The most practical position for drawing is at dead centre. 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. There is also a good conference paper on it too: Klijn, G., and Koetsier, T., 2011. The use of Stephenson’s gear quickly became widespread, particularly suiting a direct drive to inside cylinders and slide valves common in the 19 th century. The ‘Data’ sheet then has much of the simulator input material ready to transfer. Again, attention to symmetry and knowledge of the correct suspension was responsible for first class distribution. Stephenson valve gear - most common valve gear in the 19th century, normally inside the locomotive frame. Valve gears such as Stephenson's for example are variable lead valve gears. I'd just like to extend my thanks to Don also who has 'gone that extra mile' to help me out with my valve gear too. I don't know how he finds the time given all the other things he does. 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.. Several types of valves were developed over the years, but most fall within three main catagories: 1. m = lap + lead, r = half valve travel and x is the other component at 90 degrees to the lap/lead function. This gives far more accurate valve timing than the often stated method of 'playing' with the eccentric positions once the valve gear is assembled. The link motion became known as Stephenson’s gear and was first applied in late1842 to an engine already on the stocks at the Stephenson Works. The valves on a steam engine control the flow of steam in and out of the cylinders. 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 various kinds of steam engines. The throw and settings are completely different from a launch link case and my design spreadsheet will accommodate this automatically to conform to the equivalent eccentric. Such misguided practice stems from ignorance and forms no part of engineering excellence. Post by Scrat » Sun Apr 13, 2014 11:42 am Hi, my LBSC Minx needs to have the valve gear set. Some faults were found and improvements made which Don put in the Drawing Errors thread. Resort to the simulator may then suggest minor diversion to suit the running range. There is also a good conference paper on it too: Klijn, G., and Koetsier, T., 2011. You can see what I mean at Wikipedia - Stephenson's Valve Gear. By contrast the same company at the same time continued inexplicably to continue the use of early end suspension Stephenson’s gear whose geometry clearly cannot support equality of distribution. Its common appearance in the marine environment, where many miles may pass at a single expansion setting, is perhaps more excusable. Improper suspension will counter any good initial design. Firstly, the square symmetry of the reversing arrangement cannot accommodate angularity errors at all, least of all those induced by the wrong choice of expansion link. On a GWR loco (Martin Evan's Metro) with inside cylinders and Stephenson valve gear are the two sides of the gear identical or mirror image? The Stephenson valve gear or Stephenson link or shifting link [1] is a simple design of valve gear that was widely used throughout the world for various … 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. This picture shows a working demonstration model of the gear in the Science Museum, South Kensington. To use the simulator to analyse an existing design run a CAD drawing simultaneously. 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 is named after Robert Stephenson but was actually invented by his employees. It is normally driven from “eccentrics” mounted on one of the drive axles and located inside the loco’s frames. President of City of Newport M.E.S. Walschaerts valve gear was invented around the same time as Stephenson valve gear but did not become popular until the very late 1800's. The GSWR were fortunate in their design team: the Manson Class 4-4-0s used launch-type links to drive outside admission valves on top of the cylinder bores indirectly through a rocker of 180o. DON ASHTON’S STEAM LOCOMOTIVE VALVE GEARS. Traction engines are the greatest abusers of the principles of good suspension and the use of the correct link for the  driveline. During the 1830s the most popular valve … This is automatically incorporated into the spreadsheet, as is also the pin centre distance to prevent too much angular swing of the expansion link. This gives far more accurate valve timing than the often stated method of 'playing' with the eccentric positions once the valve gear is assembled. The gear can be properly designed to deliver incomparable steam distribution, highly dependent upon critical suspension. English examples for "Stephenson valve gear" - The Stephenson valve gear remained the most commonly used valve gear on 19th-century locomotives. To give you some sense of scale, the coupled wheelbase is 53mm, the driver dia. Historical background . Stephenson gear was invented