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Home > Magazine > Motors > Motorcycle and Car Fairings: aerodynamic boosts for gas Mileage and style!

Motorcycle and Car Fairings: aerodynamic boosts for gas Mileage and style!
July 06, 2006

We just made a standard Michigander vacation drive from "downstate" to "up north" of about 200 miles each way. We have little kids and 2 dogs and bikes, so we took our old minivan. 17mpg. ...For $100 in gas for this little jaunt. Ouch!

Thankfully the kids are getting bigger and more nimble and we're not going to travel with a big dog that much so our next old car is surely going to be a sipper.

Now, someone's $2K hand-me-down Honda Civic EX will get about 40mpg on the road. That should be good enough and end of story. But I still wonder... An old VW Rabbit diesel (many still out there!) or even a Chevette diesel (are any still running?) will get 55mpg. And no matter what we get I wonder if it couldn't do better. So I got to wondering what's going on in the world of "MAX MPG."

First stop: autos.groups.yahoo.com/group/maxmpg. Good friendly stuff there!

Next: www.wisil.recumbents.com/car_aerodynamics/ ---A great summary by Warren Beauchamp (of HPV bike fame) of the many ways to get more MPG from your car. Many of them aero aides, many not---like some surprising fan belts and fans themselves that cost goodly gas.

Here's a pic of Warren's concept car that includes all his add-on's to save about 7mpg (from 26 > 32mpg):



Still, it doesn't seem like enough has been done or that there's enough out there on this subject. I'd think there'd be aero aides galore for cars, trucks, vans. ...And motorcycles (but more on those in a jiffy). Anyway, the maxmpg.org guy is making a curvy fairing for his truck bed: that should really help. What about putting swinging "clamshell" fairings on the back of a minivan? Would that help? For cars: why not have snap-on wheelwell covers for the rears and partials for the fronts? Can more be done with wheels and tires? The "Car Aero 101" report at recumbents.com says narrow tires and flat wheelcovers are the way to go. What about getting rid of those lame sidemirrors? --Swap in some wide-angle vid-cam's inside the windows, with monitors on the dash and be done with it. So let's do it!

Wikipedia has a neat page about these issues. It's based on air drag. Now, each shape as a Cd, drag coefficient. A big shape can be very smooth. But its bigness has to be considered, too. So that CdA is the final figure of importance. For instance, a regular cyclist has a worse Cd than a common sports car, but he has a far smaller frontal area, giving a smaller final CdA. Anyway, here's the Wiki page and pic from it of a few cars and their Cd's... NOT their CdA's...

en.wikipedia.org/wiki/Drag_coefficient

Some examples:



1935 Tatra: Cd = .21



Honda Insight: CdA = 5.10, Cd = .25

Saab 1947: Cd = .30
GM EV1: Cd = .195
Hayabusa--most aero fast production street moto: CdA = 3.37, Cd= .56
Honda 1990 RS125 GP "cafe" moto: CdA = 2, Cd = .64
Saturn Wagon: CdA = 6.9, Cd = (.3-.35)
Volvo 740: CdA = 8.7
Hummer H2: CdA = 26.3, Cd = .57

Bikes play out like the following. But, darn, I only have metric numbers! OK, here's a metric line-up of CdA's:

*ave. car = .79
*reg. bike = .68
*Honda Insight = .47
*Hayabusa street moto = .31
*triathlon bike = .23
*aero recumbent = .21
*Honda 1990 RS125 GP "cafe" moto = .19
*street-safe fully-faired recumbent = .06
*elite racing streamliner 'bent = .01

Bryant Tucker was a race car designer who used to race bikes at the HPV races. He died a few years ago, but he had the first dialed-in aero car I ever saw. A Honda Civic EX, I think it was, with a bunch of obvious accessories. He got 70mpg. Not bad! The car looked totally normal, really. It had what I mentioned plus a tail fairing and bellypan and slightly faired front. It looked great, in all. Production accessories could be made from everything he added on. A jiffy way to add 30mpg to your sweet ride! Why not? I don't see the downside.



At the same time, when I google this kind of thing, I don't find much. Lame disconnect, there. Evolution should take care of that pretty soon, methinks. Too bad no one cared til now.

OK, everyone knows I like aero bikes. I'm into faired recumbents---I have one that goes an easy 28mph around town, with groceries. I've since improved it with a full canopy into a 30-40mph everyday bike, but since having little kids haven't had the time to use it much. When I ride now it's more for the fresh air than the pure speed, but darn whenever I do give it a whirl that pure speed sure is SWEEEET! I just love going car-fast on a bike. But one can only do so much... Lately, I've been trying to figure out if upright bikes couldn't be greatly improved with compact fairings which double as trunks, fenders, etc.---I think there's a good chance they could. I cruise 20mph on my upright---I bet I'd get 23mph if faired. But none of this gives the speed, range or cargo capacity of a moto.

