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Steam & Excursion > Basic Steam QuestionsDate: 02/20/17 12:17 Basic Steam Questions Author: wigwag Question removed
Edited 1 time(s). Last edit at 02/28/18 14:55 by wigwag. Date: 02/20/17 13:16 Re: cylinders Author: timz Guess it's a safe bet that 99-point-something
percent had two cylinders, if you're asking about all the engines that ever ran in the US. Edited 1 time(s). Last edit at 02/20/17 13:17 by timz. Date: 02/20/17 13:25 Re: Basic Steam Questions Author: LarryDoyle Alfred Bruce, in The Steam Locomotive in America, estimates that apx. 180,000 steam locomotives were built in America, and you correctly surmise that the vast majority had two cylinders, and a single rigid frame. This is the conventional design.
Four cylinder compound engines with a single rigid frame were quite common in the 1880 to 1910 period. These either placed two cylinders on each side of the locomotive, or placed two cylinders in the conventional position outside the frames and placed the other two cylinders between the frames driving cranked axles. I'd estimate that several thousand of these were built, but after 1900 almost all were rebuilt into simple two cylinder engines. Some were built with a single rigid frame but with four cylinders and a divided drive, such as the Pennsylvania's 4-4-4-4 T-1 class. Total production, PRR and other RR's combined, probably less than 100. Three cylinder engines fall into two categories. (1) Rigid frame, with the third cylinder centered between the two outside cylinders and driving a cranked axle. A few hundred of these were built. (2) Geared locomotives (Shay and Willamette) with the three cylinders mounted vertically on one side of the locomotive, with a flexible drive to swiviling trucks. A couple thousand of these. Four cylinder articulated frame simple and four cylinder articulated frame compound engines were built from 1906 'till the end of steam. Probably several thousand of these. Six cylinder articulated frame compound engines, with two of the cylinders driving an engine under the tender, were tried by a couple of railroads, but total produced was only about a dozen. Some four cylinder engines with a conventional locomotive, but with a tender as just described, were used on the Southern RR. A few steam turbine engines were build with, obviously, no cylinders. You could count these on your fingers. This, off the top of my head. Perhaps someone else will hang some meat on this skeleton, and maybe some pictures. -Larry Doyle . Date: 02/20/17 15:25 Re: Basic Steam Questions Author: wcamp1472 Engines used in heavy-duty, American, mainline railroads progressed in size rapidly after the invention of a successful design superheater. The superheater adds more heat to the steam gas......since the open end of the units is passing steam onto the cylinders, the pressure is NOT materially increased, but the heat-induced excitation ( increased frequency and amplitude) of the steam molecules forces greater separation of the molecules. The major benefit of the hotter steam is that as it cools, due to expansion in the cylinders ----- the cooling does NOT result in a portion of the steam converting to water vapor. Greater separation of the molecules, results in less weight of water doing the same amounts of work ......less steam used means greater work for the same fuel energy.
Steam is an invisible gas, water vapor is a colloidal suspension of water droplets ----- making a 'cloud'. We commonly conflate the visible vapor (cloud) with 'steam' , however, water vapor is the proper name for the stuff we can see. So, with superheated steam, expanding in the cylinders, it cools proportionate to the volume. Superheated steam with its greater heat content continues to exert exapansive pressure all the way down the stroke, until the exhaust port opens. Even then it is common for a degree of superheat rushing up the stack. Soooo, soon RRs began to employ superheated engines, as fast as designersand builders could produce them. However, the technological level of manufacturing in the nation was in its infancy, so the large machines used to manufacture large I parts were soon out-sized by the parts they were trying to make. As factories and steel making expanded before the 1920s, locos were pushed to higher boiler pressures, greater weights and higher piston thrusts. Soon the piston thrusts were so massive that conventional, bolted-up frames were continuously shaken loose. The greatest forces occurred at the conventional, 2-cylinder casting that mounts across the front of the frame, that crucial joint bore the brunt of the severe, alternating forces ---- between the wheels (anchored to the rails) and the pistons and cranks being forced, at pressure to expand, thus dragging the train ahead. As long as the wheels don't slip, the train accelerates. So, early casting improvements included the perfection of the one-piece cylinder saddle, frame front, including the pilot beam, coupler pocket, as well as the supporting structure for the crosshead she and guides. This one piece casting was bolted to the frame that carries the drive wheels & axles. A similar, simpler casting was used at the rear to anchor the frame rails and support the firebox as well as the drawbar and pins used to connect to the tender. This allowed larger locos, larger, more massive frames, and even less room for additional cylinders. In the 1920s, companies like General Steel Castings pretfected the larger, one piece cast steel frames. These were massive castings, and contained massive cross bracing and massive side rails, as well as huge cylinder castings. Many early versions were prone to cracking at the crux where the cylinders join the frames. The solutions included larger radius supports at the joint. So now, manufacturing capacities increased ,& increased sizes of machine tools used to make the bigger structures that resulted in increased structure capacities at both shipyards and loco building firms. Another, limitation to multicylinder engines was the ability to fabricate crank-axles for main rods' driving cranks between frame rails. You have two, large driver wheel centers pushed onto the axle ends, Next, you have the large diameter and long driver axle bearings/journals. Fitted over the axle journals are the mating 'driving boxes' containing the driving bearings. as these components expanded, that reduced the space available for such things as crank axles, counter weights and massive main rods. Remember that the rail Gauge is only 4' 8 1/2" wide, with crank axles, big cylinders, big axles, you don't have very much room for big-thrust engine components So, in America, what was the most successful design for multi-cylinders, were the articulated designs that evolved from smaller engines. The cast frame technology increased and allowed for the perfection of 6-coupled and 8-coupled, articulated frame, driver chassis. [ however you pluralize 'chassis' ] The 'evolution' of these engines resulted in the very successful engines based on the Early U.P. Challenger-series locos and the very successful heavy-duty eight-coupled variants, used by many heavy-haul railroads. And, the narrow track Gauge in the U.S., commonly called the " loading Gauge", limits car and loco "axle loadings". A wider track Gauge would have permittted such things as multi-cylinder 'experiments' to have been attempted... During the evolution of steamers, which included early attempts at variants that tried multi-cylinder constructions ---- all of which failed ------ to one degree or another. One striking failure is preserved in Phildelphia's Ben Franklin Museum: Baldwin's #60,000, a 4-10-2, 3-cylinder, small driver-diameter, water tube firebox ---- design disaster. Study it, and you will understand why it failed as a "sales-sample", and how complexity was eschewed by traffic sensitive freight RRs.... Their managers were very miserly lot.... W. Edited 3 time(s). Last edit at 02/20/17 15:32 by wcamp1472. Date: 02/20/17 16:46 Re: Basic Steam Questions Author: tomstp I have read that engine crews would not go near that engine because of the very high pressure used.
