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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. A locomotive is a railway Vehicle that provides the motive power for a Train. It is normally understood to be the actual force on the locomotive's drawbar or rear coupler. A coupling (or a coupler) is a mechanism for connecting Rolling stock in a train 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.

In most cases, especially for steam locomotives, this figure is a calculated, not measured one. A steam locomotive is a Locomotive powered by Steam. The term usually refers to its use on Railways but can also refer to a "road locomotive"

Contents

Steam locomotives

The normal formula used (for a 2 cylinder locomotive) is:

t = \frac {cPd^2s} {D}

where

As with any physical formula, consistent units of measurement are required: pressure in psi and lengths in inches give tractive effort in lbf, while pressure in Pa and lengths in metres give tractive effort in N. A boiler is a closed vessel in which Water or other Fluid is heated A piston is a component of Reciprocating engines Pumps and Gas compressors It is located in a cylinder and is made gas-tight by Piston A stroke is a single action of certain Engines In a steam, Otto or Diesel Piston Engine, a stroke is the action of On a Steam locomotive, a driving wheel is a powered Wheel which is driven by the Locomotive 's Pistons (or Turbine, in the

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. The Association of American Railroads is an industry trade group representing primarily the major freight railroads of Modern, roller bearing fitted locomotives were probably underestimated in this calculation.

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.

The actual starting tractive effort depends on the position in which the wheels have stopped; the above formula can give the average, maximum or minimum over a wheel revolution depending on the choice of constant c.

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. A steam locomotive is a Locomotive powered by Steam. The term usually refers to its use on Railways but can also refer to a "road locomotive" 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. The Virginian Railway was a Class I railroad located in Virginia and West Virginia in the United States. A steam engine is a Heat engine that performs Mechanical work using Steam as its Working fluid. 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).

Of more successful large steam locomotives, those with the highest rated starting tractive effort were the Virginian Railway AE-class 2-10-10-2s, at 176,000 lbf (783 kN) in simple-expansion mode. The Virginian Railway was a Class I railroad located in Virginia and West Virginia in the United States. Under the Whyte notation for the classification of Steam locomotive Wheel arrangements a 2-10-10-2 is a locomotive with two Leading wheels two The Union Pacific's famous Big Boys had a starting T. Big Boy was the name given to the Union Pacific Railroad 's twenty-five 4000 class 4-8-8-4 Mallet articulated Steam locomotives E. of 135,375 lbf (602 kN); the Norfolk & Western's Y5, Y6, Y6a, and Y6b class 2-8-8-2s had a starting T. The Norfolk and Western Railway ( N&W), a US Class I railroad, was formed by more than 200 railroad mergers between 1838 and 1982 A 2-8-8-2, in the Whyte notation for describing Steam locomotive Wheel arrangements is an Articulated locomotive with a two-wheel Leading E. of 152,206 lbf (677 kN) in simple expansion mode (later modified, resulting in a claimed T. E. of 170,000 lbf (756 kN)); and the Pennsylvania Railroad's freight Duplex Q2 attained 114,860 lbf (511 kN) — the highest for a rigid framed locomotive. The Pennsylvania Railroad was an American Railroad, founded in 1846 A duplex locomotive is a Steam locomotive that divides the driving force on its wheels by using two pairs of cylinders rigidly mounted to a single Locomotive frame The Pennsylvania Railroad 's class Q2 comprised one prototype and twenty-five production duplex Steam locomotives of 4-4-6-4 Wheel arrangement Later two cylinder passenger locomotives were generally 70,000 to 80,000 lbf (300 to 350 kN) of T. E.

Diesel and electric locomotives

For a diesel-electric locomotive or electric locomotive, starting tractive effort 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. A Diesel locomotive is a type of Railroad Locomotive in which the prime mover is a Diesel engine. "Electric Trains" redirects here For the 1995 Squeeze single see Electric Trains (song. Stall torque is the Torque which is produced when an engine or motor stalls. See also Electric vehicle, Electric motor A traction motor is a type of Electric motor used to power the driving wheels of a vehicle such as For a diesel-hydraulic locomotive the starting tractive effort depends on the stall torque of the torque converter, which can be very large. A Diesel locomotive is a type of Railroad Locomotive in which the prime mover is a Diesel engine. Stall torque is the Torque which is produced when an engine or motor stalls. A torque converter is a modified form of Fluid coupling that is used to transfer rotating power from a prime mover, such as an Internal combustion engine

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. The vis insita or innate force of matter is a power of resisting by which every body as much as in it lies endeavors to preserve in its present state whether it be of rest or of moving In Fluid dynamics, drag (sometimes called fluid resistance) is the force that resists the movement of a Solid object through a Fluid (a In order for this to occur a particularly high tractive effort is required, usually the maximum tractive effort of the engine is applied. The maximum tractive effort is the highest force that a vehicle can exert This means that the engine works to produce the highest possible force that it can exert onto the wheels to cause movement or motion. In Physics, motion means a constant change in the location of a body 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. The maximum tractive effort is the highest force that a vehicle can exert 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. In Physics, velocity is defined as the rate of change of Position. 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).

