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Truck Anatomy

Trucks operate off the same principles as cars but their components are drastically different and the way in which the engine operates.

Engine

Trucks can use all sorts of engines. Small trucks such as SUVs or pickups, and even light medium-duty trucks in North America and Russia will use gasoline engines. Most heavier trucks use four stroke turbo intercooler diesel engines, although there are alternatives. Huge off-highway trucks use locomotive-type engines such as a V12 Detroit Diesel two stroke engine. North American manufactured highway trucks almost always use an engine built by a third party, such as CAT, Cummins, or Detroit Diesel. The only exceptions to this are Volvo Trucks and Mack Trucks, which are available with subsidiary of DaimlerChrysler, which are available with Mercedes-Benz and Detroit Diesel engines. Trucks and busses built by the Navistar International can also contain International engines. The Swedish truckmaker Scania claims they stay away from the U.S.-market because of this third party tradition. In the European union all truck engines must comply with Euro 4 regulations, the regulations will become more severe in 2008 with the introduction of Euro 5.

Drivetrain

Small trucks use the same type of transmissions as almost all cars which have either an automatic transmission or a manual transmission with synchronisers. Bigger trucks often use manual transmissions without synchronisers which have less bulk and weight although synchromesh transmissions are used in larger trucks as well. Transmissions without synchronisers known as "crash boxes" require double clutching for each shift, (which can lead to repetitive motion injuries), or a technique known colloquially as "floating," a method of changing gears which doesn't use the clutch, except for starts and stops, due to the physical effort of double clutching especially with non power assisted clutches, faster shifts, and less clutch wear. Double clutching allows the driver to control the engine and transmission revolutions to synchronize, so that a smooth shift can be made e.g. when upshifting, accelerator pedal is released and the clutch pedal is depressed while the gear lever is moved in to neutral, clutch pedal is than released and quickly pushed down again while the gear lever is moved to the next highest gear. Finally, the clutch pedal is released and accelerator pedal pushed down to obtain required engine rpms. Although this is a relatively fast movement perhaps a second or so while transmission is in neutral it allows the engine speed to drop and synchronize engine and transmission revolutions relative to the road speed. Downshifting is performed in a similar fashion except the engine speed is now required to increase (while transmission is in neutral) just a right amount in order to achieve the synchronisation for the smooth non-crunching gearchange. The so called skip changing is also widely used, in principle operation is the same but it requires neutral be held slightly longer than single gearchange. Common North American setups include 9, 10, 13, 15, and 18 speeds. Automatic and semi-automatic transmissions for heavy trucks are becoming more and more common, due to advances both in transmission and engine power. In Europe 8, 10 and 12 gears are common on larger trucks with manual transmission, while automatic or semiautomatic transmission would have anything from 5 to 12 gears. Almost all heavy trucks transmissions are of a "range (double H shift pattern ) and split" type where range change and so called half gears or splits are air operated and always preselected before the main gears selection.

In Europe more new trucks are being bought with automatic or semi-automatic transmission. This may be due in part to lawsuits from drivers claiming that driving a manual transmission is damaging to their knees[citation needed]and the fuel consumption can be lowered and truck durability improved.[citation needed] The primary reason perhaps is the fact that such transmissions give a driver more time to concentrate on the road and traffic conditions.

Chassis

The chassis or frame of a truck is commonly constructed mainly of two beams, and several crossmembers. A truck chassis consists of two parallel straight C-shaped beams, or in some cases stepped or tapered beams, these held together by crossmembers. In most instances, gussets help attach the crossmembers to the beams. The "C-shape" of the beams has a middle vertical and longer side, and a short horizontal flange at each end; the length of the beams is variable. The chassis is usually made of steel, but can be made (whole or in part) of aluminium for a lighter weight. The integrity of the chemical composition (carbon, molybdenum, etc.) and structure of the beams is of uttermost importance to its strength, and to help prevent cracking or breaking of beams, and to help maintain rigidity and flexibility of the frame, welding, drilling and other types of modifications should not be performed by unlicenced persons. The chassis is the main structure of the truck, and the other parts attach to it. A tow bar may be found attached at one or both ends.

The Environment

Trucks contribute to air, noise, and water pollution in a similar fashion to automobiles. In fact, in the case of air pollution emissions, trucks may actually emit lower emissions than autos on a per pound of vehicle mass basis, although the absolute level on a vehicle mile traveled basis is higher and diesel soot is especially problematic for health.[1] With respect to noise pollution trucks emit considerably higher sound levels at all speeds compared to typical automobiles; this contrast is particularly strong in the case of heavy duty trucks.[2] Concerns have been raised about the effect of trucking on the environment, particularly as part of the debate on global warming. In the period from 1990 to 2003, carbon dioxide emissions from transportation sources increased by 20%, despite improvements in vehicle fuel efficiency. In 2005, Transportation accounted for 27% of U.S. greenhouse gas emission, increasing faster than any other sector. Between 1985 and 2004, in the U.S., energy consumption in freight transportation grew nearly 53%, while the number of ton-miles carried increased only 43%. "Modal shifts account for a nearly a 23% increase in energy consumption over this period. Much of this shift is due to a greater fraction of freight ton-miles being carried via truck and air, as compared to water, rail, and pipelines." According to a 1995 U.S. Government estimate, the energy cost of carrying a ton of freight a distance of one mile averages 514 Btu for water, 337 Btu for rail, 3,100 for trucks and nearly 20,000 for air transport and many environment organizations favor laws and incentives to encourage the switch from road to rail, especially in Europe.