Tractive Effort (abbr. TE) is the pulling force exerted, normally by a locomotive, though the term could also be used for anything else that pulls a load. It is normally understood to be the actual force on the locomotive's drawbar or rear coupler. When a bare figure for tractive effort is quoted without a speed qualification, this is normally for starting tractive effort, i.e. at a dead start with the wheels not turning. Great Western Railway No. ... Knuckle (AAR Type E) couplers in use. ...

In most cases, especially for steam locomotives, this figure is a calculated, not measured one. Union Pacific Big Boy #4012 at work on a cold November 29, 1941 A steam locomotive is a locomotive powered by steam. ...

Steam locomotives

The normal formula used (measurements in pounds and inches) is:

where

• t is tractive effort
• c is a constant representing losses in pressure and friction; normally 0.85 is used
• P is the boiler pressure
• d is the piston diameter (bore)
• s is the piston stroke
• D is the driving wheel diameter

The constant 0.85 was the Association of American Railroads (AAR) standard for such calculations, and certainly over-estimated the efficiency of some locomotives and underestimated that of others. Modern, roller bearing fitted locomotives were probably underestimated in this calculation. A boiler is a closed vessel in which water or other fluid is heated under pressure. ... piston + connecting rod Components of a typical, four stroke cycle, DOHC piston engine. ... Bore may refer to: A wave in a river caused by an incoming tide - see tidal bore The diameter of a pipe or tube, or the caliber of a gun The diameter of a cylinder and piston in a piston engine (See also: Stroke) A person who is boring The... A stroke, also known as cerebrovascular accident (CVA),[1] is an acute neurological injury in which the blood supply to a part of the brain is interrupted. ... On a steam locomotive, a driving wheel is a powered wheel which is driven by the locomotives pistons (or turbine, in the case of a steam turbine locomotive). ... A World War II era print advertisement for the Association of American Railroads (AAR). ...

European designers used a constant of 0.6 instead of 0.85, so the two cannot be directly compared without a conversion factor. In Britain, the main-line railways generally used a constant of 0.85 but builders of industrial locomotives often used a lower figure, typically 0.75.

Tractive effort is the figure most often quoted when people are comparing the power of different steam locomotives, but the use can be misleading, because tractive effort shows the ability to start a train, not the ability to do work by hauling it. Possibly the highest figure for starting tractive effort ever recorded was for the Virginian Railway's 2-8-8-8-4 Triplex locomotive, which in simple expansion mode had a starting T.E. of 199,560 lbf (888 kN) — but this did not translate into power, for the boiler was undersized and could not produce enough steam to haul at speeds over 5 mph (8 km/h). Union Pacific Big Boy #4012 at work on a cold November 29, 1941 A steam locomotive is a locomotive powered by steam. ... The Virginian Railway (AAR reporting mark VGN) was a Class I railroad located in Virginia and West Virginia in the United States. ... // The term steam engine may also refer to an entire railroad steam locomotive. ...

Of more successful large steam power, the Union Pacific's famous Big Boys had a starting T.E. of 135,375 lbf (602 kN), the Norfolk & Western's 2-8-8-2 Y6a had a starting T.E. of 152,206 lbf (677 kN) in simple expansion mode, and the Pennsylvania Railroad's freight Duplex Q2 attained 114,860 lbf (511 kN) — the highest for a rigid framed locomotive. Later two cylinder passenger locomotives were generally 70,000 to 80,000 lbf (300 to 350 kN) of T.E. The Union Pacific Railroad (NYSE: UNP) is the largest railroad in the United States. ... Big Boy was the nickname universally applied to the Union Pacific Railroads twenty-five 4000 class 4-8-8-4 steam locomotives built between 1941 and 1944 by Alco. ... Norfolk and Western Railway (AAR reporting mark: NW), a US class 1 railroad, was formed by more than 200 railroad mergers between 1838 and 1982. ... 1893 map The Pennsylvania Railroad (AAR reporting mark PRR) was an American railroad that was founded in 1846 and merged in 1968 into Penn Central Transportation. ... A duplex locomotive is a steam locomotive that divides the driving force on its wheels by using two sets of pistons. ... PRR Q2 prototype #6131. ...

Diesel and electric locomotives

For a diesel-electric or electric locomotive, starting T.E. can be calculated from the stall torque of the traction motors (the turning force it can produce while at a dead stop), the gearing, and the wheel diameter. Traction motor typically refers to those motors that are used to power the driving wheels of a railroad locomotive, electrical multi-unit train (such as a subway or light rail vehicle train), or a tram. ...

Related statistics

A related statistic is a locomotive's factor of adhesion, which is simply the weight on the locomotive's driving wheels divided by the starting tractive effort. In railroad engineering, the factor of adhesion of a locomotive is the weight on the driving wheels divided by the starting tractive effort. ...

For a locomotive to accelerate from a stationary position, it must apply a force to overcome the inertia of the train, along with the frictional forces in the form of mechanical friction, and wind resistance as the train accelerates. In order for this to occur a particularly high tractive effort is required, usually the maximum tractive effort of the engine is applied. This means that the engine works to produce the highest possible force that it can exert onto the wheels to cause movement or motion. Few engines can maintain work at the maximum tractive effort for very long, but neither is it usually necessary for an engine to do this. Once the train is running at a constant velocity the train no longer needs to overcome its inertia to remain at the same velocity, and hence must only provide power to compensate for frictional forces. This leads to one potential upper limit on the speed a locomotive can haul a train at, once the force due to wind resistance becomes greater than the tractive effort the locomotive can supply (fluid drag increases with the square of velocity), the locomotive cannot accelerate the train anymore (in reality the situation is more complicated than this due to a number of mechanical considerations). Stationary can mean: Look up stationary in Wiktionary, the free dictionary. ... The principle of inertia is one of the fundamental laws of classical physics which are used to describe the motion of matter and how it is affected by applied forces. ... An object falling through a gas or liquid experiences a force in direction opposite to its motion. ... The maximum tractive effort is the highest force that a vehicle can exert. ... This article or section is in need of attention from an expert on the subject. ... The maximum tractive effort is the highest force that a vehicle can exert. ... The velocity of an object is its speed in a particular direction. ...