first, and it is perhaps the first full-function valve gear offering not only forward and reverse but also a range of steam cutoffs during the piston stroke. It is named after Robert Stephenson but was actually invented by his employees. Hi, I have just received an HO Bachmann Spectrum 2-8-0 with Stephenson valve gear. Note that launch links should never be end suspended on locomotives and as rarely as possible in marine practice. Because Stephenson’s gear can achieve near perfection in enabling a one-piece valve to supply both ends of a double-acting cylinder equally its design in any one particular case ought to follow a complete and correct procedure, in the knowledge that straying from its basic simplicity will impair its excellence. The use of Stephenson’s gear quickly became widespread, particularly suiting a direct drive to inside cylinders and slide valves common in the 19th century. STEAM ENGINE VALVE GEAR ON THE COMPUTER Windows Version by Charles Dockstader HCR 69 Box 3111 California Valley CA 93453 805 475 2519. Valve movement is … 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. Also Valves & Pistons (lap & lead), and Cylinder design (PV indicator) (UK) Railroad Paint Shop Line drawings (GIFs) of locomotives [steam loco drawings] SteamCad.Railfan.net Collection of AutoCad Line Drawings of U.S. Locomotives. In spite of the standardisation of parts the GWR achievements with Stephenson’s gear in their Churchward locomotives cannot be surpassed and shows how the almost perfect event equality can be produced even with longer valve travels. This example shows the expansion link of the LMS Class 5 fitted with Stephenson’s valve gear experimentally. 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. Applications. It was used on … Any apparent problem is likely to be of the following: A proportion problem: a mistaken input: a suspension item misplaced. For the steam techies: Modern valve gears like Baker, Walshaert, etc. 70036 'Boadicea' now completed and ready for a steam test. The expansion links were somewhat hybrid, with pins offset in launch link fashion but too widely spaced to allow die alignment in full gear. Setting Stephenson Valve Gear. A long (near 100%) cutoff gives maximum tractive effort for starting or climbing a ruling grade, but it is not energy efficient. Stephenson’s valve gear was extensively used worldwide throughout the 19th century and through the first half of the 20th Century on Great Western Railway 2-cylinder locomotives. STEPHENSON VALVE GEAR, the joint invention of Williams and Howe in 1842, was first applied to locomotives by Robert Stephenson & Co, and is still in use throughout the world. The suspension of the link is immaculate: centred and correctly offset and employing hangers on the valve connection. Note the special form of combination lever placed horizontally. By Stephenson's Link, I mean the mechanism used to control valve timing of a steam engine. First, you want to set the cams. Tom Stamey wrote the following description for setting Stephenson valve gear on Allen Models locomotives, 20 April 2014.. (270K GIF) An even larger version with animated cycling of the cutoff and reverse linkage action. In the interests of standardisation the GWR used essentially the same valve gear to accommodate valve travels between 6″ and 7.5″ by simple magnification at the rocker drive - an excellent practice as long as it is realised that the lead is also magnified unless addressed at the eccentric setting whence it is derived. Slide valves largely used in the 19th century; 2. Where convenient, placing the weighshaft ahead of the link can be advantageous, as revealed by the excellent equality to be found on the old LNWR Coal tank 0-6-0s. The necessary two harmonic components are conveniently embodied in the eccentrics, whose advance accommodates the lap and lead as well as supplying the necessary travel. The example illustrated is a 4-shaft engine gear with a launch-type link directly driving to an outside admission valve, except that in order to propel the engine forwards the gear must run in reverse. The Stephenson valve gear or Stephenson link or shifting link [1] is a simple design of valve gear that was widely used throughout the world for all kinds of steam engine.It is named after Robert Stephenson [2] but was actually invented by his employees. Similarly, the eccentrics for Stevenson link valve gear can be set once and for all before the axle is even fitted in the loco. This setting information is the same for all Stephenson link valve gear. 