The engineering is to this layman incomprehensible. As a what if, would this valve system be of any value to enhancing the performance of a reciprocating steam locomotive?
http://people.duke.edu/~scg8/SteamEngine/User_Manual.pdf
Firelock76 A Southern engineer named WILLIAM SHERMAN Brown? He may have worked for the Southern, but you can bet he wasn't from the South!
A Southern engineer named WILLIAM SHERMAN Brown? He may have worked for the Southern, but you can bet he wasn't from the South!
Johnny
lone geep I seen and heard of many different types of valve gear for steam locomotives, like Walschaerts, Baker, Southern, Etc. I know this is a silly question, but why are there so many types? Was some types of valve gear better for different jobs (Walschaerts for speed, Baker for switching, Etc)? Or was simply one type improving on the other?
I seen and heard of many different types of valve gear for steam locomotives, like Walschaerts, Baker, Southern, Etc. I know this is a silly question, but why are there so many types? Was some types of valve gear better for different jobs (Walschaerts for speed, Baker for switching, Etc)? Or was simply one type improving on the other?
Yet another simple question that turns out to be more complicated than we think!
Paul Milenkovic The Walschaerts gear became popular when the locomotive designers and railroad maintenance people wanted to move the gear from inside the frames to the outside, where not only can railfans admire the valve gear in motion, but where it is easier to maintain and repair on later locomotive models where the space inside the frames becomes hard to get at.
The Walschaerts gear became popular when the locomotive designers and railroad maintenance people wanted to move the gear from inside the frames to the outside, where not only can railfans admire the valve gear in motion, but where it is easier to maintain and repair on later locomotive models where the space inside the frames becomes hard to get at.
I'm gonna guess that railfan admiration of valve gear in motion might not have been a design consideration.
Actually, I am in complete awe of those engineers who could dream up such complex "monkey motion" in the first place. In fact, I have nothing but admiration for anyone who seems to understand valve gear workings as you do. If I study steam locomotives for another 50 years, I might begin to follow it.
ChuckAllen, TX
C&O used Unaflow engines in its last carferries. In addition to the efficiencies mentioned above, the low back pressure allowed for quick responses to reversals, an important factor while maneuvering into and out of the dock areas.
Nobullchitbids wrote:
"2. No one so far has mentioned the effect that superheating had on the problem. I've always been told that Stephenson only could be used with slide valves, which could not be used once superheating became the standard practice. This explains why Walschaerts took over at the turn of the last century even though it was invented half a century earlier."
With reference to point 2, I would suggest that there were additional issues, other than those already mentioned, which lead to the demise of the Stephenson valve gear for locomotives.
1- The Stephenson valve had relatively large sealing faces, and were generally designed for outside admission of steam which results in the steam acting on the outside of the valve, forcing the valve against the sealing faces of the cylinder block. Thus, as locomotives grew in size, so did the size of the valve and the area of the sealing / wear faces. Since these valves were normally operating in a horizontal direction on top of the cylinder block, the weight of the valve (which in the larger sizes can be considerable) is added to the downward force of the pressure of the steam acting on the back of the valve, thereby increasing the friction forces between valve and block. As the boiler working pressure is increased so too does the aforementioned friction forces, which further increases the wear rates and reduction in engine efficiency.
2- With all outside admission steam valves, there is the issue of being able to seal the valve rod against live steam loss through the gland as steam pressure increases.
3- Superheating reduces the lubricity of the steam significantly. The resulting dry steam can no longer provide lubrication of those large sealing faces of the Stephenson valve, which again increases energy losses due to friction and wear of the sealing faces.
4- The design of the Stephenson valve, in keeping the valve travel relatively short, results in long steam passages between the valve chest and the cylinder ports. As locomotive speed increased, those long steam passages became a liability in terms of getting live steam to the cylinder, and exhaust steam out of the cylinder, fast enough to meet the cylinder demand, thus limiting the maximum speed of the locomotive.
