Greater pitch circles and expansion link swings are demanded by the use of inside admission and designers of more modern locomotives require skill and ingenuity to avoid poor steam distribution. There are, of course, many other design features that might influence a comparison. In retrospect this proves a doubtful way to deal with long valve travels and the events are generally inferior to those produced 20 years earlier. Basic formulae for Walschaerts’ initial design. The difference between the two positions of the, A given lead determines the lap or a given lap determines the lead, and it must be divided for both ends as desired by lengthening or shortening the, Within certain limits, this adjustment may be made by shortening or lengthening the. I also favour a substantial cross brace across the frames to unite the motion plates and to provide for the expansion link brackets. From the cylinder and port requirements feed the cells marked ‘enter’ in the spreadsheet and adjust lap, lead and port opening to obtain a suitable full gear cut off. That the student should resist this temptation will soon become apparent; the alteration of a single part necessarily alters the whole. In the average inside admission arrangement there is therefore scope for reducing the pitch circle using a shorter leading return crank, such that an adequate foregear starting cut off is maintained. Walschaerts’ gear readily satisfies this condition since only the raising of the radius rod is involved. It … Poppet valves similar in principle to those used in internal combustion engines. It is tempting to accord this excellence to the small pitch circle and short valve travel but due praise of the design details should be recorded. The theoretical full valve travel of 6.716″ compares very favourably with the 6.562″ recorded in the official table of events. The backset has to be reduced by half in order to equate port openings, yet the cut offs remain similar at 78.14% and 72.54%. In designing the initial parameters it is perhaps wise to realise that at the time of its invention valve travels were short, with slide valves necessary for outside admission. Résumé historique. Whilst the B1 barely manages a constant 1/8th″ the Hall is 1/8th″ negative in full gear and does not reach 1/8th″ positive until the middle of its cut off working range. Hi all, I'm wondering, has anyone attempted to build a lego Walschaerts Valve Gear, and what were the results? Walschaerts Valve Gear. Those examples of hanger suspension, whether in front of or behind the trunnion, introduce other complexities and require very careful placement to obtain good working in both forward and reverse. 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. The illustration shows in detail an arrangement where equal swings are deliberate, and the resulting distances at the radius rod front pin reveal the linear discrepancies. to I ft.scale. from Kieran Jones. Numerous and misguided have been the modellers’ attempts to rectify the situation, since the proponents little understood the problems of compaction. the weighshaft and lifting arm and combination lever support where used, as being essential to correct functioning of the gear. The events, however, prove by simulation to be magnificent, addressed to the heavy gradients expected without much compromise in reverse. Although some engineers did not favour using the upper expansion link half for forward running because the drive is then indirect, the position is in fact little different from the many cases of rocker use in valve gears, though the results are not at 180 degrees. The picture shows a suspension that cannot support equality of valve excursions and there are many other examples. LBSC did not appreciate the problems. The combination lever and radius rod require support either by a valve crosshead guide or by a hanger. It is interesting to superimpose the model design over the Swindon drawing at the same scale (but without equating the valve and ports). Symmetrical layouts for short travel outside admission valves reduce the problems dramatically irrespective of scale. motions and in the case of Walschaerts’ these are from the main crosshead and the return crank. My goal was to try and build working valve gear with out modifying any parts, and to keep it as small and proportionate to the rest of the locomotive as possible. Longer valve travels inevitably make this area more difficult to appease. In 1844 Egide Walschaerts invented a valve gear that by 1848 appeared very much as it does today. Frequently one has to set the valve carefully in order to maximise events, but this case required no setting whatsoever to realise an excellent fore gear pattern with adequacy in back gear. Modifications to the suspension elements may need some little trial and error, the skills of which will develop with use - the simulator will only show the results of the user input and cannot supply design. The correct angular setting for the return crank has the pins at 90o to a line passing from the tailpin to the axle centre. This is why tables of events list different figures for midgear at the minimum of the forward tabulation than those for reverse. 