Overmod... Keep in mind that most of the 'trouble' of higher pressure is not in the pressure in the convection shell at all. There were 'locomotive-type' boilers in oilfield service that routinely (and reasonably safely) ran 500psi for extended time. The two things that caused issues were the staybolted construction of large-area water legs, and thermal cycling of diffrent parts of the boiler. B&O reasonably happily got 350psi out of the Emerson watertube firebox, although I don't think they had an engine that could make proper use out of that steam pressure with single expansion.
Keep in mind that most of the 'trouble' of higher pressure is not in the pressure in the convection shell at all. There were 'locomotive-type' boilers in oilfield service that routinely (and reasonably safely) ran 500psi for extended time. The two things that caused issues were the staybolted construction of large-area water legs, and thermal cycling of diffrent parts of the boiler. B&O reasonably happily got 350psi out of the Emerson watertube firebox, although I don't think they had an engine that could make proper use out of that steam pressure with single expansion.
Feature that the biggest difference is that one is stationary and the other exists in a continual state of railroad beating and banging - start/stop/coupling/slack action.
Never too old to have a happy childhood!
BaltACDFeature that the biggest difference is that one is stationary and the other exists in a continual state of railroad beating and banging - start/stop/coupling/slack action.
A far more important difference is not the banging and bumping, but the starting and stopping and standing that characterize most real-world railroad service. One apparent assumption of Woodard's in designing early Super-Power fireboxes was that both the radiant heat distribution and the heat uptake would be relatively continuous -- the same assumption Porta made for the Dona Cristina 2-10-2s and his 'cyclonic' combustion boiler, and PRR made when they designed the boiler and draft system for the S2 turbine. As we know, that is not even a particularly good working assumption.
The ability of a 'standard' riveted convection section to handle expansion and contraction is a much more important concern than vibration and road shock (at least in my opinion). My understanding of the 'waist seam' leakage on the Q2s was that the boiler was overconstrained against expansion and swelling, not that there was mechanical shock transferred at the rear cylinder saddle.
It is not there, but in the sheeted structure in the firebox, that the greatest issues with changing firing conditions show up. I confess I was surprised to learn that 500psi wagon-top stationary boilers were commonplace in the oilfields, and certainly a lack of vibration would contribute to their suitability, but I do not know how continuous their load and firing would have been -- they would have been oil-fired, most probably, and that is the most strenuous kind of firing for a Stephenson boiler unless very, very carefully designed and regulated.
timz What none of us knows anything about is what "unsatisfactory" means -- how much more does a 300-psi boiler cost, considering everything? If a 300-psi engine performs better, is it worth the cost? Apparently some RRs thought so, some of the time.
What none of us knows anything about is what "unsatisfactory" means -- how much more does a 300-psi boiler cost, considering everything? If a 300-psi engine performs better, is it worth the cost? Apparently some RRs thought so, some of the time.
Well, can't we figure out what unsatisfactory means?
In this day and age we have unprecedented access to so much information instantly and freely, and a lot more for relatively low cost, that I think that we can come up with these sort of answers.
With regards to the boilers, in this case judging by the article and what is now known about those alloy boilers, boiler over 250 psi being 'unsatisfactory' probably had less to do with the pressure than it did the material (as the N&W and UP experience with 300 PSI non alloy boilers was issue free in comparison to the great boiler scrapping that other railroads had to do of their alloy boilers).
And as far as if 300 PSI boilers were worth it, all you have to do is look at repeat orders. If a railroad thought that a design was worth ordering again with no modification, it was worth it to them. Therefore the UP thought 300 PSI boilers were worth it when they did a repeat order of the Big Boys, and the N&W thought the A's and Y6's were worth it when they did their repeat orders. And that is before you look into the specific aims of a engine and evaluate if it met those goals. Returning to Big Boy, the goal was to eliminate double heading over the Wasatch. They did that and increased the allowable tonnage, so it is a success.
Finally, if your thought is that we don't know what is acceptable in locomotive design or why railroads did what they did, and we can't calculate performance or determine why choices were made the way they were, then what's the point of talking about this stuff? At that point trains become just big smoky movey things that are old and loud, as opposed to things that can be quantified and understood.
Conductor_CarlI think that we can come up with these sort of answers.
Conductor_Carl as far as if 300 PSI boilers were worth it ...
Conductor_Carlif your thought is that ... we can't calculate performance or determine why choices were made the way they were, then what's the point of talking about this stuff?
And to not suppose we know which engine was better, when we know nothing about what they cost to operate. You'd think that would be obvious to everyone, but apparently it's not obvious enough.
timz In that case: how much coal did an N&W A with 275 psi burn, pulling 11000 tons from Portsmouth to Columbus, and how much coal did an A with 300 psi burn pulling 12000 tons? How much did the coal cost, and how much more did the 300-psi engine cost in repairs?
