Southern valve gear was devised by locomotive designers on the southern railway us and used on many locomotives on that line. Gresley class p1 delivered in 1925 100 wagon trains. The middle cylinder is inclined of 10 degrees unlike 7 which was found on the union pacific 4122 9000 series. To realise the potential of the original gresley design. Spencer, an lner employee, the class was rebuilt due to reliability problems during the difficult conditions of the world war ii period, and additionally to take the opportunity to try out a different valve gear arrangement. Sir herbert nigel gresley 19 th june 1876 5 th april 1941 was one of britains most famous steam locomotive engineers, who rose to become chief mechanical engineer of the london and north eastern railway. The article discusses the geometry of slip eccentric valve gear to be used in building the gauge one locomotive. Gresley designs derived valve gear the walschaertsgresley valve gear was the source of much criticism, which is partly answered in holcrofts article, where it is stated that it may be recalled that in recent times a speed of 125 m. The walschaertsgresley valve gear was the source of much criticism, which is partly answered in holcrofts article, where it is stated that it may be recalled that in recent times a speed of 125 m. This type is the most common in britain, used on all the br standards except for the 35 br standard class 5s 73125 to 73154 and class 8.
The first steam locomotive to officially achieve 100 mph, the a3 flying scotsman 462. The function of the locomotive valve gear is to regulate the movement of the valves so that steam is admitted and exhausted from the cylinders in relation to the position of the pistons. Long lap valves therefore require longtravel valves, which gresley famously. Progear, based in bad bentheim gildehaus germany was founded by a team of specialist with the aim of supplying todays competitive valve industries with high quality products, competitive pricing and one of the shortest lead times in the industry. Holcroft patented his design in 1909 whilst he was working for the great westernshock horror. The british patent has not been found but the us patent us252224 of 10 january 1882 has. The class was rebuilt into class a22 462 pacifics during 19434. The gear was first tested on mikado 586 in february, 19 at southern knoxville shops.
Steam locomotive valve gear trains magazine trains. It was extensively used in steam locomotives from the late 19th century until the end of the steam era. Valve gear definition is any of numerous gears by which motion is given to the valves of an engine and especially a steam engine. Almost everyone has his own pet reference book on the various valve gears and the methods of how to lay them out. It enables a threecylinder locomotive to operate with only the two sets of valve gear for the outside cylinders, and derives the valve motion for the inside cylinder from them by means of levers the 2 to 1 lever and equal. Sadly, the design was never fully developed and they were rebuilt by his successor edward thompson into. Apart from the support given by the pilliod company any advantages are more apparent than real, though doubtless the. He made the software freely available by placing it in the public domain as freeware. It is purely an exercise in using modern computer software to give a more accurate picture of the valve events given by a specific design. 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.
The best known is gresley conjugated valve gear, used on 3cylinder locomotives. In early 1999 i started converting one of the valve gears to the windows format. Gresley designed his own derived gear but it was pretty complicated by comparison and so when he learnt of h. It also allows the driver to alter the length of steam admission, known as cutoff, and to reverse the locomotive. Lentz gear produced by the american franklin company have also been obtained. Allan wallace valve gear simulation software for walschaerts. This makes control of the valve gear easier for the driver. The holcroft valve gear was a type of conjugated valve gear designed by harold holcroft and used on threecylinder steam locomotives of the south eastern and chatham railway secr. Our type dml interlocks suit on all types of gears, handwheel operated example as in the picture. The gear is sometimes known as the gresleyholcroft gear, acknowledging holcrofts major contributions to its development. The valve is also used to mount to other operators such as our spring return deadman handles, gear operators, electric spring return actuators, or chain levers. Stephenson valve gear was an early type of valve gear that allowed the cut off of steam admission to be finely adjusted from the footplate. Against a background of increasing train sizes in the early 20th century, it was necessary to build locomotives that were more powerful and with a. Since being established in 2001, progear has rapidly grown into a leading player in the world of valve actuation.
One drawing even has the handwritten signature of h n gresley himself. Joy valve gear is a type of steam locomotive valve gear, designed by david joy 3 march 1825 1903, locomotive and marine engineer, and patented no. A further benefit may be obtained by admitting the steam to the cylinder slightly before front or back dead centre. The animations seen on this page were created with software written by. Permanent damage and solvable performance suppressions includes simulated cylinder explosion due to an excess of water in the cylinders, the virtual loss of connecting rods when wheelslip goes out of control, and the gresley conjugated valve gear breaking due to middle valve overrun when coasting at a cutoff greater than 25%. Valve gear on a steam locomotive is used to control the admission of steam into. He was the designer of some of the most famous steam locomotives in britain, including the lner class a1 and lner class a4 462 pacific engines. Joys gear is similar to hackworth valve gear but has a compensating mechanism which corrects for the slight inequality in the. The piston valve became more popular, even on saturated steam engines because they were easier to service, repair, and fabricate. It bore many similarities to the gresley conjugated valve gear used on the original lner a1 design. Baker valve gear, originally designed for traction engines, enjoyed some success in its home environment, america.
