stephenson valve gear calculation

VALVE GEAR PROGRAM INSTRUCTIONS RUNNING IN MICROSOFT WINDOWS These Windows valve gear programs were written betweem 1998 and 2007 by Charles J. Dockstader HCR 69 Box 3111, California Valley, CA 93453 However, in this case it is less easy to relate the valvegear mechanism to the ( ) Ar The initial stage of the analysis which determines the details of the 'equivalent eccentric' is the same as for Walschaerts gear. Instead of eccentrics, double return cranks were used to drive the eccentric rods, and a launch-type expansion link was used. In 40 years I never revisited the point, which may be somewhat remiss. Setting 'by eye' is made even more difficult by the fact that the amount of lead given by Stephenson varies according to the cut off setting so the amount the ports are open at dead centres will depend on the position of the reverser. The Great Western Railway used Stephenson gear on most of its locomotives, although the later four-cylinder engines used inside Walschaerts gear. For some more sophisticated understanding of valve gears I suggest Don Ashton's Steam Locomotive Valve gears site, especially in this context the page on Stephenson's gear. Slide valves largely used in the 19th century; 2. Steam engines with Stephenson link valvegear, https://en.wikipedia.org/w/index.php?title=Stephenson_valve_gear&oldid=993139941, Creative Commons Attribution-ShareAlike License, This page was last edited on 9 December 2020, at 00:42. For those that would like to study how valve the valves of a Stanley engine function this program is highly recommended. The Baker valve gear had one operating advantage over the Walschaerts in that it could be set up for a larger valve w/longer valve travel, 8-1/2" vs. about 7" for Wal., and was generally more rugged and could operate a heaver valve better. To change direction, the link and rod ends were bodily raised or lowered by means of a counterbalanced bell crank worked by a reach rod that connected it to the reversing lever. Moreover, the straight expansion link simplified manufacture. Apart from the usual couple of hours worth of tweeking to get it to run to my satisfaction, I am sure the valve gear has something missing. In my previous post, I mentioned Harry Allin's locomotives, a Dart and a Virginia, both in 7 1/4" gauge and both with Stephenson's valve gear. The Throw of Eccentric formula, below, applies only to locomotives using Stephenson valve gear. Walschaerts Valve Gear. The valves on a steam engine control the flow of steam in and out of the cylinders. STEPHENSON’S LINK VALVE GEAR – GWR HALL 4-6-0 This kit is designed to accurately produce in 4mm scale a working model of the Stephenson’s link valve gear. Often it is called Stephenson's Valve Gear. Because valve gears in Britain were generally placed between the frames beneath the boiler, the extremely cramped conditions made the valve gear inaccessible for servicing. The Poppet Valve gear doesn't count because it wasn't used nation wide like the Baker, Walschaerts, Stephenson valve gear. Gooch valve gear had the disadvantage of angularity between the valve spindle and the eccentric rod in full gear, whereas the best forms of the Stephenson gear, the thrust was in a straight line. It is normally driven from “eccentrics” mounted on one of the drive axles and located inside the loco’s frames. Some Stephenson valve gears have the valve … There's a good diagram of the Stephenson valve gear on page 24 of MR Cyclopedia Volume 1 - Steam Locomotives. STEPHENSON’S LINK VALVE GEAR – GWR HALL 4-6-0 This kit is designed to accurately produce in 4mm scale a working model of the Stephenson’s link valve gear. These became known respectively as the 'locomotive link' and the 'launch link'. To give you some sense of scale, the coupled wheelbase is 53mm, the driver dia. This was observed to be a disadvantage when similar locomotives fitted with either Gooch or Stephenson gear were compared in service[10] Gooch gear was never popular in Britain except with one or two engineers down to the 1860s, but it was quite common in France. It is named after Robert Stephenson but was actually invented by his employees. Apparently, rotary valve gear had an extremely limited application at the time this edition was published, since it is not even mentioned. This setting information is the same for all Stephenson link valve gear. I'll demonstrate how any valve gear can be animated logically. Note the special form of combination lever placed horizontally. The amount of lead remains constant over the whole range of cut offs that the gear is designed to provide. STEPHENSON'S LINK VALVE GEAR - 28xx 2-8-0 This kit is designed to accurately produce in 4mm scale a working model of the Stephenson's link valve gear. (A Walschaert Gear section starts on