December 29, 2020
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A site devoted to steam locomotive valve gears. It was decided that a further development process would be undertaken, and the result was the LMS 7F. This is a valve gear invented by a man named Walschaerts, so if anything could be said to have a proper name, it probably ought to be "Walschaerts valve gear" in this case. of initiating the design in unskilled hands. However, it would seem that the mathematical knowledge required write the script is well beyond my capability. the effects of a worn gear may be assessed. users will discover the finer points and be able to pinpoint the sensitivities of the variables. It does, not unexpectedly, require considerable conversancy to understand what alterations may be sensible and their effects on the whole. The Norfolk and Western M2's, built in 1910 by the Baldwin Locomotive Works, where the last and heaviest 4-8-0s in the US. He therefore produced variable lead in Walschaerts’ gear by reducing the return crank length. And, it was natural that Don’s involvement with simulators would lead him back to his own valve gear publications. The reversing lever, or "Johnson Bar", does more than simply provide the reverse function of the valve gear. individual design. Revised, enlarged printing of Don Ashton's book Walschaerts Valve Gear for Model Engineers & Stephenson's Valve Gear for Model Engineers. Perhaps the long history of pursuing the hobby in spite of the lack of valve gear knowledge (see the MINIATURES page) suffuses a natural wish for improvement in this respect. DESIGN AND INVENTION - 13 THE Stephenson, Allan, and Gooch link motions required four eccentrics on the driving axle, as explained in the chapter “Locomotive Valve Gears”.With inside-cylinder engines this requirement restricted the thickness of the crank webs - a serious matter as the engines increased in size. This verifies dimensional accuracy for the inputs, some of which may have to be gleaned from the CAD construction process – it depends on how the particular simulator wants its inputs. If the expansion link tailpin lies on the gear’s horizontal centreline, like many American designs, the return crank is at 90o to the main crank but the long tail needs a greater return crank pitch circle to produce the required amount of swing unless the trunnion is asymmetrically displaced. Post by DaveD » Wed Oct 10, 2012 8:33 pm I'm in the process of determining the length of my eccentric rods on my P7, having completed … Apart from the crosshead arm, union link, and reciprocating part of the combination lever, all very small components, no part of Walschaerts gear is considered when determining the engine’s balancing. Both diagrams and figures then provide immediate verification of any detailed alterations and confirm expected performance, once the user is to aim for a diagram that looks right! Good attributes depend on choosing the correct arrangement according to driveline, a feature rarely transgressed except by undiscerning modellers. Perhaps the most fascinating aspect of steam engines is the beautiful motion of the exposed rods and linkages. It is commonly externally mounted and driven by an eccentric crank mounted on the end of the locomotive crank-pin. Some appear to have designed from pure principle, accepting as inevitable the errant ways of impure geometry, whilst the more astute and skilled knew all the ways of overcoming the little difficulties. However, it would seem that the mathematical knowledge required write the script is well beyond my capability. Dr. Allan Wallace valve gear simulation software for Walschaerts, Stephensons and Bakers valve gear – downloadable from his own website; Valve gear simulation spreadsheets (one for Walschaerts simulation, the other for Stephensons) by Don Ashton and downloadable from his website. a slight movement. both achievable and obligatory. Design Procedures for Walschaerts' and Stephenson's Valve Gears by D.L. The analysis of existing designs reveals the Ok. The effects on the steam distribution need little imagination. However, I would like a steer on the best source of design information for Walschaerts Valve Gear using Slide Valves. ] [VALVE SETTING] [FAQ] [ANIMATION] [ANALYSES] [TRACTION & MARINE This valve gear introduces the angular elements of the Marshall gear into the Walschaerts in a complex yoke drive with a bell crank. Most of these were slide valve fitted. The culmination was Don Ashton’s production of two booklets dedicated to Walschaerts’ Gear and Stephenson’s Gear, published in 1976. Online Program for Valve Gear Design (Walschaerts, further valve gears coming later): ValveGear Constructor To get a translation function for the main site and (some) subsites, click on the flag right on top of the main site and follow the instructions. Walschaerts Valve Gear Valve timing adjustment on Roundhouse locomotives. 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. Piston valves which superseded slide valves in the 20th century; 3. Several types of valves were developed over the years, but most fall within three main catagories: 1. Yeah, you could drive just one axle but the fat motor may still be an issue unless you had an extended shaft one. Walschaerts’ gear, though fairly straightforward in concept, invokes much more skill in detailed design and the interaction of its elements than does Stephenson’s gear. This is the primary reason why events with today’s long travel valves are often poorer than those from the old short travel slide valves. It may also be found that the test is verified for the forward range but moves in the reverse range. The Forge Simulation Ltd is an up and coming content development company in the train simulation industry combining a ... Operating snifting valves. That means stating the cutoff value in his plug-in explicitly can Don was the technical lead for the 4709 project, and there's an appreciation of his life on the 4709 project web site. 'Cylinder Dimensions' is that filling all of his valve port and valve length (lap size is inherent in this valve length) parameters, the cutoff value is determined automatically by Reuleaux diagram, e.g., Henry Greenly's Walschaerts' Valve Gear book, Fig. Also known as the G3, nicknamed Austin 7, the LMS 7F followed on from the G2 and featured a long travel Walschaerts valve gear and higher boiler pressure, and was intended to allow the 0-8-0s to retire. … In spite of this screed now filling three pages of A4 the whole design and simulation process can be completed in a very short time, with more accuracy The Walschaerts’ drop link, being a fixed link, provides a convenient level from which to drive the combination lever in direct synchronisation with the piston. the user. Slide valves largely used in the 19th century; 2. Don Ashton passed away on Easter Saturday 2020, three days short of his 81st birthday. 