Gresley conjugated valve gear
The Gresley conjugated valve gear is a valve gear for steam locomotives designed by Sir Nigel Gresley, chief mechanical engineer of the LNER, assisted by Harold Holcroft. It enables a three-cylinder locomotive to operate with only the two sets of valve gear for the outside cylinders, derives the valve motion for the inside cylinder from them by means of levers; the gear is sometimes known as the Gresley-Holcroft gear, acknowledging Holcroft's major contributions to its development. The Gresley conjugated gear is an adding machine, where the position of the valve for the inside cylinder is the sum of the positions of the two outside cylinders, but reversed in direction, it can be thought of as a rocking lever between one outside cylinder and the inside cylinder, as is common on 4-cylinder steam locomotives, but with the pivot point being moved back and forth by a lever from the other outside cylinder. If we approximate the motion of each valve by a sine wave — if we say the position of a valve in its back-and-forth travel is proportional to the sine of the "driver angle", once we have set the zero point of driver angle at the position it needs to be for that valve — the mathematics is simple.
The position of the valve, pinned to the long end of the 2-to-1 lever is sin θ, while the positions of the other two valves are supposed to be sin and sin . The position of the short end of the 2-to-1 lever is − 1 2 sin θ —which, it turns out, is midway between sin and sin for any value of θ. So a 1-to-1 lever pivoted on the short arm of the 2-to-1 lever will do the trick. Locomotives with Gresley valve gear must have the three pistons operating at 120 degree intervals. In order for the inside crank to clear the leading coupled axle, the inside cylinder of a locomotive with Gresley valve gear is positioned higher than the outside cylinders and angled downward. To maintain a smooth flow of torque, the crank angles are offset from equal 120 degree spacing to compensate for the angle of the inside cylinder; the resultant timing of the blast from steam exiting the cylinders still gives these three-cylinder locomotives a regular exhaust beat. There were a number of issues with the Gresley gear.
Because the conjugation apparatus was mounted at the opposite end of the valve spindles from the valve gear, as the valve spindles lengthened with the heat of steam in the cylinders the valve timing would be affected, the gear would need to be removed before it was possible to remove valves for maintenance. However, the B17 Class "Footballer"/"Sandringham" 4-6-0s avoided this particular problem by being designed with the conjugated gear behind, rather than in front of, the cylinders; the main difficulty with this valve gear was that at high speeds, inertial forces caused the long conjugating lever to bend or "whip". This had the effect of causing the middle cylinder to operate at a longer cutoff than the outer cylinders, therefore producing a disproportionate share of the total power output, leading to increased wear of the middle big end. Sustained high speed running could sometimes cause the big end to wear enough that the increased travel afforded to the middle piston by the increased play in the bearing was enough to knock the ends off the middle cylinder.
This happened during the 113 miles per hour run of "Silver Fox". Although the problem could be contained in a peacetime environment with regular maintenance and inspections, it proved to be poorly suited to the rigors of heavy running and low maintenance levels of World War II; this gave rise to big-end problems on the centre cylinder connecting rod on the famous A4 class of streamlined Pacifics and many of these locomotives were fitted with a reduced diameter piston and had the inside cylinder sleeved down as a temporary measure. LNER Class A4 4468 Mallard suffered centre cylinder big-end damage during its world record run and was forced to limp back to its depot for repairs afterwards. Gresley's successor at the LNER, Edward Thompson, was critical of this particular valve gear; as well as introducing new two-cylinder designs, he set about rebuilding Gresley locomotives with separate sets of Walschaerts valve gear for each cylinder. Under British Railways ownership, the application of former Great Western Railway workshop practices for precise alignment of the valve gear and in the manufacture and lubrication of the inside big end bearing solved the problems.
