and 2 forward cams outside. Rotate the wheel/move the loco so the piston is at top dead centre. This is a Martin Evans design from Model Engineer of an 0-4-2 tank engine. 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. ! The front valve covers are I have seen working stevension valve gear on engines. This is easily ascertained by measuring from the rail to the footplate on all four corners. 2. Once again, there is only one correct position for them. Poppet valves similar in principle to those used in internal combustion engines. Preparation. This setting information is the same for all Stephenson link valve gear. 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. Attn: Admin. The advance setting of the eccentrics in Stephenson’s gear is directly responsible for the amount of lead steam – the smallest critical dimension on the whole locomotive. They can tell you when to stop or to go the other way etc. With the crankpin at apporximately 150 – 160 degrees of rotation, the slide valve should close the rear steam port. Valve gears such as Stephenson's for example are variable lead valve gears. With the covers off the valve/steam chest then with the lever/bar centred (mid gear) the valve should just open the ports and it should be symmetrical at top and bottom dead centre respectively. This message will no longer be displayed after IN FORWARD GEAR. Next, you will do Slide Valve and Cylinder Adjustments. This is called "centering the valve" and is absolutely necessary to be able to properly time the engine. So there is no hard rule that a inside valve gear has to be type x. Assuming your adjustment nuts never get loose you won't ever have to do this again. http://ibls.org/mediawiki/index.php?title=Setting_Stephenson_Valves&oldid=12347. For reasons of practicality two significant deviations from the prototype have been made. 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. 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. 2.) It is essential at the commencement of operations to be certain that the engine is at its correct working height. In theory, of course, the valve could be set … Stephenson valve gear - most common valve gear in the 19th century, normally inside the locomotive frame. The valve gear was adjusted electrically, and the vaves could be set in in open posion for coasting with minimum resistance. Put your revers lever in full forward. I really need to set it up to operate smoothly but can only find vague instructions. First, you want to set the cams. Two for each side, one was a froward and one was reverse. Before setting my height of the underside of my boiler, I moved the linkage into what I thought was the upper position. 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… 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. This is a Martin Evans design from Model Engineer of an 0-4-2 tank engine. Don Ashton gives several methods of doing this in his excellent book on the gear. A unique engine 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. 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 the heads off both cylinders. 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. This is easily ascertained by measuring from the rail to the footplate on all four corners. Hello, Don Ashton gives several methods of doing this in his excellent book on the gear. You will have to move the engine to do that. For reasons of practicality two significant deviations from the prototype have been made. Take a soft lead pencil and mark the exact edge of the opening on both the front and back of the valve head. Take some time to make sure you have them squarely on 12. Move the loco half a circumference and the other port should just crack. photos are not showing up on the valve gear page. Thank you! 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. Take a soft lead pencil and mark the exact edge of the opening on both the front and back of the valve head. Six locomotives, including No 4767, were fitted with double chimneys and electric headlights. 4.) 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. 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 gear in full forward set the eccentric so that the valve is just cracking the port. That is what it feels like as I try to rotate the drive shaft, it feels like the timing is way off in forward gear. Everything to me looked good. 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. 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. 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. It is essential at the commencement of operations to be certain that the engine is at its correct working height. 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. Re: Setting Stephenson Valve Gear Post by baggo » Tue Nov 22, 2011 10:52 am If you look at 'Stephenson British Outside Admission' in Charlie's software, that gives a direct drive to the valve. 1. 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. Move the forward eccentric until the valve just barely covers the opening and lock it down. Contains chapters on locomotive valves, the Stephenson valve gear, locomotive management, breakdowns, oil-burning locomotives, the Type D duplex stoker, and locomotive value setting. Allan valve gear, a straight-link valve gear. You will find the pencil marks very handy. at the very start of a stroke, the valve opens to admit steam from the boiler into that space. It is fitted to 0-4-0WT "Dolgoch", preserved on the Talyllyn Railway. Thank you kindly. Or, if you have not yet put the boiler on you can time it and see the valve from above. The bar moves back and forth, with due care since it appears to bind at the valves. 4767 sho... World Heritage Encyclopedia, the aggregation of the largest online encyclopedias available, and the most definitive collection ever assembled. Slide valves largely used in the 19th century; 2. When the site was transferred, some of the images didn’t follow. 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 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. Ian wrote on Yahoo Group: 1. 1.) 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. My loco has 2 reverse cams inside I cannot see the pics either. 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. I really need the pictures for setting up the stephenson gear. Same as the other e-mails. Timing Stevenson Valve Gear can be a real challange, especially when you do it the first time. Timing Stevenson Valve Gear can be a real challange, especially when you do it the first time. Similarly, the eccentrics for Stevenson link valve gear can be set once and for all before the axle is even fitted in the loco. stephensons valve gear etc., eccentric problem. (Railway Heritage) ... especially in this context the page on Stephenson's gear. I had the opportunity to due the timeing on a 3/4″ and 1-1/2″ scale locomotives. ... especially in this context the page on Stephenson's gear. 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. Interestingly, neither Stephenson or Howe ever applied for a patent of the idea. 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. 1. 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. Green cloth w/red cloth backstrip w/gilt spine lettering, marbled end papers, illustrated, three fold-outs. Another variation derived from the Stephenson gear was the Allan straight link motion. 1. The amount of lead remains constant over the whole range of cut offs that the gear is designed to provide. Stephenson valve gear: | | | British LMS Stanier Class 5 4-6-0 Locomotive no. I have a Stephenson setup with no manual and saw your setup but none of the drawings or pictures show on the screen. Tom Stamey wrote the following description for setting Stephenson valve gear on Allen Models locomotives, 20 April 2014.. Now the eccentrics can be set. Setting valve line-and-line again, ... FITTED WITH STEPHENSON’S GEAR. The cams consist 4 individual cams. 1 Historical background; 2 Applications; 3 Derivatives. William T. James valve gear 1832, used first by Baltimore and Ohio Railroad, United States. 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. Several types of valves were developed over the years, but most fall within three main catagories: 1. If your cams are properly spaced 90 degrees apart and you have done everything else right while building it, you should hav enot difficulty in timing it. HTML tags allowed in your comment:
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