Bit of googling suggests this is a whole, fascinating world of little improvements. However it's also both constrained and pushed forward by what's road legal.
I'm sure there's a lot more out there. The eventual switch to electric will probably come with another round of aerodynamic improvements to maximise range, as with cars.
Those figures are from the 1970s, when presumably there was a lot more low-hanging fruit. Still, I wouldn't be surprised if they invest a decent chunk into computation aerodynamical work as part of their body design.
They absolutely do design trucks for aerodynamics. Fuel economy is a huge avenue of competition for semi trucks.
The reality is just that with the drive cycles and costs and tradeoffs of implementing all this it's not worth it to go this far.
Second, this sort of "round the whole thing" approach has mostly been replaced with "the simulation says we can do a 90/10 if we just do X, someone print up a block and toss it in the wind tunnel and see how it does" type approach so the result tends to be more surgical modifications and use of dead air and less "smooth out the whole thing with fairings".
> They absolutely do design trucks for aerodynamics
I know next to nothing about trucks, and vehicles in general, but something I've noticed, and probably everyone else, is that trucks in the US looks very different from trucks in Europe, it's very easy to identify which one is a US-like truck vs a Europe-like one, because of the shape of the "cab" or whatever that part is called.
So one design has to be clearly better than the alternative, given that aerodynamics works the same all around the world, but still the designs are uniquely... unique.
But why is it like this? If trucks were designed for aerodynamics, shouldn't one of the designs have "won" by now, or are they truly equal in terms of aerodynamics?
> If trucks were designed for aerodynamics, shouldn't one of the designs have "won" by now,
Because aerodynamics is not the only concern the manufacturers are thinking about.
The difference is in the regulation. The maximum allowed length for a semi-truck is shorter in the EU than in the USA. And since they both want to transport the same length of container the European truck had to be designed shorter.
My dad used to drive concrete delivery trucks in europe. Most were the european arrangement with the cab over the engine, but one of them he drove had the American style long-nose. It was so unusual that they nicknamed the truck after this feature. They called it "csőrike" which is hungarian for "the one with the beak".
He also said it was a lot easier to maintain the long-nosed vehicle. With the european cab-over design you have to first secure everything in the cab and then tip the cab forward to have access to the engine and transmission. While with the long-nosed concrete truck you could just open the hood and get to work.
All trucks have standard shipping container trailers. Europe has strict length limits for the overall cab/trailer that preclude a hood in front of the cab. There is great resistance to changing the law, even though long-nosed trucks are vastly more aerodynamic, because the law provides protection for european truck makers from American competition.
> even though long-nosed trucks are vastly more aerodynamic
Are they? I mean by intuition I'd assume the same, but seems it isn't considered so black and white as far as I can tell, I can find reasonable research pointing both ways, but I'm guessing you're basing that on something more conclusive? Mind sharing the link so I could too read up on it?
TFA literally has NASA doing research and seemingly reaching a different conclusion than "long-nosed trucks are vastly more aerodynamic", seems to be about more things than just the hood, and those can be/are optimized on both variations.
But again, I know little about all of this, but would welcome being educated on it more.
My understanding is that in Europe regulations focused on the length of the whole vehicle, whereas in America the length of the cab and trailer were regulated separately.
Also American truckers do a lot more long-haul work and American roads are noisier, so they prefer being more insulated from the engine.
Judging by the images only, those are all the ones I called "European" trucks though, the American ones are much longer. Is that also regulated so European trucks aren't allowed in the US and American ones aren't allowed in Europe? Because here in Europe it's really uncommon to see the US ones, and I'm guessing it's the opposite in the US?
One of them must be better aerodynamically though, must'n it?
Europe has length limits on the entire thing, so US trucks would require shorter trailers, which nobody really wants. Euro trucks also have significantly smaller turning radii, which makes navigating european cities and country roads… feasible.
Furthermore Europe has relatively strict speed limits on trucks, which makes aero something of a lesser factor since drag grows to the square of speed: european trucks at european speeds have a pretty significantly higher efficiency than US trucks at US speeds.
But that goes directly against TFA, doesn't it? The final image is closer to the European design than the American one? Or am I misunderstanding the article?
> they are potenitilly safer
Maybe for the occupants, but for everyone else they seem strictly worse, not to mention the visibility much be much much worse, making it a somwhat iffy tradeoff.
You're misunderstanding the context. The US at the time regulated truck length to a patchwork of shorter lengths state by state and so cabovers proliferated and that's what NASA chose as a base. So if you start with that and "add aero" it's going to trend toward what looks like a modern European design.
This is down to regulations. The total length of the vehicle is capped in Europe so to get more useful cargo space, the cab is shortened to a cab over engine design with a completely flat (short) nose. Making the cab longer or more pointy/aerodynamic cuts from the length available to the trailer. There’s usually more money inside the trailer than in the fuel savings so everyone accepted this solution.
Bit of googling suggests this is a whole, fascinating world of little improvements. However it's also both constrained and pushed forward by what's road legal.
https://www.volvotrucks.co.uk/en-gb/news/insights/articles/2... : removing mirrors allows for much smoother cab airflow
https://go2stream.com/blog/aerodynamic-truck-legislation-rea... : UK legalization of fishtail-like devices
https://www.kudauk.ltd.uk/aerodynamics-explained : Kuda on the UK allowing higher loads, and therefore benefiting from extra wedge devices on the top of the cab.
I'm sure there's a lot more out there. The eventual switch to electric will probably come with another round of aerodynamic improvements to maximise range, as with cars.
