I’m always for energy saving ideas when they payback the effort. Here’s one that would be an advantage for our long haul American Interstate trucking companies. This semi has both side wings and a boat tail to decrease wind drag.
It is pretty simple really:
‘Boat tail’ decreases fuel consumption for trucks by 7.5 percent
From a Delft Technical University press release
A boat tail, a tapering protrusion mounted on the rear of a truck, leads to fuel savings of 7.5 percent. This is due to dramatically-improved aerodynamics, as shown by road tests conducted by the PART (Platform for Aerodynamic Road Transport) public-private partnership platform.
Here are the other places wind resistance on a semi-truck can be addressed for fuel savings:
Public highways
A boat tail is a tapering protrusion about two metres in length mounted on the rear of a truck. The boat tail had already proved itself during wind tunnel experiments and computer simulations, both conducted at TU Delft, in theory and using small-scale models. Now an articulated lorry fitted with a boat tail has also undergone extensive testing on public highways.
Emissions
An articulated lorry was driven for a period of one year with a boat tail (of varying length) and one year without a boat tail. The improved aerodynamics, depending on the length of the boat tail, resulted in reduced fuel consumption (and emissions!) of up to 7.5 percent. The optimum boat tail length proved to be two metres.
PART
The tests were conducted by PART. This is a platform in which academics, road transport manufacturers, transport companies and shippers work together. The platform aims to reduce fuel consumption in the road transport industry by improving aerodynamics. PARTs ambition is to achieve a 20 percent reduction in fuel consumption and CO2 emissions in the road transport industry by 2020. TU Delft acts as secretary of PART. PART has previously conducted road tests on a new generation of aerodynamic sideskirts, which are to make their commercial debut later this year.
More information
More on PART: www.part20.eu
More about the side wings: www.ephicas.eu
Let’s talk to independent truckers. They own the tractor but not the trailer. They pay their own fuel costs. So why would a company make a capital investment and then pay for additional maintenance costs to save an independent trucker money on fuel costs? I do not know what percent of trucking is done by independents, anyone?
Roger Sowell (21:13:20) :
“…impractical…The truck driver must stop, remove…re-install…time is money…”
This was just an experiment to test the aerodynamics in real-world conditions. In practice, I’d think you would design the boat-tail into the trailer by tapering its rear 2 meters. Of course, you’d lose some cargo space, and you’d need to be able to open out the sides to accomodate large cargo, etc. The real question is whether the fuel savings would offset the reduced revenue and added complexity of the trailer. 7.5% savings on fuel is a pretty big chunk.
Do you folks have any idea how much freight is moved in this country? If railroads could move it all, believe me they would be doing it. But rail is lacking in capacity and slow… B.
… just in time, triple screamer hot loads. Companies often do a poor job of ordering product because they run down-sized on staff and fail to spot shortages effectively. – Eddie Murphy
Ed “Just in time” is also about eliminating complete warehouses. R/R just do not cut it in efficiency. My ears still ring with the swearing from the warehouse foreman and production manager when the R/R did not bother to move our load from the flat bed to the truck for a week and no amount of screaming got us anywhere. The company would rather pay a slightly higher transport rate than shut down a production line for a week because the R/R will no get off their duffs and move a load siding on a rail siding.
Fuel efficiency could be greatly increased by redesigning trucks completely such as a V shaped snout, a smooth shroud connecting the cab and trailer and the boat tail. Unfortunately it increases the length. With sleeper cabs and 53′ trailers the laws, roads and especially the loading dock areas just will not take longer rigs.
The biggest problem with railways is the monopolies they impose. Unions take over and employees don’t ever have to worry about competing and service. Roads represent the free market.
Guys, the cheapest way to move stuff is a ship, hands down by a signicant factor. Unit BULK shipping is the best – you can stick 200,000 tonnes of cargo in one ship and GO.
Containerized ships aren’t bad either.
The second most efficient way to move stuff in $/tonnne/Mile is a “unit train” that something like 100-150 cars of one product like coal. Again containerized loads aren’t bad either if you can move whole bunches long distances.
(Way down at the other end are jet flighters on afterburner – possible the most expensive way to move something ever devised, though payload to orbit rockets are worse.)
Ok.
But $/tonne/mile is not the only thing. A personal car is not effiicent in that regard, but most of us are willing to pay for the convienience because the altnerative is the cost of messing around with public transit – iff’n you got it at all. and wasting TIME.
Same way trucks are pretty efficient because they do things , as other’s have pointed out, in a time efficient manner. (Same thing with jet fighters really, costly, but the cost of not having one can be your life, so pay up.)
The revolution of efficiency that shipping containers have been is difficult to over state. It allwoys shipping co’s to treat cargo as if it it were a unit ( nevermind waterproof/pilfer proof) so you can send and entire train/boat of “stuff” to distribution centers en masse, not mess with it at all, and allow trucks to do the “last 10/100 miles” efficiently like they do best.