Date: 02/20/17 19:07 Re: Basic Steam Questions Author: wcamp1472 I'm not sure, but I think that the high pressure portion is the water tube firebox..
The firebox replaces the much weaker, conventionally stayed furnace made of flat plates supported by stay bolts. Watertube fireboxes are vastly more capable of handling much higher pressures. Virtually every boiler built today, is high pressure water tube boilers..... All modern boilers are watertube, extremely high pressure capacity construction. The Baldwin approach may well be of a modest pressure. The high pressure, watertube fireboxes are most likely to have an individual tube fail, and not the whole firebox.. An inherently, much safer design. So, yes...old-timey crews might well have panicked, and run, such is the ways of fears and ignorance.. The main problem I swain the design is that all of the tubes that come down each side of the firebox terminate in rectangular lower 'drums'. The tubes are fitted into the bottom drum, top plate, the bottom plate ihas machined wash-out holes and fitted with 12-thread-per- inch 4" dia. brass plugs. There may be 50 tubes down each side of the firebox. The washout plugs admit water tube cleaning tools with sharp revolving tools to break up the baked-on scale.....( we called them "turbinders"). So, from a maintenance standpoint, having to pull all those plugs ---- every 30 days---- could be a nightmare. Plus , those brass plugs each form a "match" to their respective holes, and those tapered threads are nortorious for being easily cross threaded and stripped ----- so under extreme pressures in that firebox could pop out a 'stripped' brass plug. There's many reasons why that engine never sold a single duplicate..... W. Date: 02/20/17 19:53 Re: Basic Steam Questions Author: Earlk Another nail in #60000's coffin was the fact she was a compound. Not only 3-cylinders, but a 3-cylinder compound.
Ugh.... I could just see every host RR looking at that and saying "no......thanks" The center cylinder was the high pressure cylinder and outside cylinders were the low pressure cylinders. All three cylinders were the same size. I would imagine the crankpins were 120 degrees apart. With the center cylinder exhausting into the outside cylinders, one third of the the exhausts up the stack would be "mute". 3 cylinder engines had a rather bizarre cadence when working with a "1-2-3, 1-2-3" beat. The 60000 would be even odder with a "1-2--, 1-2--" beat. I wonder how that effected the draft. As ALCO held the licensing for the Gresley Valve Motion to the third cylinder, 60000 had a double Walscheart gear on the right side. Date: 02/20/17 20:29 Re: Basic Steam Questions Author: CountryBoy The L&N had 1 3 cylinder steam locomotive and it was a "round house queen" until it was rebuilt into a 2 cylinder loco for passenger train use
CB wigwag Wrote: ------------------------------------------------------- > Were most steam engines in America built with 2 > cylinders? > > I do know some were built with 3 cylinders and > some with 4. However, percentagewise, about how > many were built with 2 cylinders vs 3 and 4 > cylinders? > > Thanks for any input on this subject. > > WW Date: 02/21/17 05:56 Re: Basic Steam Questions Author: choodude wcamp1472 Wrote:
------------------------------------------------------- > > There's many reasons why that engine never sold a single duplicate..... > > W. On display at the exhibit is a letter on Baldwin Locomotive letterhead that admits they had trouble with the superheaters failing. Brian Edited 1 time(s). Last edit at 02/21/17 09:39 by choodude. Date: 02/21/17 10:13 Re: BLW 60000 Author: timz > I would imagine the [BLW 60000] crankpins
> were 120 degrees apart. Its outside cylinders were 90 degrees apart, presumably to give the best exhaust when running compound. Date: 02/21/17 11:24 Re: BLW 60000 Author: wigwag Currently, there are 5 rod type 3 cylinder steam engines preserved in America. Im not sure how many 3 cylinder Shay types survive, however. Im assuming much more. Anyone know?
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