Are Piggyback Van Trains faster then Doublestack?

[Hugh Jampton]

HOLD YER FIRE!!!!!!!!

Actually it's kW/metric tonne, but I've converted to hp/ton for you
TGVs have a hp/t ratio varying between 24 to 28 depending on the model
.

Carry on.........

[greyhounds]

Actually, we did.  The IC had the longest continuous curve in the world.  It went through the bayou around Lake Ponchatrain into New Orleans.  It was miles long. 

Longer than the curve on the Espee (now UP)  main-line south of Phoenix? That's several miles of 10 minute  (1/6 degree) curve. Asking more out of curiosity than disagreement.

The most significant resistance factor is the grade.  You can either pile on the power or reduce the tare weight to deal with the grades  The world isn't flat. The streamliner designers recognized that reducing weight had more benifits than reducing "wind resistance".

True for the speeds achieved by typical American passenger trains - emphatically not true for very high speed trains such as the TGV - they need so much power to overcome aero drag that 3% grades area piece of cake.

The first generation of American strhttp://www.railwaystation.com/1942/02.htmleamliners did benefit from streamlining along with being very lightweight. Later trains were heavier and thus benefitted less from streamlining.

Yes, I believe it was longer.  I didn't remember the exact length - that's why I didn't state it.  I like to be sure of my facts.  But, according to #48 in this thing:

http://www.railwaystation.com/1942/02.html

It was 9.45 miles without a straight piece of rail.  In latter years there was a realingment that broke the curve in two.

Steamlining does have benifits.  But they pale in comparison to reducing the weight you have to drag up a hill.  This is especially true in passenger trains where most of the weight is in the equipmnt, not the payload.

The HP/ton ratio on the TGV has to be very high.  (or is it KW/Kilo ratio?)

[erikem]

Actually, we did.  The IC had the longest continuous curve in the world.  It went through the bayou around Lake Ponchatrain into New Orleans.  It was miles long. 

Longer than the curve on the Espee (now UP)  main-line south of Phoenix? That's several miles of 10 minute  (1/6 degree) curve. Asking more out of curiosity than disagreement.

The most significant resistance factor is the grade.  You can either pile on the power or reduce the tare weight to deal with the grades  The world isn't flat. The streamliner designers recognized that reducing weight had more benifits than reducing "wind resistance".

True for the speeds achieved by typical American passenger trains - emphatically not true for very high speed trains such as the TGV - they need so much power to overcome aero drag that 3% grades area piece of cake.

The first generation of American streamliners did benefit from streamlining along with being very lightweight. Later trains were heavier and thus benefitted less from streamlining.

[greyhounds]

Illinois Central must have had some mightly long impressive curves.

Actually, we did.  The IC had the longest continuous curve in the world.  It went through the bayou around Lake Ponchatrain into New Orleans.  It was miles long. 

If you don't understand that grades and curvature are significant factors in rail operations and that "Wind Resistance" is an afterthought, you're beyond any possible reason.

The most significant resistance factor is the grade.  You can either pile on the power or reduce the tare weight to deal with the grades  The world isn't flat. The streamliner designers recognized that reducing weight had more benifits than reducing "wind resistance".

[GP40-2]

This thread is better entertainment than watching two white-trash trailer park chicks from Montanna duke it out on the Jerry Springer Show...

Pluuueeeese don't stop. I'm done with work, and I have all weekend to laugh at this...

[MichaelSol]

Well it is true that trains go uphill and the weight vector increases relative to the aerodynamic drag.

It is true the increase in motion resistance is all weight related.

But then they go downhill and the weight vector decreases relative to the aerodynamic drag. Kind of left that part out, Strawbridge. Why?

But then it is true that the decrease in motion resistance is all weight related.

And of course Strawbridge's statistical tomfoolery would like to propose that the grade goes on forever, rather than the likelihood of it being a small part of any hypothetical route mileage. However, if the grade is 40 miles long on a 400 mile run, the net effect is to add 7,200 lbs to the total average resistance, not 72,000 lbs. The Strawbridge sleight of hand disguises the fact that the average rolling resistance of the run will increase by 18% at 50 mph, rather than over 200%.  The percentage of motion resistance attributable to aerodynamic drag drops from 60% to just over 50%. While this example assumes no negative grades on the run, which would cancel out the Strawbridge scenario, it does underscore how important that continuous aerodynamic drag is -- because it is continuous.

It is also true, however, that  the wind blows. Sometimes it is a headwind and increases the aerodynamic drag. In that case the increase in motion resistance is all aerodynamic drag related.

And sometimes it is a tailwind and decreases the effect of the aerodynamic drag.  In that case, the decrease in motion resistance is all aerodynamic drag related.

The interesting point about streamlining is that it would provide an advantage regardless of grade or curvature. Strawbridge didn't mention that either. And, his example carefully assumes the grade is uncompensated. 

In general, however, where it is safe to say that motion resistance related to weight can go up or down depending on grade -- and of course trains do go downhill -- the average happens to resemble flat ground -- zero grade. Likewise, the average impact of changes in air "pressure" or density due to wind over all train movements is likely to be zero.

Choosing a specific set of assumptions to meet the pre-determined conclusion will indeed give you the results that you wish, but only if you ignore completely the conditions which produce the opposite effect. That's called cherry picking.

Of course unless you grew up in Bill Cosby's neighborhood where the road to school was uphill... both ways.

I am sure Strawbridge believes what he says. No doubt the Illinois Central was uphill ... both ways. Forever.

It is also true that curvature increases friction in a proportion to the weight of the car.  Assuming you can get the entire 7,200 ton train on a 2 degree curve at once, you would indeed incur a resistance of 11,520 lbs.