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 is named after Robert Stephenson but was actually invented by his employees. UpDated Mar 20, 2009 Windows Ver 2.7.3 In retrospect it seems odd that traction engine designers sought to follow railway practices by using similar gears when their space limitations may well have suited the development of an entirely different valve gear, yet they so frequently transgressed simple principles that governed the railway designers. Historical background . STEPHENSON-MOLYNEUX system for the employment of Walschaerts gear to actuate the valve motion of inside cylinders. English examples for "Stephenson valve gear" - The Stephenson valve gear remained the most commonly used valve gear on 19th-century locomotives. Stephenson valve gear Last updated December 09, 2020 British LMS Stanier Class 5 4-6-0 Locomotive no. For the steam techies: Modern valve gears like Baker, Walshaert, etc. This encouraged the largest eccentrics in the limited space available without the links nearing either boiler or ground in full gear. For a launch link, where the eccentric rod pin can align with the dieblock for full gear, the actual eccentric and its equivalent eccentric are the same, represented by the triangle m,x,r herewith. Often it is called Stephenson's Valve Gear. We are stuck at the moment getting the "timing" right.Can anyone supply info on which issue of M E had the write-up ? The amount of adjustment necessary to produce the finest of results should be very little, once the valve has been set. William T. James valve gear 1832, used first by Baltimore and Ohio Railroad, United States. Stephenson valve gear: where to start? I had the opportunity to due the timeing on a 3/4″ and 1-1/2″ scale locomotives. The employment of locomotive links involves larger eccentrics because the die never approaches the line of the eccentric rod pins, usually by a factor of almost 2. This forum is dedicated to the Live ... or a virtual one, there is no difference.. Valves should be set on their spindles by provided adjustment, otherwise the integrity of the gear itself is violated. Which is the best way to re-adjust the valve gear? The equivalent eccentric is the same for each case. It is difficult to understand why so many poor examples were perpetrated. The gear is therefore essentially a contemporary of Walschaerts’ rather than the forerunner it appears, since American and British acceptance of Walschaerts’ gear did not occur until some 30 years or more after its invention. Click for a larger view of this old drawing to see that end suspension can never be conducive to good event equality in both forward and back gears. This picture shows a working demonstration model of the gear in the Science Museum, South Kensington. Don Ashton gives several methods of doing this in his excellent book on the gear. Although only in post for two years Angus replaced all the wedge motions with Stephenson valve gear. The general lack of understanding this latter gave rise to widespread use of end suspension of the gear, something which should never have been perpetrated, as the results are so poor. 4767 showing experimental Stephenson valve gear unusually mounted outside the frames A simple Stephenson gear in partial cutoff. is 33mm and the cylinders are 7/16" dia. With the normal type of Stepehenson valve gear used on steam locomotives ( Open Rod type *) the lead increases as the valve cut off point is reduced. There is no particular reason to mirror eccentric layouts in plan about the frame centreline, but there are designs where back gear eccentric and rod don't exactly mirror in elevation about the gear centreline. are fixed in their construction. Almost coincident with the gear’s inception was the practice of offsetting the central suspension in order to correct angularities of both main crank and eccentrics, though this process appears to have been ill-understood and ignored by many designers. Although only in post for two years Angus replaced all the wedge motions with Stephenson valve gear. Or to put it another way, looking down on the eccentrics and from right to left should they go. Preparation. 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. Setting Stephenson Valve Gear. S tevenson Valve Gear. Eccentric rod lengths can be adjusted fractionally to equal out the half travels of the die. [HOME] [INTRODUCTION] [PROFILE] [WALSCHAERTS’ GEAR] [STEPHENSON’S GEAR] [TIMING DETAILS] [OTHER GEARS] [MORE CYLINDERS] [MINIATURES] [LEAD STEAM] [SIMULATION] [DOWNLOADS] [VALVE SETTING] [FAQ] [ANIMATION] [ANALYSES] [TRACTION & MARINE]. In the absence of other means of countering the effects of angularity it has to be accepted that perfection is unavailable and that back gear may suffer somewhat in order to satisfy forward running. With the normal type of Stepehenson valve gear used on steam locomotives ( Open Rod type *) the lead increases as the valve cut off point is reduced. Tom Stamey wrote the following description for setting Stephenson valve gear on Allen Models locomotives, 20 April 2014.. if i were doing my BOXHILL cylinders again i would set the bores 1/8" further apart and make the outer crank webs 1/4" thick and take a 1/16" off the axlebox width. 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