page 87.) It is named after Robert Stephenson[2] but was invented by his employees. Tom Stamey wrote the following description for setting Stephenson valve gear on Allen Models locomotives, 20 April 2014. (1965–74) Doble Steam Cars, Buses, Lorries, and Railcars . It is named after Robert Stephenson [ 2 ] but was actually invented by his employees. Its use on engines in which all the cylinders lie in one plane, represents, in the belief of the writer, the best choice." Thanks for the seasonal good wishes and for raising the issue, and for contributions. Larry also points out the fact that Cut-Off is always 75% when Lap equals Port Width, for all values of Port Width. is 33mm and the cylinders are 7/16" dia. Don Ashton's Formula Stephenson's Valve Gear. is 33mm pressure relief valve orifice area and maximum available flow. 2.6 Stephenson Valve Gear 16 2.7 Walschaert Valve Gear 17 2.8 Flywheel 18 2.9 Sliding valve 18 2.10 Piston and piston rod 19 2.11 Crosshead 20 3.1 Project flow chart 23 3.2 Methodology flow chart 24 4.1 Steam engine cycle Valve gears such as Walschaert's are said to be constant lead valve gears. Welcome Guest. At the time of its introduction, it was deemed important in the locomotive world to keep the centre of gravity, and therefore the boiler centre line as low as possible. Lesson 1: Gear Pump Basics Displacement (D) – The displacement of a rotary gear pump is the volume displaced during one complete revolution of the gears. Daniel Gooch , the first locomotive superintendent of the Great Western, devised a link motion in which the link itself was not raised or lowered for reversing, but swung from stationary hangers in what would be mid- position in the Stephenson motion. Quarter Turn Worm Gear Box Series 15/16 Date: August 2014 Page 1 of 1 Formulae and Conversion Quarter Turn Worm Gear Box ... Flow Line Valve and Controls, LLC P.O. This picture shows a working demonstration model of the gear in the Science Museum, South Kensington. That's what results from simply letting my design spreadsheet (downloadble, etc.....) cope without mental exertion on my part. Another valve gear animation in Blender: a Stephenson valve gear based on the Furness Railway K2. The cams consist 4 individual cams. The Stephenson valve gear or Stephenson link or shifting link is a simple design of valve gear that was widely used throughout the world for all kinds of steam engines. Young Valve Gear . It is named after Robert Stephenson [2] but was actually invented by his employees. Although a brief glance into history (except on the Continent) might place Stephenson’s gear as being largely replaced by Walschaerts’ gear around the turn of the 20 th century, both gears were invented almost simultaneously. STEAM ENGINE VALVE GEAR ON THE COMPUTER Windows Version by Charles Dockstader HCR 69 Box 3111 California Valley CA 93453 805 475 2519 UpDated Mar 20, 2009 Windows Ver 2.7.3 Central For reasons of practicality two significant deviations from the Notable UK examples are the Great Western Railway's 1361 and 1366 classes, and the narrow-gauge Ffestiniog Railway's 0-4-0TT class (which were produced by George England and Co.) and the narrow-gauge Talyllyn Railway's original locomotives, Talyllyn and Dolgoch (which were produced by Fletcher, Jennings & Co.). Launch-type links were pretty well universal for American locomotives right from the 1850s but, in Europe, although occurring as early as 1846, they did not become widespread until around 1900. Valve gears such as Walschaert's are said to be constant lead valve gears. Stephenson Valve Gear Computer Simulation Program Charles Dockstader has created an excellent program that simulates the operation of Stephenson Valve Gear action. Stephenson Valve Gear for Climax Loco Post by peterseager » Tue Feb 09, 2010 11:04 am I am looking into building Kozo's Climax scaled X 1.5 for 5" Gauge. It is named after Robert Stephenson but was actually invented by his employees. You will have to move the engine to do that. The eccentics are split and keyed to the crank axle so I need to know the angle of advance to cut the eccentric keyway in the correct position. One consequent disadvantage of the Stephenson gear is that it has a tendency to over-compression at the end of the stroke when very short cut-offs are used, and therefore the minimum cut-off cannot be as low as on a locomotive with Walschaerts gear. Click here to remove banner ads from this forum. First, you want to set the cams. Animated GIF diagrams of steam locomotive rods, drivers, and Walschaert valve gear. Stephenson's valve gear was invented by Wiliams and Howe, introduced in 1842 by Stephenson & Co.,and it was used on many locomotives for many decades. The initial stage of the analysis which determines the details of the 'equivalent eccentric' is the same as for Walschaerts gear. STEAM ENGINE VALVE GEAR ON THE COMPUTER Windows Version by Charles Dockstader HCR 69 Box 3111 California Valley CA 93453 805 475 2519. See also Valves. It was used on the overwhelming majority of marine engines. These valve gear programs were written betweem 1986 and 2000 by Charles J. Dockstader P.O. As a harmonic valve gear, the Stephenson arrangement may be considered as optimum. On trial, it proved to have no advantage, although in normal service it did gain a reputation as a good performer on banks.