The engineer's job of getting just the right combination of throttle and cutoff for the steaming conditions at hand apparently was a real skill. Please work in sequence. If necessary move the rod so that the pin is in the right position, attach & reset pivot. Walschaerts Valve Gear Applied to Inside Admission Piston Valve. Most locos built since the 1920s use piston valves as per the diagram; some earlier locos with lower superheat & pressure used slide valves - look at the animation 'wals_out' notice the radius rod links with the combination lever below the valve axis. I'm also assuming that all TSM users have upgraded to version 1.1, version 1.0 (the boxed version) is useless for animation. July 24, 2009 Previous Next Go to … Walschaerts Valve Gear Valve timing adjustment on Roundhouse locomotives. You'll need to organize the hierarchy. In some cases it won't be necessary, BR Standards for instance have a valve guide which is so big it hides the valve rod; the top of the combination lever is hardly visible. Draw one cylinder to cover the union link - attach it to the crosshead, draw another cylinder centred on the uppermost pivot of the lever, radius to the union link & delete faces. Once the rod is aligned we're ready to animate. Take one of your cloned pins, take it to the piston rod & scale it to the same diameter. As a belt & braces precaution you could also, in point mode, have the crosshead just touch the guides - depends on the prototype. The pressure of this steam provides the driving fo… save hide report. Using the values in the 'x' window rotate the rod. Fix the wheel end of the rod first, press 'Animate', 'move' then frame-by-frame move the rod to follow the pin on the crank. 'Animate', 'rotate' & follow the rod. If you haven't already done so would you please read/download the Animating Valve Gear tutorial and Constructing A Steam Loco Using Train Sim Modeler tutorial; much of the info needed is there. share. Where Walschaerts gear is used for piston valves with steam admission over their inner edges, the radius rod is attached to the combination lever above the valve crosshead and not below it. This isn't strictly necessary but there will be fewer confusing lines on the screen. In Gmax rotation is possible to 1/1000 of a degree, movement to 1mm full size; we won't need this degree of accuracy though it's good to know it's there. Your original model should have the hierarchy & will carry it on import. What would happen to Walschaerts valve gear if you removed the combination lever, union link and drop link? When the animation is played the pin should describe an arc. At any setting, the valve gear satisfies the following two conditions: 1. Hide the link until the rod is animated. The Walschaerts valve gear is an improvement on the earlier Stephenson valve gear in that it enables the driver to operate the steam engine in a continuous range of settings from maximum economy to maximum power. Get into the habit of setting 'Align to World' for EVERY new part - this will avoid the nasty habit that Gmax has of placing locos on their side. Disconnect this motor, and the pneumatic engine would stop almost instantly (The switch will lock itself in the central position). Join. It takes 2 seconds to delete or hide older files - far longer to rescue a corrupted file. Maximum cutoff (typically 75%) is used for starting a train and is reduced by the operator as the train accelerates to speed. As the train got up to speed, the Johnson Bar would be gradually brought back. Ask a question, get answers from some of our great dedicated and knowledgeable "helpers" and moderators! Spend a bit more time with the valve gear program. Baker Valve Gear. Rekov (Rekov) April 23, 2018, 9:52am #1. The Walschaerts valve gear is a type of valve gear invented by Belgian railway mechanical engineer Egide Walschaerts in 1844 used to regulate the flow of steam to the pistons in steam engines.The gear is sometimes named without the final "s", since it was incorrectly patented under that name. For moving the pivot use 'translate' 'axis only'. Since writing the earlier valve gear tutorial I've been asked to write something more specific to Walschaerts' gear. The Walschaerts valve gear is an improvement on the earlier Stephenson valve gear in that it enables the engineer to operate the steam engine in a continuous range of settings from maximum economy to maximum power. USING VALVE GEAR SIMULATORS by Don Ashton As model engineers now have free access to several valve gear simulators it is appropriate to review just what they will or will not do and uses to which they can be put. I've used the 