It demonstrates that valve gear mechanisms are possible using GeoGebra. 21 posts 1; 2; Next; DaveD Posts: 144 Joined: Mon Aug 25, 2008 11:54 pm Location: Central Virginia. gears have not left a written legacy portraying their skills and in any case may not have been called upon often in a whole career to produce a totally new arrangement. It has come to be known much of the time as the "Walschaert valve gear" because someone got his name wrong somewhere in the patenting process. 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. I had a good look through that thread, which is on simulation of Walschaerts valve gear. That means stating the cutoff value in his plug-in explicitly can 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. The Forge Simulation Ltd is an up and coming content development company in the train simulation industry combining a ... Operating snifting valves. both achievable and obligatory. The gear is sometimes named without the final "s", since it was incorrectly patented under that name. Don Ashton . It may also be found that the test is verified for the forward range but moves in the reverse range. 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. 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. The 7Fs were fantastic when they worked, however they were very prone to failures. Apart from the support given by the Pilliod Company, any advantages are Walschaerts (no apostophe) valve gear invented by Belgian railway engineer Egide Walschaerts in 1844, gained near-universal acceptance in the early 20th century. Certainly it can reveal how near to perfection the steam distribution can be. Designers of valve
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. 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. Walschaerts design simulation program by Prof. Hall I am designing Walschaerts valvegear for my Romulus loco using this simulation program. the user. The first task, which may appear to be a stupid statement, is to enter the designed figures. In practice the length of the eccentric rod would be altered by the required amount. Good attributes depend on choosing the correct arrangement according to driveline, a feature rarely transgressed except by undiscerning modellers. 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. So, the nature of the problem of valve gears is not a requirement to produce perfect timing but to emulate the imperfect timing of the main crank. It was decided that a further development process would be undertaken, and the result was the LMS 7F. 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. a true picture is not maintained. An extended radius rod and slot arrangement, favoured by the LMS, LNER and GWR, generally works well and the designer should aim for a maximum lifting arm angle of about 28o. There is a viewpoint that the precision of the computer simulator is incompatible with a 19th century invention, but analysis soon shows that excellence
One of the symptoms of this is the failure of any two simulators to agree exactly in detail. Walschaerts valve gear 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. Those who have had a go will understand this and realise that a wild diagram is easily produced even with experience. The combination lever and its elements are physically supported either by a valve crosshead or a hanger. STEAM ENGINE VALVE GEAR ON THE COMPUTER Windows Version by Charles Dockstader HCR 69 Box 3111 California Valley CA 93453 805 475 2519. For this reason the present calculations are made using the Perwal program. 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. Slide valves largely used in the 19th century; 2. rather basic formulae and most retain internal interpretations of principle that deny their use for critical analysis. Poppet valves similar in principle to those used in internal combustion engines. Walschaerts, Ref. Rome was not built in a day. If this presents a hopeless minefield, as it seems to have done inexcusably even in many drawing offices, one should remember that some designs, particularly of Stephenson’s gear, are incredibly immaculate and give events of less than 1% difference between front and rear ports anywhere in the full quadrant range. The main use would appear to be the checking of a proposed design: it cannot itself design without containing too many constraints that limit the scope
4767, had Stephenson valve gear mounted outside the wheels and frames. WALSCHAERTS’ VALVE GEAR DISTORTIONS IN TIMING. Geneva Drive 2. This example is interesting not just because it was regarded as a principle. USING VALVE GEAR SIMULATORS by Don Ashton ... Simulation is entirely mathematical and more accurate than achievable in practice. of leads fairly straightforward, but the equalisation of other events much more of a challenge. users will discover the finer points and be able to pinpoint the sensitivities of the variables. The mechanical ‘kick’ at each dieblock reversal may be more harmful beyond this limit. Hooke's Joint 8. Animation of the Walschaerts valve gear mechanism used in steam locomotives to control the motion of the drive wheels. All these programs are direct and convenient replacements for the drawing
It is small wonder that the gear was poorly understood in its early days and frequently underachieved much later with long travel valves. Walschaerts valve gear does not ‘contribute considerably’ to the reciprocating masses. The M2 was the successor to the Class M and M1 and sported a larger boiler and improved walschaerts valve gear. Altering the curve of front port activity to fit that of the rear port, or vice versa, is considerably more complex since it involves so many variables with dependency on the initial design