They were designed by sir nigel gresley in the 1930s to haul 600 ton trains on the arduous edinburgh to aberdeen route. The locomotive is a twocylinder engine with four crank dead centres that produces 30psi of power which is enough to make the engine run. The walschaerts valve gear on a steam locomotive a prr e6s. Steam engine valve gear on the computer downloadable freeware simulations of every kind of valve gear youve ever heard of by charles dockstader ca. The gresley class p2 282 mikados were the most powerful express passenger locomotives to operate in the uk. Charles dockstader created a brilliant collection of fully graphically animated valve gear simulations for windows os, starting in 1986 and continuing until approx 2007. Although the lner used a variety of different valve gears, it will forever be associated with gresleys conjugated valve gear. Early designers had to use long and tedius calculations to work out valve positions but later ones did have. He continued work and another patent was issued july 23, 1912. It enables a threecylinder locomotive to operate with only the two sets of valve gear for the outside cylinders, and derives the valve motion for the inside cylinder from them by means of levers. Derived valve motion for 3cylinder steam locomotives.
The valve gear coordinates the valve motion with the position of the piston, much like the camshaft in an engine. It varied from the gresley method of operation by using the combination lever assembly instead of the valve. It enables a threecylinder locomotive to operate with only the two sets of valve gear for the outside cylinders, and derives the valve motion for the inside cylinder from them by means of levers the 2 to 1 lever and equal lever. The largest passenger steam locomotive in the uk, the p2 282. Gear operated valve interlocks alcatraz interlocks. 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. For those that would like to study how valve the valves of a stanley engine function this program is highly recommended.
Plasgear plastic gear operator for manual butterfly. Describes gresleys famous conjugated valve gear as used used on the middle. Valve gear definition of valve gear by merriamwebster. Holcrofts design he used it in all his future 3 cylinder locos. Click for animation 626kb shockwave flash required gresley first describes the new valve gear in 1915, in his patent no. The gear used by sp and up was the holcroft design. I have made the software available by placing it in the public domain as freeware. The stanley steam engine stephenson valve gear computer simulation program charles dockstader has created an excellent program that simulates the operation of stephenson valve gear action. Design and layout of a valve gear from time to time there has appeared references to valve gears or parts, but no complete or logical method of deriving proper proportions.
It enables a threecylinder locomotive to operate with only the two sets of valve gear for the outside cylinders, and derives the valve motion. Inaccuracies in the machining and setup of the gresleyholcroft derived motion which derived the valve motion of the inside middle cylinder from those of the other two, avoiding a hardtomaintain valve gear linkage between the frames meant that the inside cylinder of the a4 did more work at high speed than the two outside cylinders. The trust looked at british caprotti valve gear using a derived drive for the centre. In addition it must be noted that gresleys successors, who were probably those most expected to solve the problems at. Holcroft had filed a patent for a similar arrangement in 1909. 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. I do not claim to be an expert on loco valve gears, more an enthusiastic amateur but i have spent a lot of time reading up on the subject and i think im getting a reasonable grasp of the subject. Today we have access to some extremely useful bits of computer software which can exactly simulate the movements of the valve relative to the position of the piston and enable us to design the ultimate valve gears. Although successful enough to warrant production in quantity the distinctly syncopated beats and the tendency of the middle valve to overtravel at speed, producing an imbalance of power and. It displays measured and computed values and a theoretical card. The steam diagram defines the potential output and efficiency of the engine. The gresley conjugated valve gear is a valve gear for steam locomotives designed by sir nigel gresley, chief mechanical engineer of the lner, assisted by harold holcroft. Available in single or double key styles, locking the valve in either the open or closed position.
Instructions for download and installation the bcwrr is delighted to host charlies valve gear program on its web site. The stephenson valve gear was developed by william howe and william williams at the stephenson locomotive works in 1841. Gear operated valve interlocks interlock description. It introduces angular elements of marshall gear into walschaerts in a complex yoke drive with a bell crank. I do not profess to be an authority of any kind on valve gears, but i agree 100% with one of the best locomotive designers. Perhaps the most celebrated example of conjugated valve gear for three cylinders is the gresley lner arrangement in which holcroft was consulted. Lner class a4 4468 mallard academic dictionaries and. Another general rule, slide valves wont be used with a superheated engine. The london and north eastern railway class p2 was a class of 282 steam locomotives designed by sir nigel gresley for working heavy express trains over the harsh edinburgh to aberdeen line. Unfortunatly, the site from which these animations were obtained is no longer active. The flowserve limitorque v series of bevel gearboxes is designed for manual and motorized operation of gate and globe valves as well as slide gates. The provision of excellent valve timing in the outside cylinders may not always guarantee the performance of the derived gear and some compromise may have to be made in.
No 2002 had walschaerts valve gear and others were fitted with the same. Other sources supposed that the rebuilding might be because the classs wheelbase was. The gear is sometimes named without the final s, since it was incorrectly patented under that name. The baker valve gear had one operating advantage over the walschaerts in that it could be set up for a larger valve wlonger valve travel, 812 vs. Thomas in the miniature locomotive for septemberoctober 1954 brings up a matter that is hard to explain. A close up on the lefthand walschaerts valve of br standard class 2 260 78019. Attempt to do a 3d model of a gresley valve gear youtube. It is hoped that the amount of alloy for the correct balance can be theoretically using solidworks software. Charlie has put this program in the public domain but is. In the walschaert valve gear, which was common among many railway companies except for the.
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