Big Rig Aero

noddaz wrote: If someone could Photoshop this on a deep space back round flying (?) past Saturn it would probably look better...

If you can add Deep Purple "Space Trucking" as background music it would make it complete.

Re: Hybrid trucks.

I have several friends who are engineers with Volvo/Mack trucks. I asked them why the diesel locomotive configuration was not used (diesel generator supplying power to electric motors). The reason?

Transient response. Although it works great at steady-state speeds (which a train operates at 99% of the time), the trucks would be nigh impossible to drive around town. Trains have miles of room to accelerate, and they (typically) only stop at their destination. Big Rigs need to be able to drive in traffic and accelerate and decelerate in a timely manner.

t25torx wrote: There's just too much frontal area on trucks like the Isuzu NPR and such that prevents them from being more aerodynamic.

the Isuzu trucks were some of the more fuel efficient. We had a GMC w7 in our fleet, the counterpoint to the big Isuzu (FPR?). was registered at 25,995 and had a 26 foot long box that was at 101 inches wide. whole truck stood almost 12'6" tall.. it was a big box truck.. and it got 11mpg. the Smaller mitsus and hinds got about 9mpg. I wanted so badly to put a spoiler on the roof and play with the aero on it.. but was never allowed

SVreX wrote:

Swank Force One wrote: There was a rather large amount of buzz on this setup a year or two ago. It is, in fact, legit. The changes were not JUST aero, but most were. Ended up looking really bizarre, but all claims were verified. http://www.google.com/search?q=airflow+bullet+truck&safe=active&source=lnms&sa=X&ei=kMm9U5nLKMeSyATb8YJg&ved=0CAUQ_AUoAA&biw=1280&bih=895&dpr=1

I like to see more of this "verified" information. There are a couple of factors suspiciously absent from their website, most notably the GVW (it sounds like a 10,000 lb load). They also offer no specs on the engine (Cummins ISX- what generation? What horsepower?), emissions controls, etc. Driving patterns? Drivers can account for about 30% variations. They DID say they set the cruise at 55 for 3000 miles. That is worth at least 2 mpg. Did they use DEF? If so, did they include the 25 gallons or so they consumed in their calculations? (Could have dropped the fuel economy by nearly 2 mpg). I am not accusing them of error, but they have not posted their methodology or specs. I am just asking the questions. Mathematically, a 20% aerodynamic improvement should equate to approximately a 12% fuel savings over 50 mph. It's just not adding up as presented. I'm not doubting it CAN happen (just like I don't doubt that hypermilers have conquered 100 mpg's). I'd like to know more, and I question the real world viability (there is a reason they are not in production 2 years after the prototype "proved" itself). It's an obvious improvement. I still doubt 2.5X in any real world application. Swanky, you said it was legit and verified. More info?? I think they took a truck that got a pretty solid 6.5 mpg, added terrific aero for a 15% improvement (7.5 mpg). Then they put a light load in it and drove using hypermiler techniques (10.5 mpg). Add to that an "oversight" in the calculations leaving out the DEF (12.5 mpg). Plus a 7% net fuel economy increase for the DEF usage would give them...13.4 mpg. But that is a very different scenario...

All i know is what's in that google search i put in the post you quoted.

There's tons of info in there on the truck. It's been awhile since i read it, didn't understand half of what you just typed, since i don't have 2 hours in the industry, let alone 2 years.

stanger_missle wrote: The Airflow Bullet Truck will haunt your dreams:

"Hi there! I'm Eddie, your shipboard computer..."

Oh yeah, the only space trucks I care about are in Cowboy Bebop.

I'm waiting for them to look like this.

Sky_Render wrote: Re: Hybrid trucks. I have several friends who are engineers with Volvo/Mack trucks. I asked them why the diesel locomotive configuration was not used (diesel generator supplying power to electric motors). The reason? Transient response. Although it works great at steady-state speeds (which a train operates at 99% of the time), the trucks would be nigh impossible to drive around town. Trains have miles of room to accelerate, and they (typically) only stop at their destination. Big Rigs need to be able to drive in traffic and accelerate and decelerate in a timely manner.

