TECHNOLOGY IN THE SERVICE OF TRANSPORT

[Music] the crucial demand made of a truck that it should transport goods in the most economical way what does that mean and what are its implications for a vehicle's specification a truck must move its load quickly and at a low operating cost and it must do its job reliably even under adverse road or site conditions a truck must carry as higher payload as possible in relation to its own weight but without its likeness affecting reliability or endurance these requirements are the same for all trucks whatever their pattern of operation or place of work a long distance or trunking vehicle should become moving a high payload quickly on the other hand a tipper is required to negotiate rough ground and severe gradients with payload capacity being less critical these variations of vitamins have to be the designers must aim to achieve a high degree of parts uniformity for a whole range of chassis and to keep down the truck's initial price and maintenance and repair costs on the mercedes-benz new generation range of heavy trucks a balance between economy quality and reliability has been reached now what is different about these new mercedes vehicles they can be equipped with a wide variation of body work according to the loads being carried they include drop sides vans tippers dump trucks and special purpose vehicles for the very different gross weights and operational requirements for this truck range mercedes-benz has developed a family of heavy v configuration diesel engines with a high percentage of common components they are a 9.6 liter v6 developing 192 dean horsepower 12.8 liter v8 developing 240 dean horsepower a 12.8 liter v8 developing 2516 horsepower and a 16 liter v10 developing 320 dean horsepower engine power has to be matched to the truck's pattern of working and the closer the engine is working to its optimum speed and load the greater is the opportunity for achieving flexibility and economy we will see how engine performance is converted into useful work at the driving wheels in other words how technology supports the transport user technology as a tool of transport efficiency a mercedes-benz film about the efficient use of engine performance in a truck in the engine the force to move the vehicle is produced by the combustion of a fuel air mixture here we see an essential factor in determining the economy of a truck the maximum performance of the engine with the minimum possible fuel consumption while meeting all the vehicle emission regulations now enforced throughout the world mercedes-benz diesel engines are able to fulfill these requirements thanks to the company's latest combustion system as the air is drawn into the engine the specially shaped inlet valve ports induce swirl or a rotational air movement in each cylinder diesel fuel is injected into this moving air stream through four minute spray holes in the tip of the injector causing the air and fuel to mix thoroughly the piston rises compressing the mixture which results in the charge igniting in the combustion chamber recessed into the piston crown the downward thrust exerted by the force of the explosion is translated into a rotating movement by the connecting rods pivoting on the crankshaft depending on the size of the engine up to 10 pistons are working to supply this thrust the rotating force exerted by the crankshaft is what the experts call torque the number of times the crankshaft rotates in one minute is defined as the engine speed engine performance is determined by the power and the revolutions per minute rpm the v10 mercedes diesel produces 320 dean horsepower at its normal maximum speed 2500 rpm nevertheless this horsepower is nowhere near sufficient to move a truck in as much that with a direct transmission of engine power to the driving wheels the engine would have to produce around 4000 dean horsepower as much as the output of many ships diesels the operation of such an impossibly heavy and costly vehicle would be quite uneconomical so how is it possible in spite of this to move both a vehicle and its payload weighing together say 38 metric tons with the engine power available because a gearbox matches the engine power and torque to each permutation of weight radiant and acceleration requirement a simple example should make clear the job of the gearbox and how it does it a child sets his tricycle in motion in order to get it moving he needs to summon up a lot of energy the performance of the tricycle depends upon the thrust exerted downwards on the pedals the length of the pedal cranks the number of gear teeth on the pedal crank wheel and the axle sprocket wheel the diameter of the wheels and the speed with which the pedals are pushed often even gentle slopes cannot be negotiated by a fixed ratio geared child's tricycle with a bicycle which has three or four gears however such slopes are relatively easy to deal with what is the reason for this the power of the rider's legs may be no greater but as in a truck gearbox the ratio between the cog sizes is important if the pedal crank wheel is large and the rear sprocket wheel small it is difficult to set off or ride up hills on the flat however such high gearing makes for speed if one wants to climb slopes with the bicycle and speed is not important the front gear wheel can be made smaller and the rear larger the more this ratio is altered the greater is the effective power of the bicycle and rider although maximum speed is reduced simplified it can be said to reach a certain altitude from a given starting level for example the energy expended on a long route is less than on a short but steeper route this principle is just as valid for a trucks gearbox and driving axle combination engine power and torque are transmitted to the gearbox via the clutch plates which are slowly pressed together until they are effectively locked to make the engine and gearbox main shaft turn at the same speed behind the clutch a cog on the main shaft of the gearbox drives the lay or counter shaft the gear wheels which form part of the lay shaft are constantly meshed with their opposite numbers which move freely on the main shaft only by engaging a sliding sleeve