> would increase fuel economy by 15-25%
Makes you wonder if/why truck companies don't have aerodynamics experts on their payroll.
Those figures are from the 1970s, when presumably there was a lot more low-hanging fruit. Still, I wouldn't be surprised if they invest a decent chunk into computation aerodynamical work as part of their body design.
They absolutely do design trucks for aerodynamics. Fuel economy is a huge avenue of competition for semi trucks.
The reality is just that with the drive cycles and costs and tradeoffs of implementing all this it's not worth it to go this far.
Second, this sort of "round the whole thing" approach has mostly been replaced with "the simulation says we can do a 90/10 if we just do X, someone print up a block and toss it in the wind tunnel and see how it does" type approach so the result tends to be more surgical modifications and use of dead air and less "smooth out the whole thing with fairings".
> They absolutely do design trucks for aerodynamics
I know next to nothing about trucks, and vehicles in general, but something I've noticed, and probably everyone else, is that trucks in the US looks very different from trucks in Europe, it's very easy to identify which one is a US-like truck vs a Europe-like one, because of the shape of the "cab" or whatever that part is called.
So one design has to be clearly better than the alternative, given that aerodynamics works the same all around the world, but still the designs are uniquely... unique.
But why is it like this? If trucks were designed for aerodynamics, shouldn't one of the designs have "won" by now, or are they truly equal in terms of aerodynamics?
> If trucks were designed for aerodynamics, shouldn't one of the designs have "won" by now,
Because aerodynamics is not the only concern the manufacturers are thinking about.
The difference is in the regulation. The maximum allowed length for a semi-truck is shorter in the EU than in the USA. And since they both want to transport the same length of container the European truck had to be designed shorter.
My dad used to drive concrete delivery trucks in europe. Most were the european arrangement with the cab over the engine, but one of them he drove had the American style long-nose. It was so unusual that they nicknamed the truck after this feature. They called it "csőrike" which is hungarian for "the one with the beak".
He also said it was a lot easier to maintain the long-nosed vehicle. With the european cab-over design you have to first secure everything in the cab and then tip the cab forward to have access to the engine and transmission. While with the long-nosed concrete truck you could just open the hood and get to work.
All trucks have standard shipping container trailers. Europe has strict length limits for the overall cab/trailer that preclude a hood in front of the cab. There is great resistance to changing the law, even though long-nosed trucks are vastly more aerodynamic, because the law provides protection for european truck makers from American competition.
> even though long-nosed trucks are vastly more aerodynamic
Are they? I mean by intuition I'd assume the same, but seems it isn't considered so black and white as far as I can tell, I can find reasonable research pointing both ways, but I'm guessing you're basing that on something more conclusive? Mind sharing the link so I could too read up on it?
TFA literally has NASA doing research and seemingly reaching a different conclusion than "long-nosed trucks are vastly more aerodynamic", seems to be about more things than just the hood, and those can be/are optimized on both variations.
But again, I know little about all of this, but would welcome being educated on it more.
Even though several Europeon truck makers compete is America. they have the designs and ability to compete
My understanding is that in Europe regulations focused on the length of the whole vehicle, whereas in America the length of the cab and trailer were regulated separately.
Also American truckers do a lot more long-haul work and American roads are noisier, so they prefer being more insulated from the engine.
Did a bit of research: https://news.ycombinator.com/item?id=47121031 - different countries have different legal requirements, despite air being the same everywhere.
Judging by the images only, those are all the ones I called "European" trucks though, the American ones are much longer. Is that also regulated so European trucks aren't allowed in the US and American ones aren't allowed in Europe? Because here in Europe it's really uncommon to see the US ones, and I'm guessing it's the opposite in the US?
One of them must be better aerodynamically though, must'n it?
Europe has length limits on the entire thing, so US trucks would require shorter trailers, which nobody really wants. Euro trucks also have significantly smaller turning radii, which makes navigating european cities and country roads… feasible.
Furthermore Europe has relatively strict speed limits on trucks, which makes aero something of a lesser factor since drag grows to the square of speed: european trucks at european speeds have a pretty significantly higher efficiency than US trucks at US speeds.
Is shipping either design of large truck across the ocean even feasible? I'm thinking they might be too tall for standard car carrier ships, but IDK.
It’s not hard. There are European cabovers in the US (see the Bruce Wilson YouTube channel).
American designs are aerodynamically better. they are potenitilly safer (crumple zone) though I haven't seen any safety studies.
> American designs are aerodynamically better
But that goes directly against TFA, doesn't it? The final image is closer to the European design than the American one? Or am I misunderstanding the article?
> they are potenitilly safer
Maybe for the occupants, but for everyone else they seem strictly worse, not to mention the visibility much be much much worse, making it a somwhat iffy tradeoff.
You're misunderstanding the context. The US at the time regulated truck length to a patchwork of shorter lengths state by state and so cabovers proliferated and that's what NASA chose as a base. So if you start with that and "add aero" it's going to trend toward what looks like a modern European design.
This is down to regulations. The total length of the vehicle is capped in Europe so to get more useful cargo space, the cab is shortened to a cab over engine design with a completely flat (short) nose. Making the cab longer or more pointy/aerodynamic cuts from the length available to the trailer. There’s usually more money inside the trailer than in the fuel savings so everyone accepted this solution.
An other important regulation is truck speed limits, because drag grows to the square of speed.
The energy of a potential impact is the main driver of that regulation. Also increasing with the square of the speed, and with the (sizable) mass.