UP 844 vs N&W J611

GNNPNUT - Thank you for the informative reference. And it clearly describes Bunker C as having a greater energy content vs. bituminous, and rather sizeable (40.0 vs. 23.9). Although not listed, I would bet lignite is pretty close to wood (17.1). So, perhaps Bob LaMessena's thesis that SP&S Challengers had a significant power output increase over NP's Challengers would be borne out. The above data I cited about the oil-burning GN (NP design) Challengers' tepid performance on the Oregon Trunk would be explained in that the OT  had many curves and grades, not anywhere near optimum Challenger operation territory. 

What if you burned wood in the 4449? Suspect you would see a significant performance drop!!

Yeah, I think there's some misunderstanding about fuels and steam locomotive power.

If I can maintain 190 psi in my locomotive on wood, and I can maintain 190 psi in my locomotive using diesel, my locomotive doesn't care one bit how the pressure got to 190. The "power" will be exactly the same.

Now, if we're going to talk "fuel efficiency," that's another discussion altogether.

Not if he could keep the pressure at MAWP!

Yes, at first blush I would think you both are correct about a steam locomotive running at full pressure would be producing full power, period, even if burning wood, garbage, bunker c, or bituminous. But, the Erie Triplex would leave a yard with a train and run out of steam on the road. Yes, too small a grate, etc. Point being, inadequate steam volume. Bob LaMassena's thesis (not mine, mind you, I am just repeating his) is that higher BTU content fuel produces a higher volume of steam, i.e. since horsepower is a measure of work performed in a unit of time, more energy is being converted into steam, hence more work is performed per unit of time.

         Wouldn't it be a pretty safe bet that a Big Boy burning bituminus will out perform a Big Boy burning lignite? Because the bituminus Big Boy will be producing a higher volume of steam per hour. Why would the Northern Pacific use bituminus coal on helper locomotives over Bozeman Pass, if their Rosebud coal would produce equivalent power?

Mark, are forgetting that a steam locomotive is actually a "heat machine"? The TEMPERATURE of the steam (higher pressure increases steam TEMPERATURE) is what does the work, not the volume of the steam. That is why shortening the valve stroke produces MORE power, since the shorter valve stroke uses LESS volume of steam, and allows the flow of steam to stay in the superheater units LONGER, and thus get HOTTER.

As I stated previously, the type of fuel being burned is immaterial to boiler/locomotive PERFORMANCE. Fuel efficiency, however, is a whole different story! Since you asked, you would be amazed at what we have had to burn in 4449 over the last 38 years.

Mark, a steam boiler can only hold so much steam. I'm not sure why you keep referring to "volume." We never talk about "volume" in the cab. We do, however, talk about pressure.

It's that pressure we use to move a train. How that pressure was created makes absolutely ZERO difference--as long as I can keep it up. Changing fuel will not allow my locomotive any more "volume." The boiler is a fixed space. When steam leaves the boiler to go to the cylinders, that frees up space for more water to turn into steam; however, that space is still fixed and limited.

Fuel efficiencey is another matter. Yes, I *might* be able to fire my engine on cardboard. But I would need MASSIVE amounts of it, throwing it in the firebox at such a rate that I would have no time to pay attention to anything else. We're talking tons and tons of the stuff. Not efficient.

Quite simply,the firebox wasn't designed to burn cardboard--it's too small (see your triplex example, above). If the firebox was built maybe ten times larger (keeping the boiler the same) it *might* fire better on cardboard.

However, when I use oil, the boiler can be kept at MAWP relatively easily. If I plan the trip correctly, I can have the pressure exactly where I want it, when I want it, and sit back and enjoy the trip for a bit.

Oh...and "Bob LaMassena's thesis?" I've never heard of the guy. Googling him informed me he was a photographer; wrote a couple railfan books. Not sure how much practical or even theoretical experience he had with running actual steam locomotives.

If I had to choose what he wrote vs. what Hot Water writes concerning the practical operation of steam locomotives, I think I know on which side of the fence I would fall.

Just sayin.'

My popcorn machine doesn't care whether it's wood, peat, lignite, bituminous, anthracite, Bunker C, No. 6, JP4, or wadded up newspaper !  This thread just keeps getting better all the time !   FWIW, the German navy of WW1, The High Seas Fleet sought out that N&W Metalurgical coal as a fuel, when there was plenty of good German coal available a lot closer to home. Fuel heat quality had to make some kind of difference, or everyone would have been just as happy running their steamers on newsprint advertising.  Heat release over time is part hot steamer, 4 sure!