Also depending on your population density building a road and driving trucks on it represents a *LOT* less capital investment on infrastructure than laying track which if you have low volumes makes $$ sense.
(Personal moving co’s are finally recogizing this too, with a slightly flimsier box.)
Re:Drafting: there was an interesting show on TV (Mythbusters) that did an episode on drafting with cars on a track behind a large truck, it was really quite shocking how close you had to be to have a useful/measureable effect. ( Think 30cm/12″ or less. YIKES.)
Hard to believe no one has brought up the recent Mythbusters episode in which golf ball-like dimples reduced a car’s fuel consumption by about 10%.
http://access.aasd.k12.wi.us/wp/baslerdale/2009/10/24/mythbusters-golf-ball-car-better-gas-mileage
As Roger Sowell (21:13:20) pointed out, it is impractical, but Gareth (05:09:58)’s suggestion might be modified to work somehow, surprised that an adjustment like shape of the rear end has not been done yet.
Luboš Motl (00:12:31) :
“I trust you but it’s surprising to me: the boat tail looks like the ultimate birthplace of turbulence and whirlpools to me. ;-)”
Lubos, from my aerodynamics courses (back before the jet age), it is true that the turbulence and whirlpools will be formed behind the boat tail. But the area of eddies and whirlpools is reduced from that of the truck sans boat tail. Also, extending the boat tail doesn’t necessarily achieve greater drag reduction, since separated flow will still occur at some point (but I’ve long ago forgotten how to calculate it). I wonder if I still have Hoerner’s book on aerodynamic drag stored away somewhere. 😉
(US perspective)
Several posters have pointed out how some modifications to trucks won’t work with existing infrastructure and laws. Well, the laws could be changed, but there would need to be significant changes made to existing infrastructure to accomodate modified trucks. Examples: bridge clearances might need to be increased, docks might need extendable/retractable ramps, intersections might need to be widened for larger turning radii, etc.
I wonder; how much fuel would have to be saved to offset the fuel expended to make the necessary infrastructure modifications? What’s the payback period in terms of fuel?
I’ve been enjoying the links to various solutions that show how hard the private sector is working to solve the problem. (Thanks to all. Great links!) It’s not as though fuel economy is under the radar in the freight industry.
As for me, I think I’ll save my pennies and try to get one of those Bentleys with a boattail instead of a boring ol’ Prius. I’m just certain my wife will go for that. How could I be wrong?
Ray (21:05:29) : et al
If they would use the railways more efficiently and just use local distribution from the railway system, they would not only make the whole moving of good more efficient but also make the highways safer. The big rigs are a real mortal danger to us little car drivers.
True. Except there is not sufficient capacity to move the freight by rail, and with fewer trucks, who’d pay for the highways?
Boat tail design has been in use with rifle bullets for many decades now. The increases in efficiency and bullet stability has made any other type extremely hard to find.
Somewhere in America, a well intentioned bureaucrat is working feverishly on drafting legislation that would make these suggestions law. Of course, he is doing so without contemplating all the unintended consequences, and would never consider the fact that if this remodeling bears any significant economic merit, it will occur naturally at the insistence of the industry itself. If it proves inefficient for truckers to implement themselves, it will be bureaucrats that are forced to take action.
It is the American way.
I would think a reasonable implementation would involve a rail system not unlike automatic side doors on mini-vans. At least the top and two sides could be slid into place using rails. Could be completely automatic with the push of a button and only extended at higher speeds.
This is excellent news. What does it look like and cost? I may have some pictures not coming through my filter.
Nobody mentioned the recent Mythbusters’ episode where they “dimpled” the surface of a car, like a golf-ball. The dimples looked around 6″ dia & maybe ~1″ deep.
The results showed significant fuel savings (can’t remember how much). So right there’s a relatively simple means of reducing air friction.
Yes, I realize “dimpling” a car or truck’s body might have manufacturing issues in addition to aesthetic ones.
I can envision this on over the road trucks running between terminals. The terminal yards, which are typically just of interstate highways (in US), could remove the tail by forklift prior to the truck backing to their dock and reattach to trucks heading to another terminal. It would make no sense on a local truck.
I have a good friend who works for a truck mfg. and they are very excited about the 2010 truck models coming out with SCR (selective catalytic reduction). These engines are more efficent than EGR systems but have greatly reduced emissions. According to him, 65 2010 trucks generate the same emissions as one 2004 model.
