Why aren't trucks designed aerodynamically?

This is an old peterbilt, they didn't care then, I guess.

To be fair the last time they drove cabovers these things were loud, hot and uncomfortable. Noise and heat were fixed over the years, but even today you have to invest into a complex and expensive suspension system to make the ride bearable. Both the cab and the seat are air suspended on European semis nowadays in addition to the axle leaf suspension, and if we didn't have such a dire need for manouverability drivers would switch to long hoods in an minutes.

Also American roads are in worse condition, further necessitating a good ride comfort, plus their truck combination weight ratings highly depend on wheelbase.

But they still build them like that, only with new headlights and a bunch of other minor details.

>tfw no aerodynamicish turbine truck-fu with built in beverage dispenser

I would love to know why.
>13.4 mpg
>$100k in mods but would drop drastically if mass produced

greencarreports.com/news/1089506_is-the-bullettruck-what-semis-will-look-like-in-the-future

typically speaking, control forward trucks are more aerodynamically dirty than traditional American style trucks. At highways speeds drag and frontal area become big concerns, the primary usage of trucks determines their shapes:

When you are on the highway the control forward design is basically pushing a wall down the road. There are Aero sensitive designs, but they have limitations. These are still used heavily in cities, inland shipping yards, and areas where long stretches of high speed are not common or tight turning radii are desired. Usually these have single rear axles which limits their usage due to road restrictions on per axle weight.

Then comes the conventional American truck from the 70's with long flat engine compartments, stiff sheet metal fenders and flat front grills and radiators. Considering what these trucks had for engines, they really got pretty decent economy.

Modern trucks with better fiberglass fairings over the fenders, plexy light buckets, and "slant hoods" are more efficient than either and have been the industry standard for 20 years for fleets. Engine tech has also come a long way. Typically speaking, convnetional trucks have tandem rear axles for better distributing heavy loads out which matters a lot on American roads since the roadbed is about 2' shallower than a European road.

Can't speak for the US with it's ridiculous fuel prices, but here in Europe, it's because they have maximum height and length laws for any given combination. This means that you have to cram as much storage space into a single combination, which leaves you with a cab over engine design. Sure, there's minor things you can improve in terms of aero, but you can't go too far away from the box. Sending 9 unaerodynamic trucks costs less fuel than sending 10 aerodynamic ones.

Actually aerodynamics aren't terribly bad. Our modern semis get similar fuel economy to American modern semis. What Americans gain through round Hoods and sleeper roofs, they absolutely piss away on the trailer gap and trailer underside.

>Believe it or not, people care what their rigs look like.
This is especially important in the American owner-operator market. You don't see it as much in other markets.

It's not manouvrability, it's legal size limits.

An exxageration of this is pic related, a Steinwinter prototype. By moving the cab down and in front of the engine, you can expand the carrying capacity even more, while staying within the legal limits.

>Usually these have single rear axles
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Aerospace Engineering student studying aerodynamics here.

Air will find a way to move around an object traveling through it. The front of a vehicle is much less important than the rear. When traveling at a fair speed, vehicles create an area of low pressure behind them because the air has trouble moving into the space where the car just was. F1 and Nascar drivers use this area of low pressure to draft. They have to move through less molecules of air which means a lower drag force.

The problem with these areas of low pressure is that they suck the car backwards, much like a vacuum cleaner which use low pressure to suck up dirt from a high pressure area.

Trailer Tails have been an innovation we've seen in recent years that actually helps to drastically reduce the area of low pressure behind trucks. Vortex generators are also common and they disrupt the flowing air from its high speed stream, eliminating it's momentum, and helping it to flow easier into these areas of low pressure.
Side skirts and aerodynamics hub caps also eliminate areas of low pressure under the trailer and in the wheels, although these are not close to as detrimental as the the very rear of the trailer.

The front of the vehicle really matters the least. A pointy front is obviously better than a flat. BUT if you had to only make a vehicle pointy on one end, the rear should get the pointy end.

Aerodynamics are not as much of a concern in Europe because of the shorter distances. But for US trucks that frequently travel across the country, it can make a big difference in fuel economy and high speed stability.