But isn't an electric motor driven hybrid (Chevy Volt) already doing? Since we know that electric motors are great torque monsters already and internal combustion can be its most efficient when tuned for a single given RPM it seems it should work.

And with all that mass going into electrical regeneration when slowing instead of a jake brake..... All sorts of win going on.

Sky_Render wrote: Re: Hybrid trucks. I have several friends who are engineers with Volvo/Mack trucks. I asked them why the diesel locomotive configuration was not used (diesel generator supplying power to electric motors). The reason? Transient response. Although it works great at steady-state speeds (which a train operates at 99% of the time), the trucks would be nigh impossible to drive around town. Trains have miles of room to accelerate, and they (typically) only stop at their destination. Big Rigs need to be able to drive in traffic and accelerate and decelerate in a timely manner.

Guess they didnt think far enough out of the box, even if they just had a super cap with 30 seconds worth of full power stored on it that would be enough to cover most transient situations.

KyAllroad wrote:

Sky_Render wrote: Re: Hybrid trucks. I have several friends who are engineers with Volvo/Mack trucks. I asked them why the diesel locomotive configuration was not used (diesel generator supplying power to electric motors). The reason? Transient response. Although it works great at steady-state speeds (which a train operates at 99% of the time), the trucks would be nigh impossible to drive around town. Trains have miles of room to accelerate, and they (typically) only stop at their destination. Big Rigs need to be able to drive in traffic and accelerate and decelerate in a timely manner.

But isn't an electric motor driven hybrid (Chevy Volt) already doing? Since we know that electric motors are great torque monsters already and internal combustion can be its most efficient when tuned for a single given RPM it seems it should work. And with all that mass going into electrical regeneration when slowing instead of a jake brake..... All sorts of win going on.

The prime mover in a diesel-electric automotive directly powers the electric motors with no battery in between. The Volt has batteries that enable it to use "extra" energy when needed, such as up hills or moving from a stop. To wit, it originally had problems making it up long inclines due to the batteries being depleted and the gas engine being unable to produce enough "oomph" to power the car up the hill.

I suppose a bank of batteries could be added to a "diesel-electric big rig" to take advantage of regenerative braking, but I wonder what that would add in terms of size and weight to an already rather large system of prime mover, rectifiers, inverters, and electric motors.

As for "not thinking outside the box," I suppose you, oh great and mighty armchair quarterback, have clearly thought of everything that people who do this for a living have not. How much does a supercapacitor cost?

My point is that a solution that seems so "simple" to us is obviously much more complicated, else it would have been developed by now. I'm sure if a company could develop a diesel-electric big rig that got double-digit MPG figures, they could make BILLIONS.

kylini wrote:

This picture is the E36 M3.

I'm surprised that making diesel hybrids hasn't happened yet. It must add a lot of weight to the already large trucks for them to not be developed yet.

Leafy wrote:

Sky_Render wrote: Re: Hybrid trucks. I have several friends who are engineers with Volvo/Mack trucks. I asked them why the diesel locomotive configuration was not used (diesel generator supplying power to electric motors). The reason? Transient response. Although it works great at steady-state speeds (which a train operates at 99% of the time), the trucks would be nigh impossible to drive around town. Trains have miles of room to accelerate, and they (typically) only stop at their destination. Big Rigs need to be able to drive in traffic and accelerate and decelerate in a timely manner.

Guess they didnt think far enough out of the box, even if they just had a super cap with 30 seconds worth of full power stored on it that would be enough to cover most transient situations.

A "supercapacitor" for "30 seconds worth of full power"? Seriously?!

Let's do some math.

A conservative figure for full power on a diesel big rig is 600 horsepower, or 400 kW. That's 400,000 J/s. Over 30 seconds, that's 12,000,000 Joules, or 12MJ, of energy.

The best supercapacitors have an energy density of 15 watt-hours (Wh) per kilogram. One Watt-hour is 3600 joules.