Illinois Central must have had some mightly long impressive curves.

Even at that, at 50 mph, assuming the train is on one huge continuous 2 degree curve constantly, the aerodynamic drag is just slightly less than half of the total motion resistance, but at 70 mph, even with Strawbridge's unusual railroad, aerodynamic drag is still the major source of motion resistance. And at 1 degree, 50 mph, aerodynamic drag is still the largest source of resistance to the locomotive.

More realistically, at 50 mph, if 20 car lengths are on the curve, the impact is 2,880 lbs, and does not change the fact that, at that speed, the majority of the resistance that the locomotive must overcome is still created by aerodynamic drag. If you postulate that the train encounters such curvature over 20% of its run, then the equivalent impact is 576 lbs on the average, where windage equals 19,000 lbs, and which shifts the average velocity threshold at which aerodynamic drag exceeds all other motion resistance up by less than 1.0 mph. Hardly signficant. Yup. "Sol pretty much left it out." So does the typical Davis formulation, for obvious reasons.

Is that 2% change in average resistance due to curvature signficant compared to the effect of continuous aerodynamic drag at 58% -60% at 50 mph?

This was a nice try at twisting and distorting facts to prove a point, but on closer examination, the effort obviously fails unless you can accept Strawbridge's sleight of hand that postulates 1) that railroads only go uphill, and 2) that railroads are continuous curvature.

In leaving out the effect of wind, apparently he also adopts Diehl's scientific theory that the wind has no effect -- that it is just the same thing as "air." Quite a pair.

[greyhounds]

The "A" term in the Davis Eq. is commonly known as "journal friction" - it is not weight related, "B" as "flange friction" - it is directly weight related, and C as "wind resistance" - which is not weight related.

For the hypothetical 7200 ton, 80 car train at 50 mph on the level, The journal friction is rougly 1000# , flange friction 11,000# and windage 19,000#.

But, on a 1/2 grade, the grade resitance - which is entirely weight related - is 76,000# - which is more than double the total rolling resistance at 50 mph.

So, is it weight or is it windage? 

It depends.....

But at least one can get a glimpse of the great cost of fast trains and ruling grades are such important determiners of which routes prosper and which fail......

Well, I'm going to declare a winner.  Congradulations!  You won!

I would have calculated the extra resistance due to a 0.5% grade on a 7,200 ton train at 72,000 not 76,000 pounds - but that's splitting hairs.  And don't forget the curves.  My information says they add 0.8 pounds of resistance per degree of curvature for every ton the train weighs.  So, using the numbers above, a 7,200 ton train going up a 0.5% grade on a one degree curve would have to overcome 108,760 pounds of resistance as opposed to only 31,000 pounds resistance on straight level track.

That slight grade and curve more than tripple the resistance - and the increase is all weight related.

Since trains go up hills and around curves, it is clearly evident that what Tom was saying is very accurate.  With good streamlining you maybe could reduce the air drag by, let's be generous, 35%.  In this case that would be around 6,650 pounds - that's just a little more than the curve adds.  You'd save about 6.1% of the resistance.

It's more important to reduce train weight - go to lightweight equipment, aluminum gons, skeleton flats for TOFC/COFC, etc.  Just like the designers of the streamliners did.

Tom was/is right.  The lightweight equipment was more important than the cosmetic streamlining. BTW, it also could be accelerated/decelerated faster.

Sol pretty much left the whole grade/curve thing out.

 

 

[TomDiehl]

For an 80 car, 7200 ton train with two six axles, here's the air resistance as a % of total train resistance (traction HP required to move train):

on the level:

10 mph - 17%  (143 HP)
30 mph - 46% (1466 HP)
50 mph - 60% (5162 HP)
70 mph - 68% (12418 HP)

TomDiehl:
No, it says that wind resistance of a train at the speeds they travelled was consuming a very small percentage of the power required to move the train, which is EXACTLY what I said.

TomDiehl:
"As big and heavy as any train is, the wind resistance is a very small factor."

I am sure Otto Kuhler is rolling over in his grave at the complete misrepresentation of his remarks by Tom Diehl. The interpretation placed by Diehl on Kuhler's remarks would make it appear that Kuhler did not believe there was much resistance from air density at higher speeds.

That interpretation is simply absurd.

In case there is any doubt, Diehl emphasized his remarks as being EXACTLY what he meant.

It is abundantly clear that Diehl is EXACTLY wrong on the point.

This is not the first time that TomDiehl has not just made an error [to err is human ...] but more disturbingly, it is not the first time that he has intentionally misrepresented the statements of an authoritative source as a cloak for his own strong, unfounded opinion or, as in the case of the steam-diesel thread, simply invented, wholesale, a variety of "studies" which he offered in support of his position, none of which he had ever even seen nor knew whether or not they actually existed. He simply made them up, as he made up Otto Kuhler's alleged belief that there was no such thing as air resistance, or that it was "negligble" as an impact on the overall power needed to move trains.

Hopefully that has been put to rest as the complete fallacy that it was and is.

The only thing that was "misrepresented" in this thread was the claim that you had any idea what was being discussed for the first 2-1/2 pages.

On a level track, two SD90's would not be able to attain 70 MPH with the said train, simply because of wind resistance, which would require over 12,000 HP just for that?

So in the end you agree with me, that the difference in wind resistance between the double stack and the piggyback would not make one run slower than the other. I still find it hard to believe that wind resistance is a function of weight rather than amount and sizes of surfaces for the wind to act against?

Especially in light of Oltmannd's post.

[oltmannd]

OK, we've had some fun playing "where is it". 

Sol has left 'a couple' of things out, and they are things that go against his argument.  I've underlined words in his first paragraph that send us off in the wrong direction.

