About Truck Tractors

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About Truck Tractors

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A semi-trailer truck, more commonly called a semi truck (often shortened to just "semi"), is the combination of a tractor unit and one or more semi-trailers to carry freight. It is variously known as a transport (truck) in Canada; semi or single in Australia and New Zealand; semi, tractor-trailer, big rig, or eighteen-wheeler in the United States; and articulated lorry, abbreviated artic, in Great Britain and Ireland.

A semi-trailer attaches to the tractor with a fifth wheel hitch, with much of its weight borne by the tractor. The result is that both tractor and semi-trailer will have a distinctly different design than a rigid truck and trailer.

 

North America

In North America, the combination vehicles made up of a powered truck and one or more semitrailers are known as "semis", "semitrailers",[1] "tractor-trailers", "big rigs", "semi trucks", "eighteen-wheelers", or "semi-tractor trailers".

The tractor unit typically has two or three axles; those built for hauling heavy-duty commercial-construction machinery may have as many as five, some often being lift axles.

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The most common tractor-cab layout has a forward engine, one steering axle, and two drive axles. The fifth-wheel trailer coupling on most tractor trucks is movable fore and aft, to allow adjustment in the weight distribution over its rear axle(s).

Ubiquitous in Europe, but less common in North America since the 1990s, is the cabover engine configuration, where the driver sits next to, or over the engine. With changes in the US to the maximum length of the combined vehicle, the cabover was largely phased out of North American over-the-road (long-haul) service by 2007. Cabovers were difficult to service, as the cab could not be lifted on its hinges to a full 90-degree forward tilt, severely limiting access to the front part of the engine.

As of 2016, a truck can cost $100,000, while the diesel cost can be $70,000 per year.[2] Trucks average from 4 to 8 miles per US gallon (59 to 29 L/100 km), with fuel economy standards requiring better than 7 miles per US gallon (34 L/100 km) efficiency by 2014.[3] Power requirements in standard conditions are 170 hp at 55 mph (89 km/h) or 280 hp at 70 mph (113 km/h), and somewhat different power usage in other conditions.[4]

 

Rocky Mountain Double

STAA double pup 28.5-foot trailers. The cargo trailer usually has tandem axles at the rear, each of which has dual wheels, or eight tires on the trailer, four per axle. In the US it is common to refer to the number of wheel hubs, rather than the number of tires; an axle can have either single or dual tires with no legal difference.[5][6] The combination of eight tires on the trailer and ten tires on the tractor is what led to the moniker eighteen wheeler, although this term is considered by some truckers to be a misnomer (the term "eighteen-wheeler" is a nickname for a five-axle over-the-road combination). Many trailers are equipped with movable tandem axles to allow adjusting the weight distribution.

To connect the second of a set of doubles to the first trailer, and to support the front half of the second trailer, a converter gear known as a "dolly" is used. This has one or two axles, a fifth-wheel coupling for the rear trailer, and a tongue with a ring-hitch coupling for the forward trailer. Individual states may further allow longer vehicles, known as "longer combination vehicles" (or LCVs), and may allow them to operate on roads other than Interstates.

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Long combination vehicle types include:

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Doubles (officially "STAA doubles", known colloquially as "a set of joints"): Two 28.5 ft (8.7 m) trailers.

Triples: Three 28.5 ft (8.7 m) trailers.

Turnpike Doubles: Two 48 ft (14.6 m) trailers.

Rocky Mountain Doubles: One 40 to 53 ft (12.2 to 16.2 m) trailer (though usually no more than 48 ft (14.6 m)) and one 28.5 ft (8.7 m) trailer (known as a "pup").

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In Canada, a Turnpike Double is two 53 ft (16.2 m) trailers, and a Rocky Mountain Double is a 50 ft (15.2 m) trailer with a 24 ft (7.3 m) "pup".

Future long combination vehicles under consideration and study for the U.S. MAP-21 transportation bill are container doubles. These combinations are under study for potential recommendation in November 2014:

40 ft (12 m) trailer Turnpike Doubles, 148,000 lb (67,000 kg) GVWR

40 ft (12 m) and 20 ft (6.1 m) trailer Rocky Mountain Doubles, 134,000 lb (61,000 kg) GVWR

Double 20 ft (6.1 m) trailers.

