(1) For particullary long articulated steam locomotives, like the big boy, was there ever a risk that the overhang in curves might be enough to collide with an oncoming train? I know that sounds like an absurd question, but I saw a recent picture of a Virginian Articulated Steam locomotive overhanging a curve in a double track section. I was surprised how close the boiler was to the other track and though that a slightly larger locomotive might do the trick.
Is there a standard for how far apart two tracks must be from one another--especially around curves? Has this changed after the retirement of most articulated steam locomotives?
(2) Shays are renown for their ability to carry loads up hill with questionable track. For instance, it has been said that a shay can handle a 6% grade or better. I don't think a Big Boy could handle the same grade. Does this mean that a shay could pull more tonnage on level ground than a Big Boy?Of course, I realize the difference is, the Big Boy could take the same load and run it at 45 mph, which the shay could not do. But, it is kind of humourous to think that the little shay could out pull the Golliath Big Boy.
Gabe
after the Big Boys were introduced, numerous curves on the double track Wahsatch grade were realigned. I think that answers question 1.
dd
Good question on the Shay. I never though about that.
Shays can pull large loads (20+ loaded 40'-50' log cars) on level ground, depending on what type of Shay you have. The larger the engine (tonnage) the more it could pull. A big boy can pull 150 loaded 40-55' coal cars on level ground. The differance here is proportion. A larger engine, with a larger boiler, superheated (although Shay 6 at Cass has a superheater) can pull a large load, while a smaller Shay is smaller, so it pulls a equally smaller load.
Now, the Shay is a geared locomotive. I can't explain it, but Wikipedia did a pretty good job.
Many applications required a low speed locomotive with ample starting tractive effort; industrial use, mines and quarries and logging operations, steeply graded lines and the like, especially when the track is cheaply built and not suited to high speeds anyway. Unfortunately, although the tradeoff of speed versus torque can be adjusted in favour of torque and tractive effort by reducing the size of the driving wheels, there is a practical limit below which this cannot be done without making the piston stroke too short on a directly driven locomotive.
The solution is to separate the crank from the wheels, firstly allowing for a reasonable piston stroke and crank radius without requiring larger than desired driving wheels, and secondly allowing for reduction in rotational speed via gearing. Such a locomotive is a geared locomotive. Most were and are still single speed, but some did employ a variable ratio gearbox and multiple ratios
Don't know if it helps, but it does give some information....
Phil
It's all in the speed. You can probably move a 100 car train (given sufficient traction) with a 5 HP Briggs & Stratton - just not very fast.
While I read somewhere that 4% was pretty much the limit for normal adhesion locomotives, if a Shay can pull up a 6% grade, so can an articulated. How much is a different story.
One of the Shay's most important attributes was (is) its sure-footedness. You can run one over track that would make most people wince, hence its popularity in logging. On the other hand, a Big Boy can move that 100+ cars over good line at 60+ without breaking a sweat.
Larry Resident Microferroequinologist (at least at my house) Everyone goes home; Safety begins with you My Opinion. Standard Disclaimers Apply. No Expiration Date Come ride the rails with me! There's one thing about humility - the moment you think you've got it, you've lost it...
gabe wrote: (1) For particullary long articulated steam locomotives, like the big boy, was there ever a risk that the overhang in curves might be enough to collide with an oncoming train? I know that sounds like an absurd question, but I saw a recent picture of a Virginian Articulated Steam locomotive overhanging a curve in a double track section. I was surprised how close the boiler was to the other track and though that a slightly larger locomotive might do the trick.Is there a standard for how far apart two tracks must be from one another--especially around curves? Has this changed after the retirement of most articulated steam locomotives?(2) Shays are renown for their ability to carry loads up hill with questionable track. For instance, it has been said that a shay can handle a 6% grade or better. I don't think a Big Boy could handle the same grade. Does this mean that a shay could pull more tonnage on level ground than a Big Boy?Of course, I realize the difference is, the Big Boy could take the same load and run it at 45 mph, which the shay could not do. But, it is kind of humourous to think that the little shay could out pull the Golliath Big Boy.Gabe
1. If a BB was on a curve that sharp it would have derailed well before the boiler got into a danger area for a collision. BBs did not have a great range of swing, they werent desinged to, thats why they were limited in their rangings to a specific area.