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. I had a good look through that thread, which is on simulation of Walschaerts valve gear. The inside gear of the GWR 4-cylinder 4-6-0s avoided this constriction to advantage. Don Ashton is a recognized expert in the design of valve gears for the model steam locomotive. 929) on 8 March 1879. Boxer Engine 6. In 1947, the London, Midland and Scottish Railway built a series of their Stanier Class 5 4-6-0 locomotives, most of which had the Walschaerts' valve gear that was normal for this class, but one of them, no. The gear is sometimes named without the final "s", since it was incorrectly patented under that name. Walschaerts valve gear invented by Belgian railway mechanical engineer Egide Walschaerts in 1844 becoming the most widely used valve gear in Europe and North America. becomes conversant with the program. He would always reflect on how the engineers in the heyday of steam would have loved these computer simulator programmes. The dieblock has to slip in the expansion link to cope with the circular swing of the link – differently according to the type of reverser arrangement. He would always reflect on how the engineers in the heyday of steam would have loved these computer simulator programmes. WALSCHAERTS’ VALVE GEAR DISTORTIONS IN TIMING. Walschaerts valve gear does not ‘contribute considerably’ to the reciprocating masses. The others allow adjustment of the valve on It is not an overstatement to say that this is a most critical and sensitive means of adjusting the equality of steam distribution without destroying or compromising the principle of equal leads. I have seen both Martin Evans and Don Ashtons' books but not had opportunity to go through them to see if Slide Valves are particularly addressed. Many of the items fed in are nominal dimensions from the design work and will require fine adjustment and valve resetting before any more serious detailed adjusting. Animation of the Walschaerts valve gear mechanism used in steam locomotives to control the motion of the drive wheels. So Stephenson's valve gear should be possible. elements. For design purposes this factor also has drawbacks and perhaps the greatest misuse of a simulator is to expect it to have some magical means Locomotive Basics - valve gear The actual gear names are confusing. This is an original project, containing a complex animation, with interesting added sounds - see all, till the end. result in producing coincidence only at one specific cut off. The number of variables is such that a mathematical solution cannot easily address each individual case. available and by regular use of a simulator the user can learn a great deal. A similar upset can occur at any swinging link in the gear, and any drive originating from the crank (eccentric or lever) to feed the valve also carries the timing error of the main crank. the design in detail. The design ideally has two perfectly timed components combining into a single valve rod output, and in relation also to the main crank. Of course there is the basic distribution valve movement to open/close inlet/outlet, but that movement can be dynamically changed during operation, giving different valve timing (even reversed if you need to drive back). It was peculiar to the Southern Railway in Britain, and borrowed from motor-vehicle practice in an attempt to create a compact and efficient design with a minimum of service requirements. Clearly there is an opportunity to ameliorate difficulties or compound them according to the skills of the designer. It demonstrates that valve gear mechanisms are possible using GeoGebra. The simulator allows of small adjustments, with due knowledge, and immediate results. Designers of valve So I started reading about the mechanisms behind the machine and came across the valve timing options given by Stephenson and Walschaerts shifting link types. The simulation of valve gears is not new: many drawing offices had the use of large adjustable frames on which to evaluate new valve gear designs and aid 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 demonstrates that valve gear mechanisms are possible using GeoGebra. For example, in the Walschaerts valve gear, the rear end of the radius rod moves up and down in the slot in the link. I have never designed valvegear before and thought I was getting on well until I started to draw out the linkages etc. Now, since we have divorced the Walschaerts out of the radial family, it is of interest to consider the Joy radial valve gear as applied in some locomotive practice, the closest relative to traction engine design, since the primary gear takeoff power was from a pivotal point in the main connecting rod between the crosshead and the crankpin. STEAM ENGINE VALVE GEAR ON THE COMPUTER Windows Version by Charles Dockstader HCR 69 Box 3111 California Valley CA 93453 805 475 2519. This forum is dedicated to the Live Steam Hobbyist Community. this single alteration advances the expansion link component in full forward gear and lessens towards mid gear, probably courting negative lead in full back gear. Baker valve gear invented by American engineers in 1903 and widely used in North America. Walschaerts valve timing . So Stephenson's valve gear should be possible. for lead with long lap employment was in most cases greater at slow speed slogs to prevent pounding than at higher speeds on shorter cut offs. There is a viewpoint that the precision of the computer simulator is incompatible with a 19th century invention, but analysis soon shows that excellence STEAM ENGINE VALVE GEAR ON THE COMPUTER Windows Version by Charles Dockstader HCR 69 Box 3111 California Valley CA 93453 805 475 2519. The main crank has rotary motion converted by the connecting rod from linear motion of the piston. In his post #22 here bs rr co noted that the two-foot gauge steamer he ran for many years had Walshaerts valve gear. 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. Predictably, manipulation within the simulator largely consists of trial and error until the skills are built up. over poor design. I looked up the term in Wikipedia and found a very interesting article here. 3D modeling with Autodesk Inventor 2014 of every part (.ipt) which compose the main mechanism of a Steam Locomotive - the ones presented in pictures and animation. 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. The bottom pin, acted upon by the crosshead in each half-stroke, produces lap + lead movement of the valve if we so proportion the pin distances of the lever, and the upper pins are reversed for outside admission so that the valve travels the opposite way. Regarded as a principle circle for a larger picture to view the offset trunnion of design information for '. Mathematical knowledge required write the script is well beyond my capability some older American locos used Walschaerts! 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