12,000,000 J = 3,333 Wh

At 15 Wh/kg, you're looking at

222 kg of "supercapacitors."

And most commercially-available supercaps have a tenth that capacity. Then you're looking at two metric tons of supercapacitors.

Sky_Render wrote:

Leafy wrote:

Sky_Render wrote: Re: Hybrid trucks. I have several friends who are engineers with Volvo/Mack trucks. I asked them why the diesel locomotive configuration was not used (diesel generator supplying power to electric motors). The reason? Transient response. Although it works great at steady-state speeds (which a train operates at 99% of the time), the trucks would be nigh impossible to drive around town. Trains have miles of room to accelerate, and they (typically) only stop at their destination. Big Rigs need to be able to drive in traffic and accelerate and decelerate in a timely manner.

Guess they didnt think far enough out of the box, even if they just had a super cap with 30 seconds worth of full power stored on it that would be enough to cover most transient situations.

A "supercapacitor" for "30 seconds worth of full power"? Seriously?! Let's do some math. A *conservative* figure for full power on a diesel big rig is 600 horsepower, or 400 kW. That's 400,000 J/s. Over 30 seconds, that's 12,000,000 Joules, or 12MJ, of energy. The *best* supercapacitors have an energy density of 15 watt-hours (Wh) per kilogram. One Watt-hour is 3600 joules. 12,000,000 J = 3,333 Wh At 15 Wh/kg, you're looking at **222 kg** of "supercapacitors." And most commercially-available supercaps have a *tenth* that capacity. Then you're looking at *two metric tons of supercapacitors.*

I guess I miss anticipated how much better supercapacitors would have gotten since the last time I checked. Some flavor of lithium battery would be better at ~400,000J/kg or 128 Wh/kg.

These have a 5.9 Cummins spinning a generator and a fairly small battery pack on the roof and accelerate plenty hard. When we got them they had to reprogram the accelerator because they would catch standing customers off guard and dump them on the floor.

Yeah, but 80,000+lbs? I know Mericans is big, but...

stafford1500 wrote:

Duke wrote: Is aero behind the increasing number of semis running big single tires instead of duallies lately?

That is possible. The tires/wheels are another big drag item for the trucks and the trailers. I suspect the load limit for single tires is lower than two narrow tires however. Not to mention there is less factor of safety in single tire applications.

The "super single" tires are lighter then a set of duals so that is one factor, less overall weight both rotational and static, less rolling resistance, and lower cost when purchased on a new trailer or tractor. The load capacity of a super single is equal to a set of duals or it wouldn't work for most trucks. I first saw then 20 years ago when the company I worked for started using them on their bulk liquid trailers. They used them to deliver gasoline from terminals to gas stations. Lower empty weight means more gas hauled and fewer loads needed to be moved for the same amount delivered. The one drawback is that in the event of a flat/blowout you can't limp the truck any distance at all. You have to stop "right now" and change it out. In local hauling like gas delivery is that isn't a problem as a service truck was never more then 30 minutes away. Now that trucks are using them on long hauls I guess that the savings offset the lost time when one does fail.

I spent 25 years in trucking both in the office and behind the wheel.

Swank Force One wrote: All i know is what's in that google search i put in the post you quoted. There's tons of info in there on the truck. It's been awhile since i read it, didn't understand half of what you just typed, since i don't have 2 hours in the industry, let alone 2 years.

I appreciate your honesty.

My skepticism comes directly from the website. There is actually very little verifiable info, and a lot of fluff.

But I am VERY interested.

jimbbski wrote:

stafford1500 wrote:

Duke wrote: Is aero behind the increasing number of semis running big single tires instead of duallies lately?

That is possible. The tires/wheels are another big drag item for the trucks and the trailers. I suspect the load limit for single tires is lower than two narrow tires however. Not to mention there is less factor of safety in single tire applications.