through selector forks and a ring attached to the main shaft is each free turning cog engaged with the sleeve and therefore with the main shaft when first gear is selected to move away from rest the smallest driving cog is engaged with the largest driven cog the engine is able to set the laden truck in motion so the truck drives off slowly but making use of full engine power once the vehicle is moving by changing into second third and fourth gears the relationship between attractive effort and speed is altered in a conventional manual transmission the possible ratios are predetermined the driver can select the gear which suits the driving requirement the gearbox delivers the engine output as it were to use either as tractive effort or as speed a four-speed gearbox is usually sufficient for a car but on heavy trucks the relative fluctuation in demand for economical operation and for performance is so great that a four-speed gearbox would not be able to transmit engine output efficiently at all times but increasing the number of gears beyond five or six in a normal layout gearbox would result in an unacceptable increase in the size of the gearbox and less ground clearance the compact solution favored by mercedes-benz is the rear mounted auxiliary splitter unit which enables a four-speed gearbox to become an eight-speed gearbox by repeating the gear changing sequence at a different overall ratio if a second auxiliary splitter is now added in front of the main gearbox 16 gears become available unlike a model steam engine the direction in which a diesel engine rotates cannot be changed so to enable a truck to travel backwards a gear wheel is engaged which changes the rotational direction of the main output shaft by the way the ratio of the reverse gear is usually the lowest of all the gears for here the smallest cog is driving the biggest let us just reiterate the more gearbox ratios available to transmit the engine output the higher is the operating efficiency of a truck fitted with the gearboxes we have discussed so far a truck in the long distance haulage or construction business on hard roads can be tailored and geared to suit its operating requirements for use on difficult ground where wheel adhesion is poor all-wheel drive transmissions are available here the output of the engine is distributed to all the wheels by a secondary or transfer gearbox this is normally achieved by means of a planetary gear set which drives the front and rear axles continuously on soft ground it offers the advantages of lighter steering since the front wheels are effectively pulling the truck in the required direction the attractive effort which can be transmitted to the road by the wheels depends of course on the grip of the tyres on the ground if one axle comes onto slippery ground the power delivered through the transfer case cannot be transmitted to the road the wheels spin so that the power is ineffective the truck can no longer do its job the rotating planetary gear set in the transfer box can now be locked to turn it into a solid gear wheel all axles are then driven positively at the same number of revolutions with no differential gear effect between them so that the wheels with the best ground contact can provide attractive effort the truck is once again mobile from the transfer box engine power is transmitted via propeller shafts to the front and rear axles the differentials in the axles consisting of the driving pinion the driven crown wheel and the planetary bevel gear set take care of the differences in left and right hand wheel speeds when the vehicle goes around a curve the inner wheels cover a shorter distance than the outside wires unfortunately the need for differential action is often a disadvantage for vehicles in use off the road as already mentioned in connection with the transfer case the power capable of being transmitted through to the road depends on wheel adhesion when the ground surface is muddy or icy the power distributed to the differential cannot be transmitted through to the ground because one wheel spins and the other remains stationary the cross differentials in the axles are therefore also made lockable the locking of the transfer box differential is called inter axle locking while that of the axle differentials can be called into wheel locking in the locked position the axles behave like that of the child's tricycle we looked at earlier with a wheel on each end of a solid shaft negotiating bends is only possible with excessive power expenditure and considerable tire wear which conflicts with the designer's object on a truck that of utilizing the engine power and auxiliaries more efficiently on the planetary gear hub reduction axles used in mercedes heavy truck range the gearing is not confined to the differential bevel gears crown wheel and pinion but additionally in the wheel hubs as sun wheel drives the five-part planetary gear set in each hub to which the wheel is attached so that the planetary gear set revolves in the outer ring gear the hub reduction axle offers the advantage of a differential assembly and pacing that can be kept small thus improving ground clearance from the engine to the wheels the power flow of mercedes-benz trucks is kept in balance let us look again at the factors which make mercedes-benz trucks economical and reliable machines for every transport application a balanced combination of engine output and transmission design to give optimum performance for every job faced by the vehicle a high degree of common components throughout the range of vehicles and engines with low inventory cost easy maintenance and low downtime the compact design of v-form engines and two or three-range gearboxes considerably increases the payload in relation to vehicle weight mercedes-benz diesel engines comply with tomorrow's emission regulations today these features combine to serve one purpose to be able to offer the right vehicle for each job with the highest efficiency and lowest operating cost this high standard of quality and efficiency is apparent in the entire mercedes-benz truck range the trucks with the three-pointed star use technology for the benefit of the transport operator you