The Underbody (flat belly pan is suboptimal - explanation & solutions offered)

[slowbro]

Originally Posted by Otto

Questions:

Flat panel belly pan: Why not slice up several old tennis balls into crescent shaped domes of ~1/2" height, then glue or velcro them to a flat belly pan and test for difference?

Corrugated belly pan: The Ford Trimotor and I think a Junkers transport plane of that era had corrugated skin, with the ridges/valleys oriented in the direction of flow. This reportedly was an elegant way to stiffen the skins while reducing aerodynamic drag, as the flow wedges (wakes) generated by surface imperfections were contained and prevented from growing laterally downstream. Corrugated fiberglass material is available very cheaply from every Home Depot or Lowes. Anybody tried using it as belly pan material, or made aerodynamic tests of it?

The Toyota video of their new SUV: I'm underwhelmed. The guys in that video crow about their design, but frankly it seems to me they left LOTS of money on the table. Maybe they studied aero at the same school whose grads did the Chevy Volt. I'd bet dollars to doughnuts that various people on this website could make significant improvements to that vehicle in a weekend, working in their driveway, for less than $100.

MTrenk, are you a seasoned, practicing aero engineer or a beginning student with years to go before that? Read Hucho yet?

I initially thought the same thing. I was stunned when he said that was the most aerodynamic wheel and tire combo. Those things are blenders! Then I realized he was pretty much saying that the design was pretty much the limit Toyota was willing to take it to. I'm sure many of the engineers would have liked to keep going, but Toyota along with other car companies generally likes to keep things conservative.

[Otto]

Originally Posted by slowbro

I initially thought the same thing. I was stunned when he said that was the most aerodynamic wheel and tire combo. Those things are blenders! Then I realized he was pretty much saying that the design was pretty much the limit Toyota was willing to take it to. I'm sure many of the engineers would have liked to keep going, but Toyota along with other car companies generally likes to keep things conservative.

That was the precise moment in the video when I got real skeptical about the self-congratulatory script. The wheels on that thing suck. Maybe he should trot on over to WalMart and pick up some aluminum pizza pans @ ~$3 each, and give them a shot.

Mirrors could use some work: Who needs a mount stalk the size of your wrist and grossly un-aerodynamic, when a pencil-thick airfoil shape would work better at a tiny fraction of the drag? The British Spitfire designed in the 1930s and flown in WW2 had an outside mirror with a skinny little stalk, flew 500+mph in a dive with no ill effects, so surely the automotive rocket scientists can come up with a better design than we see on this vehicle.

Then, there are the gaps in the undertray area, etc..

Sorry about the rant. Grumpy mood.

[Gealii]

Originally Posted by Otto

The Toyota video of their new SUV: I'm underwhelmed. The guys in that video crow about their design, but frankly it seems to me they left LOTS of money on the table. Maybe they studied aero at the same school whose grads did the Chevy Volt. I'd bet dollars to doughnuts that various people on this website could make significant improvements to that vehicle in a weekend, working in their driveway, for less than $100.

The thing is while their making a fuel efficient vehicle they can not take it to the extreme because they are following for what the consumer wants, and unlike ecomodders people want to continue stomping the pedal while having a cool looking car and get good mileage. Their concerns of good mileage is getting more then the old vehicle. This is how my dad is for example he continues to tromp the gas and then wonder why is mileage is so bad and then thinks the only way to get better mileage is to get a new vehicle....

[Xist]

Originally Posted by slowbro

I was stunned when he said that was the most aerodynamic wheel and tire combo. Those things are blenders!

I forgot to look for the original thread and see if anyone commented on that.

Maybe people associate electricity with appliances... :/

[MTrenk]

The Toyota is underwhelming, but it sure as hell made the business people happy I'm sure. That's the only way that car would make it to market. Toyota probably came up with a version of that car with a .26 Cd, and it was rejected by the marketing department because the business people know the market better than the engineers.

I am a student, but that doesn't really matter that much. I read all sorts of stuff, and I use my brain when I read it. I've read all sorts of vehicle dynamics books, and I don't agree with everything everyone says. There are some books out there that are considered 'definitive' in their respective fields, but they are matters of reference, not engineering bibles. I prefer to try to figure things out on my own, it's the best preface to a journey to the library, I've found. You people need to quit it with this Hucho talk, because a lot of the conclusions you guys have written down on these forums aren't really worth anything, IMO.

At the last Supermileage SAE competition, the highest score was 1475 mpg. Designed, budgeted, and built by 20 year olds. Most of those cars are under 10 grand. Nuff said.

[Frank Lee]

At the last Supermileage SAE competition, the highest score was 1475 mpg. Designed, budgeted, and built by 20 year olds. Most of those cars are under 10 grand. Nuff said.

Yeah, I designed a Supermileage SAE car back in the day.

[mcrews]

Originally Posted by MTrenk

The Toyota is underwhelming, but it sure as hell made the business people happy I'm sure. That's the only way that car would make it to market. Toyota probably came up with a version of that car with a .26 Cd, and it was rejected by the marketing department because the business people know the market better than the engineers.

I am a student, but that doesn't really matter that much. I read all sorts of stuff, and I use my brain when I read it. I've read all sorts of vehicle dynamics books, and I don't agree with everything everyone says. There are some books out there that are considered 'definitive' in their respective fields, but they are matters of reference, not engineering bibles. I prefer to try to figure things out on my own, it's the best preface to a journey to the library, I've found. You people need to quit it with this Hucho talk, because a lot of the conclusions you guys have written down on these forums aren't really worth anything, IMO.

At the last Supermileage SAE competition, the highest score was 1475 mpg. Designed, budgeted, and built by 20 year olds. Most of those cars are under 10 grand. Nuff said.

wow.....thank goodness you don't bring you attitude with you.....

build something....show us some aba testing.......but take your 'eureka moment' somewhere else.

[mwebb]

"At the last Supermileage SAE competition, the highest score was 1475 mpg. Designed, budgeted, and built by 20 year olds. Most of those cars are under 10 grand. Nuff said.
__________________
Max Trenkle
Student Engineer - TTU Motorsports "

i have already forgotten more than most will ever learn , yet there is one thing that never ceases to amaze me ...

the more new stuff that i learn ...
the greater is my understanding of how little it is that i really know compared to how much there is to be learned

i am not currently, nor will i ever be , a water walker.

without a little wisdom , learned from pain - and guidance from on high
none of the engineers or other mortals
are anything more than
fresh meat for the grinder

nuff said

[freebeard]

Nuff said.

We're on page 5 of 5; are we going to get to the side air dams and exhaust above the diffuser?

[Xist]

"Team member Tina Raeke, of Erie, drove that lap, keeping the 91-pound car to an average speed of 15.03 mph. Any faster, and the car would have been less efficient."

Penn State Live - Penn State Erie team wins international 'supermileage' competition

Okay. She can beat a runner, but not a kid on a bike, neither of which would use any fuel, and this would be destroyed by a smartcar. Does anyone know of highway-capable contests? That sounds more like an X-prize and they really should offer more than $1,400. It costs $650 just to compete!

Do you know what would be awesome? An MPG contest that included crash testing!

"Congratulations, you have conditionally won. Now for the head-on collision."