Gresley conjugated valve gear was used by the American Locomotive Company under license for the 4-12-2 locomotives built for the Union Paci
The Kuhn slide is part of a modified Walschaerts valve gear on steam locomotives and is named after its inventor, Michael Kuhn. The term is used to refer to this particular type of Walschaerts valve gear system as a whole. Problems arise in incorporating a Walschaerts valve gear into the design of tank and narrow gauge locomotives because of space limitations; the reversing rod, needed to change between forward and reverse running, is therefore mounted at the same level as the pivot of the expansion link. This enables the lifting link to be dispensed with, the lifting arm to be connected directly to the radius rod. To ensure the required horizontal movement, the back end of the radius rod is designed as a slide which fits into a rotatable crosshead in the lifting arm; the Kuhn valve gear was not as widespread as the classic Walschaerts valve gear as its production costs were higher. One advantage of the Kuhn slide is that it runs smoothly in either direction. For that reason it was preferred on tank locomotives which, for operational reasons had to run backwards for long periods.
A variation of the Kuhn slide was developed by the Winterthur Locomotive Works. On the so-called Winterthur valve gear the expansion link itself is attached to the reversing shaft, both having a common pivot
The EMD GP40-2 is a 4-axle diesel road switcher locomotive built by General Motors Electro-Motive Division as part of its Dash 2 line between April 1972 and December 1986. The locomotive's power is provided by an EMD 645E3 16-cylinder engine which generates 3,000 horsepower. Standard GP40-2 production totalled 861 units, with 817 built for U. S. railroads, 44 for Mexican railroads. In addition, three GP40P-2s, passenger versions of the GP40-2, were built for Southern Pacific in 1974, 279 GP40-2L and GP40-2 units, equipped with wide-nosed cabs, were built by General Motors Diesel, for Canadian National and GO Transit between 1974 and 1976. Of the CN units, 233 were built with a lighter frame to allow for a larger fuel tank; these units were classified GP40-2L but are referred to as GP40-2L. The balance of CN's fleet, 35 units, the 11 unit GO Transit fleet, used standard frames and smaller fuel tanks. Total production of the GP40-2 and its variations totalled 1,143 units. Although the GP40-2 was a sales success, it sold fewer units than the earlier GP40 and the contemporary GP38-2 and SD40-2 models.
The popularity of high-horsepower 4-axle diesels began to decline with the GP40-2, with 6-axle models gaining in popularity for their superior low-speed lugging performance. Like the SD40-2 the GP40-2 has a reputation for reliability, many are still in use. Changes such as the modular electronics system improved reliability over the GP40, their high power-per-axle rating suited them to high-speed service rather than low-speed drag freights. With the usual 62:15 gearing EMD rated the GP40-2 at 55,400 lb continuous tractive effort. Units built by General Motors Diesel, CanadaGP40P-2 List of GM-EMD locomotives List of GMD Locomotives Sarberenyi, Robert. EMD GP40-2, GP40-2W, GP40-2LW, GP40P-2 Original Owners CN GP40 Family GP40-2 order numbers EMD GP40-2 Proto Info: Conrail Cyclopedia
The EMD GP38-2 is a four-axle diesel-electric locomotive of the road switcher type built by General Motors, Electro-Motive Division. Part of the EMD Dash 2 line, the GP38-2 was an upgraded version of the earlier GP38. Power is provided by an EMD 645E 16-cylinder engine. Most built still remain in service in the modern era due to ease of maintenance and exceptional reliability; the GP38-2 differs externally from the earlier GP38 only in minor details. Its most distinctive identifying feature is the cooling water level sight glass on the right side of the long hood; the battery box covers of the Dash 2s are bolted down instead of hinged. It can be distinguished from the contemporary GP39-2 and GP40-2 in that its Roots blown engine had two exhaust stacks, one on each side of the dynamic brake fan, if equipped, while the turbocharged GP39-2 and GP40-2 has a single, larger stack; the GP39-2 has two radiator fans on the rear of the long hood like the GP38-2, while the GP40-2 has three. It was available with either a high-short-hood, common on Norfolk Southern units, or a low-short-hood, found on most other railroads.
