Résumé historique. Model Steam Trains Stirling Engine Old Gas Stations Steam Engine Steam Locomotive Gears Dankest Memes Steampunk Models Be aware of the much greater angles of swing required for inside admission cases. CN6077 motion work, Walschaerts valve gear..JPG 1,280 × 848; 371 KB. 4mm scale model locomotive Walschaerts valve gear. from Kieran Jones. The theoretical full valve travel of 6.716″ compares very favourably with the 6.562″ recorded in the official table of events. 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. HMM! The envelope of the gear is a squat rectangle containing a long anchor link, small pitch circle and minimal expansion link swings and one might expect little problem in attaining good event equality. 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 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’ gear readily satisfies this condition since only the raising of the radius rod is involved. Re: Walschaerts valve gear model Post by 52D » Wed Apr 18, 2012 6:12 pm I was about to reply in the same vein as James Brodie, im sure the Stephenson Railway Museum in Newcastle have a working set from North Blyth MIC. Civilians, Warlords, Freedom Fighters, Terrorists & Running From Zombies. Only the 1/8th″ lead is somewhat optimistic. You know, with an expansion link. 2 years ago. 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. Piston valves which superseded slide valves in the 20th century; 3. 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. Compared with the exceptionally good King Class valve gear this little tank design gave the design team a headache, compounded by the adoption of an anchor link driving directly from the crosshead little end pin. Egide Walschaerts was the chief engineer of the main workshop of the Belgian State Railways in Brussels-Midi. Walschaerts Locomotive Valve Gear Model - YouTube. 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. 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. The variables are legion and best resolved by computer simulation, where the results are assessed quickly. 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. 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. CP Class D-10-h No 1057 (8062239700) .jpg 1,280 × 960; 923 KB. This is not the whole story, of course, as the designer must be aware of all the accelerations and decelerations throughout a full cycle; the emphasis in design must be on timing values and not necessarily on distances. 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 combination lever and radius rod require support either by a valve crosshead guide or by a hanger. 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. Col train4.jpg 1,966 × 1,394; 351 KB. Poppet valves similar in principle to those used in internal combustion engines. Walschaerts valve gear is wonderful stuff on an engine, it adds complexity and detail under the footplate. 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. 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. The unequal expansion link swings have therefore been deemed to offset the fixed dieblock excursions rather well in combination with a long anchor link. This is deceptive, as the angular discrepancy is a mere 1.38o due to the short travel and squat envelope. Also bear in mind that the simulator has no means of massaging figures! 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. 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. In 1844 Egide Walschaerts invented a valve gear that by 1848 appeared very much as it does today. The spreadsheet cannot analyse other than equiangular expansion link swings, which mammoth mathematical exercise is best left to final adjustments in a simulator. Built properly, every modeller will ohh and ahh over it. By comparison the backset is much less sensitive, though useful for this purpose. 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. A small discrepancy in the equality may be acceptable or even undetectable except by simulation, but working bearing clearances and subsequent wear could easily remove the desired lead altogether. 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. 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. Walschaerts Valve-Gear Roundhouse Engineering Co. Ltd Units 6 to 9, Churchill Business Park, Churchill Road, Wheatley, Doncaster. This may be of some interest tothe readers of your paper. Inside Walschaerts' isn't common, the Great Western Castles & Kings used it; the geometry is exactly the same as outside gear. (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.). Backset of the tailpin is clearly zero and we can expect that the expansion link swings are unequal, in fact by 2.11 degrees. 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. Model engineering owes so much to this great pioneer who, however, humbly stated his poor knowledge of valve gear design. DN1 2TF. The best examples use the suspending element to counter other inherent timing errors and this minimises die slip and wear. 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. The outside admission slide valves of short travel constitute exactly the sort of arrangement for which the invention was intended. 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 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. On display. DON ASHTON’S STEAM LOCOMOTIVE VALVE GEARS. 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. Walschaerts Valve Gear Model. the weighshaft and lifting arm and combination lever support where used, as being essential to correct functioning of the gear. 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. The originaldesign was taken from a Consolationfreight engine on the L. S. & M. S., andwas laid out and made to lYz ins. Increasing the lap introduces the opposite effect on the cutoff. The lead may be increased by reducing the lap, and the cutoff point will then be slightly advanced. 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. 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. 