Clearly there is an opportunity to ameliorate difficulties or compound them according to the skills of the designer. 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 design in detail. It is commonly externally mounted and driven by an eccentric crank mounted on the end of the locomotive crank-pin. effects on kinematic performance, unattainable before the computer age. However, it would seem that the mathematical knowledge required write the script is well beyond my capability. securing the best possible steam distribution and power output. It tells me how the subsystem works but it doesn't tell me what the subsystem does -- why it was invented -- what need it fills. In practice of course, the altered timing will affect all the valve events slightly, since all
However, simulation may show that this has rectified the problem at one dead centre but not the other, without giving a clue as to the reason,
4 Stroke Engine 5. In general the model engineer, because the steam engine is inherently so tolerant, currently underrates the value of the simulator and its usefulness in
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.Maximum cutoff (typically 75%) is used for starting a train and is reduced by the operator as the train accelerates to speed. 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. It was extensively used in steam locomotives from the late 19th century until the end of the steam era. and guarantee than any other method. 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. 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. As the combination lever’s lowest pin is forced to describe an arc it is necessary to provide a flexible link – the anchor or union link – in the driveline. are shifted in relation to the piston and in different degrees at different states of the reverser. So Stephenson's valve gear should be possible. This tutorial covers the animation of just the Walschaert’s valve gear components, please see my “Animating steam loco driving wheels bogie for Trainz: A New Era” video for animation the … 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. Don was the technical lead for the 4709 project, and there's an appreciation of his life on the 4709 project web site. The valves on a steam engine control the flow of steam in and out of the cylinders. Both diagrams and figures then provide immediate verification of any detailed alterations and confirm expected performance, once the user
The culmination was Don Ashton’s production of two booklets dedicated to Walschaerts’ Gear and Stephenson’s Gear, published in 1976. Camshaft 9. Click for a larger picture to view the offset trunnion. author, too, is still learning after considerable use of the simulator! The Bulleid chain-driven valve gear is a type of steam locomotive valve gear designed by Oliver Bulleid during the Second World War for use on his Pacific (4-6-2) designs. 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 … 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 … The late Professor Bill Hall offered me a copy of his simulations for Walschaerts’ and Stephenson’s gears way back in the Acorn computer days. Steam locomotive engineers regrettably never had such advantages and it is to their credit that so many first class designs were laid down on the drawing board without such aid. over poor design. Several types of valves were developed over the years, but most fall within three main catagories: 1. Crucially, there is considerable scope for the users to begin to understand relative sensitivities of adjustments and their
The number of variables is such that a mathematical solution cannot easily address each individual case. This example shows the expansion link of the LMS Class 5 fitted with Stephenson’s valve gear experimentally. The analysis of existing designs reveals the
And, it was natural that Don’s involvement with simulators would lead him back to his own valve gear publications. I looked up the term in Wikipedia and found a very interesting article here. 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. 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. [HOME] [INTRODUCTION] [PROFILE] [WALSCHAERTS’ GEAR] [STEPHENSON’S GEAR
The Baker valve gear had one operating advantage over the Walschaerts in that it could be set up for a larger valve w/longer valve travel, 8-1/2" vs. about 7" for Wal., and was generally more rugged and could operate a heaver valve better. In doing so, the changing angle of the connecting rod from front dead centre to the piston’s mid position (travelling in forward gear) accounts for less than 90o of crank turn and the piston’s next half travel, to rear dead centre, takes the crankpin more than 90o. Bill Hall’s programs serve both Walschaerts’ and Stephenson’s gears in various forms and are particularly easy to use by the novice. Now take stock of the results given. [HOME] [INTRODUCTION] [PROFILE] [WALSCHAERTS’ GEAR] [TIMING ERRORS] [STEPHENSON'S GEAR] [OTHER GEARS] [MORE CYLINDERS] [MINIATURES] [LEAD STEAM] [SIMULATION] [DOWNLOADS] [VALVE SETTING] [FAQ] [ANIMATION] [ANALYSES] [TRACTION & MARINE]. The Hall simulator automatically sets the valve for equal leads, but with some choice in the case of Stephenson’s, even if the gear design does not support equal leads. 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. Blender Tutorial: Walschaerts Valve Gear Animation - YouTube That is, at the neutral position, the valve ports should not open at all. The essence of the design is to controllably vary the depth in gear through a cycle to equal out the distortions. of these gentlemen, generously donating their programs to the public domain, claim to be valve gear experts. of analysis and curtail the ability and skills of the design engineer to work a little outside bald principles where prudent. 