[5][6][7][8][9]. Valve … Depending on how the gear was laid out, it was possible to considerably reduce compression and back pressure at the end of each piston stroke when working at low speed in full gear; once again as momentum was gained and cutoff shortened, so lead was automatically advanced and compression increased, cushioning the piston at the end of each stroke and heating the remaining trapped steam in order to avoid temperature drop in the fresh charge of incoming admission steam. First, you want to set the cams. This meant that the link was convex (in relation to the eccentrics) instead of concave. The term "Stephenson kinematic chain", was coined by Ludwig Burmester because of the importance of the gear. Stephenson's Valve Gear: 7mm cast white-metal kit 19 th Century swing-link version - non-working, cosmetic only Instructions HEALTH & SAFETY: The castings contain some lead. The Stephenson valve gear or Stephenson link or shifting link is a simple design of valve gear that was widely used throughout the world for all kinds of steam engines. It soon drew the attention of theoreticians. Based on 4-6-2 Pacific, Soo #2714: images, data Here's a larger version , … Poppet valves similar in principle to those used in internal combustion engines. Also reversing could be a strenuous occupation as it entailed lifting the weight of the link plus eccentric rod ends. A loco with decent valve gear is a delight to watch. This one cost £13,278, which was about £600 more than those built at the same time with Walschaerts' valve gear. It was a clumsy mechanism, difficult to operate, and only gave fixed valve events. The advantages sought were reduced height for the gear and lighter action as the reversing lever was only required to lift the weight of the radius rod. As with other computer modelling start with something easy before attempting a complicated gear. White, John H. Jr. (1968): A History of the American locomotive, its development: 1830-1880; Dover republication of 1979. Preparation. One consequent disadvantage of the Stephenson gear is that it has a tendency to over-compression at the end of the stroke when very short cut-offs are used, and therefore the minimum cut-off cannot be as low as on a locomotive with Walschaerts gear. Property Value; dbo:abstract: 4767, had Stephenson valve gear mounted outside the wheels and frames. Stephenson gear. This sizing program is a powerful tool, yet easy to use. Model that took me ~20 hours for doing it and 3 hours for making the movie. Check between the first and second drivers for another hole. Stephenson valve gear is a convenient arrangement for any engine that needs to reverse and was widely applied to railway locomotives, traction engines, steam car engines and to stationary engines that needed to reverse, such as rolling-mill engines. Hello all, Have a question regarding Stephenson valve gear, particular the expansion link. STEPHENSON-MOLYNEUX system for the employment of Walschaerts gear to actuate the valve motion of inside cylinders. Above all an easy method of animating means that you're not restricting yourself to … Don's a member here as "donashton" - he also has a website. The first drawing is for Juliet with Stephenson's valve gear and shows the position of the weighshaft and link hanger pivot as given on the drawings. Take the heads off both cylinders. The reversing and cut-off functions were achieved by simultaneously raising the radius rod and lowering the link or vice versa. This concept can be used on other valve gears. The Allan straight link valve gear (invented by Alexander Allan in 1855) combined the features of the Stephenson and Gooch gears. The Gooch gear gave constant lead at whatever cutoff. "Light Steam Power" Isle of Man, UK; p. 196. In the United Kingdom, locomotives having Stephenson valve gear normally had this mounted in between the locomotive frames. It became the practice to start the engine or climb gradients at long cutoff, usually about 70-80% maximum of the power stroke and to shorten the cutoff as momentum was gained to benefit from the economy of expansive working and the effect of increased lead and higher compression at the end of each stroke. This gives far more accurate valve timing than the often stated method of 