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MetroMPG 01-28-2008 08:52 PM

Aerodynamics Seminar #1 - by Phil Knox
This post was originally written by Phil Knox (aerohead), and it first appeared on the MaxMPG group. Phil has done a lot of work educating the masses about the critical role aerodynamics play in efficiency, and has spurred many in the DIY crowd to take matters into their own hands.

This is the first in a series which I'm reproducing here with permission.

Go to: Aerodynamics Seminar Index


Aerodynamics Seminar #1 - by Phil Knox

Since we all can't sit down together,its hard to assess everyones background and get on the same page, aerodynamically speaking. Had public education not dropped the ball,we wouldn't be on an obscure website trying to fill in the blanks,and self-educate ourselves on a topic which quite literally effects all people,everywhere.

The crux of the matter is that we all live in the troposhere at the bottom of our planets ocean of air. Air as measured at a arbitrary pressure and temperature standard,weighs about 0.075 pounds per cubic foot.A 22-cubic foot refrigerator (empty) holds about a pound of air.

Since we are three dimensional,we occupy space,and anytime we move,we displace atmosphere.It takes work to do this. The power required to do work is denoted in the U.S. by HORSEPOWER. If you lift 550-pounds,one foot,in one minute,you have used one horsepower. If your electric car expends 746-Watts to do a task,it has used one horsepower.

When moving through the air,we are displacing a volume of air which has mass,in some slice of time.Our cars,when they travel,must tunnel through a volume of air which is a function of their FRONTAL AREA. When you stand at a distance in front of your car and think about the area of its height and width,you are viewing its frontal area.

A simple example would be a van,6-feet tall,and 6-feet wide.No curves,all sharp corners,lets ignore the wheels for simplicity.Your vans frontal area is 6-feet times 6-feet,or,36-square feet.For every mile our van goes,it punches a hole through the air that is 36-feet by 5,280 feet.Thats 190,080 cubic feet of air.If we multiply 190,080 by 0.075 we get the mass of the air we tunneled through,which is 14,256 pounds of air.Dividing by 2,000 pounds/ton,we get 7.128 tons of air moved for every mile driven.

How quickly we move these tons and how efficiently we move them,determines how much fuel,battery,fuel cell etc. to do it.For the current state of the art for auto design,we stand to gain up to 35% better range from our power source just by changing the shape of our cars,trucks,and SUVs.If we're happy with the size (frontal area)of our vehicle,then its shape will be the primary area of attention for improving its highway mileage.

Going back to the EVWORLD article,we consider that a hen egg and sugar cube have identical air resistance,even though the hen egg is twenty times larger than the cube, its shape is our clue as to how this virtual leviathan can move through the air with no more resistance than the tiny cube.The secrets in the shape.

Considering the bottlenose dolphin,the sailfish, canoes, kayaks, aircraft fuselage,submarine hulls, land speed record cars, all high-performers,we begin to gain insight into how nature and man work with and not against our tropospheric environment.

Since I'm running down the clock,I'll close with something to think about.If I can insulate my home against the effects of hot and cold, thereby lowering my monthly energy bill, is it possible to "insulate" my car against the effects of the troposphere in which it is emmersed? Thermal insulation has a numerical performance rating system from which one can calculate potential savings. Next time we'll see that aerodynamics offers a very similar rating system for which to anticipate change.

See ya down the road, Phil.

SVOboy 01-28-2008 08:55 PM

Good read, :thumbup:

aerohead 07-11-2008 07:04 PM

Ya Phil,you really sound like some sissy little girly-man.You probably drive some effeminate amorphous-blob jelly- bean looking girly-mobile! You should man-it-up,and get yourself a real manly car.Something cubic.You know,kinda pump yourself up and get with the program while you still can.Maybe pull a drag chute behind your new wheels.That's manly! Talk to the gas pump,it'll tell you what to do.Whatever you do,do it soon 'cause I'm about to hurl my strudel, looking at your silly aero-schmaero mobile!

ChrstphrR 07-11-2008 09:12 PM

Something reeks of troll here. C'mon, with the advent of the interweb and search engines, who couldn't find out what Phil Drives? Apparently, some dolt from Texas that likes posting on a long dormant thread...


MetroMPG 07-11-2008 10:20 PM

(Psst: ChrstphrR... aerohead IS Phil :))

ChrstphrR 07-12-2008 05:12 AM

Whoops! My apologies, I didn't know Phil had a twisted sense of humour. I hope he got a chuckle from me :P

kennybobby 08-08-2012 12:35 PM

slight correction

Originally Posted by MetroMPG (Post 7289)
[I]This post was originally written by Phil Knox (aerohead), ... If you lift 550-pounds,one foot,in one minute,you have used one horsepower.

Should be: 1 hp is 550-pounds, one foot, in one second.

aerohead 08-08-2012 07:00 PM

per second

Originally Posted by kennybobby (Post 320629)
Should be: 1 hp is 550-pounds, one foot, in one second.

Good eye! Thanks! Glad someone's watching my back.

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