So what happens when you throw in the green log, the yellow log and the red log from Doc Brown?

Larry

Bob Lamassena was a mechanical engineer who has written pretty extensively on steam locomotive performance. His propositions made pretty good sense to me.   Anyway, neither you nor Jack responded to my question re the Big Boy burning lignite vs. bituminus. Why would such big time outfits as the Pennsylvania RR pay so much attention to the quality of coal they burned? Presume it was to insure maximum performance from their motive power. Again, NP locomotives burning lignite produced less power then their oil-burning cousins over on the SP&S. Why? look at the BTU content of the fuels used. Exact same design locomotives. Anyway, we agree to disagree.   

Steve - Thinking a bit more about steam "volume". You noted "as long as the bolier can keep the pressure up". Well, when a locomotive is working hard, pulling a heavy train at speed, it is consuming large volumes of steam (and large volumes of energy). If one fuel can produce more energy, it is going to maintain steam pressure more fully and keep up more fully with the demands the work is extracting. In other words, higher energy content fuel will do more work per hour. Or pull a somewhat heavier train at higher speed. Isn't this in harmony with the basic laws of physics?

Maybe it is time for a basic refresher on exactly what a steam locomotive is? The "steam engine" is actually a heat machine, and it doesn't matter whether it is under a railroad locomotive or in a steam ship, or in a saw mill. What makes the piston move in the cylinder is the heat of expansion! The method of transferring all that heat, from the fire, is through steam. The higher the boiler pressure, then the hotter the steam temperature. Use of superheating units, increase the steam temperature even more, up to say 750 degrees F at the valves.

Once the hot steam is emitted into the cylinders, the heat of expansion takes place and the piston begins to move within the cylinder. As the speed of the pistons increase, the volume of the steam MUST be decreased, so that the steam flow is NOT passing through the superheater units so rapidly, that insufficient heating increase to the steam takes place. Thus, the art of "hooking up" the reverse gear, or shortening the stroke of the valves, provides SMALLER amounts of HOTTER steam to enter the cylinders, and maintain that heat of expansion. Contrary to popular belief, it is NOT the VOLUME, nor the PRESSURE, of the steam that does the actual work, but the TEMPERATURE of the steam.  

I was looking here...just scroll down a page or 2.  Am I reading something incorrectly?...Probablly...I'm usually wrong..  Just ask my wife...

To my uneducated way of thinking this just translates to a higher BTU fuel will mean less fuel consumed for a given amount of work.

Bingo. A very astute young man!

I think you are WAY overthinking this. When you say things like "maintain steam pressure more fully," you're really confusing the situation. "More fully" than what?

When my train is lugging up a grade--yes, it is using more steam. My pressure may start going down. That's the pressure needed to pull the train (among other things). So what do I do?

Simple: I INCREASE my firing rate (i.e., I open my atomizer and fuel valve to use MORE oil, which creates a larger fire.

Simply put, if I had a higher BTU fuel, I would simply need to use less of that fuel to create the same intensity fire. It's MORE EFFICIENT. Assuming I can get my pressure back to 190, the volume of the steam in the boiler (which never comes into the equation, so I don't even know why I'm mentioning it) stays static--again, the boiler is an enclosed and limited space.

Ok, I'll ask again. Which locomotive will perform better, a Big Boy burning lignite or one burning bituminus? If it doesn't matter, why did the vast majority of railroads burn bituminus rather then lignite?  I would presume because locomotives burning bituminus produced more ton miles, and, resultantly, better financial results. Yes, a steam locomotive is a "heat machine", but it is also an "energy conversion" machine. It converts or transfers the energy in coal into steam energy.......note, energy, which translates into horsepower, ultimately. As GNNPNUT's data indicated, bunker c has considerably more BTU energy then bituminus, and, in turn, wood.  Again, same design locomotives, heck, same locomotives, NP lignite vs SP&S oil. Who produced more horsepower with their equivalent locomotives? NP burned lignite because it was cheap and they owned the mines, not because it had equivalent power potential with bituminus.

Simply put, if I had a higher BTU fuel, I would simply need to use less of that fuel to create the same intensity fire. 

Steve - Are you not making my point? A higher BTU content fuel will do more work with less volume of fuel? The higher BTU fuel contains more energy to do work - or produce more power!

"Ok, I'll ask again. Which locomotive will perform better, a Big Boy burning lignite or one burning bituminus?"

Both locomotives will preform the same.  The difference will be in the amount of coal used.

Bingo, again!  All this assuming that the Fireman can maintain 300 psi with that lignite crap.

