed onto a coarsely threaded shaft. Surrounding the nut on one side of the shoulder or flange is a coiled spring which is anchored at its outer end via a hole in the piston. On the other side of the shouldered nut is a ball...

627 Carl Weiss constant velocity joint

Constant Velocity Joint

A successful constant velocity joint was initially invented by Carl W. Weiss of New York, USA, and was patented in 1925. The Bendix Products Corporation then adopted the Weiss constant velocity principle, developed it and now manufacture this design of joint Fig. 6.38 . Joint construction and description With this type of time constant velocity joint, double prong arm yokes are mounted on the ends of the two shafts transmitting the drive Fig. 6.37 . Ground inside each prong member are four...

371 Epicyclic overdrive gearing

Epicyclic gear train overdrives are so arranged that the input shaft drives the pinion carrier while the output shaft is driven by the annular gear ring Figs 3.27 and 3.28 . The gear train may be either of simple single stage or compound double stage design and the derived formula for each arrangement is as follows where A number of annulus ring gear teeth where A number of annulus ring gear teeth Ps number of small planet gear teeth Pl number of large planet gear teeth The amount of overdrive...