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The US federal government, which only regulates the Interstate Highway System, does not set maximum length requirements (except on auto and boat transporters), only minimums. Tractors can pull two or three trailers if the combination is legal in that state. Weight maximums are 20,000 lb (9,100 kg) on a single axle, 34,000 lb (15,000 kg) on a tandem, and 80,000 lb (36,000 kg) total for any vehicle or combination. There is a maximum width of 8.5 ft (2.6 m) and no maximum height.[7][8]

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Roads other than the Interstates are regulated by the individual states, and laws vary widely. Maximum weight varies between 80,000 lb (36,000 kg) to 171,000 lb (78,000 kg), depending on the combination.[9] Most states restrict operation of larger tandem trailer setups such as triple units, turnpike doubles and Rocky-Mountain doubles. Reasons for limiting the legal trailer configurations include both safety concerns and the impracticality of designing and constructing roads that can accommodate the larger wheelbase of these vehicles and the larger minimum turning radii associated with them. In general, these configurations are restricted to the Interstates. Except for these units, double setups are not restricted to certain roads any more than a single setup. They are also not restricted by weather conditions or "difficulty of operation". The Canadian province of Ontario, however, does have weather-related operating restrictions for larger tandem trailer setups.[10]

Because of the wide variety of loads the semi may carry, they usually have a manual transmission to allow the driver to have as much control as possible. However, all truck manufacturers now offer semi-automatic transmissions (manual gearboxes with automated gear change), as well as automatic transmissions.

Semi-truck transmissions can have as few as three forward speeds or as many as 18 forward speeds (plus 2 reverse speeds). A large number of transmission ratios means the driver can operate the engine more efficiently. Modern on-highway diesel engines are designed to provide maximum torque in a narrow RPM range (usually 1200-1500 RPM); having more gear ratios means the driver can hold the engine in its optimum range regardless of road speed (drive axle ratio must also be considered).

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A ten-speed manual transmission, for example is controlled via a six-slot H-box pattern, similar to that in five-speed cars — five forward and one reverse gear. Gears six to ten (and high speed reverse) are accessed by a Lo/High range splitter; gears one to five are Lo range; gears six to ten are High range using the same shift pattern. A Super-10 transmission, by contrast, has no range splitter; it uses alternating "stick and button" shifting (stick shifts 1-3-5-7-9, button shifts 2-4-6-8-10). The 13-, 15-, and 18-speed transmissions have the same basic shift pattern, but include a splitter button to enable additional ratios found in each range. Some transmissions may have 12 speeds.

Another difference between semi-trucks and cars is the way the clutch is set up. On an automobile, the clutch pedal is depressed full stroke to the floor for every gear shift, to ensure the gearbox is disengaged from the engine. On a semi-truck with constant mesh transmission (non synchronized), such as by the Eaton Roadranger series, not only is double clutching required, but a clutch brake is required as well. The clutch brake stops the rotation of the gears, and allows the truck to be put into gear without grinding when stationary. The clutch is pressed to the floor only to allow smooth engagement of low gears when starting from a full stop; when the truck is moving, the clutch pedal is pressed only far enough to break torque for gear changes.

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Drivers of semi-trailer trucks generally require a Class A commercial driver's license (CDL) to operate any combination vehicles with a gross combination weight rating (or GCWR) in excess of 26,000 lb (11,800 kg) if the gross vehicle weight rating (GVWR) of the towed vehicle(s) is in excess of 10,000 lb (4,500 kg). Some states (such as North Dakota) provide exemptions for farmers, allowing non-commercial license holders to operate semis within a certain air-mile radius of their reporting location. State exemptions, however, are only applicable in intrastate commerce; stipulations of the Code of Federal Regulations (CFR) may be applied in interstate commerce. Also a person under the age of 21 cannot operate a commercial vehicle outside the state where the commercial license was issued. This restriction may also be mirrored by certain states in their intrastate regulations. A person must be at least 18 in order to be issued a commercial license.

In addition, endorsements are necessary for certain cargo and vehicle arrangements and types;

H – Hazardous Materials (HazMat or HM) – necessary if materials require HM placards.

N – Tankers – the driver is acquainted with the unique handling characteristics of liquids tankers.

X – Signifies Hazardous Materials and Tanker endorsements, combined.

T – Doubles & Triples – the licensee may pull more than one trailer.

P – Buses – Any Vehicle designed to transport 16 or more passengers (including the driver).

S – School Buses – Any school bus designed to transport 11 or more passengers (including the driver).