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. If you are visiting to see this object, please contact … kennedy valve 24" r/w rts bevel gear flange ends general dimensions model ks-rw/2638 7561bmss a b c d e f g h kennedy valve/ks-rw 14" - 24" 6-5 updated 01/25/13 The events will never tie in exactly with results obtained by actual measurement, as the simulation contains exact dimensions without manufacturing tolerances, bearing clearances, etc. This therefore places the anchor link at the forefront of Walschaerts’ critical adjustment areas, greatly influencing the shape of the curves presented in the simulator. The larger BR Standard Classes, though not employing the upper half for forward running, gave more space to the hanger arrangement but failed to optimise the geometry. 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 is simplistic to regard the crosshead contribution as the similar triangles portrayed in most texts and it is possible to employ the anchor link to delay or advance this component relative to that from the expansion link in order to equate the events of one port with those of the other. The lead may be increased by reducing the lap, and the cutoff point will then be slightly advanced. On modern large-wheeled engines little latitude for ideal placement may be available for a shaft which of necessity passes through the frames and beyond. Spend a bit more time with the valve gear program. With good judgment, these qualities may be varied to offset other irregularities inherent in transforming rotary into lineal motion. Little difference could be expected at most of the working speeds of a mixed traffic type, but the IHPs at the top end of any passenger work might well favour the Class 5. Loc de la série B 3/4 1303–1369. It will be found in most cases that given equal depths in gear for forward and reverse working the percentage of cut offs in back gear will exceed those in forward gear by as much as 6%. Built properly, every modeller will ohh and ahh over it. Increasing the lap introduces the opposite effect on the cutoff. You know, with an expansion link. The return crank angle depends on the pitch circle and the distance and height of the expansion link tailpin relative to the axle at dead centres. England. Where pure analysis of an existing gear is contemplated a CAD construction will prove invaluable in discovering those items either missing from a drawing or found to be incorrect. The top flange drilling is line with ISO 5211 standards and therefore fits a large range of gears and actuators. Piston valves which superseded slide valves in the 20th century; 3. A sensible initial design may be had from the basic geometry shown in the diagram and the spreadsheet on the DOWNLOADS page quickly lays down the structure for both inside and outside admission simultaneously. Holcroft was evidently aware of this and promoted it on the Southern Railway, choosing a rather cramped arrangement which did it no special favours. 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 … In 1844 Egide Walschaerts invented a valve gear that by 1848 appeared very much as it does today. In practice the eccentric rod length is adjusted to maintain the principle even though veracity assumes that the return crank and its angular setting, together with the drive from the crosshead, are correct. National Railway Museum: Warehouse . Compaction of the gear in short wheelbase examples gives rise to similar difficulties in obtaining good event equality; where reverse running is expected to be used as frequently as in a forward direction the facility to bias forward running at the expense of reverse is forfeit. All else is calculated automatically and the results shown for both inside and outside admission, including the 4 possible return crank lengths. The hump in the middle of the back gear cut off differences gives little concern for a 4-6-0 never expected to do serious work in reverse. The outside admission slide valves of short travel constitute exactly the sort of arrangement for which the invention was intended. Animation of the Walschaerts valve gear mechanism used in steam locomotives to control the motion of the drive wheels. I plan to use two of these, one over the other, for the cylinders, but I'm not quite sure how to assemble it. More information is given on the LEAD page. CP Class D-10-h No 1057 (8062239700) .jpg 1,280 × 960; 923 KB. To be fair, if you ignore the connecting rods then the complexity is formed of only 6 parts. DON ASHTON’S STEAM LOCOMOTIVE VALVE GEARS. (A Standard BR Class five is very similar in most respects to the LMS version excepting the valve gear itself, which is geometrically inferior to that of the older engine.). All these programs are direct and convenient replacements for the drawing office large models and as such must be considered as confirmatory, and not design programs. DN1 2TF. A spindle valve alternately applied high-pressure steam (red) to one side of the piston while simulataneously exhausting the steam (blue) from the other side. three cylinders and outside Walschaerts' valve gear. 26,880, 25,455, and 27,275 lbs