Aerodynamics can get really complicated.
Witness the not-entirely-scientific study done by "Mythbusters" regarding driving a pick-up with the tailgate open or closed.
As I recall, they found that having the tailgate closed was actually more aerodynamic. It has to do with a circulating cushion of air in the truck bed that is not there with the tailgate open. This rather flies in the face of what one may think would happen with the tailgate closed and blocking the perceived airflow through the bed.
I know that before I put a bed cover on one of my pick-ups, anything loose in the bed would tend to end up behind the cab, rather than flying out of the bed.
Larry Resident Microferroequinologist (at least at my house) Everyone goes home; Safety begins with you My Opinion. Standard Disclaimers Apply. No Expiration Date Come ride the rails with me! There's one thing about humility - the moment you think you've got it, you've lost it...
rossiHowever, the Arrowedge generates an additional/extra/delta tail wake/vacuum resistance for the total combined resistance(of all combined containers).
Please explain better what you mean in this sentence. I think we have discussed the general pointlessness of putting a 'legacy' Arrowedge on the front of a train with no container(s) immediately behind its trailing edge, but that is because all the benefits of the leading streamlining would be lost by the time the deflected airflow reached the front of the next following container (leaving only the drags produced by the device as the net effect on train resistance). There is likely to be some trailing resistance due to the gap between the rear of the older Arrowedge and the front of the immediately following container, but presumably the high shaped airflow coming off the forebody shape is expected to persist over that gap. What is pointedly not discussed is whether the vacuum effect behind the forebody induces relatively high-pressure air or wind to move up as well as laterally into the gap, or where the collapsing flow from the forebody may be inducing larger vortices or flow instability/buffeting that might actually increase mean aerodynamic resistance on following containers.
I despaired of the UP team having a good knowledge of aerodynamics when they added the transom to make the Arrowedge easier to handle with a traditional crane and spreader. It would be interesting to see video of an array of yaw strings behind that set of struts. On the other hand, it can easily be interpolated that the transom didn't impair the actual overall train resistance very much...
It should be noted here that the "Arrowedge 3.0" has very little in common with the devices we have been discussing so far: it's a normal 53' container with the front 13' chopped off and fashioned into a fairly simple wedge beak. Here is a description of the system. This is said to have about 88% of the efficiency of the original at much lower cost (and, although it is not said, ease in handling the device with standard intermodal equipment).
I had thought that the use of wedge beaks to streamline the front of railroad equipment had been discredited long, long ago. Perhaps the BYU kids thought that because it wasn't on a locomotive, and they calculated the wind pressure as the resultant of so many psi incident over the whole of the flat (and corrugated) leading end, it would produce meaningful resistance reductions.
Where they may be missing something is in applying some form of abbreviated beaks, or probably better, parabolic deflectors, to the fronts of containers in the train, sized to deflect the vortices generated off the previous container end. One historical problem with the Airtab approach was that, while those devices were supposed to produce a set of clean trailing vortices, unlike the situation with a trailer those vortices may drift into incidence, perhaps more highly drag-inducing incidence, with the bluff fronts of the following containers, and this would be particularly troublesome when adding to the effect of a quartering wind.
(I have yet to relocate the Canadian report on the Airtab devices; can someone please provide a reference?)
Something I have requested, but not yet seen, is the actual dynamometer-car testing with and without an Arrowedge 3.0 device that shows the actual reduction in overall train resistance produced by the device over, say, a 'control' empty 53' in that position. (I have little doubt that instrumentation showing a substantial percentage of drag reduction on the modified container, measured relative to the twistlocks holding it to the container underneath, would show a reduction, but that's not the concern here.)
RME I was a bit surprised, when the 'original' stack cars (the ones with the large brackets to support the second level) came out, that some sort of 'wide diaphragm' arrangement that inflated or folded out wasn't provided to cut down on the drag between stacks. I remain surprised that Airtab 'sticks' that go into the side twistlocks at the rear of each container haven't caught on. I would like to surmise that wise heads have worked out the potential economies in detail. But the whole Arrowedge experience, including the aerodynamic bridge 'encounters' that indicate the designers didn't even fully comprehend aerodynamic lift principles, have left me with a bad taste and suspicion about that.