To understand why weight is a much more critical factor than "air resistance" we need to know that these two "resistance" factors are in the Davis formulas.  They relate to the weight and increase or decrease depending on....

For first place, be the first to name these two resistance factors AND thier values per ton of train. 

Well, I am curious where this is going ....

The "A" term in the Davis Eq. is commonly known as "journal friction" - it is not weight related, "B" as "flange friction" - it is directly weight related, and C as "wind resistance" - which is not weight related.

For the hypothetical 7200 ton, 80 car train at 50 mph on the level, The journal friction is rougly 1000# , flange friction 11,000# and windage 19,000#.

But, on a 1/2 grade, the grade resitance - which is entirely weight related - is 76,000# - which is more than double the total rolling resistance at 50 mph.

So, is it weight or is it windage? 

It depends.....

But at least one can get a glimpse of the great cost of fast trains and ruling grades are such important determiners of which routes prosper and which fail......

[MichaelSol]

OK, we've had some fun playing "where is it". 

Sol has left 'a couple' of things out, and they are things that go against his argument.  I've underlined words in his first paragraph that send us off in the wrong direction.

To understand why weight is a much more critical factor than "air resistance" we need to know that these two "resistance" factors are in the Davis formulas.  They relate to the weight and increase or decrease depending on....

For first place, be the first to name these two resistance factors AND thier values per ton of train. 

Well, I am curious where this is going ....

[MichaelSol]

For an 80 car, 7200 ton train with two six axles, here's the air resistance as a % of total train resistance (traction HP required to move train):

on the level:

10 mph - 17%  (143 HP)
30 mph - 46% (1466 HP)
50 mph - 60% (5162 HP)
70 mph - 68% (12418 HP)

TomDiehl:
No, it says that wind resistance of a train at the speeds they travelled was consuming a very small percentage of the power required to move the train, which is EXACTLY what I said.

TomDiehl:
"As big and heavy as any train is, the wind resistance is a very small factor."

I am sure Otto Kuhler is rolling over in his grave at the complete misrepresentation of his remarks by Tom Diehl. The interpretation placed by Diehl on Kuhler's remarks would make it appear that Kuhler did not believe there was much resistance from air density at higher speeds.

That interpretation is simply absurd.

In case there is any doubt, Diehl emphasized his remarks as being EXACTLY what he meant.

It is abundantly clear that Diehl is EXACTLY wrong on the point.

This is not the first time that TomDiehl has not just made an error [to err is human ...] but more disturbingly, it is not the first time that he has intentionally misrepresented the statements of an authoritative source as a cloak for his own strong, unfounded opinion or, as in the case of the steam-diesel thread, simply invented, wholesale, a variety of "studies" which he offered in support of his position, none of which he had ever even seen nor knew whether or not they actually existed. He simply made them up, as he made up Otto Kuhler's alleged belief that there was no such thing as air resistance, or that it was "negligble" as an impact on the overall power needed to move trains.

Hopefully that has been put to rest as the complete fallacy that it was and is.

What is clear from Don's figures is that, at 50 mph, 60% of the horsepower utilized at that speed is utilized overcoming the resistance caused by air density, and 40% of the horsepower utilized is utilized overcoming the resistance due to the weight of the train and the moving friction caused therefrom.

Without detailed specific cross sectional measurements, the following numbers from my spreadsheet are simply relative, but that the air drag or aerodynamic resistance of a standard boxcar at 50 mph is slightly less than COFC, but that air resistance for TOFC is approximately 89% greater than for a standard boxcar. and 65% greater than COFC. This is notwithstanding the fact that overall resistance of the COFC and boxcar are within 1% of each other, and the TOFC only 16% greater, in overall motion resistance, than a standard boxcar.

I am assuming Don's figures come from the AREMA Manual for Railway Engineering.

My notes are from AREMA, with a 2003 copyright.

"In general, rolling resistance of a train, R (in lb.), can be calculated using an empirical
expression as follows:

R = A + B V + C D V2

where A, B, C & D are coefficients defining the different resistive forces that are either independent, dependent or affected by the square of the train speed V.

Davis Formula

The first empirical formula to compute rolling resistance was developed by W.L. Davis in 1926. The original Davis formula provided satisfactory results for older equipment with journal bearings within the speed range between 5 and 40 mph. Roller bearings, increased dimensions, heavier loadings, higher train speeds and changes to track structure have made it necessary to modify the coefficients proposed by Davis. Since then, there had been various modifications. Interested readers may refer to Section 2.1 of Chapter 16 in the AREMA Manual for Railway Engineering for more information."

From the US Army Corp of Engineers, August, 2000
Analysis of Energy, Emission and Safety Impacts of Alternative Improvements to UMR-IWW, discussing railroad energy consumption:

"Air resistance varies approximately with the cross-sectional frontal area of the vehicle and the square of speed (Hay, 1982). It is affected also by equipment profiles and the potential for localized air disturbances in vehicle frontal areas and under frames. Trailer-on-flatcar (TOFC) shipments and automobile carriers or “autoracks” are thought to be especially problematic.[The term TOFC , as used in this report, encompasses container-on-flatcar (COFC) shipments on traditional flatcars. Double-stack container cars are considered as a separate category for purposes of energy analysis.]"

[MP173]

buycsxstock:

 

Thanks for the details on the intermodal schedules.  I have been poring over those this morning.  That website is interesting.  I can piece together schedules of the NS intermodals that run like clockwork thru town.

What I find interesting with NS operations is the consistency that they run their trains, particularly the intermodal trains.  These trains are almost always within an hour each day.  For example train 217 is nearly always between 6am-7am.  Always.

Customers no doubt need that consistancy more than fast service.  Do you know anyother intermodal schedule sites?