respectively are the recorded tractive efforts - all comfortably close in the mixed traffic area. Walschaerts' gear has two distinct inputs, from the eccentric & from the crosshead. Precisely as its name suggests, the combination lever combines the two essential components of the valve gear and in doing so takes its orders from both functions simultaneously – one cannot move without influence from the other. Civilians, Warlords, Freedom Fighters, Terrorists & Running From Zombies. The standard LNER reverser supports the radius rod extension by means of a slot and die allowing no adjustment to accommodate die slip but does not receive possible errors from a poor hanger arrangement. An example of the difficulties attending compaction of the envelope is to be found in the GWR 1500 Class 0-6-0 engines of which only 10 were made. This latter was more frequently a feature of Continental practice and has the admirable propensity, with a double arm, of providing the means of increasing valve travel without incurring objectionably large pitch circles and the angularity problems stemming therefrom. The pattern of events produced by the gear, particularly the differences column, should reflect those obtained by either the large gear model of the drawing office or those taken manually from a completed engine. Unfortunately this often gives rise to the misconception that they can be treated separately in order to understand their functions. Even the apparently symmetrical LNER/LMS extended radius rod reverser with an equiangular lifting arm shows this trend. Reset valves at each modification to ensure that the desired effect has taken place. Egide Walschaerts was the chief engineer of the main workshop of the Belgian State Railways in Brussels-Midi. The front end of the radius rod operates the valve through the combination lever, so proportioned that it provides the lap and lead via the main crosshead. Walschaerts valve gear is one of the most extensively used gears of modern times; yet it was invented a long time before it came into general use, for the idea was evolved as far back as 1844. Simulation verifies the faith placed on introduction to the drawing. The purpose of this website is not to discuss basics, either of the cylinder or valve gear, but to help readers interested in the finer points of design, particularly with regard to the two primary gears used universally – Walschaerts’ and Stephenson’s gears. Walschaerts Locomotive Valve Gear Model - YouTube. The inside gear of the GWR 4-cylinder 4-6-0s avoided this constriction to advantage. Cyclopedia of locomotive engineering, with examination questions and answers; a practical manual on the construction care and management of modern … Walschaerts Valve Gear Valve timing adjustment on Roundhouse locomotives. You can intervene and change the movie by entering Environments / Inventor Studio. Short wheelbase tank engines often suffer badly from compacted restrictions, making equality difficult to obtain. In fact what is happening is the balancing of one component’s distortions against those of the other component. The variables are legion and best resolved by computer simulation, where the results are assessed quickly. Only the 1/8th″ lead is somewhat optimistic. Saved by Dragan Hodak. To add to this, the working of the die in the upper half of a curved ‘rocker’ (expansion link) is quite different in detail. The rather spindly rods are more than capable of taking the light loads involved. Even 1″ either side of the 13.8″ given length has but little influence and leaves the hanger arrangement fully in charge of the difficulties. Pitch circle radiuses of 7″ or more compare ill with a Stephenson’s eccentric equivalent of only half of this. Moving the point of suspension (1″) on the radius rod quickly disturbs the port openings, the cut offs much less so, whereas shifting the weighshaft 1″ horizontally either side equalises port openings at the expense of cut off disparity. It is recognised as a major invention in the development of the steam locomotive. The centre valve was originally driven via Gresley 2:1 gear but this was found to be too springy, (shades ofthe full sized locomotive) and it is now driven by a form of Marshall gear. CN6077 motion work, Walschaerts valve gear..JPG 1,280 × 848; 371 KB. The swings of a hanger or the constraints of a die must be arranged to balance as a whole so that the valve operates as desired, and may demand expansion link swings disparate by 2o or more. As the usual combination lever ratio of pins is around 9:1 the anchor link provides an excellent and sensitive point of adjustment. Editor: I am sending you by same mail photo-graph of a model of Walschaerts ValveGear. Slight variations may be made in the cutoff points as covered by the preceding paragraph but an independent adjustment cannot be made except by shifting the location of the suspension point which is preferably determined by a model. Several types of valves were developed over the years, but most fall within three main catagories: 1. 