MichaelSol wrote: TomDiehl: No, you're trying to take my original statement by itself rather than an answer to Chad's statement, which is how it was originally posted. Read the first sentence of Chad's original entry above. I offered the Kuhler, Loewy, and Dreyfus statemnt as an example that this has been known for quite some time. Known by who? You? Streamlining had little actual effect on the power needs of trains. That's what Kuhler, et. al. meant and said, because streamlining had little actual effect on overcoming the resistance of trains to air density with increasing speed. It does not say that air density is not important, it simply says that streamlining didn't offer much improvement. Lowering the motion resistance by reducing weight had a bigger effect, because there just wasn't much that could be done about air resistance. Weight, however, could be reduced. That's what Kuhler said and meant. That has nothing, absolutely nothing, to do with what Chad was speaking to. It is, absolutely, not the same thing as saying that air resistance has a "negligble effect" on the power needs of trains attempting to reach higher speeds. As a matter of information, COFC is somewhat higher in the air drag coefficient than a regular boxcar, and TOFC's air drag coefficient more than twice the air drag coefficient of a boxcar. Accordingly, to operate at higher speeds, not only does more power have to be assigned to overcome the air drag coefficient, but more power would be necessary on TOFC to reach the higher speeds than an equivalent boxcar unit even though the loaded boxcar or hopper car was no doubt heavier.
TomDiehl: No, you're trying to take my original statement by itself rather than an answer to Chad's statement, which is how it was originally posted. Read the first sentence of Chad's original entry above. I offered the Kuhler, Loewy, and Dreyfus statemnt as an example that this has been known for quite some time.
TomDiehl:
No, you're trying to take my original statement by itself rather than an answer to Chad's statement, which is how it was originally posted. Read the first sentence of Chad's original entry above. I offered the Kuhler, Loewy, and Dreyfus statemnt as an example that this has been known for quite some time.
Known by who? You?
Streamlining had little actual effect on the power needs of trains. That's what Kuhler, et. al. meant and said, because streamlining had little actual effect on overcoming the resistance of trains to air density with increasing speed. It does not say that air density is not important, it simply says that streamlining didn't offer much improvement.
Lowering the motion resistance by reducing weight had a bigger effect, because there just wasn't much that could be done about air resistance. Weight, however, could be reduced. That's what Kuhler said and meant.
That has nothing, absolutely nothing, to do with what Chad was speaking to. It is, absolutely, not the same thing as saying that air resistance has a "negligble effect" on the power needs of trains attempting to reach higher speeds.
As a matter of information, COFC is somewhat higher in the air drag coefficient than a regular boxcar, and TOFC's air drag coefficient more than twice the air drag coefficient of a boxcar. Accordingly, to operate at higher speeds, not only does more power have to be assigned to overcome the air drag coefficient, but more power would be necessary on TOFC to reach the higher speeds than an equivalent boxcar unit even though the loaded boxcar or hopper car was no doubt heavier.
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.
Just stating facts & not conjective
chad thomas wrote: spbed wrote: Sorry I do not agree with your theroy. When I was doing it I used a routing of UP-Fre then CNW to Chicago. My company's traffic moved on the UP/CNW hottest train then called the "Falcon" 40 some odd hours LAX/Chic. As that train arrived in Chic in the AM & containers destined for like NY, Balt, Bost, Philly were then DRAYED by the CNW to the eastern RR to connect to trains departing in the PM . From the PNW we used the BNRR & there TT Sea/Chic was 3rd morning delivery in Chic & they also would dray the containers to the eastern RR. I think today those probably are the still the fastest TT out there that I mentioned. Also you did look up in this thread of a BNSF stacker being paced at 70MPH? . greyhounds wrote: BNSF has enough intermodal business so that it is able to facilitate segmentation of the traffic based on customer need. There's no sense in wasting money powering up a train with a high HP/ton ratio and running it Hell Bent for Leather if the customer doesn't want or need such service. More importantly, there's no sense in doing that if the customer won't pay extra for it. So BNSF offeres different service levels at different prices. The highest service level is used by the most service sensative customers. UPS and perishable commodity truckers like Stevens Transport are examples. This freight moves TOFC on the BNSF. There are some extra steps with COFC that at least have the potential to slow things down. I recall the BNSF standard for this level of service as being 750 miles/day. On the other hand, a container that's taken a slow boat from China isn't going to get much benifit from a fast ride from LA to Chicago. They get a slower ride at a lower price. I recall the BNSF standard for this level of service as being 400 miles/day. This is their double stack business. It all makes sense, at least on the BNSF. And it's the customer's choice as to what level of service is selected. Other railroads have different markets and different conditions. Yea Ken, Your theory is all wrong. Because Spbecialed said so, so it must be. There is just no such thing as multiple service levels. Just look at his lame video, that will prove it.
