Gearbox Management of Cars and Tractors - Essay Example

THE POWER TRAIN: GEAR BOX MANAGEMENT OF CARS AND TRACTORS INTRODUCTION The development of transmissions to raise the total effectiveness of power train and support the beneficial operating systems of today’s usage-optimised engines, diesel or benzine, is one of most priorities of large companies specialising on gearboxes. Gearbox Management generally means maintenance, troubleshooting and proper handling of or working on gearbox of cars and tractors. Gearbox and power train is interchangeably used in this paper. The gearbox runs or manipulates the speed of the car or tractor; experts say it is the power itself. It varies in every make of vehicle although the principle, usage and purpose may be universal. Cars and tractors – in fact, almost every vehicle – have a gear box or transmission which allows the driver to shift from slow to fast or maintain speed. Management is very important in the life of the vehicle, so do with the proper handling of the gearbox. The life of the driver or owner also depends partly in its proper management. Accidents can be avoided with proper management, not to mention the financial savings accumulated. A power train is where the power from the engine goes to and maybe said to be synonymous to the power of the vehicle itself. The driver train is also everything after the power train, i.e. on a rear wheel drive, clutch, transmission, driveshaft, differential, and axle, on a front wheel drive. Another definition of power train is: it is a train of gears and shafting transmitting power from an engine, motor, etc., to a mechanism being driven.1 There are a lot of concepts on the words power train (in some sites in the internet these two words are written as one word). Some experienced drivers and mechanics state that on front wheel driver cars, the power train consist of the engine, transmission, rear end, which are made (read: assembled) together … and on rear wheel driver, the engine, transmission, drive shaft and rear end … if the car has a standard transmission, the power train would include the clutch.2 In other words the power train runs the vehicle – in this case, the car or the tractor – for purposes of our discussion. And when we speak of maintenance, this may involve a wide array of expertise and the mechanic/driver can not just focus on the gearbox but the entire connections relative to the power train, the different shafts, up to the differential. Maintenance here is overloaded and, to be precise, sensitive; meaning go to details, a simple crack, slight noise, anything you notice peculiar that may lead your car to be left on the road must be given proper attention. The manufacturing of powertrain components and systems is a key factor in the competitive position of companies in the automotive and other vehicle industrial sectors. These companies have to manufacture/make powertrain system that are more economical, higher product quality and reliability, higher in performance, more fuel efficient, less polluting, and longer in life expectancy.3 With this trend, warranties to powertrain products have been extended to some more years because of their durability. Powertrain designs give emphasis on their flatness, waviness, roughness, and porosity. Over the years and with the advent of advanced metrology and technology, there are improved materials and material forming methods on powertrain manufacturing. Efficient maintenance leads to improvement of powertrain performance, reduction of engine and vehicle emissions and fuel consumption. Some of the well developed and innovative technologies are being introduced by Powertrain Research & Technology to encompass the areas of: Diesel Engines, Gasoline Engines, Alternative Fuel Engines, Transmissions and Alternative Propulsion – and involve its three Transversal Engineering Areas – Mechanical Engineering & Basic Technologies, Electronic Engineering & Basic Technologies, Testing Facilities. They provide Powertrain Research and Technology with the necessary capabilities to independently develop the basic technologies necessary for the achievement of its main engineering and development goals.4 Focus on Gears On the other hand, a gearbox is also known as transmission or the system of gears that transmits mechanical power from a prime mover – such as an engine or electric motor, to some form of useful output device.5 Gears are mechanical parts with cut teeth designed to mesh with teeth on another part so as to transmit or receive force and motion. Gears are also sometimes called toothed wheels or cogged wheels or cogs. The cut teeth are also sometimes called cogs. There are ways of looking at a gearbox and it depends primarily on the user. Generally gearboxes are classified by their ratios. With regard to durability, high quality gear last long and easily detected when the teeth become broken. But as it is said, because of high quality, warranties last