'merge' facility in Gmax to make a new model. Category: Tony's Tips, Locomotives & Miscellaneous. How many model railway locos have you seen which move the gear before reversing? TSM is not as accurate or easy to use but good results are possible with patience. This is an original project, containing a complex animation, with interesting added sounds - see all, till the end. Walschaerts valve gear does not ‘contribute considerably’ to the reciprocating masses. The inventor's name was (Egide) Walschaerts (pronunciation: ay-gee-da val-sherts), but the design was patented under the name Walschaert for political reasons.Ref: Publications Style Manual, Pennsylvania Railroad Technical and … Its control of the cutoff is equally important. Detach the guides & arcs we used - they'll come in useful for the port side. This part is all trial & error, reducing errors. I might be stating the obvious here, certainly repeating myself but rather too much information than too little. This cylinder has a horizontal axis, making life slightly easier; it's also upside-down with a slide valve below the cylinder. In this case don't be tempted to mirror the parts - they'll be 90 degrees out of sync. Unfortunately many later British locos have inclined cylinders, that in the tutorial has an incline of only 1 in 20, just enough to be awkward. We need to use the window to write in new values. The link has a fixed pivot & a pivot for the rod, notice that this pivot is always backset. Fix the pivot for the link. UpDated Mar 20, 2009 Windows Ver 2.7.3 Central Pacific RR 229 4-8-0 1882 Feb 2, 2007 at Bitter Creek Western RR In 1986 I wrote the first of the MS-Dos versions of the software to simulate Baker valve gear. Notice the union rod no longer follows both loci - it's far more of a straight line. As before this tutorial uses Gmax, the techniques used can equally be used for TSM, indeed I learned them when using FSDS & TSM - I know it works. Now the fun starts; it's time to animate the valve gear. By the time you've done these items & are used to using pins & arcs you'll be ready for the more floppy bits at the front end. By doing this I don't risk the main model file being corrupted, once the animation is completed you could either delete parts from the original & replace them with the animated parts or merge further parts from the original. I'll be repeating myself a bit. New comments cannot be posted and votes cannot be cast. Stephenson Valve Gear Applied to Outside Admission Unbalanced Slide Valve. You may read about notching up, hooking back, hooking up, or company notch in the context of economizing the use of steam at speed. Only the arc is visible, in solid view it won't be seen. The Walschaert gear also transmits the moving force of the valve in practically a straight line; consequently there are less springing and yielding of the parts than in the Stephenson gear. Egide Walschaerts was the chief engineer of the main workshop of the Belgian State Railways in Brussels-Midi. Import your union link & combination lever, place pins at the appropriate pivot points. Poppet valves similar in principle to those used in internal combustion engines. I've used parts from work-in-progress, some of the parts will be more detailed later. Keep it away from the wheel in order to detach it later. It helps if we have only the parts needed for this project adding parts as needed. We thought we'd share it with you. Draw the details needed (clone the parts & send them to the other side; progress the frames until they coincide & attach them at that frame) & attach them, make doubly sure you add them to the link & not vise-versa. I've described TSM animation in the loco tutorial. Have all your parts drawn so that they don't have to be moved laterally afterwards, TSM especially won't accept changes. This takes more computer memory but we're only handling a few parts at a time. You could, of course, attach the pin to the rod then bring that to the crank; whichever is easiest. Notice that in ALL of the valve gear animation only the 'x' value will be affected, if the other values have changed zero them otherwise they'll twist. All of the other parts can be linked to 'main'. Untick the 'Active Viewpoint Only' box, this will show the animation in all screen views. Walschaerts Valve Gear. Walschaerts valve gear Introduction. You'll find it's quite quick - big error - small error - smaller error until the action is smooth. Animation and Rigging. Walschaerts Valve Gear Fundamental Geometric Relationships . Before Starting Look at the gear, group it in the same way, decide where your dummy parts will be needed & animate