In that case: how much coal did an N&W A with 275 psi burn, pulling 11000 tons from Portsmouth to Columbus, and how much coal did an A with 300 psi burn pulling 12000 tons? How much did the coal cost, and how much more did the 300-psi engine cost in repairs?
a mostly different question that what makes a boiler above 250 PSI unsatisfactory and one that does not need to be answered. If your point is that we do not and cannot know as much as the railroads back in the day did then its pretty clear that the N&W (with all the data they had from the 275 PSI A in terms of consumption, maintenance and over the road performance) determined that the 300 PSI engine was superior seeing as how they uprated all of the engines and built every new engine after the first 300 PSI batch in 1943 to the same pressure.
Conductor_CarlI asked why the N&W would keep the A at 275 PSI if in the initial tests they ran them at 300, per BigJims theory based on the high starting pull recorded.
Conductor_Carl"... you can't actually determine if it was good or not."
timz Conductor_Carl "... you can't actually determine if it was good or not." Exactly -- you can't "determine" it. And since you can't, it's silly to sneer at 1940 railroaders for not doing what looks smart to you. (Especially when what looks smart to you is an engine with lots more drivers.)
Conductor_Carl "... you can't actually determine if it was good or not."
Exactly -- you can't "determine" it. And since you can't, it's silly to sneer at 1940 railroaders for not doing what looks smart to you. (Especially when what looks smart to you is an engine with lots more drivers.)
Interesting. So are you able to say if, for example, Big Boy was good or not. Or the PRR Q2? Or the ACL R-1? or any locomotive really?
A bit of the interest of history is looking at a event and proposing what you consider to be plausable counterfactuals, and this allows you to investigate those events and get a better understanding of what happened in actuality (for example, the Battle of Midway and how that would go differently if one guy decided to turn his plane around instead of keep looking for the japanese, a plausable counterfactual). In train terms, this translates into looking at what a railroad set as its design criteria and what it intends to accomplish, what their design could and did accomplish, and then making a judgement on if their criteria was well matched to their goals and if their design was well suited to the goals and criteria. Sometimes the criteria is bad (IMO the PRR Q2), sometimes the criteria is good but the design has issues (IMO the ACL R-1), and sometimes you just nail it (Something like the N&W Y6).
As far as that last statement of yours ("what looks smart to you is a engine with lots more drivers") I think you are still talking about my critique of the WM M-2 (which I drew way back). considering that the B&O had EM-1 Yellowstones heading into Cumberland and had a route paralleling the WM's tracks that the M-2 would have been on, you can get a decent comparison between the two and see what had more over the road success. I'm still gathering sources on this but it is a entertaining enough excercise.
Conductor_CarlSo are you able to say if, for example, Big Boy was good or not.
Conductor_Carl ... looking at what a railroad set as its design criteria and what it intends to accomplish, what their design could and did accomplish, and then making a judgement ...
My comment about too-few-drivers referred to the WM 4-6+6-4 (Pennypacker agreed with you about them, by the way) but more to the C&O 2-6+6-6. You weren't around for the forum fights about them. Don't worry, you didn't miss anything. It was all Keystone Kops.
timz I feel kind of silly, repeatedly stating the obvious: if you don't know about costs, you can't judge anything -- you don't have the evidence needed to judge. Why isn't that obvious to you?
I feel kind of silly, repeatedly stating the obvious: if you don't know about costs, you can't judge anything -- you don't have the evidence needed to judge. Why isn't that obvious to you?
Maybe it is as you insinuated repeatedly, and I just kept taking the high road on. I'm just stupid. You convinced me. None of this is worth talking about.
It's worth talking about -- no one said different. We just have to keep in mind how ignorant we are. Too bad so many fans don't do that.
Try this. N&W pulled 10,300-ton coal trains to the Allegheny divide with two 2-8+8-2s, climbing 5+ miles of just under 1%. L&N pulled 8300-ton coal trains up 7 miles of just under 1% Ford to Patio with three 2-8-4s. Who was smarter? Safe bet most fans will vote for N&W. So: should talking ensue? Sure. Will much of the talk be dumb? Sure. Are we worse off after the talking? No.
Supposedly L&N couldn't handle articulateds in its shops, or something like that. Easy to imagine fans sneering at L&N: "Jeez! That's the reason you don't use the right engines? Build a proper shop, fer crissakes!" As usual, the fans think they know something L&N didn't.
Infrastructure did have a lot to do with locomotive choices on some roads.
When UP bought the Big Boys, they installed longer turntables at several critical terminals and had enginehouse stalls extended at several places. They also did some curve work to ensure horizontal clearances on curves.
Not all railroads could afford to do that. So they rolled with the biggest power that fit the railroad.
timz Try this. N&W pulled 10,300-ton coal trains to the Allegheny divide with two 2-8+8-2s, climbing 5+ miles of just under 1%. L&N pulled 8300-ton coal trains up 7 miles of just under 1% Ford to Patio with three 2-8-4s. Who was smarter?
Try this. N&W pulled 10,300-ton coal trains to the Allegheny divide with two 2-8+8-2s, climbing 5+ miles of just under 1%. L&N pulled 8300-ton coal trains up 7 miles of just under 1% Ford to Patio with three 2-8-4s. Who was smarter?