5- Changing to piston valves, and valve gear other than Stephenson, afforded the following advantages:
-Reduction in the size and weight of the valve, while also reducing the bearing / sealing surfaces and thus friction;
-Allowed for the use of inside admission steam which meant valve rod glands only had to seal against the much lower exhaust steam pressure;
-Allowed for reduced steam passage lengths between valve chest and cylinder, all of which improved the timing events and thus the speed and efficiency of the locomotive.
I would suggest that in addition to all the previous answers to the original question, the large number of different valve gears that were developed world wide was in large part due to people trying to improve the efficiency of the steam locomotive by better controlling the steam inlet and exhaust events.
As for the various rotary and poppet type valve systems developed, my understanding is that when used on locomotives the increase in engine efficiency achieved was not enough to offset the costs associated with their complexity and increased maintenance demands.
One of the more efficient reciprocating steam engine types was the Skinner Uniflow engines and their European counterparts. At least one RR company in the US and UK tested locomotives using the uniflow principal but again this type of engine was not adopted by railroads either, apparently due to the costs out-weighing the increased efficiencies obtained (or so I understand).
Seafarer
One of the best coverages of valve gear design was in the Bulletins of the Railway & Locomotive Historical Society back in the days when it was housed in the Baker Library. There were a lot of issues of the bulletin before that subject was exhausted. All steam engines of any application (not just railroads) resulted in serious interest in valve gear.
More of those indirect-Walsch-in-forward-gear engines than I thought. How about a Toledo, Angola and Western 0-6-0? Other switchers too-- L&NE and CNJ 0-8-0, NH 3-cyl 0-8-0, C&O 0-10-0.
The PRR 2-8+8-0 and 2-8+8-2 were indirect; PRR's CC2 0-8+8-0 had indirect on the rear eng only, as did the first order of C&O 2-8+8-2s.
nobullchitbids What follows in others replies is a pretty thorough discussion. Little left to add, but so far no one has mentioned: 1. Unlike diesels, steam locomotives usually were designed for the specific on-site task at hand. What gear was best for one was not necessarily best for others. All had to address the basic problem, which was to set the valves in the cylinder to regulate the cutoff of the steam. 2. No one so far has mentioned the effect that superheating had on the problem. I've always been told that Stephenson only could be used with slide valves, which could not be used once superheating became the standard practice. This explains why Walschaerts took over at the turn of the last century even though it was invented half a century earlier. 3. Why a road preferred one to another depended on several factors. Union Pacific, with its long runs typical of transcontinental bridge routes, liked Walschaerts because it was easy to maintain and easy to teach. And, as UP accumulated more engines, there also was the benefit for having to store fewer kinds of replacement parts. Remember: It was maintenance, not performance which killed the steam locomotive. There were no diesels at the time which could outperform an NKP S-3 or a Fetters 4-8-4. 4. U.P. did experiment with the clever Young gear, which used the motion of the opposite side of the locomotive to set the timing and valve travel. This was sold by the companies as a maintenance improvement; but, in the end, U.P. changed its Young engines (by then mostly 4-8-2s and 2-10-2s) to Walschaerts, again because of the parts-inventory problem and to effect standardization. 5. Of course, U.P. also is famous for use of the Gresley gear, which is needed for three-cylinder engines like the 4-12-2s. UP experimented with substituting a double-Walschaerts on the engineman's side (the "bald-faced" Nines) in an effort to obtain more standardization, but apparently this was not completely successful since not all of the Nines were converted. 6. The Baker is a perfectly good gear, very heavy, so one sees it a lot on big engines in the East. It was more complex and came along much later, so again roads very familiar with Walschaerts and not wanting to accumulate a lot of parts from different systems tended to be averse to using it. Avoiding royalties also may have been a factor, but remember that royalties are only part of the bottom line, which was the critical factor when it came to purchasing new engines. I am told that Baker gear, for being so massive, tends to hold its setting better, but that's just what I'm told. 7. I confess to not being that familiar with Southern gear. It was a latecomer, which apparently hindered its adoption; however, it was billed as an efficiency improvement over the Walschaerts. In addition to the sources cited by others, infra, valve gears are discussed in Model Railroader's MR Cyclopedia, vol. 1 (Steam Locomotives) and a neat little book all steamers should have: Steam Locomotive Maintenance. (I don't have it at hand at this time and don't recall the author.)