But in return operating costs in Europe are higher. Also the issue with making the rear pointy is that it's also the part where payload goes, and a box shape can hold the highest amount of payload. If I were a trucker and hauled a tanker trailer I'd see about making it more pointy (they're usually below the length limit anyway), but on box trailers it's going to be an issue.

>But in return operating costs in Europe are higher
But you can't fix those by improving aerodynamics, because better aero would intrude on carrying capacity, which would, in fact, increase operating costs.

>Sending 9 unaerodynamic trucks costs less fuel than sending 10 aerodynamic ones.

Doubt some aero fairings are going to weigh five tons. The main issue with them so far has been that legislation is incredibly slow to catch up on anything new, and that our overall length restrictions are pretty strict.

Looks like a modern eurotruck, just without sideboards/skirts

Weight isn't the problem, the problem is physical space for carrying stuff. Less room in a trailer means less stuff to transport, and thus less revenue per mile/km.
Fairings won't weigh a lot, and they'll make their money back, but they simply intrude on cargo space if you want some decently effective ones.

See and that's just the issue. That's why you have to look for ways to improve aerodynamics without affecting size of the vehicle.

This is where vortex generators, rear diffusers, hubcaps, sideskirts, caps, and air dams all come into play. Because none of them reduce payload capacity or increase vehicle size, which is the primary concern.

Overall length doesn't really need to be changed. Having a pointed rear end to a trailer is really not feasible in any capacity due to loading, saftey, and size concerns.

>Vortex generators are also common and they disrupt the flowing air from its high speed stream, eliminating it's momentum, and helping it to flow easier into these areas of low pressure.
How do you design where to put the vortex generators? Is that a CFD problem? Is it something that you can figure out using yarn tufts or something?

Why don't they put them on econocars?

So that's what the japs ripped off for Speed Racer.

>Overall length doesn't really need to be changed.

How do the length regs address pic related?

Trailer Tails fold completely flat and are considered a removable accessory or something like that. Just like how putting a bike rack onto the back of your car doesn't increase its official length, even if it's always on there.

Essentially you want them as close as possible to point of low pressure while still being in highest velocity flow.
For trucks, this is just right around the rear edge. Move them forward and you give the air a chance to get back into a steady flow which is what you're trying to destroy in the first place.

Now as for density and how far to space them apart, that's some not just a concept but more complex mathematics based on size and shape of vortex generators and magnitude of the low pressure zone. Basically more is better, but there are obviously lessening results.
Ignoring math, yeah you kinda can do it with pieces of string and a wind tunnel or for less accurate results, a road.
Vortex generators are effective on cars, but to a lesser ressult. You probably won't see much of a mpg improvement unless you drive cross country all the time. But for lighter cars you will see greater high speed stability.
The EVO is known for having those little spikes on the roof right? Those are vortex generators. Well they mix up the air so that the rear wing is more effective. Without them air would just flow down the back window and under the wing. Mitsubishi engineers saw a big enough difference to implement them on a performance production vehicle so there's that.

You will see some vortex generators on serious econocar people. But they are pretty damn ugly and companies would lose sales if they plastered them all over the sides and top.

probably because they are already long?

Thanks. What speed do they become effective at? Faster you go the bigger the difference? so a car going 60mph maybe not so much but one going 120mph could be a multiplier of difference?

Fairings literally do not intrude on cargo space AT ALL. It makes zero sense to think they would because they're not inside the cargo area, they're on the outside of the fucking truck. Stop pretending like you have ANY idea what you're talking about.

they should work even at highway speed because they're not producing a force like a wing, they're just altering the flow of the air. You would need to place them appropriately, though.

When the exterior of your truck has to fit within certain length, width and height requirements, then any fairing will make the effective cargo capacity lower. Again, we were discussing Euro trucks, which have prettty strict size requirements, hence the COE designs.

Which sounds kind of trial and error, huh?

For putting vortex generators on a truck, could the manufacturers do CFD work to determine where to place them? Or is it not that exact of a science where software can optimize it?

Are you actually retarded?

Doesn't matter what the drag coefficient of the truck is when the trailer is triple the worst numbers for a tractor.

Trucks do more than drive forward. Ripping the nose off backing into a 60 year old dock in Chicago negates all fuel savings.

Biggest issue with trailer fairings is maximum legal trailer length. 53'0" is the max, and most new trailers are that long from the factory. Modern trailer trails are still illegal in some states, and their maintenance costs fat outweigh fuel savings.

