Overmod,That is a very good picture and it only supports the fact that the computer animation is correct. As I said, you need to look at the interactive animation where you can change the gear from forward to reverse. I believe Mr. Paul and others are looking at the animation wrong and that is crux of this discussion.
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BigJimThat is a very good picture and it only supports the fact that the computer animation is correct.
Not to me, it doesn't. Look at fig. 16 in the ICS reference, particularly with respect to pins E and the location of pin F. (Fig. 21A shows the relationship between the gear connecting rod and the 'radius bars' a bit more clearly.) Now look at the section regarding the movement of parts at the reverse yoke (sec. 31) and particularly the arcs drawn in Fig. 33.
No part of the reverse yoke oscillates with the gear connecting rod. As you move the yoke over from forward to reverse position, the radius bars swing independently, with pin F, the fulcrum of the gear connecting rod, moving in an arc at the bottom of the 'swing link' arrangement. Anything that purports to show these links connected to the bell crank, or oscillating fully and directly with the movement of the eccentric, is simply wrong, no matter whether it is interactive or not.
The portion of the valve motion that is of interest is that proceeding from the eccentric rod through the gear connecting rod (pivoted at its center) to the bell crank. What would be nice to have at this point would be one of those 'apprentice models' with all the parts of the gear modeled to scale, and a crank to turn the arrangement and show positions of the components and arcs at the joints for different points on a driver rotation for different degrees of reverse-yoke angle. This would certainly show something different from what is on the steamlocomotive.com site.
I doubt that Charlie Dockstader got this wrong in the original, but without access to a Windows computer I can't pull up the program to see. Can somebody prepare an animated view from his program and provide it here?
Big Jim: Whether you or Paul are correct is beside one point: Paul has remained thoroughly polite in this discussion. The Forum would benefit if everyone did so. Please don't use words like baloney and troll in the future. We all have respect for your vast hands-on railroad experience, and you do not need to belittle anyone who disagrees with you for us to retain that respect. Please keep the conversation polite. Thanks!
OvermodNo part of the reverse yoke oscillates with the gear connecting rod. As you move the yoke over from forward to reverse position, the radius bars swing independently, with pin F, the fulcrum of the gear connecting rod, moving in an arc at the bottom of the 'swing link' arrangement. Anything that purports to show these links connected to the bell crank, or oscillating fully and directly with the movement of the eccentric, is simply wrong, no matter whether it is interactive or not.
The portion of the valve motion that is of interest is that proceeding from the eccentric rod through the gear connecting rod (pivoted at its center) to the bell crank.
Going back to the linked web site animation, the Gear Connecting Rod is shown in the shape of a backward S "Zig-Zag" with three pivot points. The bottom point connects to the eccentric crank. The top point connects to the bell crank. The middle point connects to the bottom of the radius bars. From this mid-point in the GCR, the radius bar extends up to be connected to the reverse yolk.
Dave,Go back to my first post. The "baloney" part stems from Paul's misconception that the Baker valve gear was a "Minority" valve gear, when in fact it was used by many locomotives. Please read at the bottom of page 9: http://www.railarchive.net/bakervalve/parts_09.htm and the top of page 10: http://www.railarchive.net/bakervalve/parts_10.htm No small number, eh?By the end of steam, Baker and Walschaerts were the majority of valve gears used on mainline locomotives. Also his statement that "no one seems to understand how it works geometrically let alone how to make adjustments to its proportions to get different valve gear "events" is shown to be completely false by the book, that I linked to. That book was written by steam people (who knew and understood exactly what they were writing about) for the education of steam people, firemen and engineers (to name two) wanting to better understand the machines in their charge. It is but one volume of the vast number of volumes published by the International Correspondence School for the education of railroad employees of the day. These books are, in my opinion, the best books available for anyone who is a student of the steam locomotive. The books themselves are hard to come by. However, ICS has scanned many of them for which we should be grateful. They are available online at their web site, which is where my link came from.
I will also say that I never questioned "Prof. Milenkovic's understanding of machine geometry".
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.)
Overmod,This the best I can do. I think this screen shot shows things a little clearer. Also note that in the program you can change all sorts of parameters, such as speed, amount of cut-off, visual steam, sound and a lot of variable geometry.
OvermodIn the animated diagram on steamlocomotive.com, as near as I can make out, the swing link depends from the arm of the bell crank, and the top of the gear connecting rod (which ought to attach to the bell crank) is on a fixed pivot in the reverse yoke.
Look closer at the colors-- the gear connecting rod is magenta, top and bottom, and the radius bars are brownish. On the diagram they form a sort of Y, and you've misidentified the legs of the Y.
BigJim Overmod,This the best I can do...
Overmod,This the best I can do...
Now, this drawing shows the arrangement EXACTLY (although I suspect the gear connecting rod as drawn has been moved to the right a bit relative to the reverse yoke in order to show the arrangement of the parts better). THANK YOU, JIM!
Note when I said (pivoted at the center) I meant as a fulcrum. Otherwise the motion of the eccentric at the bottom of the gear connecting rod would not create the proper motion at the top pin joint to the bell crank.
Many 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.
I asked this question over on RyPN, and I am delighted to note that someone there has scanned the entire Baker catalogue #3 from 1946, and provided it here (PDF download). I encourage anyone who appreciates his doing this to go to RyPN and thank him.
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.
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
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.
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).
Johnny
Overmod, I really thank you a lot. I was able to download the Pillard book and save it.
Overmod,Thank you. The Bitter Creek site worked. I had not seen that one in my search.
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."
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.)
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".
So all agreed inside-admission Walschaerts engines were known to be indirect in forward gear?
timz So all agreed inside-admission Walschaerts engines were known to be indirect in forward gear?
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).
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).
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.)
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.
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?
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.
There is no description of the Baker-Pilliod gear in Locomotive Up To Date.
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!
_____________
"A stranger's just a friend you ain't met yet." --- Dave Gardner
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.)
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.
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