2. Ton for ton, the 3 truck Shay could easily outpull a BB. Now I'm saying that a 100ton Shay (the largest made, Cass RR) could outpull the BB in a side by side matchup (although that would be a hellova sight!) PROPORTIONALLY - The Shay had a huge advantage which its direct drive via the geared shafts, it gave a tremendous amount of torque via the three drive cylinders and the trucked drive gave a tremendous amount of tractive effort even over the famed BB.
Its kinda an unfair comparison, BB were designed for fast freight service over Shermans Hill and could meve a 100 car train at 70mph. A Shay was designed to dragging heavy loads over uneven trackage and up steep grades, its top speed was rarely over 15mph.
The Unitah RRs 2-6-6-2 Articulated locos had perhads the greatest "swing" of any articulated locos ever made, open the link and look at the image on the cover of the second book, this shows that swing pretty well.
http://www.heimburgerhouse.com/railfan_books/uintah_railway_gilsonite.htm
Have fun with your trains
Fortunately the Unitah did not have to deal with double track on those 66 degree curves -- there wasn't room. The few passing sidings on the grade were in straighter track portions.
.....Shouldn't the main point of the strength of the Shay be it's GEARING.... The power train of Shay's with their 3 cylinders {and they for the most part were smaller in diameter}, than regular piston /rod driven directly to the dive wheels of ordinary steam engines.
Mechanical gearing in Shays were "deep" in ratio hence developed much torque to get a load moving and it's hill climbing ability....but payed for it by having a very slow operating road speed. Of course this was not an overriding problem since they were used on rough track of logging operations for the most part.
Quentin
Modelcar wrote: .....Shouldn't the main point of the strength of the Shay be it's GEARING.... The power train of Shay's with their 3 cylinders {and they for the most part were smaller in diameter}, than regular piston /rod driven directly to the dive wheels of ordinary steam engines.Mechanical gearing in Shays were "deep" in ratio hence developed much torque to get a load moving and it's hill climbing ability....but payed for it by having a very slow operating road speed. Of course this was not an overriding problem since they were used on rough track of logging operations for the most part.
Exactly! A greater percentage of mechanical force gets transfered directly to the wheels via the gearing. Also the weight distribution for tractive effort on a Shay was more efficient.
To use an automotive comparison, its like having two cars but in each the transmission is only stuck in one gear. The Chevro-Shay only has first gear which gives it a great deal of starting and pulling power but severly limits is top speed, And the Ford Big Boy only has 3rd gear but has a bigger HP engine, it takes much more care to get a load going but once moving can move at a much faster top speed relative to the Chevro-Shay.
Question 1 has been answered, and I won't even bother with question 2 since comparing one of the largest reciprocating steamers ever built to a Shay locomotive is too apples and oranges IMHO.
However, I would like to clear up some of the misconceptions and information that is lacking here regarding the Shay. Shays are capable of ascending grades up to about 15%. Every day on the Cass Scenic Railroad these engines ascend a grade of 11% above the upper switchback. The largest Shay that ever existed was GC&E 12, which as rebuilt into a 4 truck Class D weighed a little under 200 tons. Were it as large as the largest of articulateds (instead of less than half their size) it could have definitely pulled twice the train on level ground, couplers permitting. Class I's using the Shay were the WM, C&O, KCS, UP (owned one from an absorbed branch line, I believe), and a couple of others that I can't think of right now. The Shay was largely a failure in Class I service due to it's slow speed, with only the WM keeping any until the end of steam, for use on some of their steeper coal branches. Shays are capable of traversing rough tracks, even tracks that are somewhat unevenly gauged, with little risk of derailing. Some of the lighter Shays built in the late 19th century were even designed to run on wooden rails, providing lumber companies an alternative to laying steel rails on lines that only lasted as long as the timber in the area.