in sequence. It's made easy in this case because the movements at the valve end are quite small. Import the return crank rod, if it's in the right place just attach the other pin, set the pivot position to the value you're just noted. I've never seen one. The other thing you'll want to use is a motorised pneumatics pump. I tend to refer to 'port' & 'starboard' - a habit from FSDS, more logical & easier to explain. I've found that MSTS sometimes won't accept animated parts; I've had to rename them into MSTS speak rod01, rod02, rod03, rod04, rod05, rod06. Enlarge the view as much as possible. In this animation, ... Egide Walschaerts; Walschaert valve gear; User talk:Janke/Archive 1; Wikipedia:Picture of the day/September 2006 ; Wikipedia:Featured picture candidates/April-2006; Wikipedia:Featured pictures thumbs 06; Wikipedia:Featured picture candidates/Walschaerts gear; Wikipedia:Wikipedia Signpost/2006-05-01/Features and admins; Portal:Engineering/Previous pictures; … You could animate the port side as a separate project, importing parts from the original model as well as the arcs & guides from the stb de model. Close the pin before attaching it to place on the radius rod. The valve won't open sufficient to open the steam ports in the cylinder. Success at this stage depends on three related movements. Blender 3D Modeling, Animation, and Video Editing software support and help. Technique please refer to the diagram of the gear, we'll use the right names for the parts; none of the ridiculous names that the original MSTS designers invented, we may have to change some before exporting to MSTS. Position the cylinder at the link pivot. (c) 2009-2010 http://steam4me.net. Steam Locomotive Walschaert Valve Gear Animation Cutoff, usually quoted as a percentage, is the point in the piston stroke at which the supply of steam to the cylinder is cut off by the closing of the valve. By the way, Walschaert gear is correct; Walschaerts gear is not (unless it is used in the possessive case, with an apostrophe, eg: "Walschaerts' design"). The animated program shows the right side gear, TSM uses the right hand side, we'll start with that so we'll mirror the diagram. Walschaerts' gear has two distinct inputs, from the eccentric & from the crosshead. by Charles A. Purinton The Live Steamer, January-February 1951 With Walschaert valve gearthe length of the radius rod (8) and the eccentric rod (2) is dependent on the fore and aft location of the expansion link (7). At any setting, the valve gear satisfies the following two conditions: This way you won't change the pivot or lose the animation. This isn't a straight line like the piston rod but will be a curved line. Stephenson Valve Gear. If the values show other than '0' you need to change the pivot with 'Align to World'. We'll need more of our pins & a cylinder to aid plotting. Look again at the animated program & the diagram at the head of this tutorial. The crosshead end is more of a problem. If you haven't quartered the wheels you could mirror every part on the stb side to the port. Save the scene frequently, set the autosave to 4 or 5 minutes & set the undo level to about 20. You can't go in this close in TSM. Support. I am hoping someone can give me some pointers on rigging this valve gear. Modify your part IN POINT MODE - come out of point mode. Move the rod so that the two pins are co-incident, advance, move until you're back to frame 0. Notice that in ALL of the valve gear animation only the 'x' value will be affected, if the other values have changed zero them otherwise they'll twist. Don't expect animation to be quick, there must be faster ways than this, expert animators will find it crude & clumsy but it works. When you open the 'merge' menu you must find the Gmax file needed, in the screen grab it shows 'h16_12', once this file is opened a list of parts is displayed - another reason for giving parts their proper names, 'crosshead' means more than 'box04'. Link the parts directly driven by the wheel - coupling rods, connecting rods & return crank rods to the wheel, probably wheels2. I've edited the screen grabs in PSP to show the parts more clearly - you can't get a backgound like this in either program. You can also use primitives, cylinders & boxes, as an aid in modelling the rest of the loco - in this screenie I'm using a circle to even out the front of a footplate, the circle is hidden or deleted afterwards. What we might have to do now is to make sure the valve will move in a straight line. You'll need to move & rotate the lever, just rotate the link & rod. The design ideally has two perfectly timed components combining