for years, and extended even if ownership of the vehicle has been transferred. (This may vary from country to country, as the case maybe.) The majority of gears are composed of carbon and low-alloy steels, including carburised steels. Among the carburised steels used in gears are 1018, 1524, 4026, 4118, 4320, 4620, 4820, 8620 and 9310. The purpose of the gear dictates the material used in its creation. For example gears to be used in food processing are made of stainless steels or nickel-base alloys because of their corrosion resistance.6 For cars and tractors, it’s a different thing. Steel is most usually used. Gears are also positive type drives which transmit motion between two shafts or a shaft and a component having linear motion. The motion is caused by the meshing of two or more gears. Their definite velocity ratio is an advantage over other drives in precision machines such as watches that depend upon an exact velocity ratio. Steels are commonly used in the manufacture of gears because of their high strength to weight ratio and low cost, but numerous nonferrous alloys, cast irons, powder-metallurgy and even plastics are also used. In cases where driver and follower are in close proximity gears also have an advantage over other drives in the reduced number of parts required. However, gears are more expensive to manufacture and their lubrication requirements may impose a higher operating cost. Gears of differing size are often used in pairs for a mechanical advantage, allowing the torque of the driving gear to produce a larger torque in the driven gear at lower speed, or a smaller torque at higher speed. The larger gear is known as a wheel and the smaller as a pinion. This is the principle of the automobile transmission, allowing selection between various mechanical advantages. Most modern gearboxes either reduce an unsuitable high speed and low torque of the prime mover output shaft to a more useable lower speed with higher torque, or do the opposite and provide a mechanical advantage (i.e increase in torque) to allow higher forces to be generated. However, some of the simplest gearboxes merely change the physical direction in which power is transmitted.7 Gearboxes are also enclosed in casings that proper handling and knowledge are necessary. You don’t need to dismantle them, or you might have more trouble. Just observe and know the proper replacements, or what to be replaced. It’s just like the ordinary appliance at home, where you also have the necessary knowledge and expertise in electronics before you can do some troubleshooting and parts repair. Definitions The American Heritage Science Dictionary defines a gear as “a wheel with teeth around its rim that mesh with the teeth of another wheel to transmit motion. Gears are used to transmit power (as in a car transmission) or change the direction of motion in a mechanism (as in a differential axle).”8 Another definition from the American Heritage Dictionary on power train is that it is an assembly of gears and associated parts by which power is transmitted from an engine to a driving axle; or a wheelwork consisting of a connected set of rotating gears by which force is transmitted or motion or torque is changed.9 In a gearbox are several gears mesh with each other to add more power to the engine, aside from the fact that it changes the speed of the vehicle. This is almost the life of the vehicle, although the engine is the real and literal life of the vehicle. Without the engine, the car won’t run. But here, the gearbox adds life to the engine and/or the vehicle. You can’t change the speed or apply brake to the engine without the gear box. Furthermore, you can’t have a weak or low-quality gearbox, meaning not properly managed or maintained. It will not simply last. Gears get busted when proper lubrication is not done. Lubrication must have to be periodic. Transmission is an assembly of parts including the speed-changing gears and the propeller shaft by which the power is transmitted from an engine to a live axle; also : the speed-changing gears in such an assembly. Early transmissions or gearboxes included the right-angle drives and other gearing in windmills, horse-powered devices, and steam engines, mainly in support of pumping, milling, and hoisting. Most modern gearboxes either reduce an unsuitable high speed and low torque of the prime mover output shaft to a more usable lower speed with higher torque, or do the opposite and provide a mechanical advantage (i.e increase in torque) to allow higher forces to be generated. However, some of the simplest gearboxes merely change the physical direction in which power is transmitted. The simplest transmissions are often called gearboxes to reflect their simplicity, but some complex ones are also called gearboxes, and they provide gear reduction (or, more rarely, an increase in speed), sometimes in conjunction with a right-angle change in direction of the shaft. Great importance