Lost World wrote: Question 1 has been answered, and I won't even bother with question 2 since comparing one of the largest reciprocating steamers ever built to a Shay locomotive is too apples and oranges IMHO.However, I would like to clear up some of the misconceptions and information that is lacking here regarding the Shay. Shays are capable of ascending grades up to about 15%. Every day on the Cass Scenic Railroad these engines ascend a grade of 11% above the upper switchback. The largest Shay that ever existed was GC&E 12, which as rebuilt into a 4 truck Class D weighed a little under 200 tons. Were it as large as the largest of articulateds (instead of less than half their size) it could have definitely pulled twice the train on level ground, couplers permitting. Class I's using the Shay were the WM, C&O, KCS, UP (owned one from an absorbed branch line, I believe), and a couple of others that I can't think of right now. The Shay was largely a failure in Class I service due to it's slow speed, with only the WM keeping any until the end of steam, for use on some of their steeper coal branches. Shays are capable of traversing rough tracks, even tracks that are somewhat unevenly gauged, with little risk of derailing. Some of the lighter Shays built in the late 19th century were even designed to run on wooden rails, providing lumber companies an alternative to laying steel rails on lines that only lasted as long as the timber in the area.
The contrast of the two is exactly why I picked each respective locomotive--so as to understand better exactly where the tractive effort of a shay comes from.
I thought of several lines to match the disdain that you impolitely expressed in answering my question, but it simply isn't worth it.
...I might add one additional item: Regarding tractive effort of the Shays....Each set of wheels in a "truck" assembly was powered....and the complete engine was supported by these "trucks"...Hence all the locomotive weight was on the powered wheels....Not so on most conventional steamers.
vsmith wrote: Exactly! A greater percentage of mechanical force gets transfered directly to the wheels via the gearing. Also the weight distribution for tractive effort on a Shay was more efficient.To use an automotive comparison, its like having two cars but in each the transmission is only stuck in one gear. The Chevro-Shay only has first gear which gives it a great deal of starting and pulling power but severly limits is top speed, And the Ford Big Boy only has 3rd gear but has a bigger HP engine, it takes much more care to get a load going but once moving can move at a much faster top speed relative to the Chevro-Shay.
I can't claim any expertise in engineering, but in all stream engines, including the turbine, all drivers got all available power "directly" after friction losses, whether Shays that were geared or rod-driven conventional steamers. Since in both cases, rod and gear, the drivers were physically (mechanically) coupled, it is by definition direct drive from cylinders, so they got everything the cylinders could transfer to main rods or to gear-driven shafts.
In fact, since the Shays had 90 degree angles on their drives (piston shafts to drive shafts via cranks), there is a loss, from an engineering and physics point of view, that places the conventional steamers at an advantage, all things being equal. This was explained in my motorcycling magazines way back when I drove them and read the mags. Chain drives are more efficient because all the rotating shafts are linked by a chain, that is, they all rotated in parallel with minimal loss of efficiency. Not so when they introduced shaft drives a la Gold Wing and other models that emerged in the 70's. The tech types were quick to point out that they were not quite as efficient at getting power to the rear wheel. So, the Shay, with its 90 deg gearing such as you would find in a rear wheel drive motorcycle or a car, is not as efficient as drive rods that rotate parallel to their drivers.
The advantage is in the torque. The Shays had gears on the driven wheels that were somewhat closer in effective diameter to the gears at the drive shafts near the cylinders. On a conventional steamer, the side rod is well within the diameter of the tires on the drivers, the diameters that count for computing ratios, so they did not have the power to circumference ratios that the Shays enjoyed. When you look at conventional steam switchers that are logging engines, such as the tank engines, though, you can see that the main rod pin is much closer to the rim of the tire, relatively to that of the Big Boy. More torque = more rotation force = greater ability to start a train given traction on the rails.
There is probably an engineering advantage to the three cyinders on the one shaft on the Shay, too, but I don't have the background to explain it...I'll leave it to someone else.
This is perhaps my flawed understanding, or at least limited, but I think you were incorrect to state what I hi-lited in orange, Vern. Every loco gets a full percentage of the available force impacted at the cylinders, it is just where it is applied, or the leverage/mechanical advantage that matters.
-Crandell
If a Shay had the same starting tractive effort as a Big Boy (no Shay ever came close!) it could START the same train. But, if you put a Shay on one track and a Big Boy on a second, parallel track, the Shay would max out on speed just about the time the Big Boy's engineer was beginning to work his reverse lever to adjust the cutoff (whereupon the Big Boy would first walk and then run away and disappear over the horizon.)