The GP38-2W is a forerunner of today's wide-nose units. It is distinguished by its wide-nose Canadian comfort cab. 51 of these locomotives were produced for Canadian National Railways during 1973–1974. Although a W is suffixed to the name, it is an addition by enthusiasts to help specify the presence of a CN-spec comfort cab. No locomotives built using CN's design of comfort cab featured a W in their designation, as the presence of the cab did not mechanically alter the locomotive; this is reflected by the lack of the "W" in the model designation on the builders' plates of these units. There are snow shields above the inertial-filter central air intakes behind the cab, they are otherwise identical. 1,799 examples of this locomotive model were built for American railroads and industrial concerns, 257 for Canadian railroads and industrials, 156 for Mexican railroads and industrials, 1 export unit for the Saudi Government Railways. A total of 31 GP38-2s were built with high-short-hoods containing steam generators for passenger service on Mexican railways.
In addition, all 257 of Southern Railway's GP38-2s had Southern's "standard" high-short-hoods. The GP38-2 is a player-drivable locomotive in Microsoft Train Simulator. Parts of the EMD GP38-2 are used to form the children's TV series Dunbar; the train in the 2007 PC game Team Fortress 2 is based on the GP38-2. A number of higher horsepower 40 Series locomotives have been rebuilt into the equivalent of a GP38-2, by removal of the turbocharger and the substitution of twin Roots blowers. CSX and Norfolk Southern have both started replacing cabs on the aging locomotives. NS still calls them GP38-2 while CSX calls them GP38-3. List of GM-EMD locomotives List of GMD Locomotives David Thompson. EMD GP38-2 and GP38-2W Original Owners The Family Lines Rail System: Condensed List of Locomotives. 1 Feb.1982 US Government test of GP38-2 with biodiesel. CN GP38-2 family
MPXpress is a series of diesel-electric passenger train locomotives designed for commuter rail service. The locomotives are built by a subsidiary of Wabtec. To date, MPI has offered five main variants: MP36PH-3S, MP36PH-3C, MP40PH-3C, MP32PH-Q, MP54AC. However, due to federal emissions standards, the MP54AC is the only locomotive for sale in the United States, as it is the only MPXpress locomotive that meets Tier 4 standards; the MPXpress line of locomotives were the first production passenger locomotives to meet FRA safety regulations regarding crashworthiness and fire safety. The line meets APTA crashworthiness standards. Production of the locomotives have kept pace with stringent emissions regulations from the United States Environmental Protection Agency. Between 2002 and 2015, the EPA has issued four "tiers" of emissions standards and in each case the MPXpress was the first passenger locomotive to meet the standard. Numerous public transit agencies in Canada and the United States have ordered MPXpress locomotives for their commuter rail services.
GO Transit is the largest client for MPI MPXpress locomotives, with 67 in their fleet and an additional 18 on order. The MP36PH-3S uses a 16-cylinder EMD 645F3B diesel engine as its prime mover, capable of generating 3,600 hp. Head-end power is generated by a static inverter that receives its power through connections to the prime mover. Compared to a locomotive with a separate HEP generator, the prime mover must maintain a higher RPM in order to supply power to the passenger cars; the setup leads to higher noise levels and higher fuel consumption. When providing the maximum 500 kW HEP load, maximum traction power is reduced to 2,930 hp since HEP generation diverts some power from the prime mover; the MP36PH-3S was the first variety of MPXpress locomotive to be built and the launch customer was Metra, a commuter railroad in the Chicago area. Metra ordered 27 of these locomotives in 2001, which were built and delivered between 2003 and 2004. Fourteen were to replace the railroad's aged F40C fleet.