of Steering & Suspension The steering and suspension system of a car is not only important for safety reasons but also enhances the comfort level of the vehicle. The two systems are directly related to each other, which is why they are always referred to together. This is also a part of this discussion since it is important in gear management. There are two basic types, standard mechanical steering and rack & pinion steering. The standard mechanical steering can be either power assisted or non-power. Rack & pinion is almost always power assisted although there are rare cases where it is not. Standard mechanical steering uses a series of links and arms to insure both wheels turn in the same direction at the same time. It hasnt changed much in all the years its been used and is quite simple. Basically this is how it works: the steering wheel is connected to the steering box through the steering column. The steering box turns the rotation of the steering wheel 90 degrees and, in the case of power steering, uses high-pressure fluid to help actuate the steering. The steering box has an arm attached to the output shaft called the pitman arm. This connects the steering box to the steering gear. The pitman arm is connected to one end of the center or drag link. In the other end of the center link is an idler arm. Between the idler and pitman arms, the center link is supported in the proper position to keep the left and right wheels working together.10 The inner tie rod ends are attached to either end of the center link and provides pivot points for the steering gear. From there it goes to the outer tie rod ends through an adjustment sleeve. This sleeve joins the inner and outer tie rod ends together and allows for adjustment when the front wheels are aligned. The outer tie rod ends are connected to the steering knuckle that actually turns the front wheels. The steering knuckle has an upper and lower ball joint that it pivots on and creates the geometry of the steering axis. Rack and Pinion Rack and Pinion is not connected directly to the gearbox but is somehow influenced by it. It is therefore fit and proper to discuss about this, before we go deeper on the topic of gearbox maintenance. Rack and Pinion is a simple mechanical connection from the steering wheel to the front wheels. The weaknesses of the system are at the pivot points. The pivots are ball and socket joints that do wear out over time and will require replacement. Loose steering parts make a car difficult to handle and cause the front tires to wear out prematurely. A once-a-year check-up on the steering is suggested. Mechanics are instructed to check the steering and suspension while the car is up in real work waiting for the oil to drain out. Rack and pinion steering combines the steering box and center link into one unit. The steering wheel, through the steering column, is directly connected to the rack. Inside the rack is a pinion assembly that moves a toothed piston to move the steering gear. One end of the inner tie rod ends is connected to either end of this piston and the other end is connected directly to the outer tie rod end. The inner tie rod end is actually threaded into the outer tie rod end and can be rotated to make adjustments during a wheel alignment.11 The advantage of rack & pinion steering is that it is more precise than the mechanical system. By reducing the number of parts and pivot points, it can more accurately control wheel direction and is more responsive. The down side of a rack & pinion steering system is that they are prone to leakage requiring replacement of the rack assembly. FARM TRACTORS Most farm tractors use manual transmission. They have several sets of gear ratios divided into speeds. To change ratio it is usually necessary to stop the tractor. Between them they provide a range of speeds from less than one mile per hour suitable for working the land, up to about 25 miles per hour for road use. For tractors, it is usually not necessary to change gear in order to reverse, one simply selects a lever. Older tractors usually require that the operator depress the clutch in order to shift between gears (a limitation of straight-cut gears in the gearbox), but many modern tractors have eliminated this requirement with the introduction of technologies such as power shifting in the 1960s and more modern continuously variable transmissions. This allows the operator more and easier control over working speed than the throttle alone could provide. Tractors and large trucks have numerous forward gears which vary from a crawling speed at high torque to high speed at low torque. Slow, controllable speeds are necessary for most operations that are performed with a tractor. They help give the farmer a larger degree of control in certain situations, such as field work. However, when traveling on public roads, the slow operating speeds can cause problems, such as long queues or tailbacks, which can delay