That's one thing that has always made the 611 lose style points for me. Her "feets look too small".  The shrouding doesn't bother me in the least, although an unshrouded engine always looks beefier than a shrouded one and that's the look I prefer.

I'm one of those weirdos that prefers the late Pennsy look with the cast steel pilot over the earlier "more dainty" look.

That said, I agree with Mr. Melvin: "Both were good locomotives and reliably served their respective railroads for many years."

I think the problem is that when most of us talk about "locomotive performance," we're thinking in terms of tractive effort or drawbar horsepower--what the engine could "do." Obviously, two identical steam locomotives will perform the same (in these terms) if the pressure can be maintained at the same level in each engine, regardless of fuel.

Mark seems to be looking at it like one of the sharp-pencil boys in the railroad accounting department might think about "locomotive performance:" Not only is he concerned with power output, but also fuel cost/efficiency, and what those different fuels add to the bottom line. I think he agrees power output at the drawbar might be the same with crappy fuel vs. good fuel in equivilent engines, but at what cost to maintain the same pressure using both fuels?

IF you run Lignite in your hypothetical Dual Fuel Big Boy, you'll be running the stoker at a higher speed, and using more steam to do it.  Most likely, you'll have to dump the ash pans more often and pay more attention to the fire.  A giant PITA, and in the long run, I have to question the savings of using junk fuel. N&W has awesome coal available in their backyard...they'd be idiots to use anything else.  And those poor western roads stuck with Lignite or anything close to it were wise to make the jump to oil, for a bunch of reasons. However the lure of cheap fuel will always be around, back around 1980 or so, GE got this brilliant idea of trying to run a powdered coal slurry mixed with fuel oil in an FDL 16 locomotive prime mover!  I'm not kidding!  Can you imagine what the result of that would be???? Must have been thinking that since the engine would have to be opened up periodically anyway, might as well ruin it completely en route !   OTOH, Lignite is likely OK for people with coal heating For their homes out there...and it makes pretty decent popcorn.

Steve:  no, alas, i don't agree. I am relying on primal physics. In an energy conversion machine, higher energy fuel will produce more power. I am not concerned with fuel economics, but will cite better profit performance resulting from better performing locomotives. Union Pacific had a better financial performance then Northern Pacific, despite both having relatively lucrative long hauls. Why? One element may well have been more productive steam motive power burning superior fuel. An accountant, I am not. An empiricist, convinced with empirical data, hopefully I am. And not subject to being convinced by imperial decrees.

Believe what you like...At a given pressure, the power of a steam engine will be exactly the same, regardless of what kind of fuel was used to get it to that pressure.

The formulae for tractive effort or horsepower don't include variables for fuel BTUs.

Ok, different twist on the tail:  take a dragster, put in premium, high octane gasoline. run it. Then take the same dragster, put in nitro, and run it. Same chasis, same engine. which one produces a better performance? Same compression ratio.

       Or why would a high performance automobile manufacturer such as Porsche specify high octane gasoline for their high performance cars? If fuel BTU content is of no consequence, why not just design their engines around standard gasoline?

Apples, meet oranges...

Sorry Mark, but you are now trying to compare apples to water melons! Try to remember that steam locomotives are EXTERNAL COMBUSTION devices, while dragster and automobile engines are INTERNAL COMBUSTION devices.

Mark, try wrapping your head around this: I can run my steam locomotive with NO FIRE WHATSOEVER IN THE FIREBOX! Could even pull a train, using NO FUEL AT ALL!

Hey, now THAT's cheating! Even John Force can't do THAT.

Sorry Mark, but you are now trying to compare apples to water melons! Try to remember that steam locomotives are EXTERNAL COMBUSTION devices, while dragster and automobile engines are INTERNAL COMBUSTION devices.

      Both machines rely on the expansion of energy in their cylinders. At the end of the day it is the expansive power in the cylinder that produces the power.

Mark, try wrapping your head around this: I can run my steam locomotive with NO FIRE WHATSOEVER IN THE FIREBOX! Could even pull a train, using NO FUEL AT ALL! 

 Steve - You would be employing energy already transfered to the steam remaining in your boiler.......from the previously burned fuel. Or your engine lives on the "Magic Planet"   !!!     (jesting, please take no offense)

Well not exactly. The heat expansion in steam engine cylinders is provided from an external source. The firing pressures within an internal combustion cylinder is provided by the chemical EXPLOSION within that cylinder, and is only single acting.

Thing is, your dragster needs fuel actually combusting in the cylinder at the time you want the car to move. My steam engine doesn't actually need fuel combusting concurrently for me to be able to move a train.