Having worked the logistics field for a number of years and, as can be seen in the many comments above, one size does not fit all. The whole business is a lot more complicated than most people would imagine. All the bells and whistles of aerodynamic fuel savings might work well for an over-the-road (OTR) shipping company that owns its fleet of integrated tractor/trailers. For the less-than-truckload (LTL) firm [such as YRC – formerly Roadway & Yellow Freight], a different mix would be in order. They might use one type of tractor/trailer combo to ship from Atlanta to Chicago, then, in the insane chaos of their destination terminal, transfer freight from a long-haul trailer to a city trailer which would be a simple “classic” tractor/trailer rig without all those fuel saving bells & whistles. And then there are the independents who would absorb some increased fuel costs while offering a less expensive alternative to the shipper. And then there is that other breed, the 3PL (third party logistics provider), who may offer warehousing/shipping services to smaller companies, by putting a number of companies under one roof so they can all realize the savings the 3PL offers. And that’s just the tip of a huge and complex industry.
And then along comes some fantasyland bureaucrat with visions of implementing fuel savings ideas nationwide, and the biggest thing he’s driven is his desk. Okay, I’d humor him and might listen to his ideas after he’s driven a 53′ rig on a city delivery run (including backing that thing up to a loading dock straight and in under three tries) and can pick up a dime off a concrete floor … using only the forks of a lift truck.
Richard Owens (00:59:18) :
“considering one trailer might do say 60,000 miles per year at maybe 8 mpg, the fuel cost and CO2 output is frightening”.
You really love the drama, don’t you Richard Owens.
Remember this:
CO2 is not a problem. It’s plant food. The greenest trees can be found next to the highway’s with the biggest traffic jams.
Just face the reality. This whole “CO2 is frightening” act serves an ideological driven crowd who have totally different plans for humanity than you and me. Besides that, it will push the costs for distribution much higher than they are already without any sound scientific grounds.
Even with the high fuel prices, distribution costs hardly play a role in consumer prices.
The problem is with the independent truckers who drive the cargo based on fixed contracts. When fuel prices go up, they pay from their own pocket.
Off topic/delete when reviewed: Putting a “Boat Tail” on the Tips & Notes page would significantly cut AGW caused by computers overheating waiting for the page to open. Last count there were 10,247,654,386,456,782 entries that had to open before you could make a comment.
Anyone with a good engineering background will realize that with Reynold’s numbers below 2000 (typical for less than about 90 MPH on a truck!) the primary air resistance is ram air against the cross section.
What many engineers might forget is that the “shedding vortex” on the back of the truck creates a vacuum, which adds a “parasitic drag”.
Pamela Grey is quite correct, “Damn, there goes my free ride!”. I was with a friend 10 years ago, and she had a milage readout on her SUV. We were driving from Duluth to Mpls. It was a “no wind” day. I explained the parasitic drag vacuum phenomenon. We experimented moving in and out of the vortex shedding. Indeed milage went up by about 20%, when you were about a car length behind a “big rig”. Two car lengths you were still in the “wind shadow”, 3 to 4 car lengths you could feel the buffet of the vortex.
Wind shadow gave about 10% better milage, and vortex buffet zone. Nothing.
However, it should be noted: Driving 1 car length behind a “big rig” is NOT, repeat NOT a wise idea!
Here’s a guy who did the same thing on a 92 Honda Civic, and got 95 highway MPG.
I imagine you could easily break 100 with a professional looking job.
http://www.gizmag.com/diy-honda-civic-as-aerodynamic-as-an-aptera-gets-95-mpg/10869/picture/65680/
In the mean time the quest for bio fuels continues to level tropical forests:
http://heliogenic.blogspot.com/2009/11/biofuel-madness-continues-to-level.html
I remember reading about these trailer-stream,lining schemes back in the late 60s. The terminal problem then was that the overall length of the vehicle was set, so streamlining had to be done at the expense of cargo space. The economics at that time were that it was cheaper to use more fuel and gain the extra capacity. The increased cost of fuel may alter the balance of costs.
Ray (21:05:29) :
-ot-
“If they would use the railways more efficiently and just use local distribution from the railway system, they would not only make the whole moving of good more efficient but also make the highways safer. The big rigs are a real mortal danger to us little car drivers.”
I have worked as a professional Driver as well as a Pilot.The Eighteen Wheelers are ,
for the most part,not the problem.If you understand the dynamics of momentum,
and the need to simply get out of the way,like a truck tailgating you because you are
in your Pious,exactly at the speed limit(or below) just as a long grade is coming up,
the Trucker has to preserve momentum uphill-just dropping a couple of gears more costs in fuel and time-all money.It is not an easy way to make a living.
Having been on the other side of the steering wheel, I understand.
-subject-
There was a similar experiment done back in the 70’s that worked, but nothing came of it as they had problems with dings and dents,also certain states, had
arcane laws about trailer length (Oregon was one.)…
Roger Carr (00:18:22) :
Here try this one for the 29-trailer road train…
http://www.strangecosmos.com/content/item/122009.html