 

ed

[oltmannd]

For an 80 car, 7200 ton train with two six axles, here's the air resistance as a % of total train resistance (traction HP required to move train):

on the level:

10 mph - 17%  (143 HP)

30 mph - 46% (1466 HP)

50 mph 60% (5162 HP)

70 mph 68% (12418 HP)

on a 1/2% grade

10 mph - 1% (2610 HP)

30 mph - 8% (8868 HP)

50 mph 18% (17500 HP)

70 mph 29% (29690 HP)

 

[TomDiehl]

In this example, known by Kuhler, and by anybody that read his work. He used to lecture on this topic back in the 30's, so that's a long time.

No, it says that wind resistance of a train at the speeds they travelled was consuming a very small percentage of the power required to move the train, which is EXACTLY what I said.

An even older reference (1910 to 1920) was from a Baldwin paper on locomotove performance - the train resistance graph for passenger cars shows the resistance at 60 MPH to be double that at 10 MPH. Assuming that the increase in resistance was primarily due to air drag, that would imply that the horespower to needed overcome air drag equalled the horsepower needed to overcome rolling resistance at 60 MPH. For a more modern reference, over 90% of the power consumed by the TGV is used to overcome air drag and those trains have a significantly lower drag coefficient than the average American passenger train.

Remember that the earliest streamliners, e.g. the UP M-1000 and the Q's Pioneer Zephyr, did have a lot of attention focused on reducing aero drag.

A similar thing happened with automobiles after the 1975 fuel economy standards were set - the initial improvements came from lowering weight, but additional improvements required reduction in drag coefficient.

I wouldn't assume that, considering in 1910 to 1920 time frame, we're talking about open lubricated, babbetted bearings on the axles. I can almost guarantee that the TGV uses sealed, roller bearings, plus it moves a bit faster than 60 MPH.

[TomDiehl]

TomDiehl:

Yes, I do "get it," you have no clue what we're talking about here and refuse to admit it. You remind me of the Pointed Hair Boss in the Dilbert comic strip. You're hung up on an anology and have completely lost the original question.

Just in case this has a remote chance of helping you, the original question/debate was, "would the air/wind resistance of a given train (in this case, a double stack compared to a piggyback) be high enough to effect the maximim speed?"

Your specific comment was: "As big and heavy as any train is, the wind resistance is a very small factor."

NOW, you're finally starting to come around to the actual question at hand.

Now, let's see if you can take the statement above and apply it to the original question: "will the wind resistance of two different types of trains, double stack compared to piggyback, be high enough to effect the top speed of one more than the other."

And before you try to twist this around again, this is back on page one of this post, in my answer to Chad's statement.

[Chris30]

Ooops! I must have been half-awake... I did mean Willow Springs, not Western Springs. Close though.

CC

[greyhounds]

TIME OUT HERE!!!!! WHAT I ASKED - etc.... Well, the answer to your question is yes, sometimes, it all depends.

[erikem]

In this example, known by Kuhler, and by anybody that read his work. He used to lecture on this topic back in the 30's, so that's a long time.

No, it says that wind resistance of a train at the speeds they travelled was consuming a very small percentage of the power required to move the train, which is EXACTLY what I said.

An even older reference (1910 to 1920) was from a Baldwin paper on locomotove performance - the train resistance graph for passenger cars shows the resistance at 60 MPH to be double that at 10 MPH. Assuming that the increase in resistance was primarily due to air drag, that would imply that the horespower to needed overcome air drag equalled the horsepower needed to overcome rolling resistance at 60 MPH. For a more modern reference, over 90% of the power consumed by the TGV is used to overcome air drag and those trains have a significantly lower drag coefficient than the average American passenger train.

Remember that the earliest streamliners, e.g. the UP M-1000 and the Q's Pioneer Zephyr, did have a lot of attention focused on reducing aero drag.

A similar thing happened with automobiles after the 1975 fuel economy standards were set - the initial improvements came from lowering weight, but additional improvements required reduction in drag coefficient.

[MichaelSol]

How much of the horsepower, by percentage, produced by the locomotive to move the train, is consumed to overcome the wind resistance of the train?

Air resistance, you mean. If you give us the total train tonnage, the total number of cars (and axles) and some idea of what type of car, we can take a shot at it. But we could be off by a factor of two, depending on which version of the so-called "Davis formula" we use.

Oh yes-- tell us the speed too.

Wind is air in motion, so they would be pretty much the same thing. Since Michael wanted to take this to the higher engineering math, maybe you should ask him.

Ask me.

I am sure a train going against Hurricane force winds of 140 mph would perform just the same as a train going through still air ... "pretty much the same thing."

Good grief. I guess it takes "higher engineering math" to see that one for what it is.

[youngengineer]

I think its time to call the mythbusters!!!

[MichaelSol]

GP-402:

If anyone wants to see where MichaelSol copied his answers from just click the following link and look about half way down the page:

http://www.uwm.edu/~horowitz/PropulsionResistance.html

Now come on Michael, shouldn't you at least aknowledge other people's work, or does being a lawyer give you the right to steal it and claim it as your own?

Wow, you're soooooo freaking smart.

Looking more closely at Horowitz, if you had taken the time you would see that my definition of the K1, K2, and K3 components of the Davis Algorithim are different than Horowitz's.

I set forth my definitions above, Horowitz sets his out at page 4 of his internet text. They are quite different.

In particular, the Horowitz paper defines K2 as equaling the coefficient of moving friction x weight per axle x number of axles.

My definition of K2 defines it as the coefficient of moving friction x Velocity x total weight.

Horowitz defines K3 as drag coefficient of air x cross sectional area of the vehicle.

