The valve gear is there to move the valve over the cylinder ports allowing steam to enter the cylinder at the correct time and then allow it to escape once its job is done. Thomas in the miniature locomotive for septemberoctober 1954 brings up a matter that is hard to explain. Simulation is entirely mathematical and more accurate than achievable in practice. Chuck modeling central japan in september, 1964 with walschaerts valve gear 2cylinder steam. That is, at the neutral position, the valve ports should not open at all. Steam locomotive valve gear trains magazine trains. Walschaerts valve gear for model engineers stephensons valve gear for model engineers ashton, d. Walschaerts valve gear wikipedia republished wiki 2. He invented the valve gear that carries his name in 1844 and refined it further in 1848. Specifically, im at the point where i have scaled the valve gear from the prototype, tweaked it with docstaders program and with a lot of help from the good people on this forum, built the gear, and as a final step built a template to precisely size the center distance of the eccentric rods.
Valve gear simulation software for ms windows, showing twenty different valve gear designs. This interpretation is especially appropriate for walschaerts gear in which the valve motion is. Locomotive valve gears 2 railway wonders of the world. Simulation by computer relieves the tedium of complex mathematics and provides the means of speedy evaluation and adjustment. Animating walschaerts valve gear at the steam4me site. Don ashtons steam locomotive valve gear treatise on full and scale valve gears, including simulation and setting of model valve gears, is quite useful.
The program works these out and displays them, on the not unreasonable assumption that a line runs through the axle centre from the expansion. The valve gear of a steam engine is the mechanism that operates the inlet and exhaust valve s to admit steam into the cylinder and allow exhaust steam to escape, respectively, at the correct points in the cycle. Allan has developed several valve gear simulation software suites that he makes. Bill hall papers and locomotive simulation software. Full text of walschaerts valve gear internet archive. Allan wallace also has a steam locomotive valve gear simulator and notes on full and scale valve gears. The first drawing is for juliet with stephensons valve gear and shows the position of. Walschaerts valve gear for model engineers stephensons valve gear for model engineers.
At the present time it holds the field in great britain, the lms and southern railways fitting it to all new engines. Almost everyone has his own pet reference book on the various valve gears and the methods of how to lay them out. Im having trouble with the radius bar and everything it interacts with. 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. It was a 480, had a very high pressure boiler and used poppet valves. In the simple case, this can be a relatively simple task as in the internal combustion engine in which the valves always open and. The valve gear on a 15 locomotive if accurately represented walschaert gear. A practical treatise on the locomitive valve actuating mechanism originally invented by egide walschaerts, with the history of its development by american and european engine designers, and its evolution into the mechanically correct locomotive valve gear of the present day. The animations seen on this page were created with software written by charles. The stephenson, walschaerts, and young valve gears are also discussed, as well as the southern gearcomplete with instructions for setting each type of gear. Model of walschaert s valve gear, for teaching and demonstration, at the hillside railway workshops, dunedin atlib 311886.
Originally i wanted a quick way to calculate the valve gear action for my arkona steam boat engine. It was extensively used in steam locomotives from the late 19th century until the end of the steam era. 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. Apparently, rotary valve gear had an extremely limited application at the time this edition was published, since it is not even mentioned. The gear is sometimes named without the final s, since it was incorrectly patented under that name. Bill halls programs serve both walschaerts and stephensons gears in. This is a walschaertstype gear in which the combination lever is linked to an arm on the connecting rod, near its small end, instead of to the crosshead. Please note this model and explanation contain a glaring error.
Baker valve gear was similar to walschaerts valve gear except that it. For the nontrain people, this is what all the parts are called. Animations of 5 stephenson, walschaert, baker, southern, and. Valve gear academic dictionaries and encyclopedias. The design used eccentrics on the driving axle of the locomotive to control valve motion. As an instructional video, this is admittedly still a work in progress.
The valve gear is responsible for timing the cylinders inlet and exhaust. The valve gear also controls the distance that the valve travels across the ports and the time that. I am hoping someone can give me some pointers on rigging this valve gear. The first simulator software i came across was the famous one by charlie. For steam locomotive enthusiasts whove always wondered what all the complicated rods and linkages do. Full text of walschaerts valve gear see other formats 7. Allan wallace valve gear simulation software for walschaerts, stephensons and bakers valve gear downloadable from his own website. Dr allan wallace has proofread predicting locomotive performance and has found a few minor typographical errors in some of its equations. This is a simulation of the walschaerts valve gear, one of the most widely used designs towards the end of the steam era. There are other valve gear analysis tools available. On my gauge 1 model, after several valve gear adjustments, i did want to have one more notch on the sector for the cab reverse handle bar whereas for the forward gear, it was ok as is. Allan wallaces own valve gear simulation software can be downloaded. A helper who offered some help last week, long story short he determined that the trunnions on the valve gear frame seemed to not be correct as that frame seemed to be bent a bit.
Early designers had to use long and tedius calculations to work out valve positions but later ones did have. Valve gear simulation spreadsheets one for walschaerts simulation, the other for stephensons by don ashton and downloadable from his website. Steam locomotive walschaerts valve gear 3d cad model. I do not profess to be an authority of any kind on valve gears, but i agree 100% with one of the best locomotive designers.
The primary reason for a more universal adoption of walschaerts gear was its general suitability for mounting outside the frames, convenient for maintenance and permitting more strongly braced frames. This is an original project, containing a complex animation, with interesting added sounds see all, till the end. Valve gear design simulator software charles dockstader has written a program for ms windows which will take the geometry of your valve gear design pretty much every gear type imaginable and show the physical arrangement of the motion, animate the events, draw an indicator card, etc. Walschaerts valve gear for model engineers stephensons. In 1844 egide walschaerts invented a valve gear that by 1848 appeared very much as it does today. Diagrams of walschaerts valve gear and stephenson valve gear, as supplied on working steam model locomotives. Alternating reciprocal motion simulation symmetric. Steam engine valve gear on the computer downloadable freeware simulations of every kind of valve gear youve ever heard of by charles dockstader ca. 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. This steam engine valve gear was invented by a belgian, egide walschaerts, and patented in 1844, with an improved patent in 1848 being much closer to the way his invention became used in practice a german inventor, edmund heusinger, came up with the same idea shortly afterwards as a totally independent invention, and for this reason. In 1986 i wrote the first of the msdos versions of the software to simulate baker valve gear. Then i added a visualization subroutine to the program. At long last the walschaerts gear received its welcome in great britain, and by 19 about 150 locomotives were running with it. The gear is sometimes named without the final s, since it was incorrectly patented under that name, it was extensively used in steam locomotives from the late 19th century until the end of the steam era.
Its only rivals on the lner in new stock are a few poppet valve gears which are camoperated. Today we have access to some extremely useful bits of computer software which can exactly simulate the movements of the valve relative to the position of the piston and enable us to design the ultimate valve gears. One end connects to the combination lever, the other end to the lifting link, and a connection point in the middle moves with the. Egide walschaerts was the chief engineer of the main workshop of the belgian state railways in brusselsmidi. The copy below is taken from page 88, walschaert valve gear, of locomotive boilers and engines, a practical treatise on locomotive boiler and engine design, construction, and operation, by llewellyn v.
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