'playing' with the eccentric positions once the valve gear is assembled. Another benefit of the Stephenson gear, intrinsic to the system, is variable lead: usually zero in full gear and increasing as cutoff is shortened. I would be most grateful for any assistance fron onyone who can unravel my rambling request. Larry suggests adding up to 0.002 inches to the Throw of Eccentric value for each pin in the valve gear (including the eccentric, too) because, even when new, there will be lost motion, possibly enough to eliminate the lead. Stephenson gear is interesting to watch but animating it is like knitting with jelly! The Stephenson valve gear or Stephenson link or shifting link is the oldest and simplest standard design of steam locomotive valve gear.The design is normally attributed to George Stephenson.. Valve setting with Stephenson link valve timing on our 7 1/4" Forney locomotive. It is based on the eccentric rod valve gear developed for stationary steam engines, but with the added complexity that unlike a stationary steam engine, a steam locomotive needs to reverse. Southern Valve Gear. Angle of Advance of the Eccentric calculator uses Angle of advance of the eccentric=asin((Steam lap+Lead)/The eccentric centre line) to calculate the Angle of advance of the eccentric, Angle of advance of the eccentric is the angle in excess of 90° that a steam-engine valve gear is in advance of the crank. For adhesives, read manufacturer's instructions regarding vapour … STEPHENSON'S LINK VALVE GEAR - 28xx 2-8-0 This kit is designed to accurately produce in 4mm scale a working model of the Stephenson's link valve gear. I own a 5" Hunslet Don Young design, had it for close to 3 yrs and currently have the boiler off and remaking some of the valve gear as it very loose and worn. I just acquired a Catatonk Shay that had been ignored but apparently not significantly miss-used for a few years. Preparation Take the heads off both cylinders. This process was popularly known as "linking up" or “notching up”, the latter because the reversing lever could be held in precise positions by means of a catch on the lever engaging notches in a quadrant; the term stuck even after the introduction of the screw reverser. Please Login or Register. The intermediate valve spindle worked by the eccentric and carrying the left- hand end of the combination lever is clearly seen alongside the rectangular guide bar in the centre of the picture. Take a soft lead pencil and mark the exact edge of the opening on both the front and back of the valve head. The following pic is the Stephenson valve gear that Gordon fitted to the 45mm gauge Philadelphia models that he built about 20 years ago. A further intrinsic advantage of the Stephenson gear not found in most other types was variable lead. The entire wiki with photo and video galleries for each article … Steam Engine Valve Gear On The Computer Downloadable freeware simulations of every kind of valve gear you've ever heard of by Charles Dockstader (CA). Its many features include quick and accurate calculations, user-selected units of measurement, selection of The launch link superseded the locomotive type as it allows more direct linear drive to the piston rod in full gear and permits a longer valve travel within a given space by reducing the size of eccentric required for a given travel. Dispose of filings safely and wash hands after handling. For reasons of practicality two significant deviations from the prototype have been made. For reasons of practicality two significant deviations from the prototype All the parts look good and no sign of significant issues with the running gear. 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Ca 93453 805 475 2519 i never revisited the point, which was about £600 more than those built the... In 40 years i never revisited the point, which was about £600 than. Larry also points out the fact the link or vice versa was actually invented by employees... To relate the valvegear mechanism to the 45mm gauge Philadelphia Models that he built 20... Its analysis in the arrangement of the cylinders are 7/16 '' dia it! Cut-Off is always 75 % when Lap equals Port Width that took ~20!, London that Gordon fitted to the eccentrics ) instead of concave placed between the frames! As it entailed lifting the weight of the drive axles and located inside loco. The engine to do that as with the Gooch gear gave performance to! Arrangement may be considered as optimum a harmonic valve gear is designed to provide valves were developed over whole... Radius rod and lowering the link needed to be constant lead at whatever cutoff valve! 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Museum, South Kensington, was coined by Ludwig Burmester because of Stephenson...

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