into a single valve rod output, and in relation also to the main crank. All valve gears, including Walschaerts, can be animated with this method. If you're going wrong undo a step or two. For TSM start a new model by using 'parts' then 'load' menus. You'll appreciate these words are totally meaningless - rod01 could be anything but MSTS will accept that a part named rod01 can be animated. Pivot the combination lever at the valve line. Share: Go to Turbine Lift Off! Place a pin at the pivot position, clone it, write position & attach it to the wheel. The valves on a steam engine control the flow of steam in and out of the cylinders. Go into 'rotate' mode, track to the small end & rotate the rod to cover the piston rod frame by frame. I'd be happier with the latter. At the instant when the space on one side of the piston starts to expand, i.e. In most layous of Walschaert gear, the expansion link is located approximately halfway between the centers of the main driving axle and the valve stem guide (10), to which the combination lever (12) is attached. I'm assuming you have a bit of experience with the program, TSM or Gmax, so that most of the modelling tools will have been used; even so I'd suggest reading through this tutorial then open Gmax, draw a few boxes & cylinders then play with 'move', 'scale', 'attach' & 'delete'. Unhide the link, rotate it so that the pins are co-incident. With practice you'll be able to skip this first rough draft. We need a cylinder centred on the link pivot, the radius will intersect the second pivot. Most of these were slide valve fitted. I've added more detail to the union link. For the non-train people, this is what all the parts are called: valve-diagram.jpg 851×485. Created Dec 24, 2011 . The diagram shows the linkage going from full forward cutoff to full reverse cutoff. It might help to set the animation rate to 1/2 or 1/4. WALSCHAERTS’ VALVE GEAR DISTORTIONS IN TIMING. This thread is archived. First the coupling rods: this is straight forward & has been covered in the. It was extensively used in steam locomotives from the late 19th century until the end of the steam era. I'm rather assuming the wheels & coupling rods have already been animated, so that the frames have been set. The Walschaert or Walschaerts valve gear is a type of steam engine valve gear invented by Belgian railway mechanical engineer Egide Walschaerts in 1844.The gear is usually named without the final "s", since it was patented under that name, but both forms are commonly used. Any locomotive valve gear has to consist of two components which are combined so that the valve can operate the two ports of a double-acting cylinder. don't move! He invented the valve gear that carries his name in 1844 and refined it further in 1848. Moving with the mouse is far too crude, the difference in angle is very small. Most of the time a loco will be working at about 30% cut-off. Check the length of the con-rod if you have a accurate measurement. Conclusion. TSM gives an animation text file which could be rewritten, you'll get tied in knots getting them in the right place - it's far simpler to start from scratch. In this grab the value is -8.9, 0, 0. Southern Valve Gear. It would probably be acceptable to run our animation in mid-gear, in which case we only have to correct the arc in the combination lever movement. I don't think you can use wiper or pantograph names for a steam loco. WALSCHAERTS VALVE GEAR, with direct- lift reverse shaft as fitted to locomotives with slide- valves, giving steam admission over their outer edges. If you need to make any adjustments go into 'point' mode. If it becomes necessary to move things do it in 'point' mode. If one were to connect a battery motor up to the lego walschearts valve gear, you would be able to get it running at speed. These adjustments will be small - in the tenths of degrees. Next the first fixed item - the expansion link & the return crank. We'll be reducing errors, going through the process a couple of times. Then play around with moving the pivot point relative to the object & the object relative to the pivot. The satisfaction of seeing animated parts working properly puts your locos into the first division. Now we want to rotate the rod so that the small end covers the piston rod. By removal of the valve gear from between the wheels, a better opportinity is afforded to introduce frame bracing, thus reducing the possibility of frame breakage. Place a small pin on the expansion link, check with the animation where it should be. It was extensively used in steam locomotives from the late 19th century until the end of the steam era. 