Metra is the only operator of the MP36PH-3S variant of the MPXpress. When the locomotives were first delivered, the onboard computer systems proved problematic. At one point in 2004, because Metra had so many MPXpress locomotives out of service, two F40Cs had to be placed back into service for a short time. Starting in 2015, Metra is converting its MP36PH-3S locomotives to the MP36PH-3C specification by removing the static inverter and replacing it with a separate HEP generator; this is being done in an effort to boost fuel efficiency. Metra's MP36PH-3C locomotives all have extended radiators to supply the extra cooling for the new Caterpillar generators. Locomotive No. 417 was the first one to be was sent to MPI in Boise. The following units are being converted in-house at Metra's 47th Street shops on the South Side of Chicago; the MP36PH-3C has the same EMD 645F3B prime mover as the MP36PH-3S model, but with a separate head-end power generator, a Caterpillar C-27 diesel engine. In this arrangement, when providing HEP, the full 3,600 hp from the prime mover is available for traction, the prime mover is allowed to idle at a lower RPM.
Having two engines is more complex, but results in lowered noise emissions and lower fuel consumption. The launch customer for the MP36PH-3C was Caltrain, a commuter railroad in the San Francisco Bay Area. Caltrain ordered 6 of these locomotives in 2003, which were delivered that same year; this locomotive has gone on to become the most popular MPXpress variant, with 100 delivered to nine different customers. The MP40PH-3C introduced a new prime mover, the larger 16-cylinder EMD 710GB series diesel engine, capable of generating 4,000 hp; the MP40PH-3C uses an EMD alternator and traction motors. The launch customer for the MP40PH-3C was a commuter railroad in the Toronto area; the MP40PH-3C was developed in response to a bid request from GO Transit for locomotives capable of generating 4,000 hp, hauling 12 passenger cars and traveling at speeds up to 93 mph. MotivePower and GE Transportation responded to the request, with MotivePower being selected as the winning bidder. GO Transit placed an order for 27 locomotives in 2006, which were built and delivered between 2007 and 2008.
In 2011, MotivePower upgraded the MP40PH-3C to comply with the EPA's more stringent Tier 3 emissions standard, in effect between 2012 and 2014. Three locomotives meeting this standard were built, all delivered to Sounder commuter rail in the Seattle area. Ten additional locomotives for GO Transit are Tier 3 compliant; the MP32PH-Q was built from 2013 to 2014 for SunRail. They have similar specifications as new MPXpress locomotives, but are rebuilt and refurbished from units that had operated on MARC as GP40WH-2 locomotives. Inside the locomotive, the 3,000 hp EMD 16-645E3C prime mover has been rebuilt and electronics have been upgraded using the same equipment as other MPXpress locomotives. On the exterior, the MP32PH-Q retains the hood unit layout of the former GP40WH-2, but a new four-window MPXpress cab replaces the original cab; the MP54AC is the latest locomotive in the MPXpress family and the only model available for sale in the US. It is designed to both meet the EPA's stringent Tier 4 emissions standard and offer higher performance than the MP40PH-3C.
The MP54AC uses a pair of Cummins 16-cylinder QSK60 engines rated at 2,700 hp each, which qualifies it as the most powerful diesel-electric passenger locomotive in North America and historical
Bagnall–Price valve gear
Bagnall–Price valve gear is a type of steam engine valve gear developed at locomotive manufacturer W. G. Bagnall as an alternative to the more common Walschaerts valve gear; the gear was patented in 1903 by W. G. Bagnall and T. S. Price, the manager of the works; the valves are driven from an eccentric cam mounted on one of the driving axles and linkage from the crosshead. The driving axle cam drives a rocking shaft, mounted inside a cylindrical sleeve above the cylinder. A drop lever and connecting link from the crosshead oscillates the sleeve to control the lap and lead of the cylinder. W. G. Bagnall claimed that Bagnall–Price valve gear eliminated some of the complexity of the Walschaerts gear the combination lever and return gear.