I was a bit surprised, when the 'original' stack cars (the ones with the large brackets to support the second level) came out, that some sort of 'wide diaphragm' arrangement that inflated or folded out wasn't provided to cut down on the drag between stacks. I remain surprised that Airtab 'sticks' that go into the side twistlocks at the rear of each container haven't caught on. I would like to surmise that wise heads have worked out the potential economies in detail. But the whole Arrowedge experience, including the aerodynamic bridge 'encounters' that indicate the designers didn't even fully comprehend aerodynamic lift principles, have left me with a bad taste and suspicion about that.
https://www.youtube.com/watch?v=Wn3keSazR7o
http://www.up.com/aboutup/community/inside_track/arrowedge-redesign-04-27-2016.htm
https://www.youtube.com/watch?v=hbSF-EXminQ
New Arrowedge 3.0.
UP put it into operation!
RME Cotton Belt MP104 this ......."McKeen-like relationship".....ref your post Wednesday, April 12, 2017 5:14 PM A little 'fast and loose' and not scrupulous scholarship, but relatively easy to fact-check: As I recall, some of the development of Arrowedge was done by people "connected" with the Union Pacific organization, as I recall was the case with McKeen and how he got his 'foot in the door' with Union Pacific and then had assistance with his further development. In a sense this might be an example of a 'scientific engineering' achievement that has benefited much more from 'who they knew' than from 'what they knew'. I was not trying to make any connection between Arrowedge and the 'windsplitting' streamlining on McKeen cars.
Cotton Belt MP104 this ......."McKeen-like relationship".....ref your post Wednesday, April 12, 2017 5:14 PM
A little 'fast and loose' and not scrupulous scholarship, but relatively easy to fact-check:
As I recall, some of the development of Arrowedge was done by people "connected" with the Union Pacific organization, as I recall was the case with McKeen and how he got his 'foot in the door' with Union Pacific and then had assistance with his further development. In a sense this might be an example of a 'scientific engineering' achievement that has benefited much more from 'who they knew' than from 'what they knew'.
I was not trying to make any connection between Arrowedge and the 'windsplitting' streamlining on McKeen cars.
More than just "connected" with the UP.
http://www.uprr.com/newsinfo/releases/environment/2013/0903_arrowedge.shtml
So it's automatically a success.
Jeff
zugmann Shadow the Cats owner Your also forgetting one thing weight of the containers. Not all of them are loaded with light items. There is a weight limit for each well and you also better take that into consideration. Failure to do so can lead to bigger problems down the line. Also where the weight is in the train and how it is made up can make for either a smooth handling train or one that is a bucking bronco for the crew to handle due to the slack running in and out of it. Not really issues for trailer trains. Not much slack and the weight isn't much compared to other train types.
Shadow the Cats owner Your also forgetting one thing weight of the containers. Not all of them are loaded with light items. There is a weight limit for each well and you also better take that into consideration. Failure to do so can lead to bigger problems down the line. Also where the weight is in the train and how it is made up can make for either a smooth handling train or one that is a bucking bronco for the crew to handle due to the slack running in and out of it.
Your also forgetting one thing weight of the containers. Not all of them are loaded with light items. There is a weight limit for each well and you also better take that into consideration. Failure to do so can lead to bigger problems down the line. Also where the weight is in the train and how it is made up can make for either a smooth handling train or one that is a bucking bronco for the crew to handle due to the slack running in and out of it.
Not really issues for trailer trains. Not much slack and the weight isn't much compared to other train types.
I second Zug.
rossiI saw some canadian govenment research that airtab does even not work for truck.
By all means find the reference (and if possible a link) and post them here. I have never been quite convinced that those vortex generators worked quite as well as claimed for trailers (and by extension containers).
I remain surprised that Airtab 'sticks' that go into the side twistlocks at the rear of each container haven't caught on.
[/quote]
I saw some canadian govenment research that airtab does even not work for truck.
The opinions expressed here represent my own and not those of my employer, any other railroad, company, or person.
Loading stack trains isn't a trivial exercise. Ideally, you'd have everything stacked and nothing empty. Here are some of the hurdles:
You need to spot the right cars for loading.
You need to minimize switching of empties in the terminal.
You need to know what boxes need to be loaded.
You need to know how many boxes are going where (blocking).
You need to set the loading tracks as few times as possible and make your cut-off for building the train.
You have to be sure you can cover all your work for the day. Can't optimize for this train that'll leave you hanging for the next.
If you can have a computer algorithm do the heavy lifting, then the terminal mgr just has to tweak the plan. NS paid a good bit for a process to optimize intemodal loading including "selling" it to terminal operations. It seems to have worked.
-Don (Random stuff, mostly about trains - what else? http://blerfblog.blogspot.com/)
traisessive1 challenger3980 Something that I think you are forgetting here, is that the Railroad DOESN'T OWN the containers, so they would basically be asking to use someone else's boxes for the sole purpose of reducing their fuel usage. CN, CP and CSX all have MANY of their own containers. When you look at a CN domestic intermodal train, 40-50% of the containers will be CN containers. Also, if you look at an average CN intermodal train, doubles/empties/singles will be randomly spread all through the train in no logical order at all. They just don't care.