or aggravate other road users.12 Roll Over Protection System The Roll Over Protection System is a steel beam that extends above the operator’s seat. Modern tractors have ROPS to prevent an operator from being crushed if the tractor rolls over. This is especially important in open-air tractors. For tractors with operator cabs, the ROPS is part of the frame of the cab. Before ROPS were required, some farmers died when their tractors rolled on top of them.12 Row-crop tractors, before ROPS, were particularly dangerous because of their tricycle design with the two front wheels spaced close together and angled inward toward the ground. Some farmers were killed by rollovers while operating tractors along steep slopes. Others have been killed whilst attempting to tow or pull an excessive load from above axle height, causing the tractor to pivot around the rear axle. ROPS were first required by legislation in New Zealand in the 1960s. Modern farm tractors employ large diesel engines, which range in power output from 18 to 575 horsepower (15 to 480 kW). Tractors can be generally classified as two-wheel drive, two-wheel drive with front wheel assist, four-wheel drive (often with articulated steering), or track tractors (with either two or four powered rubber tracks). There are classic variations of lawn tractors, like the small ones and others like the garden tractors which range from about 10 to 25 horsepower, used for smaller farms and garden tasks. Gearboxes included the right-angle drives and other gearing in windmills, horse-powered devices, and steam engines, mainly in support of pumping, milling, and hoisting. Gearboxes in cars and tractors either reduce an unsuitable high speed and low torque of the prime mover output shaft to a more usable lower speed with higher torque, or do the opposite and provide a mechanical advantage (i.e increase in torque) to allow higher forces to be generated. However, some of the simplest gearboxes merely change the physical direction in which power is transmitted.13 Many systems, such as typical automobile transmissions, include the ability to select one of several different gear ratios. In this case, most of the gear ratios (simply called "gears") are used to slow down the output speed of the engine and increase torque. However, the highest gears may be an "overdrive" type that increase output speed. Regardless of where they are used, these simple transmissions all share an important feature: the gear ratio cannot be changed during use. It is fixed at the time the transmission is constructed. The need for a transmission in an automobile is a consequence of the characteristics of the internal combustion engine. Engines typically operate over a range of 600 to about 7000 revolutions per minute (though this varies from design to design and is typically less for diesel engines), while the cars wheels rotate between 0 rpm and around 2500 rpm.14 The engine provides its highest torque outputs approximately in the middle of its range, while often the greatest torque is required when the vehicle is moving from rest or traveling slowly. Therefore, a system that transforms the engines output so that it can supply high torque at low speeds, but also operate at highway speeds with the motor still operating within its limits, is required. Transmissions perform this transformation. Most transmissions and gears used in automotive and truck applications are contained in a cast iron case, though sometimes aluminum is used for lower weight. There are three shafts: a mainshaft, a countershaft, and an idler shaft. For high-quality brand cars, these gearboxes are very durable that sometimes maintenance is not necessary. But to be safe though, it is advisable to check on them once in a while. Automatic transmission modes Studying automatic transmission modes is necessary in our study of gearbox management and maintenance. Automatic transmission is now common in most countries because of the ease in handling or driving the car. The number of gears a transmission has depends on the model, but the most common range from 3, 4; the 5 or 6 is found in VW/Audi Direct Shift Gearbox; and 8 in the new model of Lexus cars. Automatic transmissions are easy to use. With the new high-technology, computerized gear boxes have been in use. They use electronically-controlled device called actuators to shift the gears and manipulate the clutch, eliminating many of previous drawbacks of a hydraulic automatic transmission. Automatic Transmissions have various modes depending on the model and make of the transmission. The following are some of the common modes and their characteristics, with effective management clues: a.) Park – This selection mechanically locks the transmission, restricting the car from moving in any direction. A pin prevents the transmission from moving forward (although wheels, depending on the drive train, can still spin freely), it is recommended to use the hand brake (or