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 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 events will never tie in exactly with results obtained by actual measurement, as the simulation contains exact dimensions without manufacturing tolerances, bearing clearances, etc. 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. It is interesting to superimpose the model design over the Swindon drawing at the same scale (but without equating the valve and ports). 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. Basic formulae for Walschaerts’ initial design. Hi all, I'm wondering, has anyone attempted to build a lego Walschaerts Valve Gear, and what were the results? It is assumed that those readers are already conversant with what the gears are expected to achieve. 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. This feature immediately contracted the combination lever to give pins so close to each other at the top end to warrant especially small pins and render it necessary to crank the front end of the radius rod for adequate clearances. 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. I'm planning to make one using pneumatics components for the cylinders. All else is calculated automatically and the results shown for both inside and outside admission, including the 4 possible return crank lengths. Spend a bit more time with the valve gear program. The valves on a steam engine control the flow of steam in and out of the cylinders. 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. That the student should resist this temptation will soon become apparent; the alteration of a single part necessarily alters the whole. B3/4 1367 (CFF Historic 1) by Jean-Daniel David 88 44 B 3/4 1367. 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 events, however, prove by simulation to be magnificent, addressed to the heavy gradients expected without much compromise in reverse. The correct angular setting for the return crank has the pins at 90o to a line passing from the tailpin to the axle centre. CP95 valve gear and motion.JPG 4,928 × 3,264; 4.02 MB. All three contestants proved worthy of building in large numbers. 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. Long travel valves exacerbate the problems, none of which could be conjectured at the time of the invention. 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 … 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. 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 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. It is powered using magnets from the Electromagnets mod and is designed to run on 7u gauge tracks (tracks have 7 blocks between the rails). 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. Jun 21, 2019 - What has turned out to be the most difficult part of building these models is the working Walschaerts Valve Gear. Depending on control valve model, regulation of steam, liquids (in combination with KLINGER ball valves) and slurry, powder and paper pulp; Actuators. Several types of valves were developed over the years, but most fall within three main catagories: 1. Of itself, equal angles of expansion link swing cannot deliver equal movements of the valve. Excepting the drop link the gears appear closely matched and shows just how so very near a design can produce hopelessly different results. 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. 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. The inside gear of the GWR 4-cylinder 4-6-0s avoided this constriction to advantage. 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. This then sets the leads exactly equal once the valve is also set so. The top flange drilling is line with ISO 5211 standards and therefore fits a large range of gears and actuators. Quite clearly the backset is shown to be relatively insensitive to adjustment, as expected. I did an article on Walschaerts' for Romulus in Engineering in Miniature, May 2007. 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. Not only does this impose mediocre performance but the shortness of full gear cut off often leads to poor starting. 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. 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 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. When this condition become serious the Stephenson gear was abandoned in favor of the Walschaert type shown in this animation, … The error increases with pitch circle diameter increase, calling for the least that will provide sufficient travel to the valve. The Walschaerts valve gear on a steam locomotive (a PRR E6s). 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 . It is mechanically necessary to provide in the anchor or union link a flexible connection. 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. 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%. Longer valve travels inevitably make this area more difficult to appease. 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. 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. As the usual combination lever ratio of pins is around 9:1 the anchor link provides an excellent and sensitive point of adjustment. All gears have to provide the combination of two harmonic. 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. Swindon fought for decent results but LBSC was clearly out of his depth. Could it have been better? 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. 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. There are, of course, many other design features that might influence a comparison. This required several weeks of trial and er… You will need to flesh out the geometry, and if you use a double slide bar arrangement there is little room for the combination lever to align with the valve rod. The design becomes an exercise in deciding at what running cut off it is best to equalise events without too much sacrifice elsewhere. Reset valves at each modification to ensure that the desired effect has taken place. 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