See above.

Vortext generators were a fad 4 years ago to get around California's trailer skirt mandate. Fuel saving tasting was so inconclusive that they had to mandate them on the merit of "road spray reduction" which is about all they do in the real world other than getting ripped up before seeing theoretical ROI.

With semis, you have two options.

1. Make it look nice

2. Make it aerodynamic

Can't have both in good taste.

Well just like a wing, how they're working depends on the speed you're traveling.

The idea is, the fast you go, the larger the pocket of low pressure gets behind you.
Also the faster you go, the greater the velocity of the air that's hitting the wing or the vortex generators. In the case of a wing it's transferred into downwards force. With vortex generators it's transfered into randomizing the air flow.

While both wings and vortex generators work at lower speeds, they both work better at higher speeds.

Note, a wing pushes the car down and reduces top speed in exchange for grip. Vortex generators just eliminate drag created by the area of low pressure and will actually increase your top speed without sacrificing grip.

Placing vortex generators is easy. It's not determined by math really, you want them in the main flow of air and as close as possible to the area of low pressure.

With Vortex generators the fuel savings aren't that amazing when compared to trailer tails, which are better. They do reduce road spray some but they drastically reduce rear instability. RV drivers and truckers have said how much more comfortable they feel when passing other trucks or on heavy side wind days.

>modern pete is old

I'm too disappointed to laugh.

>Vortext generators were a fad 4 years ago to get around California's trailer skirt mandate. Fuel saving tasting was so inconclusive that they had to mandate them on the merit of "road spray reduction" which is about all they do in the real world other than getting ripped up before seeing theoretical ROI.
Interesting. Yeah, I mean I see them on airplane wings all the time so I imagine they are useful in the right application, but maybe it's just so slight on a truck it's not worth it.

Do the trailer skirts help? Why did people want to get around them?

>Note, a wing pushes the car down and reduces top speed in exchange for grip. Vortex generators just eliminate drag created by the area of low pressure and will actually increase your top speed without sacrificing grip.
That's really interesting. I'm surprised they aren't used more on sportscars then. I guess just aesthetics? Seems like they might look pretty cool.

>stuck in outlaw romanticism about the past.
You've never been to the midwest, have you?
It's not "romanticism" about the "past", it's their daily reality. When you have to deal with old shitty things all the time and making the best out of it, you gain an appreciation for the aesthetic. Thus, when they've got enough money to get something decent, they still prefer the old style so they just class it up a bit.

That whole paragraph was about the negative aspects of trailer skirts. In a crosswind they actually add drag. They get ripped up all the time, and at $2500 parts and labor, they never would make real world ROI if they had wind tunnel gains on the road.

Well a proper sports car is aerodynamically designed to reduce these areas of drag and to use the largest sides (top and bottom) for down force (diffuser and wing).

And is right. They really aren't that great for use with trucks. RV drivers are a better target crowd purely for more confident driving, especially when next to other large vehicles.

But they have their uses. I plan to buy a small amount to place on my AW11 because the engine lid behind the rear window is a huge area of low pressure and reduces the effectiveness of the spoiler.
Placing them on the roof and sides by the engine lid can help the spoiler become more affective and help increase high speed stability because that MR2s rear end gets real squirelly over 90mph.

The EVO properly implemented them to help the spoiler more affective which increased downforce. Although I haven't done much testing, I've read the Y shaped ones like the one I'm posting are much more affective than the EVO fin shaped ones.

Might want to look into vorblades. Air tabs aren't substitutes for trailer skirts, but vorblades are.

Weight and lesser energy reward. Same reason they don't have regenerative braking.

It should be legal to run them down.

I haven't looked into them much just because they're so damn big and ugly and not feasible for me.
Realistically I can't see why it wouldn't work. The issue is going to be more that these things are going to break much faster than Airtabs would.

With just doing some quick googling I couldn't find anything from some quick googling. No research present by anyone but themselves and even their own link to their downloadable PDF on Design and Assessment is broken so I can't even look at that.

Because peterbuilts look like sex

unlike you they were put on this earth with a purpose

>claims that romanticism about the past is not a factor
>tells dumb story about how truckers romanticising the past