I dont think that I will.
Earlier in this thread I was learning things. I learned about compensated HP. Neat! Q2 testing was posted. Really cool!
What am I learning now? That I dont know anything and it is worthless to try and learn anything new because it is not possible to evaluate if someone made a good choice or not because I will never have as much information as them. Wahoo.
My instinct would have been to look at the L&N, try and determine how often they would haul those sort of trains (many times a day?), try and determine what infrastructure changes would be required to accommodate a more powerful articulated, try and determine if the route favors high tractive effort or high horsepower to color what theoretical engine they could get, try and get comparative costs so I could figure how many M-1's you would lose out on if you replaced part of the order with the hypothetical articulated and capital required to support it, and then see if that makes more sense than just triple heading M-1's. If I did that I would learn all kinds of stuff about the L&N. Their operating practices, their routes, the M-1 and its usage, its infrastructure, and why they made the choice to buy the most expensive berkshire.
But I wouldn't know as much as the L&N did when they were making those decisions, so I would be wrong. and that would take a decent amount of money and time to learn this crap just to get to that wrong conclusion, and it really doesn't matter, so I think I won't bother.
Conductor_CarlMy instinct would have been to ... try and get comparative costs ...
Conductor_CarlWhat am I learning now? That I dont know anything and it is worthless to try and learn anything new ...
He's on the Empire Builder in 1937, in the cab of the 2588.
"We thus arrived at Fort Browning. The station stop lasted 1 min but an additional 2.5 min elapsed before the train was moving again. The start took place on a 1/100 gradient. Heavy trains such as ours were started on mountain gradients by what was known as the 'compression method'. The train was held on the gradient by the air-brake with all the slack stretched out. The reverse lever was placed in full forward gear, the throttle 'cracked' and the air released. The train slowly dropped back about a quarter-turn of the driving wheels and then, as it was brought to a standstill by the compression of the steam in the cylinder, the throttle was pulled wide open and the train started as a unit with all the draft gear stretched and without jerking. To start a 1260-[metric]-ton train on a 1/100 gradient without slipping, with a two-cylinder locomotive having 6 ft 8 in driving wheels, is quite a feat."
He rode a MILW 4-4-2 on a nine-car Hiawatha in 1937
"The locomotive rode remarkably well. At 96 mph I wrote my notes conveniently standing up and not leaning against anything. At 106 mph I took them quite comfortably, sitting down."
The Emmas were 2-8-4s instead of 4-8-4s because of short tables and lack of wye facilities. What would make someone think an articulated -- even one with six-coupled engines -- would be any shorter?
The instructive thing to learn about N&W practice is in Ed King's book on the A (which I regrettably don't have to hand). Study the calculations involved in 15,000T with a single A from Williamson to the Scioto River (Kenova) bridge. There is a picture there of an A arriving with very little coal left in that tender...
timz Conductor_Carl My instinct would have been to ... try and get comparative costs ... Try how? Where would you look?
Conductor_Carl My instinct would have been to ... try and get comparative costs ...
Try how? Where would you look?
The L&N historical society has a book coming out on the M-1. I would hope that it has test data to determine fuel costs, and costs of each order (which I think I can already get). But it probably won't have maintenance costs so I wouldn't be able to compare it to a hypothetical L&N articulated (not to mention costs of updating infrastructure to accommodate said hypothetical articulated) so won't bother trying to find this out.
BigJim Conductor_Carl Well, imma learn you up! https://archive.org/details/sim_railway-age_1936-09-26_101_13/page/435/mode/1up "Riddle me this Batman", according to the article, it lists the starting tractive effort at 104,500 lbs. Yet, the graph shows it to be about 118,000 lbs. Where did this figure come from? Did the N&W possibly turn the screws up to 300 psi on said test?
Conductor_Carl Well, imma learn you up! https://archive.org/details/sim_railway-age_1936-09-26_101_13/page/435/mode/1up
"Riddle me this Batman", according to the article, it lists the starting tractive effort at 104,500 lbs. Yet, the graph shows it to be about 118,000 lbs. Where did this figure come from? Did the N&W possibly turn the screws up to 300 psi on said test?
Great discussion. In my opinion, it's not outside the realm of possibility that an A could develop 6,300hp as the graph shows. I have looked at this before and based on calculated boiler capacity and machinery friction of its 6-coupled configuration that had lower weight on drivers than the 8-coupled articulated Big Boy or the Allegheny 6,300 seems reasonable (although possibly at firing/steaming rates in excess of how the locomotives were used in service).
I have never found the claim from the 1936 Railway Age article that an A could "attain a speed of 64 m.p.h. with a 7,500-ton train" to be remotely believable, unless on a downgrade or with decreasing speed. Using Davis equation estimates, a 7,500 ton train of 85 ton cars would have about 8 lb/ton of resistance, requiring 60,000lbs of DB pull at 64mph. Based on the Railway Age DB pull graph, a single A could develop approximately half that much at 64mph, or a still respectable 5,100 DBHP. Taking the 7,500 tons at 64mph at face value implies over 10,000 DBHP!
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