Something that I think you are forgetting here, is that the Railroad DOESN'T OWN the containers, so they would basically be asking to use someone else's boxes for the sole purpose of reducing their fuel usage.
I don't think it is a matter of "they don't care", I think it is more a matter that it is not ecconomical to care... if there were some ecconomic reason to spend extra time (pronounce that, "money!") to arrange the train in some particular order, they'd do it (they do when the train must be split at some intermediate terminal!).
I am surprised that they will take the time (pronounce that, "money!") to be sure the lead container car has only one container on it, so that this ArroWedge device can be applied and that they take the time (pronounce that, "money!") to put the thing on the lead car.
Semper Vaporo
Pkgs.
challenger3980 Something that I think you are forgetting here, is that the Railroad DOESN'T OWN the containers, so they would basically be asking to use someone else's boxes for the sole purpose of reducing their fuel usage.
10000 feet and no dynamics? Today is going to be a good day ...
ROBBIE SPAIN Hey All, I heard somewhere that the arrowhead only really works for about the first ten or so cars back. Afterwhich, air flow returns to "normal" for such a train. So I don`t think you`d find much of a fuel savings from this thing. As another poster noted, it does sound like some kind of "an interesting relationship" is going on here between some company and who? EPA maybe? Or the bunny huggers? On some steamers though, there was SOME advantage to streamlining. (i.e. smoke ears on 844, streamlined casing on 611) Remember seeing something about the arrowhead on a website of the school eng. kids that were doing some of the design work on it. Didn`t seem to me to be much of an advantage in the real world though. Esp. if it`s only good for the first few cars. Just a few of my thoughts.
Hey All, I heard somewhere that the arrowhead only really works for about the first ten or so cars back. Afterwhich, air flow returns to "normal" for such a train. So I don`t think you`d find much of a fuel savings from this thing. As another poster noted, it does sound like some kind of "an interesting relationship" is going on here between some company and who? EPA maybe? Or the bunny huggers? On some steamers though, there was SOME advantage to streamlining. (i.e. smoke ears on 844, streamlined casing on 611)
Remember seeing something about the arrowhead on a website of the school eng. kids that were doing some of the design work on it. Didn`t seem to me to be much of an advantage in the real world though. Esp. if it`s only good for the first few cars. Just a few of my thoughts.
The ArroWedge Concept seemed to be around a lot several months back, when operating out of the K.C. area. Then it apparently wound up in Chicago,in April, and got interchanged(?) on a train to Milwaukee; it was ok til it hit the 35th St. Bridge there, and wound up Apparently, not nearly as areodynamic when running backwards?
It has been pointed out elsewhere that McKeen got the streamlining backwards, it should have been rounded in front and tapered in the back.
Cotton Belt MP104this ......."McKeen-like relationship".....ref your post Wednesday, April 12, 2017 5:14 PM
RME: I tried to google this and am still wondering, however reading between the lines I have an idea as to the meaning, but can you 'splain this ......."McKeen-like relationship".....ref your post Wednesday, April 12, 2017 5:14 PM Thanks endmrw0426171219
tree68Such devices were used on a lot of locomotives - and other approaches were used for the same purpose (see ATSF's stack extensions) - and that was to get the smoke a little higher over the locomotive/train.
Two things about this: (1) as I recall the ATSF stack extensions, they were for better drafting (more ideal 'chimney' proportions) where clearance permitted, with the option to retract when not; and (2) the purpose of the practical smoke deflectors turned out to be less "lifting" the smoke as aerodynamically moving it away from the sightlines from the cab past the boiler, with minimum 'structure' obstructing that view. The elephant ears and their reinforcement are very 'thin' seen from the cab, and the displacement and vortex generation is 'just enough' to roll the smoke and steam away from the view -- where it goes after that, particularly with high-efficiency low-back-pressure front end designs, will be down around the train (but that will presumably be air-conditioned equipment for fast service...)
"Lifting" a plume of smoke is obviously not going to work too well, and result in substantial drag -- as was unsurprisingly found by most of the people tinkering with 'smoke lifters' at the top and front of the smokebox area.
ROBBIE SPAIN ...smoke ears on 844...
Such devices were used on a lot of locomotives - and other approaches were used for the same purpose (see ATSF's stack extensions) - and that was to get the smoke a little higher over the locomotive/train. They really had little to do with streamlining, and probably actually caused drag.
OK, so it can make a difference, and every little bit helps.
Thanks!