spbed wrote: Sorry I do not agree with your theroy. When I was doing it I used a routing of UP-Fre then CNW to Chicago. My company's traffic moved on the UP/CNW hottest train then called the "Falcon" 40 some odd hours LAX/Chic. As that train arrived in Chic in the AM & containers destined for like NY, Balt, Bost, Philly were then DRAYED by the CNW to the eastern RR to connect to trains departing in the PM . From the PNW we used the BNRR & there TT Sea/Chic was 3rd morning delivery in Chic & they also would dray the containers to the eastern RR. I think today those probably are the still the fastest TT out there that I mentioned. Also you did look up in this thread of a BNSF stacker being paced at 70MPH? . greyhounds wrote: BNSF has enough intermodal business so that it is able to facilitate segmentation of the traffic based on customer need. There's no sense in wasting money powering up a train with a high HP/ton ratio and running it Hell Bent for Leather if the customer doesn't want or need such service. More importantly, there's no sense in doing that if the customer won't pay extra for it. So BNSF offeres different service levels at different prices. The highest service level is used by the most service sensative customers. UPS and perishable commodity truckers like Stevens Transport are examples. This freight moves TOFC on the BNSF. There are some extra steps with COFC that at least have the potential to slow things down. I recall the BNSF standard for this level of service as being 750 miles/day. On the other hand, a container that's taken a slow boat from China isn't going to get much benifit from a fast ride from LA to Chicago. They get a slower ride at a lower price. I recall the BNSF standard for this level of service as being 400 miles/day. This is their double stack business. It all makes sense, at least on the BNSF. And it's the customer's choice as to what level of service is selected. Other railroads have different markets and different conditions.
Sorry I do not agree with your theroy. When I was doing it I used a routing of UP-Fre then CNW to Chicago. My company's traffic moved on the UP/CNW hottest train then called the "Falcon" 40 some odd hours LAX/Chic. As that train arrived in Chic in the AM & containers destined for like NY, Balt, Bost, Philly were then DRAYED by the CNW to the eastern RR to connect to trains departing in the PM . From the PNW we used the BNRR & there TT Sea/Chic was 3rd morning delivery in Chic & they also would dray the containers to the eastern RR. I think today those probably are the still the fastest TT out there that I mentioned. Also you did look up in this thread of a BNSF stacker being paced at 70MPH? .
greyhounds wrote: BNSF has enough intermodal business so that it is able to facilitate segmentation of the traffic based on customer need. There's no sense in wasting money powering up a train with a high HP/ton ratio and running it Hell Bent for Leather if the customer doesn't want or need such service. More importantly, there's no sense in doing that if the customer won't pay extra for it. So BNSF offeres different service levels at different prices. The highest service level is used by the most service sensative customers. UPS and perishable commodity truckers like Stevens Transport are examples. This freight moves TOFC on the BNSF. There are some extra steps with COFC that at least have the potential to slow things down. I recall the BNSF standard for this level of service as being 750 miles/day. On the other hand, a container that's taken a slow boat from China isn't going to get much benifit from a fast ride from LA to Chicago. They get a slower ride at a lower price. I recall the BNSF standard for this level of service as being 400 miles/day. This is their double stack business. It all makes sense, at least on the BNSF. And it's the customer's choice as to what level of service is selected. Other railroads have different markets and different conditions.
BNSF has enough intermodal business so that it is able to facilitate segmentation of the traffic based on customer need.
There's no sense in wasting money powering up a train with a high HP/ton ratio and running it Hell Bent for Leather if the customer doesn't want or need such service. More importantly, there's no sense in doing that if the customer won't pay extra for it.
So BNSF offeres different service levels at different prices. The highest service level is used by the most service sensative customers. UPS and perishable commodity truckers like Stevens Transport are examples. This freight moves TOFC on the BNSF. There are some extra steps with COFC that at least have the potential to slow things down. I recall the BNSF standard for this level of service as being 750 miles/day.
On the other hand, a container that's taken a slow boat from China isn't going to get much benifit from a fast ride from LA to Chicago. They get a slower ride at a lower price. I recall the BNSF standard for this level of service as being 400 miles/day. This is their double stack business.
It all makes sense, at least on the BNSF. And it's the customer's choice as to what level of service is selected.
Other railroads have different markets and different conditions.
Yea Ken, Your theory is all wrong. Because Spbecialed said so, so it must be. There is just no such thing as multiple service levels. Just look at his lame video, that will prove it.
