setting stephenson's valve gear


IN FORWARD GEAR. Once again, there is only one correct position for them. You will find the pencil marks very handy. I owned at one time a 3/4" 4-4-0 that had inside Walschaert valve gear. 3. Take a soft lead pencil and mark the exact edge of the opening on both the front and back of the valve head. With the crank pin a few degrees past read dead center, the slide valve begins to open the rear steam port, for the admission of fresh steam, and the front port, for the ejection of used steam through the exhaust port. 1. For reasons of practicality two significant deviations from the prototype have been made. Several types of valves were developed over the years, but most fall within three main catagories: 1. ... Lead is governed by the valve gear and its setting. Can you email them to me? Correct about left, drivers left standing on footplate facing forward, cannot help with valve setting, sorry. This is a Martin Evans design from Model Engineer of an 0-4-2 tank engine. This is called "centering the valve" and is absolutely necessary to be able to properly time the engine. 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. at the very start of a stroke, the valve opens to admit steam from the boiler into that space. If not use the adjustment screw on the valve rod to center it. 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. The valve must be equally located between the front and rear openings in the head. 2.) The front valve covers are For reasons of practicality two significant deviations from the prototype have been made. The valves on a steam engine control the flow of steam in and out of the cylinders. Would love to get a copy with photos Thank You 316-644-3606 I have a stained glass company for 35 years, I aslso would like to view pictures please. photos are not showing up on the valve gear page. With the gear in full forward set the eccentric so that the valve is just cracking the port. Another variation derived from the Stephenson gear was the Allan straight link motion. To make a proper trial, Ivatt included the standard Walschaerts valve gear, but for the first time in almost 100 years, one locomotive, No 4767, was fitted with an experimental set of outside Stephenson motion. Also, if the eccentric rods incorporate the small addition in length to satisfy centralising of the leads, Stephenson’s gear can be set for equal leads at any reverser setting instead of achieving this at only one preferred notch. Tom Stamey wrote the following description for setting Stephenson valve gear on Allen Models locomotives, 20 April 2014.. I had the opportunity to due the timeing on a 3/4″ and 1-1/2″ scale locomotives. Tom Stamey wrote the following description for setting Stephenson valve gear on Allen Models locomotives, 20 April 2014.. Do this on both sides of the engine. At rear dead center, both steam ports are closed by the slide valve. At any setting, the valve gear satisfies the following two conditions: 1. 8-31-12 10:55 p.m. CDT Ian wrote on Yahoo Group: 1. Everything to me looked good. Thank you kindly. Stephenson valve gear - most common valve gear in the 19th century, normally inside the locomotive frame. Similarly, the eccentrics for Stevenson link valve gear can be set once and for all before the axle is even fitted in the loco. Take a soft lead pencil and mark the exact edge of the opening on both the front and back of the valve head. The rest of the rotation, through the foward dead center, is performed with the help of steam expansion. Take the heads off both cylinders. Move the loco half a circumference and the other port should just crack. Contents. When the reversing lever (Johnson Bar) is in mid gear position there WILL be movement of the valve spindle however it will be at a minimum. Place the rods on the engineer side of the engine at 3 o'clock taking care to position them properly as close to 3 as possible and lock the drivers down. ... the eccentric rod pivots were set behind the link slot (or below on a vertical engine). Your illustration notes It is essential at the commencement of operations to be certain that the engine is at its correct working height. and 2 forward cams outside. Next, you will do Slide Valve and Cylinder Adjustments. Again the pencil marks come in handy. Don Ashton gives several methods of doing this in his excellent book on the gear. At the instant when the space on one side of the piston starts to expand, i.e. Tom Stamey wrote the following description for setting Stephenson valve gear on Allen Models locomotives, 20 April 2014. As a live steamer. Assuming your adjustment nuts never get loose you won't ever have to do this again. I had the opportunity to due the timeing on a 3/4″ and 1-1/2″ scale locomotives. Allan valve gear, a straight-link valve gear. David Bothwell 1: 17/01/2020 17:05:39: 155 forum posts: Thanks for that Baz, a big help, I,ll get to the bottom of the valve setting somehow/some way! Poppet valves similar in principle to those used in internal combustion engines. This is easily ascertained by measuring from the rail to the footplate on all four corners. So there is no hard rule that a inside valve gear has to be type x. Not the simplest solution, but the gear had the distinctive feature of the drive rod having a large mass at the valve gear end, and thus a taper in the reverse