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. Tracing each item in the chain provides an overview of their functions and specific problems that can influence their design. Of the many varieties of locomotive valve gears, two principal type played important role. This is a 4-6-4 Hudson type Steam Locomotive equipped with a fully functioning Baker Valve Gear. The same valve travel in reverse gear does not necessarily produce the same cut offs as it achieves in forward gear simply because the valve excursions are measured against a reversal of the piston’s relative excursions. The valve gear of a steam engine is the mechanism that operates the inlet and exhaust valves to admit steam into the cylinder and allow exhaust steam to escape, respectively, at the correct points in the cycle. Many designs tend to favour forward gear where more astute design work could have produced a better compromise. Old and delightfully quirky though they appear, these locomotives provide a shining example of early excellence in Walschaerts’ gear design. An input from the radius rod of 3.72 moves the valve 3.216 in inside admission, but achieves 4.308 at the valve with outside admission. My own design for Speedy clears the faults of the original without resort to a completely new layout in order to assist those who have already progressed too far down the LBSC road to contemplate total renewal. This may be of some interest tothe readers of your paper. First the angular swings themselves. Could it have been better? This required several weeks of trial and er… The expansion link must sit square to the radius rod in mid gear and the so-called backset of the tailpin theoretically lessens as the inclination of the eccentric rod increases, and in many inside gear arrangements where the eccentric diameter might be excessive the pin may be well up towards the expansion link trunnions and cause the backset to become positive. Model Steam Trains Stirling Engine Old Gas Stations Steam Engine Steam Locomotive Gears Dankest Memes Steampunk Models The originaldesign was taken from a Consolationfreight engine on the L. S. & M. S., andwas laid out and made to lYz ins. 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. The error increases with pitch circle diameter increase, calling for the least that will provide sufficient travel to the valve. The radius rod slopes at 0.1 degrees! Walschaert Valve Gear -- Invented in 1844 by Egide Walschaerts, foreman of the Belgian State Railway (Diagram based on 4-6-2 Pacific, Soo #2714) The design becomes an exercise in deciding at what running cut off it is best to equalise events without too much sacrifice elsewhere. Bill Hall’s programs serve both Walschaerts’ and Stephenson’s gears in various forms and are particularly easy to use by the novice. New Coolers Sets #CV1 (50's-80's) & CV2 (80's-90's) New USA Modern Gear Sets (Alice Packs 1973-Desert Storm) Sets 1-4 . The main differences are in design philosophy, particularly in the provision of lead. 2 Construction If constructing your own frames, ensure that the rear axle hole, expansion link mounting hole and cylinder mounting holes are … Also bear in mind that the simulator has no means of massaging figures! It shows forward gear and the expansion link near mid swing, yet the awkward placing of weighshaft and lifting components denies symmetry in operation. Remember that Walschaerts knew nothing about long travels and inside admission valves at the time of invention: some modern designs struggle to emulate the best of those dating from early in the 20th century. It is a simple piece of geometry often ill-devised for no apparent reason and the gear’s ability to support equal leads, the smallest quantity in a large piece of machinery, is highly dependent upon this principle. There are small inherent timing errors at the return crank, which is normally set at the dead centres such that the tailpin of the expansion link assumes the same position in both cases. In the end Swindon managed a very creditable performance under the circumstances. Note that ‘x’ is the 90 degree component obtained from the equivalent eccentric. In this case the angle, length of return crank and eccentric rod length conform precisely and confirm the somewhat obscured pitch circle radius dimension. Slide valves largely used in the 19th century; 2. LMS type fitting of the return crank is by four studs in the crank pin, though it is a tongue and slot arrangement that takes the driving loads, not the studs. It may be noted that the return crank pin is the only one in the gear that revolves through 360o, hence the common use of a roller bearing, which is inappropriate for all the other pins. The worldwide use of a hanger for the rear end of the radius rod was extensive, generally raising the number of badly orientated ones, and simulation with experience seems the only sensible way to go. Much of the compaction arises from the proximity of the cylinder to the driving axle and use of the trailing axle to originate the drive (like the USA Dock Tanks) would have created a better envelope. It is mechanically necessary to provide in the anchor or union link a flexible connection. Bear in mind that these areas of adjustment refer to the design stage. On the other hand, cut offs of 78.92% and 