My K3 defines it as the drag coefficient x the cross section x the velocity of the machine squared.

He apparently adjusts for the differences later. Why he did it that way, I do not know, but our definitions are clearly different insofar as how we structured the components of the Davis Algorithm. For some reason, he does not include velocity, but must do so at some point as the spot check of results roughly checked out.

I don't know that they give the same answers all across the board as I don't have the current inclination to walk all the way through his paper in detail. It would take some time as I really don't follow why he did what he did or how he did it. The definitions I used are pretty standard.

However, as clearly set forth above, this is the Davis Algorithm, not the Horowitz Algorithm, and notwithstanding GP-402's false and mendacious insinuation, all of the results presented by myself are based entirely on the Davis Algorithm and I have made no pretensions otherwise.

 

[MichaelSol]

TomDiehl:

Yes, I do "get it," you have no clue what we're talking about here and refuse to admit it. You remind me of the Pointed Hair Boss in the Dilbert comic strip. You're hung up on an anology and have completely lost the original question.

Just in case this has a remote chance of helping you, the original question/debate was, "would the air/wind resistance of a given train (in this case, a double stack compared to a piggyback) be high enough to effect the maximim speed?"

Your specific comment was: "As big and heavy as any train is, the wind resistance is a very small factor."

[Anonymous]

TIME OUT HERE!!!!!

WHAT I ASKED WAS......OR WHAT I MEANT TO ASK WAS.....

Are Pig trains on a Faster scedule then Stack trains?

Does one get priority over the other?

as far as air resistance goes I belive that a all boxcar train like the old Silk Express or the Western Maryland fast freights have the least wind resistance or the Amtrak Mail only train on the NE Corridor

[MichaelSol]

Whoa, not so fast, you proposed that air resistance was negligble compared to the effect of the weight of the train. Nothing about horsepower in your proposition. You're trying to change the subject here (I don't blame you, you're dead wrong on your facts on the topic at hand).

I am proposing that air resistance is more significant that the motion resistance of weight at a certain point due to the effects of velocity. You are saying length and weight are always most important, that by comparison, air resistance is always negligble, by comparison to weight, presumably at the speeds we are talking about -- presumably in the 40-80 mph range.

Why don't you propose to answer, specifically, why "wrong again, Michael"?

What would Kuhler say specifically was the effect of motion resistance on a train or a locomotive, and what components relate to weight and what component relates to aerodynamic drag?

Where are your numbers to back up your statement besides allusions to speeches given in the 1930s which I am sure you never actually heard but which you now claim in support. Kind of like all the dieselization studies you claimed existed and "relied" on when you actually hadn't seen a single one, isn't it?.

Where and how do you show that air resistance is always "negligble" compared weight?

A peek at your question however, on a 2500 hp six axle locomotive at 220 tons, at 83% efficiency, the aerodynamic drag begins to exceed the combined weight friction and motion friction at just about 50 mph, and a machine with those characteristics would be unable to exceed 127 mph, at which point 78% of the total motion resistance would be due entirely to the aerodynamic drag on the locomotive.

At that point, the total motion resistance would equal the tractive effort available from the locomotive and it would be unable to accelerate past that point assuming it was still on the track.

Now, support the answers you claim to have to the proposition you made, and don't try and change the subject. You made the allegation, support it for once with facts and numbers, not misquotes out of magazines.

If anyone wants to see where MichaelSol copied his answers from just click the following link and look about half way down the page:

http://www.uwm.edu/~horowitz/PropulsionResistance.html

Now come on Michael, shouldn't you at least aknowledge other people's work, or does being a lawyer give you the right to steal it and claim it as your own?

Wow, you're soooooo freaking smart.

I could make some interesting comments about this thread, but I am having too much fun watching you guys fight over this.

Whoa, whoa, whoa! I beg your pardon, I've used a variety of tonnages and hpowers, in various posts. I've also used industry standard measurements. My results come from an Excel spreadsheet model, and if you want it, I'll send it to you. I first used Davis Algorithms professionally, highly modified, in 1976 specifically for aerodynamic drag modelling. Not sure what Horowitz was doing then.

Indeed, if you will look back, my first post on the matter happened to use a 3200 hp, 250 ton loco with six axles as a hypothetical ... not picking a particular loco, just typing in numbers. None of those numbers to be found in Horowitz that I can see.

Indeed, looking around, it looks like about 90% of what I have posted is not in Horowitz. On the other hand, for two discussions of the identical named Algorithm, how would there not be ... discussions of the identical Algorithm? I am pretty sure that if two different users use the same assumptions built into the same model, the results will look the same. Isn't that the point?

I've been scaling up and down the weight/hp continuum depending the post. I went on an internet search to double check modern data on TOFC/COFC. I did indeed then see Horowitz and a reference to 2500 hp. Since he had some results, I entered his 2500 hp to double check my Spreadsheet. However, I also left in the 220 ton figure I happened to have previously entered, which Horowitz did not reference, and he also appears to have utilized only four axles in his calculations. At a glance, everything appeared to be roughly consistent and I went no further and stayed with my six axles and greater weight. That's clearly in my posts. My data is, in fact, different than his. Nor did he reference the air drag % at the velocities I used. I also have COFC and TOFC numbers that I don't see in his paper.

The Algorithm is in fact shown in a variety of engineering texts and papers, and was apparently created by someone named Davis, not Horowitz, and to whom I gave precise and immediate acknowledgment.

You have an opportunity to retract the libel that anything was "stolen." Davis was clearly acknowledged.

 

[greyhounds]

OK, we've had some fun playing "where is it". 

Sol has left 'a couple' of things out, and they are things that go against his argument.  I've underlined words in his first paragraph that send us off in the wrong direction.