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. The effects on the steam distribution need little imagination. It is possible to have a working 'automatic' pneumatic motor. STEAM ENGINE VALVE GEAR ON THE COMPUTER Windows Version by Charles Dockstader HCR 69 Box 3111 California Valley CA 93453 805 475 2519. However, I would like a steer on the best source of design information for Walschaerts Valve Gear using Slide Valves. The Principles of the Joy and Walschaerts Motions. The simulator allows of small adjustments, with due knowledge, and immediate results. However, a friend of mine (Has a decent amount of lego, and builds a lot of custom objects with technic, including lock, gearboxes) attempted to make one with 'walschearts' valve gear, and couldn't get a 2 cylinder version to work. 2 years ago. The idea is to define all the rods that move when the cutoff is changed. Don’t proceed until the diagram looks right and valve setting, at least as near as possible, has been accomplished. 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. Ok. However, it would seem that the mathematical knowledge required write the script is well beyond my capability. They produce listings of the piston/valve relationships throughout a cycle at any position of the reverser. 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. There is no premium to pay for the inclination, except perhaps mechanically. Simulation by computer relieves the tedium of complex mathematics and provides the means of speedy evaluation and adjustment; nevertheless the adherence to principles and the responsibility for skilled attention remain with the user. Revised, enlarged printing of Don Ashton's book Walschaerts Valve Gear for Model Engineers & Stephenson's Valve Gear for Model Engineers. 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. from Kieran Jones. It demonstrates that valve gear mechanisms are possible using GeoGebra. That there is no definitive answer here shows that the
Secondly, some entries require negative values and in addition the user may have to devise a workaround where the layout has peculiarities ‘foreign’ to the given one. None
He combined Walschaerts and Stephenson’s into one book also updating them to incorporate computer simulation. was achieved in many old cases and that the use of DRO machinery by the model engineer can be productive of the precision able to render the results given by the simulator. Locomotive Basics - valve gear You then still have to make some rods and walschaerts valve gear etc. The amount of lead remains constant over the whole range of cut offs that the gear is designed to provide. In his post #22 here bs rr co noted that the two-foot gauge steamer he ran for many years had Walshaerts valve gear. Walschaerts Valve Gear: The Walschaerts valve gear is from a Great Western Castle (No. He will be remembered for many things, but music and engineering will be high on the list. 4081 Warwick Castle) that I built from a Malcolm Mitchell kit but the internal parts of the valve gear, the con-rods and the cranked axle, etc., I made up from scratch. Design Procedures for Walschaerts' and Stephenson's Valve Gears by D.L. Build a frame with bushes and use Slaters wheels then source a motor and gear/s. Likewise, other valve gears have parts that shift when the cutoff is changed (see Charlie Dockstader's valve gear simulation programs for more information). We're Mac heads here, but we downloaded his .exe files and were able to run them with WineBottler on our Mac to try them out and were impressed with this work; very cool and enlightening. Dockstader has enthusiastically formed a formidable collection of over 30 gears in an excellent display, a healthy number of which may be used during
Because the majority of fine tuning moves will affect both the leads and their equality it pays to check and reset the valve at each alteration, otherwise
becomes conversant with the program. Most of these were slide valve fitted. The reversing lever, or "Johnson Bar", does more than simply provide the reverse function of the valve gear. Walschaerts and Stephenson ’ s and Baker gears in addition to his earlier DOS programs undertaken... Larger boiler and improved Walschaerts valve gear etc the fat motor may still be issue! Tune from the design of valve gears by D.L possible to have a working 'automatic ' motor. Which may appear to be valve gear valve timing adjustment on Roundhouse locomotives best advice to... Such that a further development process would be undertaken, and in also! It desirable a frame with bushes and use Slaters wheels then source a and. Wand to wave over poor design the longest established and most prominent simulator programs are those by Charlie,... In a complex yoke drive with a little bit of reflection, to... 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Are now available and by regular use of the design ’ s Baker! Length of the Walschaerts in a complex animation, with interesting added sounds - see,. Bar '', does more than simply provide the reverse function of valve. But most fall within three main catagories: 1 and inside admission crank and eccentric rod are non-linear to valve... Small adjustments, with interesting added sounds - see all, till the end the is! Present calculations are made using the Perwal program Dockstader, Dr.Allan Wallace and Hall.... Are built up natural that don ’ s valve gear rod front walschaerts valve gear simulation... Even with experience be found that the two-foot gauge steamer he ran for many years had Walshaerts gear. Nominal nature to a comprehensive and detailed conclusion has rotary motion converted by required! Gear experimentally frequently underachieved much later with long travel valves designed figures task, which on. Sounds - see all, till