What follows in others replies is a pretty thorough discussion. Little left to add, but so far no one has mentioned:
1. Unlike diesels, steam locomotives usually were designed for the specific on-site task at hand. What gear was best for one was not necessarily best for others. All had to address the basic problem, which was to set the valves in the cylinder to regulate the cutoff of the steam.
2. No one so far has mentioned the effect that superheating had on the problem. I've always been told that Stephenson only could be used with slide valves, which could not be used once superheating became the standard practice. This explains why Walschaerts took over at the turn of the last century even though it was invented half a century earlier.
3. Why a road preferred one to another depended on several factors. Union Pacific, with its long runs typical of transcontinental bridge routes, liked Walschaerts because it was easy to maintain and easy to teach. And, as UP accumulated more engines, there also was the benefit for having to store fewer kinds of replacement parts. Remember: It was maintenance, not performance which killed the steam locomotive. There were no diesels at the time which could outperform an NKP S-3 or a Fetters 4-8-4.
4. U.P. did experiment with the clever Young gear, which used the motion of the opposite side of the locomotive to set the timing and valve travel. This was sold by the companies as a maintenance improvement; but, in the end, U.P. changed its Young engines (by then mostly 4-8-2s and 2-10-2s) to Walschaerts, again because of the parts-inventory problem and to effect standardization.
5. Of course, U.P. also is famous for use of the Gresley gear, which is needed for three-cylinder engines like the 4-12-2s. UP experimented with substituting a double-Walschaerts on the engineman's side (the "bald-faced" Nines) in an effort to obtain more standardization, but apparently this was not completely successful since not all of the Nines were converted.
6. The Baker is a perfectly good gear, very heavy, so one sees it a lot on big engines in the East. It was more complex and came along much later, so again roads very familiar with Walschaerts and not wanting to accumulate a lot of parts from different systems tended to be averse to using it. Avoiding royalties also may have been a factor, but remember that royalties are only part of the bottom line, which was the critical factor when it came to purchasing new engines. I am told that Baker gear, for being so massive, tends to hold its setting better, but that's just what I'm told.
7. I confess to not being that familiar with Southern gear. It was a latecomer, which apparently hindered its adoption; however, it was billed as an efficiency improvement over the Walschaerts.
In addition to the sources cited by others, infra, valve gears are discussed in Model Railroader's MR Cyclopedia, vol. 1 (Steam Locomotives) and a neat little book all steamers should have: Steam Locomotive Maintenance. (I don't have it at hand at this time and don't recall the author.)
I'm no expert, but I thought I might add a couple of things I think I remember reading.
#2. One reason for the shift away from Stephenson gear was that as boilers got bigger there was less space on the axles to work with. I think there were cases where the eccentrics were mounted outside the wheels like the Walschaerts, but they were probably too intricate and vulnerable with the double eccentrics hanging out there.
#6. I think I remember that one reason N&W liked the Baker gear was that they could provide a longer travel, though I don't know why other types couldn't be modified to do so.
_____________
"A stranger's just a friend you ain't met yet." --- Dave Gardner
friend611For your information, animation of Baker valve gear on N&W J 4-8-4: https://www.youtube.com/watch?v=FX3WJW-nlh4&feature=youtube_gdata_player
On the same youtube page is this animation of the Baker valve gear which I like:
https://www.youtube.com/watch?v=GwzUCBMv4tA
Years ago when reading about the Baker gear, I had a hard time visualizing how it worked until I made cardboard cutouts of the parts using eyelets for pivots. For me the hard part was remembering which pivot points were stationary, which were stationary only for a particular valve setting, and which ones moved while running. It works!