To understand why weight is a much more critical factor than "air resistance" we need to know that these two "resistance" factors are in the Davis formulas.  They relate to the weight and increase or decrease depending on....

For first place, be the first to name these two resistance factors AND thier values per ton of train. 

.
The Davis Equation breaks the forces down into three components. K1 is the resistance or friction resulting from the weight of the machine and the number of axles. For a 250 ton non-streamlined locomotive K1 shows 499 lbs of resistance at 10 mph. It's 499 lbs of resistance at 50 mph, and 499 lbs of resistance at 100 mph, because the frictional resistance due to the weight of the machine does not change with velocity.

K2 is the component that measures the moving friction of the train. Weight is part of this, but so is speed and includes the coefficient of rolling friction empirically measured, which happens to be close to 0.03 for steel wheels on steel rails all of the time. K2 is 75 lbs of resistance at 10 mph, 375 lbs of resistance at 50 mph, and 750 lbs of resistance at 100 mph.

K3 is the component that measures the resistance on the machine (train) due to air drag. In this instance we are only looking at the locomotive itself (since the air drag coefficients are different for different pieces of equipment), but for that 250 ton locomotive, at 10 mph, the resistance due to air drag is only 30 lbs. At 50 mph it is 750 lbs, and at 100 mph it is 3,000 lbs of resistance due to air drag friction. That is 70.6% of the total motion resistance of 4,249 lbs encountered at a speed of 100 mph.

[TomDiehl]

Well, you are permanently disconnected here.

The advantages of streamlining compared to a "normal" locomotive just wasn't part of the discussion.

Why you think it is relevant is beyond me.

What the streamline engineers said was that streamlining did not offer substantial advantages over "normal" design insofar as aerodynamic drag, all things considered. The density of air remained the same before and after streamlining, and a basic locomotive was already fairly streamlined as it was.

However, we are not talking about "streamlined" trains. So comparing them to "normal" designs isn't really much use to anyone.

TomDiehl:
<>If not related to the horsepower required to move the train, why would wind resistance even be a concern?

And if the aerodynamic drag begins to exceed the weight resistance and motion resistance provided by the weight of the train, do you begin to see why it can be "a concern"?

Or as you would put it: "Then why would the weight of a train even be a concern?"

Getting it yet?

Yes, I do "get it," you have no clue what we're talking about here and refuse to admit it. You remind me of the Pointed Hair Boss in the Dilbert comic strip. You're hung up on an anology and have completely lost the original question.

Just in case this has a remote chance of helping you, the original question/debate was, "would the air/wind resistance of a given train (in this case, a double stack compared to a piggyback) be high enough to effect the maximim speed?"

[TomDiehl]

How much of the horsepower, by percentage, produced by the locomotive to move the train, is consumed to overcome the wind resistance of the train?

Air resistance, you mean. If you give us the total train tonnage, the total number of cars (and axles) and some idea of what type of car, we can take a shot at it. But we could be off by a factor of two, depending on which version of the so-called "Davis formula" we use.

Oh yes-- tell us the speed too.

Wind is air in motion, so they would be pretty much the same thing. Since Michael wanted to take this to the higher engineering math, maybe you should ask him.

[GP40-2]

Whoa, not so fast, you proposed that air resistance was negligble compared to the effect of the weight of the train. Nothing about horsepower in your proposition. You're trying to change the subject here (I don't blame you, you're dead wrong on your facts on the topic at hand).

I am proposing that air resistance is more significant that the motion resistance of weight at a certain point due to the effects of velocity. You are saying length and weight are always most important, that by comparison, air resistance is always negligble, by comparison to weight, presumably at the speeds we are talking about -- presumably in the 40-80 mph range.

Why don't you propose to answer, specifically, why "wrong again, Michael"?

What would Kuhler say specifically was the effect of motion resistance on a train or a locomotive, and what components relate to weight and what component relates to aerodynamic drag?

Where are your numbers to back up your statement besides allusions to speeches given in the 1930s which I am sure you never actually heard but which you now claim in support. Kind of like all the dieselization studies you claimed existed and "relied" on when you actually hadn't seen a single one, isn't it?.

Where and how do you show that air resistance is always "negligble" compared weight?

A peek at your question however, on a 2500 hp six axle locomotive at 220 tons, at 83% efficiency, the aerodynamic drag begins to exceed the combined weight friction and motion friction at just about 50 mph, and a machine with those characteristics would be unable to exceed 127 mph, at which point 78% of the total motion resistance would be due entirely to the aerodynamic drag on the locomotive.

At that point, the total motion resistance would equal the tractive effort available from the locomotive and it would be unable to accelerate past that point assuming it was still on the track.

Now, support the answers you claim to have to the proposition you made, and don't try and change the subject. You made the allegation, support it for once with facts and numbers, not misquotes out of magazines.

If anyone wants to see where MichaelSol copied his answers from just click the following link and look about half way down the page:

http://www.uwm.edu/~horowitz/PropulsionResistance.html

Now come on Michael, shouldn't you at least aknowledge other people's work, or does being a lawyer give you the right to steal it and claim it as your own?

Wow, you're soooooo freaking smart.

I could make some interesting comments about this thread, but I am having too much fun watching you guys fight over this.