direction. emailed.This would be most appreciated. Setting valve line-and-line again, ... FITTED WITH STEPHENSON’S GEAR. This is a Martin Evans design from Model Engineer of an 0-4-2 tank engine. Understand that moving the reverse cams will slightly affect the forward valve position and vice versa and that you will have to repeat the above steps a couple of more times to get the engine to time as close as possible. With the crankpin at apporximately 150 – 160 degrees of rotation, the slide valve should close the rear steam port. The reversing shaft goes across the frames and activates both sets of valve gear, (and there is no reach rod on the left hand side of course) but the rock shafts and rock arm assemblies are on both sides of the locomotive and independant of each other. These became known respectively as the 'locomotive link' and the 'launch link'. http://ibls.org/mediawiki/index.php?title=Setting_Stephenson_Valves&oldid=12347. What I did not realize was the die block was not up the full height in line with the eccentric rod, hence my problem. Once again, there is only one correct position for them. This experimental set of outside Stephenson valve gear was developed with two fly cranks rather than eccentrics to give a maximum travel of about 6½in, the same as the piston valves in the Walschaerts gear engines. The difference is that stevension valve gear used 4 eccentrics. The amount of lead remains constant over the whole range of cut offs that the gear is designed to provide. 4 cams. Put rods at 3 o'clock, lock down the drivers, reverse lever in full reverse and move reverse cam until the valve covers the back of the opening. Just blank with a red X in the left corner. 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. When it comes to valve gear, I don't pretend to be an expert, but I'm presently setting up Stephenson valve gear on the 7 1/4" Dart (inside cylinders) I'm building. 1. Take a soft lead pencil and mark the exact edge of the opening on both the front and back of the valve head. First, you want to set the cams. Interestingly, neither Stephenson or Howe ever applied for a patent of the idea. 1. The front valve covers are 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. In theory, of course, the valve could be set … 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. The cams consist 4 individual cams. My loco has 2 reverse cams inside Preparation. I really need the pictures for setting up the stephenson gear. Valve gears such as Walschaert's are said to be constant lead valve gears. but I cannot view the essential Images.Iwas wondering if they could be Better to set the eccentrics at full gear so that the valve only just cracks the ports at TDC/BDC and adjust the spindle length or slide position so it is sy… Timing Stevenson Valve Gear can be a real challange, especially when you do it the first time. to avoid excessive lead when notched up, the gear must be set for negative lead in fullgear. When the site was transferred, some of the images didn’t follow. 3.) The drivers set on a 7.5″ width track. (Railway Heritage) Take the heads off both cylinders. This page was last modified on 11 May 2018, at 15:17. This is easily ascertained by measuring from the rail to the footplate on all four corners. Everything to me looked good. Take the heads off both cylinders. 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. First, you want to set the cams. In the past I know that if the links of this type of gear are not positioned right it will not time correctly. I cannot see the pics either. This will need some extrapolation and a dial indicator. The reversing shaft goes across the frames and activates both sets of valve gear, (and there is no reach rod on the left hand side of course) but the rock shafts and rock arm assemblies are on both sides of the locomotive and independant of each other. I really need to set it up to operate smoothly but can only find vague instructions. Same as the other e-mails. The Gooch valve motion set for running ahead. This fine model in the Science Museum, South Kensington, can be operated by the public and clearly shows the application and working principles of the Gooch gear. Download Windows Valve Gear Programs File 10A, 1.57 MB, Version 2.7.3 Download Windows Valve Gear Programs File 10B, 1.26 MB, Version 2.7.3 Download Windows Valve Gear Programs File 10C, 1.25 MB, Version 2.7.3 Download Windows Valve Gear Programs File 10D, 1.28 MB, Version 2.7.3 It GREATLY simplifies things if you have one person watching the valve while another is under the engine moving the cams. The amount of lead remains constant over the whole range of cut offs that the gear is designed to provide. Valve gears such as Stephenson's for example are variable lead valve gears. Go to the fireman's side and put the rods at 9 o'clock, lock drivers down, reverse lever in full forward, move the forward cam to where the valve just covers the front opening, and lock it down. William T. James valve gear 1832, used first by Baltimore and Ohio Railroad, United States. Or, if you have not yet put the boiler on you can time it and see the valve from above. Piston valves which superseded slide valves in the 20th century; 3. How do the reverse cams enter into the illustration ? 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.

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