W – Tow Truck

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Modern day semi-trailer trucks often operate as a part of a domestic or international transport infrastructure to support containerized cargo shipment. Various types of rail flat bed train cars are modified to hold the cargo trailer or container with wheels or without. This is called Intermodal or piggyback. The system allows the cargo to switch from highway to railway or vice versa with relative ease by using gantry cranes.

The large trailers pulled by a tractor unit come in many styles, lengths, and shapes. Some common types are: vans, reefers, flatbeds, sidelifts and tankers. These trailers may be refrigerated, heated, ventilated, or pressurized, depending on climate and cargo. Some trailers have movable wheel axles that can be adjusted by moving them on a track underneath the trailer body and securing them in place with large pins. The purpose of this is to help adjust weight distribution over the various axles, to comply with local laws.

 

 

 

Merriam-Webster

^ Smith, Allen (25 May 2016). "What It Really Costs to Own a Commercial Truck". Ask The Trucker. Retrieved 18 May 2017. pay over $100,000 for your first commercial vehicle. 18-wheeler drinks .. easily more than $70,000 annually

^ Dyer, Ezra. "10 Things You Didn't Know About Semi Trucks". Popularmechanics.com. Retrieved 25 March 2016.

^ "Understanding Tractor-trailer Performance" (PDF). Caterpillar. 2006. p. 5. LEGT6380.

^ "Guidelines on Maximum Weights and Dimensions" (PDF). Ireland Road Safety Authority. February 2013. Retrieved 26 June 2014.

^ Crismon, Fred W (2001). US Military Wheeled Vehicles (3 ed.). Victory WWII Pub. p. 10. ISBN 0-970056-71-0.

^ "Commercial Vehicle Size and Weight Program". Freight Management and Operations. US Department of Transportation. May 2003. FHWA-OP-03-099. Retrieved 7 August 2016.

^ "Federal Size Regulations for Commercial Motor Vehicles". US Department of Transportation. Retrieved 2 October 2012.

^ Jakubicek, Paul (16 January 2015). "Top 10 Heaviest Semi Trucks in the United States and Canada". BigTruckGuide.com. Retrieved 12 July 2016.

^ [1]

^ "A Guide to Haulage & Courier Vehicle Types & Weights". Returnloads.net. Retrieved 28 July 2016.

^ "Moving goods by road". HM (UK) Revenue & Customs. 5 April 2016. Retrieved 28 July 2016.

^ to: a b c Ramberg, K. (October 2004). "Fewer Trucks Improve the Environment" (PDF). Svenskt Näringsliv.

^ Wideberg, J.; et al. (May 2006). "Study Of Stability Measures And Legislation Of Heavy Articulated Vehicles In Different OECD Countries" (PDF). University of Seville, KTH and Scania.

^ "Två regeringsbeslut för längre och tyngre fordon". Regeringskansliet. 16 April 2015. Retrieved 27 September 2015.

^ "The next environmental improvement: Long truck rigs". Volvo Trucks. 3 October 2008.

^ Krantz, Olivia (2014). "Where Size Matters". Uptime (2): 8–15.

^ "Dispensation for 90 Tonnes Truckes is Favorable for All Concerned". Northland.eu. 30 October 2012. Archived from the original on 28 January 2013.

^ full law text in Finnish language, explanation by Finnish Forest Association in English, 76 tons in the newspaper

^ "Vaile Announces the B-Triple Road Network" (Press release). Ministry for the Department of Infrastructure. 9 July 2007. Archived from the original on 2 June 2008.

^ Rogers, Brian. "Truck Jackknife Accidents". Fried Rogers Goldberg. Fried Rogers Goldberg LLC. Retrieved 12 January 2017.

^ "COST 334: Effects of Wide Single Tyres and Dual Tyres" (PDF). European Union. European Commission, Directorate General Transport. 29 November 2001.

^ "EPA Smartway Verification of Trailer Undercarriage Advanced Aerodynamic Drag Reduction Technology". EPA Smartway. Retrieved 2 October 2012.

^ "Underride Guard". Everything2. Retrieved 29 November 2007.

^ United States Congressional Committee on Commerce (1997). Reauthorization of the National Highway Traffic Safety Administration. p. 39.

^ to: a b "Gettiing Started". Underride Network. Underride Network. Retrieved 7 June 2014.

^ Underride Guard on Everything2; Retrieved: 29 November 2007.

^ "Z" endorsement

^ Ontario drivers classes

^ "Official Rigs of Rods Forum". Rigs of Rods. Retrieved 18 August 2012.

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