The Arnoux system is a train articulation system, for turning on railroad tracks, invented by Jean-Claude-Républicain Arnoux and patented in France in 1838. Arnoux was the chief engineer of the Ligne de Sceaux, built with tight radii in the area around Sceaux, Hauts-de-Seine. With the support of the French Academy of Sciences, Arnoux devised a new articulation system that allowed train wheels to turn, the système ferroviaire dit Arnoux, the Ligne de Sceaux was built to test his prototypes; the line started commercial use in 1846. But the operating cost and the use of a broad gauge of 1,750 mm meant it was not taken up more widely. Invention of the bogie made it redundant, it was abandoned by 1893. When steam railways were in their infancy, trains comprised a steam locomotive and one or more railway carriages with two fixed axles; as speeds increased, this design caused significant wear to the track and instability in the track ballast. To ameliorate these faults, Arnoux proposed a system of essieux articulés whereby the yaw angle of the wheels was reduced to zero.
Arnoux adapted the system used on horse-carts, which pivoted each axle at its centre, to be applied over the two axles together. Arnoux devised a system of chains and pulleys so that each of the wheels' adjusted in yaw through the curve: as soon as the leading axle started to turn, all other axles would turn by the same amount; this was a fatal design flaw since in a long train not all carriages are on the same part of the curve. A compromise was to use pulleys of different diameters, with guide wheels on the locomotive to control their motion. Using a broad gauge of 1,750 mm was expected to give greater stability; this system was not suitable for steam locomotives. The locomotives had a 2-4-2 wheel arrangement and the driving wheels were flangeless; the carrying wheels were controlled by near-horizontal guide wheels. Arnoux applied for his patent, number 8342, on 28 March 1838. Trials took place at Saint-Mandé between 1839 and 1840 in a 1 km circuit constructed by Alexis Dulong; these trials demonstrated the stability and safety of the system.
Public bodies, the Duke of Aumale and numerous members of the French Academy of Sciences, including François Arago. All unanimously praised the system. After this experience, Arnoux was awarded the Grand Prix de Mécanique by the Institute. At the suggestion of François Arago, the Arnoux system was implemented on the Ligne de Sceaux from Paris to Sceaux, Hauts-de-Seine. On 5 September 1844, Arnoux and the Minister of Public Works signed a contract to build and operate the line; the line begain service in 1846, starting from the Barrière d'enfer with a curved passenger building of 25-metre radius on a balloon loop to allow trains to reverse direction. The route had its first stop at Arcueil Bourg-la-Reine on a 30-metre radius curve; the incline towards Sceaux was straight until the station at Fontenay-aux-Roses had a succession of curves at 63,-70-and-50-metre radii. All together the line was 10.5 km long. In fact, the problem was solved by the bogie, invented in the USA shortly after opening, but this was unknown in Europe at the time.
The Arnoux system bears some similarity to Cleminson's patent system. Both are designed to keep the axles radial to the curvature of the track. Use of the Arnoux System from Paris to Limours was abandoned in 1883 during negotiations with the government and the Compagnie du Chemin de Fer d'Orléans à Rouen for construction of new lines, and the Ligne de Sceaux was the only one built to its design, with its unusual track gauge and specific construction of carriages and locomotives. The track was replaced overnight with standard gauge in May 1891. Jean-Claude-Républicain Arnoux Ligne de Sceaux Anjubault Armengaud, Jacques-Eugène. Publication industrielle des machines, outils et appareils les plus perfectionnés et les plus récents employés dans les différentes branches de l'industrie française et étrangère: Notices sur les machines locomotives envoyées à l'exposition universelle. Paris: A. Morel. Retrieved 28 November 2008. Lequeux, James. François Arago, un savant généreux: physique et astronomie au XIXe siècle.
EDP Sciences. ISBN 2868839991. Jacobs, Gaston. La ligne de Sceaux, 140 d'histoire. La Vie du Rail. ISBN 2-902808-28-3. Revue Générale des Chemins de Fer, 1895