Wayne Kennedy’s article was an interesting read and nice to have some recent data on freight train resistance as opposed to the Davis article in an 1926 issue of GE Review. The article did leave me with a few questions.
First us how much time do “conventional” freight trains spend at 60mph and above? This is the speed where air resistance dominates on a conventional freight train, noting empty hoppers and gondolas are an exception. The flip side is is easier to get some improvement with conventional freight cars.
Second is what kind of progress is being made with reducing air resistance with intermodal trains? These trains typically run faster than conventional freights and have a lower speed where air drag dominates so would be where the most payoff for reducing air resistance occurs.
Third is how much of the fuel consumption is due to ascending hills, or energy wasted by the need to use braking on descending grades?
Fourth is how accurate is computational fluid dynamics in estimating the air drag of a freight train? This a a much modre complicated problem than trying to model air resistance of aircraft.
Another person who read that article, huh? It may not be quite as accurate as an aircraft, because railcars trail other ones, and planes don’t really follow close enough for this to be an issue, I not knowing much of anything about aerodynamics, think that it should still be a somewhat accurate representation, however.
I think only UP and BNSF have a significant amount of 70 MAS for freight. CSX has a bit in Georgia. I think that’s it. Need to add anyone/ anywhere else?
Kind of what I expected. There is still some benefit by reducing air drag of conventional freight, but won’t be a dramatic as reducing intermodal air drag.
I believe there’s a difference between speed limit and the actual speed that most freights operate at, especially since the inception of PSR and the commodization of container traffic.
When I had the territory West of Willard as a part of my job - a Quartering wind would slow the intermodal train fighting it by about 15 MPH from the normal speed. If the direction was favorable the maximum allowed speed was attained with minimal effort.
I picked up the issue to see if I wanted to try to resubscribe. That article reminded me of the articles that appear in Railway Age. (It probably belonged in RA. There the author would be called a “contributing editor” in RA.) Someone has an idea or product they think will revolutionize the industry and needs to be adopted ASAP.
He may have some valid criticisms, but some ideas make me wonder if they really are as cost efficient as he maintains. Concerning covered hoppers, I would think other parts of the car body design would be more of a problem rather than the roof walk.
Remember way back when EMD rounded the edges on a locomotive. It did provide some savings but not enough to offset the cost of manufacturing locomotives.
I also wonder if he developed the arrowedge that went on top of a container right behind the lead locomotive consist. I haven’t seen one in years. I think the last picture of one, also some years back, was of an arrowedge that didn’t clear a bridge when the train was routed down the wrong track.
He talked about modifying couplers on auto racks so the cars are closer together. The reason those cars have a big gap when the slack is stretched out is because the cars are equipped with long, cushioned drawbars. Reefers and most new large box cars have the same kind of cushioning devices. It’s to protect the loads from rough handling on the road and in the yard. Would getting rid of the cushioned drawbars in favor of better aerodynamics be cost effective? I don’t know, not that I would shed tears if there would be less cushioned drawbars out there.
What I found lacking in the article was any mention of grade resistance. I did some work with the Davis formula when I was with RoadRailer. The resistance produced by having to drag a train up a grade just overwhelmed the other resistance factors. If you add weight to make the trains more aerodynamic there will be a payback when that extra weight has to be drug uphill,
What I see as a real need is a validated predictive model of the railroad that can quickly indicate the financial effect of changes such as this.
Keep in mind that grade resistance is a different beast than “journal resistance”, “flange resistance” and “air resistance”. The energy used to overcome the resistance of an ascending grade can theoretically be recovered on a descending grade. The energy lost in overcoming “journal”, “flange” and “air” resistance is simply lost.
The graph of resistance vs speed for TOFC tops out at 14lbf/ton at 100 mph, which is equivalent to a 0.7% grade - you are correct in asserting grade resistance can overwhelm all other sources of resistance.
His comment about aerodynamic improvements costing an extra 2% imply that these do not significantly increase weight. OTOH, it’s possible that spending 2% more to reduce tare weight may have better payback than reducing air resistance. In the case of auto racks, the reduced air resistance may translate into less dirt and dust getting into the auto racks.
Oh I’m very aware of that. But if a track is only class 4 it’s over 60 time is going to be zero now with PTC. There really isn’t much track over class 4.
But I do think most intermodals are probably going over 60 on the stretches where they can on UP and BNSF. Otherwise why would they bother with class 5?
It’s been a while since I’ve paced a BNSF or UP freight across the desert but I have timed them going pretty close to 70 for a long stretch
Truckers are increasingly using aerodynamic fairings on both the tractors and trailers. There must be a benefit or they wouldn’t be using them. And they’re very lightweight.
I’d have to image that the aerodynamic resistance between an intermodal railcar and a highway truck trailer would be fairly similar.
That logic appeals to me… then I get reminded of CMStPnP hawking AI. That being said, I do believe that those streamlinings do probably have a net positive effect.
A bit off topic, my son and I drove past Willard two weeks ago on our way to Plymouth to visit my grandparents grave. The former B&O Willard to Mansfield line is on the western boundary of the cemetery.
Reading all of these comments, maybe closing this gap may be a more viable solution, albeit for these intermodal trains that routinely run at or above 65 miles an hour. So maybe more aerodynamic containters/well cars or however that would work, but for instance, these coal trains are unaerodynamic, yes (I don’t know if that’s a word but I think ya’ll get the gist) but they also don’t generally run at such high speeds as these hotshot Z trains that BNSF and UP run. Like on BNSF’s Southern Transcon, Z trains are supposed to run at or near 70mph, Q and S trains are supposed to run at or near 60-65mph. However, manifests are only allowed to run at about 55mph, so while it is near that 60mph threshold, it is not as much of an impact as the intermodals, especially when you consider that drag increases exponentially. I say all this to say that maybe a dedicated railcar pool of high-speed intermodal equipment for the Transcon for BNSF and UP might work as they have the higher running speeds than say CSX or NS. Or was there sonething like that the ATSF did, what was it, the Super Hoppers or something that didn’t work well, because they couldn’t really be interchanged with other hoppers and had to run as straight unmixed unit trains or something?