walschaerts valve gear animation

Posted by on Dec 29, 2020 in Uncategorized

Zoom in close to the wheel hub. All of the other parts can be linked to 'main'. I’ve got a start on it, but now I’m stuck. You'll need to organize the hierarchy. The rod will be close to, but not over the piston rod. If you're going wrong undo a step or two. 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. It might help to set the animation rate to 1/2 or 1/4. To start we only need the driven wheel, connecting rod & piston rod. The crosshead: animating this is straight forward if your cylinder axis is horizontal. Online. Stephenson Valve Gear Applied to Outside Admission Unbalanced Slide Valve. All valve gears are derived and follow a logical sequence. It was extensively used in steam locomotives from the late 19th century until the end of the steam era. 382 during 1910–11. Walschaerts valve gear Introduction. At any setting, the valve gear satisfies the following two conditions: 1. You can't go in this close in TSM. Especially in TSM make sure your loco runs as it should, is at the right height etc BEFORE animating. Archived. Since writing the earlier valve gear tutorial I've been asked to write something more specific to Walschaerts' gear. 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. If we want to take our animation a stage further we'll put the loco into forward gear. The valves on a steam engine control the flow of steam in and out of the cylinders. Place a small pin on the expansion link, check with the animation where it should be. The movement of the radius rod will be visible & will influence the action of the combination lever. From the simulation it is clear that the rocker is needing to be constrained in some way however I do not know how to do this, I have tried various different mates and even adding in other parts too. Maximum cutoff (typically 75%) is used for starting a train and is reduced by the operator as the train accelerates to speed. 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. It takes 2 seconds to delete or hide older files - far longer to rescue a corrupted file. Notice that the return crank trails the crankpin by 90 degrees. As the crosshead drives the union link we must make sure the animation here is spot-on otherwise we'll have to correct it & the link later. 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. It helps if we have only the parts needed for this project adding parts as needed. The pressure of this steam provides the driving fo… 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. TSM doesn't have the sophisticated animation tools of Gmax; I want to make this tutorial useful for TSM users - in other words I still don't know Gmax that well; I haven't had any success with bones. TSM is not quite as exact, you'll need to be working in the 'transform', 'rotate' menu. Have all your parts drawn so that they don't have to be moved laterally afterwards, TSM especially won't accept changes. 'Animate', 'rotate' & follow the rod. TSM seems to link animation to the datum point - if you move a part after animating it will leap back to its original position; there is no quick fix. The reversing lever, or "Johnson Bar", does more than simply provide the reverse function of the valve gear. The example here has the cylinders inclined slightly, movement will be a combination of along & up, we want the pin to coincide with the pin on the con-rod. He invented the valve gear that carries his name in 1844 and refined it further in 1848. 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. 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. Press the 'Animation' button. How many model railway locos have you seen which move the gear before reversing? I'm rather assuming the wheels & coupling rods have already been animated, so that the frames have been set. Now the fun starts; it's time to animate the valve gear. Success at this stage depends on three related movements. These adjustments will be small - in the tenths of degrees. The result is as good as your patience. It is assumed that those readers are already conversant with what the gears are expected to achieve. Only the arc is visible, in solid view it won't be seen. Don't expect animation to be quick, there must be faster ways than this, expert animators will find it crude & clumsy but it works. In 1844 Egide Walschaerts invented a valve gear that by 1848 appeared very much as it does today. For moving the pivot use 'translate' 'axis only'. Technique Attach the crank to the driven wheel. 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 used the 'merge' facility in Gmax to make a new model. This isn't strictly necessary but there will be fewer confusing lines on the screen. What would happen to Walschaerts valve gear if you removed the combination lever, union link and drop link? Its control of the cutoff is equally important. It was fitted to the Garstang and Knot-End Railway's 2-6-0T Blackpool (built 1909) and to Midland Railway No. It was extensively used in steam locomotives from the late 19th century until the end of the steam era. Most of these were slide valve fitted. 9. If I remember TSM will only draw 32 sides; you could, however, rotate points in the area you want to see in order to make the circle less lumpy. I've always assumed that MSTS gives a rotary motion to wheels1 - wheels5 & other animation to rod01 - 06. STEAM ENGINE VALVE GEAR ON THE COMPUTER Windows Version by Charles Dockstader HCR 69 Box 3111 California Valley CA 93453 805 475 2519. 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. share. In this case don't be tempted to mirror the parts - they'll be 90 degrees out of sync. Get used to F3 & F4 to switch from wireframe to solid views. Position the cylinder at the link pivot. I've described TSM animation in the loco tutorial. 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. To convert the movement at the link end we need a guide. This describes the procedure for adjusting the slide valves on the simplified Walschaerts valve gear as fitted to certain Roundhouse locomotives, so that they open and close at the correct time. GB190727899, published 13 August 1908. 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. We'll be reducing errors, going through the process a couple of times. Constructing A Steam Loco Using Train Sim Modeler. For TSM start a new model by using 'parts' then 'load' menus. (c) 2009-2010 http://steam4me.net. If you haven't quartered the wheels you could mirror every part on the stb side to the port. Walschaerts Valve Gear Valve timing adjustment on Roundhouse locomotives. I'm trying to rig a Walschaerts valve gear, which looks like this: I've got some of it working, but I can't figure out how to get the combination lever (the mostly vertical bar between the wheels and pistons) to be influenced from both sides while attached to the valve stem (the upper piston) which it rotates about. From a page on SteamLocomotive.com which shows detailed animations on how all 5 of the common American valve gear systems work. Walschaerts' gear has two distinct inputs, from the eccentric & from the crosshead. 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. I am hoping someone can give me some pointers on rigging this valve gear. Egide Walschaerts was the chief engineer of the main workshop of the Belgian State Railways in Brussels-Midi. 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 20th century, both gears were invented almost simultaneously. 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. Rekov (Rekov) April 23, 2018, 9:52am #1. Keep it away from the wheel in order to detach it later. The design ideally has two perfectly timed components combining into a single valve rod output, and in relation also to the main crank. Walschaerts valve gear does not ‘contribute considerably’ to the reciprocating masses. This way you won't change the pivot or lose the animation. You could ignore them until the animation is done. 'Move' & 'rotate' the lever, the rod & link will just be nudged with 'rotate'- this is where the arrows are most useful. Moving with the mouse is far too crude, the difference in angle is very small. Untick the 'Active Viewpoint Only' box, this will show the animation in all screen views. 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; … Share: Go to Turbine Lift Off! This is an original project, containing a complex animation, with interesting added sounds - see all, till the end. 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. 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. Import the radius rod, a pin over the combination lever pin, move the pivot to the link end.

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