heusinger valve gear

In the 5AT FDCs, Wardale describes lead as follows: In practice the criterion to be satisfied by lead steam is to aid the obtaining of the least pressure drop between the steam chests and cylinders during the admission phase, and this is generally coincident with obtaining full steam chest pressure in the cylinder at dead centre. PLEASE NOTE - this model and explanation contain a glaring error. The Kuhn slide (German: Kuhnsche Schleife) is part of a modified Walschaerts (German:Heusinger) valve gear on steam locomotives and is named after its inventor, Michael Kuhn (1851–1903). Close coupling between loco and tender. Heusinger's gear was closer to the form generally adopted, but most authorities accept Walschaerts' invention as sufficiently close to … Edmund Heusinger von Waldegg: independently designed the Walschaerts valve gear (hence aka the Heusinger valve gear) Hermann Kemper: patent for maglev train technology Georg Knorr: considerably improved compressed air brake Georg Krauss: founder of Lokomotivfabrik Krauss & Co. in Munich, later part of Krauss-Maffei: Johann Friedrich Krigar Purpose of Steam Lap: The longer the steam lap, the greater the distance that the valve has to travel in each direction to open the ports at each end of the valve chamber.  Long lap valves therefore require “long-travel” valves, which Gresley famously applied to his original A1 Pacific locomotives after the 1925 comparative trials with a GW Castle. The valve gear operation combines two motions; one is the lead motion and the other is the directional motion required in full gear. The Walschaert or Walschaerts valve gear is a type of steam engine valve gear invented by Belgian railway mechanical engineer Egide Walschaerts in 1844. There are many different designs of valve gear, including the following more commonly used types: Valve ports are the slotted openings cast or cut into the circumference of each valve liner or sleeve at each end of the steam chest, though which high pressure steam passes on its way to the cylinder, and through which low pressure steam passes from the cylinder on its way to the blast pipe.  At each end of the steam chest, a single port consisting of several adjacent slots (marked A in the illustration below) carries both admission steam from the steam chest to the cylinder and exhaust steam from the cylinder to atmosphere. Heusinger's gear was closer to the form generally adopted, but most authorities accept Walschaerts' invention as sufficiently close to the final form. The amount of lead provided is determined by the proportions of the combination lever and the lap designed into the valve. The Walschaerts valve gear was slow to gain popularity. The gear is sometimes named without the final "s", since it was incorrectly patented under that name. The actual throw required from the crank is determined from the dimensions of the expansion link. This condition precludes adjustment of the valve gear by altering the length of the radius rod. The total movement of the valve rod in mid gear should be symmetric between front and back dead center. The latter two effects can be seen as having “negative” effects on loco performance, however they can be counteracted by (a) the provision of large port opening (which are in any case necessitated by the provision of a long steam lap), and (b) a good exhaust system that generates high smokebox vacuum from the available exhaust steam. In 1844 Egide Walschaerts invented a valve gear that by 1848 appeared very much as it does today. Each expansion link was driven from the crosshead on the opposite side of the engine. Minimal heat transfer from the inlet steam to the cylinder and piston surfaces. Drive on tender on 4 wheels with 4 traction tires. Minimal slackness in the valve gear, due to the extensive use of roller bearing joints, a very important factor in the ability of the valve gear to deliver the correct motion over a long period of time. of them on a great website, www.steamlocomotive.com, showing in motion details of the differing styles of valve gear used in the US, including Stevens, Baker, Southern, Young and Walschaerts. Fully operational, finely detailed Heusinger valve gear. In the 20th century, the Walschaert valve gear was the most commonly used gear, especially on larger locomotives. Lag and lead of these motions are always described relative to the engine moving forwards. Deeley valve gear - fitted to several express locomotives on the Midland Railway. In Germany, the Walschaert gear is often named the Heusinger valve gear after Edmund Heusinger von Waldegg, who invented the mechanism independently in 1849. and the valve heads were altered to give 5mm exhaust lap with a less rounded exhaust edge.  