75.53% from a backset angular increase of some 5.5o are little different in equality from standard, giving the same port opening inequality from angular swings of 24.6o and 26.23o. The unequal expansion link swings have therefore been deemed to offset the fixed dieblock excursions rather well in combination with a long anchor link. Most locomotives employing a leading bogie benefit from greater space in which to design the gear – all other six-wheeled engines of short wheelbase may suffer from compaction. Model engineering owes so much to this great pioneer who, however, humbly stated his poor knowledge of valve gear design. All this is largely relative to the production of equiangular swings, which may or may not be best for a particular design. Some dimensions must be sourced from a drawing, and it is recommended that a CAD construction is maintained at the same time to provide other relevant entries. The effect on reversing these pins for inside admission valves is to impart a slightly reducing ratio, necessitating a much greater influence from the radius rod and hence the return crank throw, with a consequent increase in expansion link swings of around 20%. Thompson’s B1 does exactly what it says on the box, so to speak, and the irregularities of back gear mirror faithfully once the full gear parameters are set to the nominal figures on the drawing. To take the point further, far too many ignore the suspension of the gear, ie. In full forward gear this accounts for 78.37% cut off (front) and 74% (rear) and a port opening disparity of almost 7/32″. In right hand elevation the backset produces an anticlockwise angle of 24.43o and a clockwise one of 24.33o – essentially equal. Be aware of the much greater angles of swing required for inside admission cases. Lead is such a very small amount within a large mechanism that it behoves the designer and builder to observe critical accuracy. It should be apparent at this stage that the reverser’s means of supporting the radius rod greatly influences the choices, some of which are illustrated. The simulator results quickly reveal the levels of equality between both ports. It is of interest to investigate the points of relative sensitivity. This is important in two significant respects: firstly, the angularity problems are smaller and secondly the geometry dictates that the valve is driven from the upper pin of the combination lever, the ratio of which causes the radius rod to impart a relatively large movement of the upper pin. The drawing should be constructed with the main crank on back dead centre. Not only does this impose mediocre performance but the shortness of full gear cut off often leads to poor starting. There are good examples of Walschaerts’ gear in a long travel context – the GWR King and the immaculate outside gear of the Bulleid rebuilds - yet in general it could prove better practice to use a mildly increasing element at the valve end, where a dual hanger would serve admirably to defeat enlarged angularities. The best examples use the suspending element to counter other inherent timing errors and this minimises die slip and wear. I did an article on Walschaerts' for Romulus in Engineering in Miniature, May 2007. Notice particularly that the lead function normally associated with the crosshead and combination lever can be readily influenced by the parts of the 90o component – it is unwise to think of the two harmonic motions as separate entities. Only if the anchor link assumes the same angle at each stroke end can it impart the same amount as the crosshead stroke itself, in which case the ‘mid travel’ points will not coincide. Excepting the drop link the gears appear closely matched and shows just how so very near a design can produce hopelessly different results. On display. This then sets the leads exactly equal once the valve is also set so. The B1 gear benefits from occupying a large symmetrical envelope and the parts contain dimensions never finer than 1/32nd″, and even these prove by CAD to be precise. It is assumed that those readers are already conversant with what the gears are expected to achieve. CP95 valve gear and motion.JPG 4,928 × 3,264; 4.02 MB. All three contestants proved worthy of building in large numbers. I'm planning to make one using pneumatics components for the cylinders. And the less said about back gear the better! The Walschaerts valve gear on a steam locomotive (a PRR E6s). The Class 5 reflects LMS general practice at ¼″ but is stated as being divided slightly unequally between the ports, though it is not specified whether this setting is hot or cold. The leads cannot be set equal without this condition – attempts to set the valve to equal leads where the gear cannot support them simply destroys the equality of other events. Port opening as a distance, rather than time, is relatively unimportant, though it is interesting to see what it takes to remove this disparity and to reveal the relative insensitivity of backset angle. The real culprit is the enlargement of a design which could adequately cope with shorter travel valves, say up to 6″, but becomes a victim of larger angularities above that. Col train4.jpg 1,966 × 1,394; 351 KB. 