emergency brake) because this actually locks the wheels and prevents them from moving, and increases the life of the transmission and the park mechanism. In order for the car to be moved out of park, the driver must depress the brake fully, same goes for putting it into park. The driver also must come to a complete stop before putting it into park to prevent damage to the transmission. This is only one of two selections in which the car can be started. b.) Reverse – This puts the car into the reverse gear, giving the ability for the car to back up. In order for the driver to select reverse they must come to a complete stop, and push the shift lock button in and select reverse. If reverse is executed without coming to a complete stop, great damage will be done on the transmission. c.) Neutral – This disconnects the transmission from the wheels so the car can move freely under its own weight. This is the only other selection in which the car can be started. Try not to go neutral and start the car, a great damage will be done. d.) Drive – This allows the car to move forward and accelerate through a range of gears. Unique gear sets There are unique gear sets used in automatic transmission and they are known as Ravigneaux, Lepelletier, or Simpson planetary gear sets. These ones use some arrangement or one or two central sun gears, with a ring gear, in a differing arrangements of gears, known as planet gears, that surround what they call the sun. The Hondamatic line from Honda uses sliding gears on parallel axes like a manual transmission, without any planetary gear sets. It is different from an automated manual transmission. The CVT Continuously Variable Transmission or CVT is a different type of automatic transmission. It can smoothly alter its gear ratio by varying the diameter of a pair of belt or chain-linked pulleys, wheels or cones. Some continuously variable transmissions use a hydrostatic drive consisting of a variable displacement pump and a hydraulic motor to transmit power without gears. CVT designs are usually as fuel efficient as manual transmissions in city driving, but early designs lose efficiency as engine speed increases. The toroidal CVT or Infinitely Variable Transmission (IVT) is a different approach to CVT. They provide zero and reverse gear ratios. Hybrid vehicles like Toyota, Lexus and those of Ford Motor Company, have an "electronically-controlled CVT" (E-CVT). In this system, the transmission has fixed gears, but the ratio of wheel-speed to engine-speed can be continuously varied by controlling the speed of the third input to a differential using an electric motor-generator. Maintenance of electronically controlled CVT is simple – replacement, i.e. simply get a replacement from the manufacturer if it gets busted, although this trouble seldom occurs. Manual Transmission Manual transmissions come in two basic types: a simple unsynchronized system where gears are spinning freely and must be synchronised by the operator to avoid noisy and damaging “gear clash”. This is used by some rally cars and heavy trucks. The other one has a synchronised system that automatically mesh while changing gears. Manual Transmissions are cheaper, lighter, usually give better performance, and fuel efficiency. In Japan, New Zealand, Germany, the UK, Ireland, Sweden, France and Finland at least, a test pass using an automatic car does not entitle the driver to use a manual car on the public road unless a second manual test is taken. Manually controlled automatic transmissions Manually controlled automatic transmissions are also called driver-aided auto-transmissions. The driver exerts a certain amount of control over the shifts in transmissions. The following are some of the driver’s control over these auto-transmissions: Throttle kickdown – includes a switch on the throttle linkage to force the transmission to downshift into the next lower ratio if the throttle is fully engaged. The switch generally only functions up to a certain road speed. Low gear ranges: Many transmissions have switches or selector positions that allow the driver to limit the maximum ratio that the transmission may engage. Manual controls: Some transmissions have a mode in which the driver has full control of ratio changes (either by moving the selector or through the use of buttons or paddles), completely overriding the hydraulic controller. Some automatic transmissions have been modified or designed specifically for drag racing, and are modified with a transmission brake, or "trans-brake," as part of a manual valve body. It is activated by electrical solenoid control which simultaneously engages the first and reverse gears, locking the transmission and preventing the input shaft from turning. This allows the driver of the car to raise the engine rpm against the resistance of the torque converter, then launch the car by simply releasing the trans-brake switch.15 Management of this type has to be as professional