Examples

A table to illustrate the speed the maximum tractive effort, continuous tractive effort and the speed at which the tractive effort should be reduced on a selection of trains operating in the United Kingdom: The maximum tractive effort is the highest force that a vehicle can exert. ... The continuous tractive effort is the highest force that a vehicle can exert over an extended period of time. ...

The power at rail of a train follows the equation power (kW) = force (kN) x speed (m/s) D3312 at Kings Cross, 1963 in British Railways green livery 08 910 at Carlisle, 1975 in British Rail blue livery. ... D6547 in original green livery without yellow warning panels, 1963. ... Electroputere-built 56006 at Doncaster in 2003 painted in rail blue livery Preserved 56003 in Load-Haul livery. ... 58001, on display at Doncaster Works open day on 27th July 2003. ... The Class 59 Co-Co diesel locomotives were built by General Motors Electro Motive Diesel for private British companies, initially Foster Yeoman (59/0). ... Class 60s at Peak Forest In the mid 1980s British Rail was faced with an aging fleet of freight locomotives which required overhaul or replacement. ... The Class 66 locomotive is a development of the Class 59 and used both on British and European railway networks—where it is marketed as EMD Series 66. ... Two Class 67s lead a freight train through Bristol Parkway 67006 Royal Sovereign at Evesham on 26 March 2005. ... The power at rail is the amount of power which a train applies to achieve the tractive effort. ... In physics, power (symbol: P) is the rate at which work is performed. ... Kwai Lo is Chinese slang for foreigner or ghost person. ... In physics, force is an influence that may cause a body to accelerate. ... The kilonewton, symbol kN, is an SI unit of force. ... Speed is the rate of motion, or equivalently the rate of change of position, many times expressed as distance d moved per unit of time t. ... Metre per second (U.S. spelling: meter per second) is an SI derived unit of both speed (scalar) and velocity (vector), defined by distance in metres divided by time in seconds. ...

In general, it is more common for heavy freight trains (such as Class 59, Class 60 and Class 66 locomotives) to have a high maximum tractive effort due to the mass which they haul. Light freight trains (such as Class 56, Class 58 and Class 67 locomotives) and passenger trains (such as Class 33 and Class 43 / Intercity High Speed Train locomotives) usually have much lower maximum tractive efforts. The Class 59 Co-Co diesel locomotives were built by General Motors Electro Motive Diesel for private British companies, initially Foster Yeoman (59/0). ... Class 60s at Peak Forest In the mid 1980s British Rail was faced with an aging fleet of freight locomotives which required overhaul or replacement. ... The Class 66 locomotive is a development of the Class 59 and used both on British and European railway networks—where it is marketed as EMD Series 66. ... Unsolved problems in physics: What causes anything to have mass? The U.S. National Prototype Kilogram, which currently serves as the primary standard for measuring mass in the U.S. Mass is the property of a physical object that quantifies the amount of matter and energy it is equivalent to. ... Electroputere-built 56006 at Doncaster in 2003 painted in rail blue livery Preserved 56003 in Load-Haul livery. ... 58001, on display at Doncaster Works open day on 27th July 2003. ... Two Class 67s lead a freight train through Bristol Parkway 67006 Royal Sovereign at Evesham on 26 March 2005. ... D6547 in original green livery without yellow warning panels, 1963. ... HST power car 43127 is shown here crossing the Kennet and Avon Canal The British Rail Class 43 is the classification used for the InterCity 125 High Speed Train power cars, built by BREL from 1976 to 1982 The class are officially the fastest diesels in the world, with an...

Special cases

The tractive effort for steam locomotives is multiplied by 1.5 for 3-cylinder engines and by 2 for 4-cylinder engines. This seems valid in the case of a 4-cylinder engine with cranks at 180° because two cylinders would be in the starting position at the same time. However, its validity seems doubtful in the case of a 3-cylinder engine with cranks at 120°, or a 4-cylinder engine with cranks at 135°, because only one cylinder would be in the starting position.

In the case of compound locomotives the tractive effort is calculated using the dimensions of the low-pressure cylinder(s) with a constant of 0.80 instead of 0.85. Again, the validity seems doubtful because the actual starting tractive effort would depend upon which cylinder (high-pressure or low-pressure) happened to be in the starting position. A compound locomotive is a type of steam locomotive where steam is passed that has already passed through one cylinder is then passed through another; i. ...

See also

• maximum tractive effort
• continuous tractive effort
• power at rail
• power classification

The maximum tractive effort is the highest force that a vehicle can exert. ... The continuous tractive effort is the highest force that a vehicle can exert over an extended period of time. ... The power at rail is the amount of power which a train applies to achieve the tractive effort. ... The London, Midland and Scottish Railway (LMS) maintained a simple, if imprecise, method of classifying its locomotives. ...

External links

• A simple guide to train physics
  
• Tractive effort, acceleration and braking