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:

 Class   Type   Top speed   Maximum
tractive
effort 		  Speed to
reduce
tractive effort 		  Continuous
tractive
effort 		  Maximum
power
at rail 		  Mass 
 mph   km/h 
Class 08 Shunter 15 156 kN 8. 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 British Rail Class 08 is a class of Diesel locomotive designed for shunting 8 mph 49 kN 194 kW 49. 6 - 50. 4 t
Class 33 Passenger 85 200 kN 17. The British Rail Class 33 also known as the BRCW Type 3 or Crompton is a class of Bo-Bo Diesel locomotives ordered in 1957 and built for the Southern 5 mph 116 kN 906 kW 77. 7 t
Class 56 Light freight 80 275 kN 16. The British Rail Class 56 is a type of Diesel locomotive designed for heavy freight work 8 mph 240 kN 1790kW 125. 2 t
Class 58 Light freight 80 275 kN 17. The British Rail Class 58 is a class of Co-Co Diesel locomotive designed for heavy freight 4 mph 240 kN 1780 kW 130 t
Class 59 Heavy freight 60 or 75 506 kN 14. The Class 59 Co-Co Diesel locomotives were built and introduced between 1985 and 1995 by General Motors Electro-Motive Diesel (EMD for private British 3 mph 291 kN 1889 kW 121 t
Class 60 Heavy freight 60 500 kN 17. The British Rail Class 60 is a class of Co-Co Diesel locomotive designed for heavy freight work 4 mph 336 kN 1800 kW 129-131 t
Class 66 Heavy freight 75 409 kN 15. 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. 9 mph 260 kN 1850 kW 126 t
Class 67 Light freight 125 200 141 kN ?? mph 90 kN 1860 kW 90 t

The power at rail of a train follows the equation power (kW) = force (kN) x speed (m/s)

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. The Class 67 Locomotives were built from 1999 to 2000 by Alstom in Valencia Spain under sub-contract from General Motors Diesel in Canada 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 or energy is transmitted or the amount of energy required or expended for The watt (symbol W) is the SI derived unit of power, equal to one Joule of energy per Second. In Physics, a force is whatever can cause an object with Mass to Accelerate. The newton (symbol N) is the SI derived unit of Force, named after Isaac Newton in recognition of his work on Classical Speed is the rate of motion, or equivalently the rate of change in position often expressed as Distance d traveled per unit of The Class 59 Co-Co Diesel locomotives were built and introduced between 1985 and 1995 by General Motors Electro-Motive Diesel (EMD for private British The British Rail Class 60 is a class of Co-Co Diesel locomotive designed for heavy freight work 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. Mass is a fundamental concept in Physics, roughly corresponding to the Intuitive idea of how much Matter there is in an object 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 British Rail Class 56 is a type of Diesel locomotive designed for heavy freight work The British Rail Class 58 is a class of Co-Co Diesel locomotive designed for heavy freight The Class 67 Locomotives were built from 1999 to 2000 by Alstom in Valencia Spain under sub-contract from General Motors Diesel in Canada The British Rail Class 33 also known as the BRCW Type 3 or Crompton is a class of Bo-Bo Diesel locomotives ordered in 1957 and built for the Southern 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

Special cases

The tractive effort for steam locomotives is multiplied by 1. 5 for 3-cylinder engines and by 2 for 4-cylinder engines.

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. A compound engine unit is a type of Steam engine where steam is expanded in two phases 80 instead of 0. 85.

See also

External links

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. A number of different numbering and classification schemes were used for the locomotives owned by the London Midland and Scottish Railway (LMS and its constituent companies Truck and tractor pulling, also known as power pulling, is a competition using Tractors and large Trucks to pull a heavy drag along a 'track' and is very Thrust is a reaction force described quantitatively by Newton 's Second and Third Laws.
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