Living nearby to MP 186 of the UPRR Austin TX Sub
Here's a little proof that CSX engineers could care less whether they've got trailers, double stacks, or autoracks behind them. The timetable says they're cleared for 70mph, and that's what they're run at if clear signals are present. If the trailers' are producing more drag; just kick the engines up a notch! I will say that the uneven trailer spacing produces a great deal more wind when they go by though! (which is good for those hot, gnat-inducing days in FL)
http://www.youtube.com/watch?v=7egWCJh20Iw
anb740
Joe H. (Milepost S256.0; NS Griffin District)
Pictures: http://anb740.rrpicturearchives.net
Youtube: http://www.youtube.com/anb740
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.
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.
But, that's not what they said, and what you said happens to be wrong, absolutely, unequivocally wrong. You are completely mixed up here, and as usual can't even understand why.
They said streamlining had a relatively small effect on the air drag coefficient. That's exactly what the coefficients of air drag friction show.
The Davis Algorithm and its refinements are generally accepted by the industry, and any industry that deals with mechanical motion and propulsion. You can ignore them until you are blue, but it doesn't change the fact that 1) you are misrepresenting what Kuhler said, and 2) you are factually wrong.
It is easy to put Kuhler's remarks, or anyone else's, into context.
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.
MichaelSol wrote: 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.I am sure you remember it well. 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. But, that's not what they said, and what you said happens to be wrong, absolutely, unequivocally wrong. You are completely mixed up here, and as usual can't even understand why. They said streamlining had a relatively small effect on the air drag coefficient. That's exactly what the coefficients of air drag friction show. The Davis Algorithm and its refinements are generally accepted by the industry, and any industry that deals with mechanical motion and propulsion. You can ignore them until you are blue, but it doesn't change the fact that 1) you are misrepresenting what Kuhler said, and 2) you are factually wrong.
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.
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.
Wrong again Michael.
Since you like digging up formulas and figures, how about one that would actually apply to what was being discussed here: 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?
TomDiehl wrote: MichaelSol wrote: 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.I am sure you remember it well. 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. But, that's not what they said, and what you said happens to be wrong, absolutely, unequivocally wrong. You are completely mixed up here, and as usual can't even understand why. They said streamlining had a relatively small effect on the air drag coefficient. That's exactly what the coefficients of air drag friction show. The Davis Algorithm and its refinements are generally accepted by the industry, and any industry that deals with mechanical motion and propulsion. You can ignore them until you are blue, but it doesn't change the fact that 1) you are misrepresenting what Kuhler said, and 2) you are factually wrong. Wrong again Michael. Since you like digging up formulas and figures, how about one that would actually apply to what was being discussed here: 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?
MichaelSol wrote: TomDiehl wrote: MichaelSol wrote: 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.I am sure you remember it well. 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. But, that's not what they said, and what you said happens to be wrong, absolutely, unequivocally wrong. You are completely mixed up here, and as usual can't even understand why. They said streamlining had a relatively small effect on the air drag coefficient. That's exactly what the coefficients of air drag friction show. The Davis Algorithm and its refinements are generally accepted by the industry, and any industry that deals with mechanical motion and propulsion. You can ignore them until you are blue, but it doesn't change the fact that 1) you are misrepresenting what Kuhler said, and 2) you are factually wrong. Wrong again Michael. Since you like digging up formulas and figures, how about one that would actually apply to what was being discussed here: 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? 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.
You're the one trying to change the subject. Chad originally made the statement that one type of train would run slower than the other due to a difference in wind resistance. I replied that the wind resistance wasn't a major factor in the overall power required to run the train, and made reference to major designers in the early streamlining era that stated it was for cosmetic and public relations, rather than functional purposes. Streamlining, in the functional sense, is to reduce wind resistance.
If not related to the horsepower required to move the train, why would wind resistance even be a concern?
TomDiehl: <>If not related to the horsepower required to move the train, why would wind resistance even be a concern?
Getting it yet?
TomDiehl wrote: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.
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
MichaelSol wrote: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.
timz wrote: TomDiehl wrote: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.
MichaelSol wrote: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?
TomDiehl:<>If not related to the horsepower required to move the train, why would wind resistance even be a concern?
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?"
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.
MichaelSol wrote: .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.
.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.
GP40-2 wrote: MichaelSol wrote: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.
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
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."
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.
I think its time to call the mythbusters!!!
TomDiehl wrote: timz wrote: TomDiehl wrote: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.
TomDiehl wrote: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.
WHAT I ASKED - etc....
Well, the answer to your question is yes, sometimes, it all depends.
Ooops! I must have been half-awake... I did mean Willow Springs, not Western Springs. Close though.
CC
MichaelSol wrote: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.
erikem wrote: TomDiehl wrote: 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.
TomDiehl wrote: 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.
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.
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)
-Don (Random stuff, mostly about trains - what else? http://blerfblog.blogspot.com/)
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
Our community is FREE to join. To participate you must either login or register for an account.