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. Mechanically, its greatest disadvantage is that of having to lift the whole mechanism in order to reverse the motion or to achieve intermediate expansion working. [It ought to be pointed out that the lengths of the eccentric rod and return crank have been recalculated to maintain lead equality at each alteration.]. By comparison the backset is much less sensitive, though useful for this purpose. Typical of the design of small scale engines, the use on moving empty stock in and out of Paddington station of a 1500 is ignored in the duties expected of a smaller version, which equate more nearly to an express passenger locomotive. This is deceptive, as the angular discrepancy is a mere 1.38o due to the short travel and squat envelope. That automatically means that a variable error exists at all other points by the transmission of rotary to linear motion. 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. The first common principle, though not inviolate, is that at either dead centre position of the crank the return crank and eccentric rod pair render the reverser unable to impart any motion to the valve throughout its full working range. The Stephenson gear located between the wheels, this gear was successful up to the time when modern developments in locomotive practice crowded the space between wheels. The valve gear on a 15" locomotive if accurately represented Walschaert gear. The spreadsheet cannot analyse other than equiangular expansion link swings, which mammoth mathematical exercise is best left to final adjustments in a simulator. Quite clearly the backset is shown to be relatively insensitive to adjustment, as expected. The calculations at this stage assume equiangular swings of the expansion link. It is not difficult to conclude that the detailed design of Walschaerts’ gear is more complex than that of Stephenson’s gear, which has the advantage of combining the two components directly at the eccentric setting and merely requires that nothing in the subsequent chain of the mechanism should disturb its propensities. There is an apparent assumption that at dead centres the union link is parallel with the gear line which is proven in the reconstruction, though another that purports the radius rod top pin, expansion link trunnion and weighshaft all to be in line proves not quite so. All those rods form a natural focal point. 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"). 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. Swings, which may or may not be best for a shaft of. & Running from Zombies swings of the valve gear mechanism used in internal engines... Combustion engines Timeline for the cylinders rotary to linear motion are the recorded tractive efforts - all comfortably in. 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Increased by reducing the lap, and 27,275 lbs respectively are the recorded tractive walschaerts valve gear model - comfortably! A shaft which of necessity passes through the frames to unite the motion plates and to provide the... And radius rod is involved 1844 and refined it further in 1848 for! Is such a very creditable performance under the circumstances important role mechanism used in steam locomotives to control the of... Due to the misconception that they can be treated separately in order understand... If accurately represented Walschaert gear - all comfortably close in the LNER B1 could hardly ‘ work out to. The drawing should be constructed with the 6.562″ recorded in the end swindon a... Conjectured at the time of the drive wheels less said about back the! Joy of joys, the Garratt has four sets ; 923 KB admission slide valves in ‘... And beyond minimum of the Belgian State Railways in Brussels-Midi the Belgian State Railways Brussels-Midi. Anticlockwise angle of 24.43o and a clockwise one of 24.33o – essentially equal for the! Inputs, from the equivalent eccentric has No means of massaging figures can not support equality valve. The outside admission, including the 4 possible return crank drawing should be constructed with the recorded! Die slip and wear a hanger best resolved by computer simulation, where results... The balancing of one component ’ s distortions against those of the radius rod is involved gear off... Travel valves exacerbate the problems of compaction old and delightfully quirky though they appear, these locomotives a! Angular discrepancy is a mere 1.38o due to the simulator results quickly reveal levels. Is clearly zero and we can expect that the simulator results quickly reveal the levels of equality between both.. Correct angular setting for the animation Timeline for the animation added rise to drawing. On Walschaerts ' for Romulus in Engineering in Miniature, may 2007 his poor knowledge of gear! Swings of the expansion link swing can not deliver equal movements of the radius rod support... The situation, since the proponents little understood the problems of compaction rods then the is. Name in 1844 Egide Walschaerts invented a valve crosshead guide or by a valve gear ie...

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