Shays, because of their gearing and low drivers, were limited to speeds any self-respecting pickup can exceed in first gear. Trying to push the speed beyond the safe limit would have scattered engine parts all over the county.
Comparing a Shay to a Big Boy is sort of like comparing a forklift to a Kenworth tractor (10 wheel highway variety.) The forklift can move the Kenworth's (semi)trailer - just not very fast.
Chuck
vsmith wrote: 1. If a BB was on a curve that sharp it would have derailed well before the boiler got into a danger area for a collision. BBs did not have a great range of swing, they werent desinged to, thats why they were limited in their rangings to a specific area.
spokyone wrote: vsmith wrote: 1. If a BB was on a curve that sharp it would have derailed well before the boiler got into a danger area for a collision. BBs did not have a great range of swing, they werent desinged to, thats why they were limited in their rangings to a specific area.This brings up another question I have wondered about Big Boy. How did they negotiate the curves and turnouts when they were delivered from the factory in New York?
They were air lifted.
dldance wrote:after the Big Boys were introduced, numerous curves on the double track Wahsatch grade were realigned. I think that answers question 1.dd
A while back (after UP's 4-6-6-4 went back in service) Trains or R&R did an article on it whre they asked someone at UP if a BigBoy would ever be brought back to steam. His reply was there would be too many clearance issues to deal with to make it worth their while.
Great question and a lot of great responses.
As for the over hang on curves.
I built a overhead double track "G" gauge layout in my front room. It has rod hangers holding up both sides of the roadbed.
I originally build it to fit Aristo heavy height passenger cars around the curves..
I purchased MTH's pacific. It ran both tracks. When I placed MTH's Northern on the inside track. I had to move the outside track out slightly. The engine rubbed the passenger cars centers.
Then I purchased MTH's Challenger and I could not run it on the outside track. I also had to move the outside track to clear the passenger cars on the outside track to clear the over hang of the Challenger on the inside track. The challenger would not clear the hangers on the outside track.
When I purchased MTH's Big boy. I had to extend out all the outside hangers 2 inches and move the outside track for clearance.
I am still playing with everything to get all the clearances correct.
I have a book published 30 years ago. It states when U.P. finished designing the Big Boy. It immediately started to realine all the curves. It also had to rebuild all the bridges and tunnels where the engines were destined to run.
U.P. also had the same problem when I made its "DD" designed diesels.
spikejones52002 wrote: I have a book published 30 years ago. It states when U.P. finished designing the Big Boy. It immediately started to realine all the curves. It also had to rebuild all the bridges and tunnels where the engines were destined to run.
I have no specific knowledge of what was done, but railroads have procedures for moving oversized loads. The route was carefully planned, meets and passes were located in places without interference possibilities, and I would expect that a geometry car was included in at least one delivery.
There is a large difference between a delivery - which is a one time event - and normal operation. UP was planning for normal operation - thus the realignment work. All of the delivering railroads only needed to plan for a few trains making the deliveries.
Even today, delivering locomotives is not the same as just another car in the train. I saw the 2nd Utah Frontrunner locomotive being delivered last week. It was carefully located in the train about 10 cars from the end. The 1st Frontrunner locomotive was delivered with flat spots on new wheelsets. So even in the 400 miles from Boise to SLC UP had a problem with that delivery.
Gabe - you might spend some time (as if you have any) studying the Unitah RR. It is one railroad that used both articulateds and Shays in the same service - The climb from Mack, Colorado to Baxter pass had both 7.5% grades and 66 degree curves.
someone back there (forget who, sorry...) almost nailed the Shay's big advantage: the trucks. The extreme flexibility which the trucks gave the engine meant that not only were all wheels driven, but more important all wheels (and therefore all axles) carried very nearly exactly equal weight, even on very rough track. I honestly doubt that a Shay could out-pull an all wheels coupled regular engine (say an 0-8-0) on really good track, pound for pound. But give that track much irregularity, oh yes!
One might be inclined to note that a B-B diesel or electric has exactly the same advantage, except that if it does not have wheel slip control it can slip an axle (a Shay can't -- sort of steam engine posi-traction, if you like).
....Believe I'm guilty of talking of the "trucks" and their work and capabilities.....Taking full engine load and powered, etc....
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