[Anonymous]

OK OK....... In my alter ego as the Hypothetical Hobo who hypotheticaly rides freight trains I have noticed that I get from Buffalo to Selkirk much faster on a Trailer train then I do on a double Stack. The New York Central Water level route is the prime testing ground for this sort of thing. I beleive that the reason is that the weight of the Rolling Stock is much less on a Piggyback because of the spine cars vs the 60 foot long articulated Double Stack cars..Acceleration is faster too..Here is a run down of TOFC and COFC scedules for you guys to make your own conclusions-

Origin: CHI - Chicago, IL	Dest: NYC - New York Metro, NY

Cutoff/ Depart  Leave Arrive/  Avail. Arrive Origin Carrier  Dest Carrier  Eq  SL  Hours  First Train  Last Train  Route  Hour Day Trml Hour Day Trml Detail CO 02:00 Mo N63 AV 10:30 Tu NJT NS NS T   31 20K (TOFC)     Detail CO 02:00 Tu N63 AV 10:30 We NJT NS NS T   31 20K (TOFC)     Detail CO 02:00 We N63 AV 10:30 Th NJT NS NS T   31 20K (TOFC)     Detail CO 02:00 Th N63 AV 10:30 Fr NJT NS NS T   31 20K (TOFC)     Detail CO 02:00 Fr N63 AV 10:30 Sa NJT NS NS T   31 20K (TOFC)     Detail CO 02:00 Sa N63 AV 10:30 Su NJT NS NS T   31 20K (TOFC)     Detail CO 02:00 Su N63 AV 10:30 Mo NJT NS NS T   31 20K (TOFC)                                       Detail CO 03:00 Mo BPA AV 12:00 Tu NBG CSXI CSXI T   32 L110 L110   Detail CO 03:00 Tu BPA AV 12:00 Mo NBG CSXI CSXI T   320 L110 L110   Detail CO 03:00 We BPA AV 12:00 Th NBG CSXI CSXI T   32 L110 L110   Detail CO 03:00 Th BPA AV 12:00 Fr NBG CSXI CSXI T   32 L110 L110   Detail CO 03:00 Fr BPA AV 12:00 Sa NBG CSXI CSXI T   32 L110 L110   Detail CO 03:00 Sa BPA AV 12:00 Su NBG CSXI CSXI T   32 L110 L110   Detail CO 03:00 Su BPA AV 12:00 We NBG CSXI CSXI T   80 L110 L110                                     Detail CO 11:00 Mo BPA AV 21:00 Tu LTF CSXI CSXI C   33 Q118 Q118   Detail CO 11:00 Tu BPA AV 21:00 We LTF CSXI CSXI C   33 Q118 Q118   Detail CO 11:00 We BPA AV 21:00 Th LTF CSXI CSXI C   33 Q118 Q118   Detail CO 11:00 Th BPA AV 21:00 Fr LTF CSXI CSXI C   33 Q118 Q118   Detail CO 11:00 Fr BPA AV 21:00 Sa LTF CSXI CSXI C   33 Q118 Q118   Detail CO 11:00 Sa BPA AV 21:00 Su LTF CSXI CSXI C   33 Q118 Q118   Detail CO 11:00 Su BPA AV 21:00 Mo LTF CSXI CSXI C   33 Q118 Q118                                     Detail CO 11:00 Mo BPA AV 21:00 Tu LTF CSXI CSXI T   33 Q118 Q118   Detail CO 11:00 Tu BPA AV 21:00 We LTF CSXI CSXI T   33 Q118 Q118   Detail CO 11:00 We BPA AV 21:00 Th LTF CSXI CSXI T   33 Q118 Q118   Detail CO 11:00 Th BPA AV 21:00 Fr LTF CSXI CSXI T   33 Q118 Q118   Detail CO 11:00 Fr BPA AV 21:00 Sa LTF CSXI CSXI T   33 Q118 Q118   Detail CO 11:00 Sa BPA AV 21:00 Su LTF CSXI CSXI T   33 Q118 Q118   Detail CO 11:00 Su BPA AV 21:00 Mo LTF CSXI CSXI T   33 Q118 Q118                                     Detail CO 12:00 Tu N63 AV 00:30 Th NJT NS NS T   36 24W     Detail CO 12:00 We N63 AV 00:30 Fr NJT NS NS T   36 24W     Detail CO 12:00 Th N63 AV 00:30 Sa NJT NS NS T   36 24W     Detail CO 12:00 Fr N63 AV 00:30 Su NJT NS NS T   36 24W     Detail CO 12:00 Sa N63 AV 00:30 Mo NJT NS NS T   36 24W                                       Detail CO 14:00 Mo BPA AV 08:00 Th PNE CSXI CSXI C I 65 Q112 Q162   Detail CO 14:00 Tu BPA AV 08:00 Fr PNE CSXI CSXI C I 65 Q112 Q162   Detail CO 14:00 We BPA AV 08:00 Mo PNE CSXI CSXI C I 113 Q112 Q162   Detail CO 14:00 Fr BPA AV 08:00 Mo PNE CSXI CSXI C I 65 Q112 Q162   Detail CO 14:00 Sa BPA AV 08:00 Tu PNE CSXI CSXI C I 65 Q112 Q162   Detail CO 14:00 Su BPA AV 08:00 We PNE CSXI CSXI C I 65 Q112 Q162                                     Detail CO 14:00 Mo BPA AV 08:00 We EMT CSXI CSXI C I 41 Q112 Q112   Detail CO 14:00 Tu BPA AV 08:00 Th EMT CSXI CSXI C I 41 Q112 Q112   Detail CO 14:00 We BPA AV 08:00 Fr EMT CSXI CSXI C I 41 Q112 Q112   Detail CO 14:00 Th BPA AV 08:00 Su EMT CSXI CSXI C I 65 Q112 Q112   Detail CO 14:00 Fr BPA