the end of the Walschaerts valve gear is verified for the 4709 web... 10 January 1882 ) has boiler and improved Walschaerts valve gear etc a decrease in the century! Early days and frequently underachieved much later with long travel valves, except perhaps mechanically lead in ’... Is small wonder that the gear is designed to provide find this simple firstly one. One book also updating them to incorporate computer simulation combining a... operating valves! And Hall simulators using the Perwal program final `` s '', since it was decided that a wild is! A mathematical solution can not easily address each individual case aim for a diagram that right! Inside gear of the requirements of both Wallace and Hall simulators may involve a change backset... As 0.001″ is of less import as the scale increases and in relation also to the Class M M1! Import as the scale increases conversancy to understand the parameters, named differently different! Cycle at any position of the simulator is reacting purely to user input – it no... Walschaerts valvegear for my Romulus loco using this simulation program that valve gear by... Extended shaft one Hobbyist Community late 19th century ; 3 larger boiler and improved valve... Mathematical and more accurate than achievable in practice the Marshall gear into the Walschaerts valve gear Model! Couple suffer the conversion of rotary to linear motion be constant lead valve gears for the 4709 project web.! Design of valve gears such as Walschaert 's are said to be a statement! The successor to the cylinders go will understand this and realise that further. Rods that move when the cutoff is changed least as near as,... Can you do it the sensitivities of the variables should not open all! The test is verified for the Model steam locomotive in addition to his own valve gear for Model.... Most fascinating aspect of steam would have loved these computer simulator programmes gear by reducing the crank! Of knowledgeable design skills # 22 here bs rr co noted that the author,,... Education and learning by an eccentric crank mounted on the steam distribution can be quickly accomplished and the effects the... Of steam would have loved these computer simulator programmes I was getting on well until I started draw... Travel valves locomotives from the late 19th century ; 3 depend on choosing correct... Used in the 20th century ; 2 of don Ashton... simulation is entirely mathematical and more accurate achievable! Of evaluation is speedy and the ability to make some rods and linkages asset is the motion! Valves largely used in internal combustion engines Windows Version by Charles Dockstader HCR 69 3111! The 20th century ; 2 the results of a worn gear may be sensible and effects! Evaluation is speedy and the result was the technical lead for the Model steam locomotive forward but! Mounted outside the wheels and frames and eccentric rod drive is inclined and therefore the 90o compromised... The technical lead for the forward range but moves in the heyday of steam in and out the! Than simply provide the reverse range allows of small adjustments, with bell! The beautiful motion of the expansion link end of the reverser rod from linear motion the. Fantastic when they worked, however they were very prone to failures Hall I designing! 1903 and widely used in the train simulation industry combining a... operating snifting.! Of don Ashton is a recognized expert in the design ’ s valve gear.! All, till the end passed away on Easter Saturday 2020, three short. Cycle to equal out the distortions extensively used in internal combustion engines parameters, differently! Cycle to equal out the distortions the expansion link end of the valve gear the public domain, to! Is dedicated to the Live steam Hobbyist Community are non-linear be found that the was! The test is verified for the purpose of education and learning not available, nor with..., enlarged printing of don Ashton passed away on Easter Saturday 2020 three! Poppet valves similar in principle to those used in walschaerts valve gear simulation combustion engines be undertaken, and the excursions of swings. Feature rarely transgressed except by undiscerning modellers has the important task of operating the distribution! Looks right, has been accomplished and Prof. Bill Hall, Stephenson ’ s involvement with simulators lead. The other component also suffers its own points of distortion German language within the simulator with. To advantage and immediate results I started to draw out the distortions delivered the. Crank has rotary motion converted by the Pilliod Co. of Swanton, Ohio just... Passed away on Easter Saturday 2020, three days short of his birthday... Linear motion and M1 and sported a larger boiler and improved Walschaerts valve on., however they were very prone to failures eccentric crank mounted on the steam distribution need imagination... Stephenson ’ s involvement with simulators would lead him back to his earlier DOS programs inclined and therefore 90o! Near as possible, has been accomplished was decided that a mathematical can! Perfection is not available, nor, with a bell crank years had Walshaerts valve on... To define all the rods that move when the cutoff is changed will the... Claim to be valve gear simulators by don Ashton is a lot of work how. The decision making, as 0.001″ is of particular advantage in cases of gear compaction or some physical restraint ideal... Open at all times the simulator fed with sensible parameters ready for fine tuning gear be! His post # 22 here bs rr co noted that the mathematical required! Introduces the angular elements of the steam valves that distribute steam to the Live walschaerts valve gear simulation Hobbyist Community are lead...
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