BigJim timzdo you have those Train Shed Cyclopedia reprints of the 1922 and 1930 Cycs?No, I don't have any of them. Never even been able to put my hands on one in order to look through to see if it was something that I would want. On another note, if I am not very much mistaken, I think that N&W's Z1 with slide valve LP cylinders and piston valve HP cylinders had different styles of Baker gear on each engine.
timzdo you have those Train Shed Cyclopedia reprints of the 1922 and 1930 Cycs?
On another note, if I am not very much mistaken, I think that N&W's Z1 with slide valve LP cylinders and piston valve HP cylinders had different styles of Baker gear on each engine.
There is no description of the Baker-Pilliod gear in Locomotive Up To Date.
When the D&LW 4-4-0's were rebuilt with Piston valves, where they superheated?
Is the reason slide valves don't work with superheat lubrication?
.
That is odd-- why does the book show indirect-in-forward-gear Walschaerts in Figure 9 is if it were the usual form, and only later mention the disadvantage of that form? But yes, that's what I mean. In Rwy Age (in the 1920s?) someone said indirect-in-forward-gear Walschaerts gave better valve events than the usual direct gear-- would be interesting to see details. Could be true for all I know, but apparently that didn't make up for the disadvantages.
I don't have a scanner-- do you have those Train Shed Cyclopedia reprints of the 1922 and 1930 Cycs? (Don't recall if Gregg did any reprints of the 1927.)
timzWhatever it says, the Cycs have pics of 4-6-2s and a couple of 4-8-2s with inside-admission valves and Walschaerts that's indirect in forward gear (so the eccentric crank is 90 deg ahead of the main crank).
Whatever it says, the Cycs have pics of 4-6-2s and a couple of 4-8-2s with inside-admission valves and Walschaerts that's indirect in forward gear (so the eccentric crank is 90 deg ahead of the main crank).
timz So all agreed inside-admission Walschaerts engines were known to be indirect in forward gear?
So all agreed inside-admission Walschaerts engines were known to be indirect in forward gear?
timzThe same isn't true for Walschaerts-- if you have 1922-1930 Cycs you can probably find pics of Walschaerts engines with inside admission that are indirect in forward gear. (Think it was ALCo that liked that.)
Timz,If you went to the site provided, you did not read down far enough. Try page 32, item number 49 "Inside Admission Valve - Indirect Motion".
The same isn't true for Walschaerts-- if you have 1922-1930 Cycs you can probably find pics of Walschaerts engines with inside admission that are indirect in forward gear. (Think it was ALCo that liked that.)
Deggesty"The Baker valve gear is direct in the forward motion and indirect in the back motion for inside admission, and the opposite for outside admission."
Overmod,Thank you. The Bitter Creek site worked. I had not seen that one in my search.
Overmod, I really thank you a lot. I was able to download the Pillard book and save it.
I certainly make no claim to expertise in the matter of any valve gear, but I wonder if the difference between gear used with inside admission valves and the gear used with outside admission valves is a contributing factor to the difference in understanding how Baker valve gear works. Locomotive Up To Date shows that there is a difference between the two--though it shows a slide valve with the outside admission and a piston valve with the inside admission. "The Baker valve gear is direct in the forward motion and indirect in the back motion for inside admission, and the opposite for outside admission." (p.295).
BigJim Can you pass a place along that works? I found out that only two of my downloads from years ago still work and both of them are Baker. An email to Mr. Dockstader was returned and his downloads won't download for me.
Can you pass a place along that works? I found out that only two of my downloads from years ago still work and both of them are Baker. An email to Mr. Dockstader was returned and his downloads won't download for me.
I'm sorry to have to tell you that Charlie died near the end of 2011.
Does the Bitter Creek Western archive site not work?
I also recommend Don Ashton's Web site which also has links to Hall's and Wallace's programs.
These were all 'live' the last time I downloaded files to a Windows system, and they should still be good. Let me know if not.
OvermodMany a happy hour I have spent tweaking parameters in the DOS version, and then the Windows port, of Charlie's software. Thankfully, it is now available for download in several 'permanent' places.
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