AV 08:00 Su EMT CSXI CSXI C I 41 Q112 Q112   Detail CO 14:00 Sa BPA AV 08:00 Mo EMT CSXI CSXI C I 41 Q112 Q112   Detail CO 14:00 Su BPA AV 08:00 Tu EMT CSXI CSXI C I 41 Q112 Q112                                     Detail CO 17:00 Mo BPA AV 05:00 We LTF CSXI CSXI T   35 Q166 Q166   Detail CO 17:00 Tu BPA AV 05:00 Th LTF CSXI CSXI T   35 Q166 Q166   Detail CO 17:00 We BPA AV 05:00 Fr LTF CSXI CSXI T   35 Q166 Q166                                     Detail CO 17:00 Mo BPA AV 05:00 We LTF CSXI CSXI C   35 Q166 Q166   Detail CO 17:00 Tu BPA AV 05:00 Th LTF CSXI CSXI C   35 Q166 Q166   Detail CO 17:00 We BPA AV 05:00 Fr LTF CSXI CSXI C   35 Q166 Q166                                     Detail CO 18:00 Mo C59 AV 08:00 Th NKR CSXI CSXI C   61 Q156 Q156   Detail CO 18:00 Tu C59 AV 08:00 Fr NKR CSXI CSXI C   61 Q156 Q156   Detail CO 18:00 We C59 AV 08:00 Sa NKR CSXI CSXI C   61 Q156 Q156   Detail CO 18:00 Th C59 AV 08:00 Su NKR CSXI CSXI C   61 Q156 Q156   Detail CO 18:00 Fr C59 AV 08:00 Mo NKR CSXI CSXI C   61 Q156 Q156   Detail CO 18:00 Sa C59 AV 08:00 Tu NKR CSXI CSXI C   61 Q156 Q156   Detail CO 18:00 Su C59 AV 08:00 We NKR CSXI CSXI C   61 Q156 Q156                                     Detail CO 18:00 Mo C47 AV 15:00 We EMT NS NS B   44 24V     Detail CO 18:00 Tu C47 AV 15:00 Th EMT NS NS B   44 24V     Detail CO 18:00 We C47 AV 15:00 Fr EMT NS NS B   44 24V     Detail CO 18:00 Th C47 AV 06:00 Mo EMT NS NS B   83 24V     Detail CO 18:00 Fr C47 AV 06:00 Mo EMT NS NS B   59 24V     Detail CO 18:00 Su C47 AV 15:00 Tu EMT NS NS B   44 24V                                       Detail CO 20:00 Mo C47 AV 07:30 We ERL NS NS B   35 20R     Detail CO 20:00 Tu C47 AV 07:30 Th ERL NS NS B   35 20R     Detail CO 20:00 We C47 AV 07:30 Fr ERL NS NS B   35 20R     Detail CO 20:00 Th C47 AV 07:30 Sa ERL NS NS B   35 20R     Detail CO 20:00 Fr C47 AV 07:30 Su ERL NS NS B   35 20R     Detail CO 20:00 Sa C47 AV 07:30 Mo ERL NS NS B   35 20R     Detail CO 20:00 Su C47 AV 07:30 Tu ERL NS NS B   35 20R                                       Detail CO 20:30 Mo C59 AV 12:00 We KRN CSXI CSXI C I 39 Q164 Q164   Detail CO 20:30 Tu C59 AV 12:00 Th KRN CSXI CSXI C I 39 Q164 Q164   Detail CO 20:30 We C59 AV 12:00 Fr KRN CSXI CSXI C I 39 Q164 Q164   Detail CO 20:30 Th C59 AV 12:00 Sa KRN CSXI CSXI C I 39 Q164 Q164   Detail CO 20:30 Fr C59 AV 12:00 Su KRN CSXI CSXI C I 39 Q164 Q164   Detail CO 20:30 Sa C59 AV 12:00 Mo KRN CSXI CSXI C I 39 Q164 Q164   Detail CO 20:30 Su C59 AV 12:00 Tu KRN CSXI CSXI C I 39 Q164 Q164                                     Detail CO 20:30 Mo C59 AV 12:00 We NKR CSXI CSXI C   39 Q164 Q164   Detail CO 20:30 Tu C59 AV 12:00 Th NKR CSXI CSXI C   39 Q164 Q164   Detail CO 20:30 We C59 AV 12:00 Fr NKR CSXI CSXI C   39 Q164 Q164   Detail CO 20:30 Th C59 AV 12:00 Sa NKR CSXI CSXI C   39 Q164 Q164   Detail CO 20:30 Fr C59 AV 12:00 Su NKR CSXI CSXI C   39 Q164 Q164   Detail CO 20:30 Sa C59 AV 12:00 Mo NKR CSXI CSXI C   39 Q164 Q164   Detail CO 20:30 Su C59 AV 12:00 Tu NKR CSXI CSXI C   39 Q164 Q164                                     Detail CO 22:00 Mo N63 AV 11:00 We NJT NS NS C   36 24Z (Internatio     Detail CO 22:00 Tu N63 AV 11:00 Th NJT NS NS C   36 24Z (Internatio     Detail CO 22:00 We N63 AV 11:00 Fr NJT NS NS C   36 24Z (Internatio     Detail CO 22:00 Th N63 AV 11:00 Sa NJT NS NS C   36 24Z (Internatio     Detail CO 22:00 Fr N63 AV 11:00 Su NJT NS NS C   36 24Z (Internatio     Detail CO 22:00 Sa N63 AV 11:00 Mo NJT NS NS C   36 24Z (Internatio     Detail CO 22:00 Su N63 AV 11:00 Tu NJT NS NS C   36 24Z (Internatio

[MikeSanta]

Today on the BNSF/KCS tracks north of Dallas I saw a KCS van train stopped for an hour while three other trains passed it. One was a stacker, another was a hot shot covered hopper train with four or five engines pulling it and another engine pushing it; and the third was a manifest train. I was surprised to say the least.