as possible, giving constant or periodic check on the engine, transmissions and powertrains. Hydrostatic Hydrostatic transmissions transmit all power with hydraulics; there is no solid coupling of the input and output. One half of the transmission is a variable displacement pump and the other half is a hydraulic motor. A movable swash plate controls the piston stroke to change the pump’s displacement. They are used in some types of heavy equipment. The Power Split Transmission PST is a transmission that uses two different types of power sources for separate inputs to produce one output, usually in conjunction with an epicyclic gear system (which is also known as a planetary gear system, as mentioned earlier) that includes three fundamental gearing components. The PST is the essential method for transmitting power in most hybrid vehicles, usually enabling an Internal Combustion (ICE) to be used in conjunction with an electric motor and/or motor-generator for vehicle propulsion. PERSONAL EXPERIENCE HELPS The reason why study of gearboxes of cars and tractors is synchronised here in one study is because of the uniqueness of each individual parts relative to their workings in the machine. Like any other human endeavor, experience helps in the management of gearboxes of cars and tractors. The gearbox is a precious piece of systematized metals connected with each other through its teeth that a personal knowledge of this is specially required in order to have good working and maintenance. Its characteristics vary but sometimes may be the same all throughout its lifelong service, and if you are well versed with these characteristics, you’re on your way to have a successful management of gearboxes. Movements of transmissions and engines cause relative movements between transmissions and actuating arm. The gears interact. The decoupling of these relative movements results in a variety of constructions for the transfer of traction and pressure forces that are needed for shifting a transmission. The total difficulty is ending up in the development of divers drive-by-wire systems. For shifting mechanical systems smooth running, zero backlash, fast adjusting possibilities, maintenance freedom, stiffness and elasticity as well as the possibility to decouple vibrations is requested regardless if it concerns steering-column shifting, car dashboard shifting or center console shifting that is positioned above or below floor. PROFESSIONAL AND EFFECTIVE MANAGEMENT A MUST As stated in the above discussion, various parameters have to be considered. Transformer, conventional stepped automatic transmissions, manual and automated manual shifting transmissions double clutch transmissions, CVT transmissions or even the variety of special transmissions (with or without synchronization) need the conversion of gear shift fluctuation, selection and shifting. Inner shifting whether manual or by actutoric or outer shifting have to function direct or indirect. Shifting powers have to be little, shifting trends need to be constant, shifting travel short and comfortable, actuating arm free of clearance, the snap-ons exact.  Likewise, natural stepping errors also have to be avoided, and the actuating elements need to be coordinated and addressing design should be available. If you additionally consider a parameter it would be the total avoidance and hold-off of engine and transmission vibrations of the control element and the interior.    RECOMMENDATIONS The following is recommended for tests on a transmission and its behaviour: a. Functional tests b. Stability and durability c. Validation Damage analyses can be done through checks such as thermal check-ups, optical tests, and if possible, a total check in a qualified service shop or that recommended by manufacturer, or the manufacturer itself. Proper care and service and insisting on quality products for replacements are also recommended. In determining the problem for power train, effectiveness is the most important criteria. How effective is it now than before it was first purchased? Is it cost effective especially of the high prices for fuel? These things have to be considered. Finally, constant checking is necessary, especially if the car has already lasted for years. References: 1. http://dictionary.reference.com/browse/gear. Retrieved on 2007-10-27. 2. renegades.http://answers.yahoo.com/question/index 3. http://en.wikipedia.org/wiki/Power_train 4. http://www.fptpowertrain.com/eng/eng/powertrain_research_technology.htm 5. http://www.wiki-mirror.be/index.php/Gear_box.Retrieved 2007-1-27. 6. http://en.wikipedia.org/wiki/Gearbox#Hydrostatic_transmission 7. http://www.About.com 8. http://en.wikipedia.org/wiki/Gear materials. Retrieved on 2007-10-28. 9. http://autorepair.about.com/library/. Retrieved on 2007-01-28. 10. http://www.kwdr.net/2/gearbox/ 11. http://en.wikipedia.org/wiki/Tractor. Retrieved 2007-01-28. 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