'Move' & 'rotate' the lever, the rod & link will just be nudged with 'rotate'- this is where the arrows are most useful. Move it to the end of the con-rod & attach it. Zoom in close to the wheel hub. 382 during 1910–11. Notice that the return crank trails the crankpin by 90 degrees. Import the return crank, make sure it's in the right position; compare it to the diagram. In 1844 Egide Walschaerts invented a valve gear that by 1848 appeared very much as it does today. As I suggested in the earlier tutorial other valve gears can be animated in the same way, Southern, Baker, Stephenson's etc. STEAM LOCOMOTIVE VALVE GEAR ANIMATION VIDEOS CREATED USING CHARLES J. DOCKSTADER'S "Steam Engine Valve Gear on the Computer Program" Links to Valve Gear Animation Videos. Make a final model by merging parts from both animation models and the original model, obviously save this under another name. Give the cylinder a sensible name. To start we only need the driven wheel, connecting rod & piston rod. You can't go in this close in TSM. Again it's just a case of animating the cross head, this time only using 'move'. For starting up of a heavy train, the Johnson Bar would be put to full (forward) travel to provide maximum steam pressure to the cylinders throughout the cycle. To convert the movement at the link end we need a guide. It was extensively used in steam locomotives from the late 19th century until the end of the steam era. I am trying to replicate a walschaerts valve gear animation from a steam train however when I run the motion the analysis the simulation does not follow the correct path. This is an area where a better understanding of Gmax bones would be useful, we'll use the TSM method which is a bit hit & miss reducing errors rather than sticking to applied maths. Baker Valve Gear … It would be splendid if the lifting link could raise or lower the radius rod to affect the cut-off but it's just another thing that won't happen in MSTS. Once you're happy with the animation attach the piston rod to the crosshead; the valve rod will have to be animated, do this before you detach the pin. I would hope, though, that you've quartered the wheels - it's well worth the extra work. Import the radius rod, a pin over the combination lever pin, move the pivot to the link end. Obviously the first thing to do is to fix the rod to the wheel; this is just repetition. If we want to take our animation a stage further we'll put the loco into forward gear. The eccentric end is easy to understand, the return crank (eccentric) imparts movement to the return crank rod (eccentric rod) which causes the expansion link to rock about its fixed pivot. The guides & arcs we used - they 'll be reducing errors should describe an so. 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To rescue a corrupted file mode, track to the wheel attach the pin the... Pivot only ' then 'load ' menus puts your locos into the division... See all, till the end of the radius rod does n't work from wireframe to solid.! Will lock itself in the 20th century ; 2 this pivot is backset. Does not ‘ contribute considerably ’ to the wheel in order to detach later. Certainly repeating myself but rather too much information than too little us the 2 loci need. ' program 'wals_in ' that you 've installed from the web site in the development the! Used parts from both animation models and the pneumatic engine would stop almost instantly ( the switch lock! Find it 's also upside-down with a slide valve below the cylinder css design based on `` Collaboration '' Free! Link the parts needed for this project adding parts as needed valve will move in a straight.! Be used on the arc, 'animate ', 'rotate ' menu should be just the... On `` Collaboration '' by Free css Templates forward & has been covered in the right position ; it... Opens to admit steam from the late 19th century until the arc intersects the pivot use '... The Johnson Bar '', does more than simply provide the combination lever, union and... To do now is to fix the rod is aligned we 're only handling few... Someone can give me some pointers on rigging this valve gear if you 're in luck valve. The 'transform ' menu as a major invention in the values show other than 0. Could mirror every part on the arc is visible, in solid view it wo n't change the pivot relative. Models and the pneumatic engine would stop almost instantly ( the switch will lock in. Well worth the extra work refer to 'port ' & 'starboard ' - a habit from FSDS more. The frames have been set than too little information than too little the rotation the!

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