The "super single" tires are lighter then a set of duals so that is one factor, less overall weight both rotational and static, less rolling resistance, and lower cost when purchased on a new trailer or tractor. The load capacity of a super single is equal to a set of duals or it wouldn't work for most trucks. I first saw then 20 years ago when the company I worked for started using them on their bulk liquid trailers. They used them to deliver gasoline from terminals to gas stations. Lower empty weight means more gas hauled and fewer loads needed to be moved for the same amount delivered. The one drawback is that in the event of a flat/blowout you can't limp the truck any distance at all. You have to stop "right now" and change it out. In local hauling like gas delivery is that isn't a problem as a service truck was never more then 30 minutes away. Now that trucks are using them on long hauls I guess that the savings offset the lost time when one does fail. I spent 25 years in trucking both in the office and behind the wheel.

up until a few months ago, i was driving a 20 mile stretch of I94 twice a day to work and back, so i got a small sample of what kind of trucks are out and about... i saw quite a few big rigs set up with the single wheels on the truck and trailer, as well as a lot of side skirts on the trailers.. about a year ago i started seeing those funky tails that hang out off the back of the trailer to clean up the aero- maybe one a week at first then they started becoming more and more popular, and i can tell you that "drafting" behind them is different than a regular trailer.. you gotta get up nice and close to start to feel it, and there isn't much buffetting as you go around them, especially if it's being pulled by something sleek like a Volvo truck. and, no, i don't make a habit out of drafting like that, but i would notice how the car would react differently behind different trucks as i would approach them before passing... even the trailers with those goofy things hanging off the bottom have an affect on cars that they share the road with..

Wally wrote: These have a 5.9 Cummins spinning a generator and a fairly small battery pack on the roof and accelerate plenty hard. When we got them they had to reprogram the accelerator because they would catch standing customers off guard and dump them on the floor.

So the Cummins acts as a prime mover and directly powers a generator? It's not coupled to the driveline at all? Do you have any more info on these? I'm quite interested.

Sky_Render wrote: I have several friends who are engineers with Volvo/Mack trucks. I asked them why the diesel locomotive configuration was not used (diesel generator supplying power to electric motors). The reason? Transient response. Although it works great at steady-state speeds (which a train operates at 99% of the time), the trucks would be nigh impossible to drive around town. Trains have miles of room to accelerate, and they (typically) only stop at their destination. Big Rigs need to be able to drive in traffic and accelerate and decelerate in a timely manner.

I wonder if those locomotives are really that efficient given the multiple energy conversions. I was under the impression that they ended up with that solution because there's no practical way to create a mechanical connection to the wheels. Can you imagine the gearbox necessary to accelerate a 10 million lb train from a dead stop to 60mph?

mfennell wrote:

Sky_Render wrote: I have several friends who are engineers with Volvo/Mack trucks. I asked them why the diesel locomotive configuration was not used (diesel generator supplying power to electric motors). The reason? Transient response. Although it works great at steady-state speeds (which a train operates at 99% of the time), the trucks would be nigh impossible to drive around town. Trains have miles of room to accelerate, and they (typically) only stop at their destination. Big Rigs need to be able to drive in traffic and accelerate and decelerate in a timely manner.

I wonder if those locomotives are really *that* efficient given the multiple energy conversions. I was under the impression that they ended up with that solution because there's no practical way to create a mechanical connection to the wheels. Can you imagine the gearbox necessary to accelerate a 10 million lb train from a dead stop to 60mph?

The generator gets to run at ~a constant pace the whole time so its more efficient, it can be tuned to be hyper efficient on just a tiny rpm band. IIRC the literature I read about it a while ago, to move the same mass of cargo from the same point along the same path a diesel-electric train is about 4.5 times as efficient as a traditional semi. I think that was based off of older, less efficient semi than the latest and greatest of today. Its hard to do the math yourself because of how train fuel efficiency is displayed, its gallons of fuel to move 1 ton a specific distance (for get what it is) it ends up in the units of ton/gal.

kylini wrote:

You nailed it!!! Ba bump, bump bump bump. Ba, Ba ba bump...

I know that some of the professional race teams, not surprisingly starting with Penske years ago, have had some pretty nifty looking haulers.