Not ever having heard of Kantola streamlining, I just had to look it up - and I found a really great article by the man himself, Carl F. Kantola !
https://nycshs.files.wordpress.com/2014/07/pages-from-1981q3.pdf
It runs from page nos. 8 to 30 (23 pgs. net). Aside from the numerous pictures of that result and others, the photos at the bottom of pgs. 13, 19, and 22 may be of interest to those here.
RME - thanks for your insights and comments ! (some of which are over my head, but that's OK)
- PDN.
Firelock76I'm reminded of the streamlined steam locomotives of the pre-war era. I read as good as some of them looked it really was just for looks, the streamlining had little or no effect of performance or economy.
There were two fundamental kinds of steam streamlining (a bit like good taste vs. tasting good). Some (the MILW A class, the British A4s, and the German 4-6-4s and streamlined tanks) were scientifically designed to aid in high speed (some combining lower drag with better smoke-lifting for visibility at speed). On the other hand, some -- probably most -- were little more than colorful period tin intended to give a modern appearance for marketing.
There was a middle ground - the Kantola streamlining for the Commodore Vanderbilt provided something like a gain of 400 usable HP at 85-90mph (there is a number in Staufer's Thoroughbreds, but I don't have access to it now). This is meaningful but not essential in the usual range of steam 'express' service in the United States. PRR conducted wind-tunnel testing on that wacky 3768 clown-with-a-dump-in-its-drawers scheme, and there's probably some objective range of drag-reduction numbers there; I'd be interested to see the counterpart for the S1 (a more sophisticated and far higher-speed design).
The famous NYC Dreyfuss streamlining, on the other hand, was a pathetic thing as far as actual drag reduction went. I don't have my Quadrant Press book on streamlined steam at hand, either, so I can't work through the list, but it might also be remembered that many designs with fancy shrouds didn't have the machinery to make actual speed where the drag reduction would matter. C&NW E4s, the ATSF Blue Goose, and just about anything south of the Mason-Dixon line probably come in that category, although I will listen to demonstrable counterproof. We should also remember that even though we call the streamlining 'tin' it was often not thin-gauge and required considerable bracketry to install; the specific reason ATSF 3765 was not streamlined (with the same sort of Mae West look as 3460) was that the rig would have made the locomotive significantly overweight.
The thing about freight trains and 'streamlining' is that even very small improvements in aerodynamics, if they are consistent, can add up to meaningful economy. As Shadow's owner can probably relate better than I can, even things that improve fuel mileage by 0.1% can be worth doing if they can be cost-effectively implemented; part of the argument for things like TOR lube, the GE supersonic rail cleaner, and those spring-magazine stick flange lubricators was that they consistently provided small improvements in cost per mile.
Very clearly, things that decrease the aerodynamic train resistance for doublestacks can be valuable. And for automotive engineers unfamiliar with railroad history and experience (the Adams Windsplitter and locomotives a bec being two very useful precedents, if they had cared to look) I'm sure the idea of a MIRV forebody was an attractive design pattern, obvious to the lay audience as being Really, Really Streamlined.
The problem is that 'marketing' streamlining is no more effective on freight consists than it was for '30s passenger trains to the North Woods.
At the speed most freight trains travel does any attempt at streamlining really make a difference?
I'm reminded of the streamlined steam locomotives of the pre-war era. I read as good as some of them looked it really was just for looks, the streamling had little or no effect of performance or economy.
challenger3980Something that I think you are forgetting here, is that the Railroad DOESN'T OWN the containers, so they would basically be asking to use someone else's boxes for the sole purpose of reducing their fuel usage.
Something I think you are forgetting here is that there is an enormous glut of used containers, and UP could easily acquire all the containers they might deem 'needed' for the purpose in any given lane, probably for less aggregate cost than one new Arrowedge. Treat them as being in dedicated service like barrier cars for hazmat service. [EDIT: see the construction of the new Arrowedge 3.0, actually built out of a modified 53' container.]
But still, I think little practical gain to using empties for streamlining -- I don't have time or patience to set up computations to analyze, but someone here will.
Dakguy201 wrote:
I am wondering that since the railroad finds the efficiency of the Arrowedge sufficient to surrender a revenue producing place on the train, would it also make sense to ship an empty container on any car that would otherwise be a single stack?
Add in the labor expense of loading and unloading the empty boxes, in the end is there really any savings at the end of the day doing it?
It may look reasonable at first glance, but it may not be worth the effort/expense for the POTENTIAL savings. I don't know enough to evaluate the possible savings myself, but I do see another side to the equation.
Doug
May your flanges always stay BETWEEN the rails
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