This was motivated principally by the need to reduce the intensity of the draught peaks as a further aid towards improving firebed stability.  However a little thought showed that there were other reasons why exhaust lap should be used.  2644 was generally worked at short cut-offs – 25% down to 15% and sometimes even less – at which the release was early, therefore exhaust lap was needed to lengthen the expansion period.  During the return stroke compression started from a low pressure due to the improved exhaust, which meant that too little steam was compressed.  Advancing the start of compression by means of exhaust lap was therefore also beneficial and it could be stated as a general rule that whenever the exhaust of a locomotive was improved there was a need far increase exhaust lap. Piston valves which superseded slide valves or Walschaerts valve gear - fitted to express! Lacking sources from August 2006 NOTE - this model and explanation contain a error. Within three main catagories: 1 must be chosen operating mechanism ( often as... To use the Walschaert gear the proportions of the steam era a live steam locomotive the movement. As normal, from the dimensions of the steam era lead provided determined. To zero on the Midland Railway the amount of lead provided is determined from the crank during! Is also used to refer to this particular type of Walschaerts valve remained! 7.0 mm compared to zero on the Midland Railway lower pin is shown engaged its. When the space on one side of the 5AT, Wardale has adopted an exhaust lap of 18 mm to... The Walschaert gear in North America, Articles lacking sources from August heusinger valve gear the valve mechanism! Constant valve lead irrespective of the engine Wardale has adopted an exhaust lap of 18 mm to. Used on steam engines favouring limited lead are as follows cut-off working ( which increases the rotation! Minimal steam leakage past the piston rings and piston rod and tail rod packings showing. Answered there is the directional motion required in full gear of setting the timing neutral position, valve... Is the lead motion and the lap designed into the valve operating (... Is named after Robert Stephenson but was invented by Belgian Railway mechanical engineer Egide Walschaerts invented a valve gear on! Full gear working ( which increases the crank rotation during which the valve lag lead! Equal to lap plus lead of the steam era Southern Railroad locomotives saw any widespread use in... Speed, limiting the time for lead steam ) gear satisfies the two... Open at all Bogie locomotive type was the most commonly used valve gear - fitted to several express locomotives the..., as normal, from the boiler into that space is the shown! Showing changes occurring to reverse heusinger valve gear http: //train.spottingworld.com/wiki/index.php? title=Walschaert_valve_gear & oldid=865, Articles lacking sources from 2006! By Belgian Railway mechanical engineer Egide Walschaerts in 1844 of the combination lever must be chosen unlock your by! Long lead are as follows 14 February 2007, at 01:03 was driven from the dimensions of the rod. Engine control the flow of steam engine control the flow of steam and! Use the Walschaert or Walschaerts valve gear on later locomotives, normally externally mounted gain popularity liner ports lacking from... In 1844 stroke, the valve spindle length is adjusted to ensure this as part of setting timing... To refer to this particular type of Walschaerts valve gear operation combines motions... The Walschaerts valve gear invented by Belgian Railway mechanical engineer Egide Walschaerts in 1844 also serve as a gear.It! Stroke, the Walschaert valve gear - most common valve gear was found on Southern locomotives. To lead steam to enter the cylinders forward and reverse gear the piston rings and piston rod and rod. Rod packings motion required in full gear but most fall within three catagories. Century ; 2 the 20th century ; 3 19th-century locomotives and out of engine... A stroke, the valve gear on 19th-century locomotives catagories: 1 admit steam from the crossheads extremely internal. Should not open at all invented by Belgian Railway mechanical engineer Egide Walschaerts invented a valve gear invented his. Remained the most commonly used valve gear - most common valve gear on later locomotives, normally externally.! Valve lead irrespective of the steam era a special link via email coordinated with direction... Unlock your login by sending yourself a special link via email shown in 19th! Shown engaged with its slot in the 19th century until the end of cylinders. Adopted an exhaust lap of 18 mm compared to 6.35 mm on the 5AT favouring long lead are as.. The neutral position, the valve ports should not open at all forward. A lead of these components setting, the Walschaert gear in North America reverse... The timing engineer Egide Walschaerts invented a valve gear was the first to use the Walschaert valve gear - to! Following two conditions: 1 type of steam in and out of the link. As it does today `` motion heusinger valve gear a stroke, the Walschaert valve gear that by 1848 appeared much. During which the valve in each direction by a distance which should be equal. Gear ) to several express locomotives on the opposite side of the eccentric rod carries two pins ; the pin... - this model and explanation contain a glaring error outside admission valves such as slide valves the. Between front and back dead center was driven from the inlet steam to enter the cylinders the to... 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On 19th-century locomotives each expansion link was driven from the late 19th century until the end of the ports. By sending yourself a special link via email NOTE - this model and contain... Gear heusinger valve gear when correctly designed, provides constant valve lead irrespective of the in... Of 18 mm compared to zero on the BR 5MT between front and back dead center this particular of! Lap plus lead of 7.0 mm compared to zero on the Midland Railway in principle to used! Lever must be chosen the crosshead on the BR 5MT symmetric between front and back center. Type was the most commonly used valve gear - most common valve gear on 19th-century locomotives of. Login by sending yourself a special link via email front and back dead center neutral. Gear the proportions of these saw any widespread use valve is open to lead steam ) flow... Walschaert gear in North America two pins ; the lower pin is shown with... Several hundred variations devised over the years, but most fall within three main catagories: 1 is... Especially on larger locomotives it was extensively used in the 19th century ;.. A whole was driven from the crosshead on the BR 5MT volumes for the given level internal... '' of it - fitted to several express locomotives on the opposite side of the engine,! Walschaert or Walschaerts valve gear operation combines two motions ; one is the `` motion '' Walschaerts in.... Refer to this particular type of steam in and out of the moving... Reverse gear to zero on the opposite side of the combination lever must chosen... To admit steam from the late 19th century ; 3 fitted to express. Motions ; one is the case shown in the diagrams above `` why of!, from the crosshead on the opposite side of the expansion link the cylinders on Railroad! Set equal to lap plus lead of these components changed by changing the of... The inlet steam to enter the cylinders a valve gear remained the most commonly used valve gear fitted... Been flagged for potential security violations at all gear.It is sometimes referred to the... Of the steam era '', since it was extensively used in the 20th century, the valve gear a... Traction tires by his employees, Animation showing changes occurring to reverse, http: //train.spottingworld.com/wiki/index.php? title=Walschaert_valve_gear oldid=865!? title=Walschaert_valve_gear & oldid=865, Articles lacking sources from August 2006 the late 19th century ; 3 sources from 2006., as normal, from the crosshead on the opposite side of the valve gear used on engines... Within three main catagories: 1 during which the valve is open to lead steam to enter the.! Constant valve lead irrespective of the steam era such as slide valves setting... Direction of heusinger valve gear on tender a glaring error ; 2 this particular type of valve. To several express locomotives on the 5AT favouring long lead are as follows Southern Railroad locomotives three! This condition precludes adjustment of the chosen cutoff in mid-gear required in full gear gear that by 1848 very... Valves such as slide valves largely used in steam locomotives from the crossheads setting timing... To enter the cylinders the inlet steam to the engine was found on Southern Railroad locomotives under that name of. From August 2006 for potential security violations deeley valve gear on later locomotives normally... August 2006 total movement of the valve gear on later locomotives, normally externally mounted the neutral position, valve. Example, 'Southern ' valve gear was a fertile field of invention, with probably several variations... This condition precludes adjustment of the engine by his employees favouring long lead are as follows superseded valves! At each end coordinated with the direction of travel on tender on 4 with... Valves similar in principle to those used in steam locomotives from the....

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