So, what about motorcycles? In the 70's, there were lots of small CC road bikes. 90, 125, 150, 175, 200, 250. Now each major brand has like one model at or under 250cc. And their average is 750cc. I don't see MPG touted anywhere in motorcycle-land.

I've explored scooters, step-thru's and "feet-forward" bikes, too. Even there: hardly anything said about MPG. A little scooter I notice only gets 60-80mpg. A fully-faired FF moto gets 55mpg. C'mon! This is lousy! I recall mopeds getting 200mpg and 125cc moto's getting 100mpg, no problem. Anything with an aero FF position---and hopefully lower overall height (due to sweet low seat-height and fairly serious recline)---plus some fairing action---should get 200mpg easy!

I'm guessing that the omnipresent Hog gets 15mpg? Something tells me that the overkill scene in cars and motos for speed, power and HP is going to go bye-bye shortly. I mean, who needs it. If you can pass perky enough, you're good. An aero moto in 75cc should be able to go as fast as a human could desire---100mph? 1000cc just isn't that smart. [I stand corrected on my Hog mpg: it's about 40-55mpg, actually. Not bad for a moto, really. Still, the mainstream mpg world rather sucks all around. I checked the Kawasaki 125 roadbike: 50mpg also! Suzuki 250: 50! Honda 250 Rebel: 65. Really, it's amazing how low this is for the engine size. I suppose the key here isn't engine size but engine efficiency, vehicle weight and aero. A big Harley engine idling along is obviously just as efficient as a small engine revving higher. I'm guessing that these little street bikes are designed to optimize their speed and torque. Altho I saw a review saying that the 125 maxes out at about 65 for tolerable rpm's. --JP]

Hot cars used to have 200hp. The top muscle car would have 300hp. Today we see MOST fancy SEDANS coming in with useless 250hp barnburners. We see minivans that can almost pop wheelies. Lame!

Then I found Craig Vetter's website. A fellow member of the Max-MPG forum put me onto it. I'd heard of it but never checked. Now I remember the name: he made the Windjammers of the 70's for the Goldwings, right? Hmm, better check that. (Just did---I'm right.) Anyway, it looks like he had some of the same ideas and frustrations I've had. And tons more expertise and resources. He's designed some amazing (and popular) moto stuff! He said when he first started designing in the 70's cars got 10mpg and motos got 40mpg. By the 80's cars got 40mpg and motos were still at 40mpg. He was pissed. So he promoted an event that resulted in a fully-faired record-setting 470mpg motorcycle. (He emailed me---cool!---that he's now going to launch a new mileage contest for bio fuel vehicles.) He also made, from a plain old little street bike, a safe and user-friendly bike with luggage space that he called the Hile Mileage Luxury Touring motorcycle, which got 125mpg. Here it is:



Here's the info: www.craigvetter.com/pages/Motorcycle_Designs/Streamliner.html.

By the way, he then made fairings based on the 470mpg bike...which are still available to custom-fit to a FF moto. They weigh 32 lbs and cost $1300. Here's his page that shows you how: www.craigvetter.com/pages/470MPG/high%20mileage%20fairing.html



Here's the HQ for the FF scene: www.bikeweb.com.

Here's the FAQ for the FF concept, written by Royce Creasey, the Jobst Brandt of the FF world (ahem): www.hightech.clara.net/feetfirs.htm

They also celebrate some of the star power that has propelled the FF scene: Akira's moto of anime' fame and some of the actual bikes being built around the idea:



I see clear windshields on some motorcycles. And some Windjammer-type bikes seem to have body-shrouding of a sort. I suppose they help MPG. But it doesn't look like anyone other than Vetter is really trying these days in terms of everyday bikes. Let's see some aero wheels/tires. And more front and rear fairings for MC's! The front can be a slightly more extended and aero version of today's windshield. A rear fairing could enclose a lot of a bike and easily include a trunk---and is really where big gains could be made.

Now, the Feet Forward format of moto is where it's at for aero. Your feet are in, not out: more aero from the start. Yet in an extreme world even the wild versions of FF bikes look pretty tame. Let's get those seats down a bit further and recline them a bit more. You could really boost the aero stats that way! If a tail fairing were to be as tall as a rider's head it could include a rollbar. There are several semi-production faired FF motos---and couple which have "safety cells," I think they're called in race lingo. --Crash cages to protect the human jelly sacks riding the bike. They work. REALLY WELL. So there's that. In any event, even a shorter rear fairing could include something like a rollbar to probably really boost safety. I do believe that the FF people really say that safety is on their side---they offer a big front impact crumple area. They offer much more powerful, safer braking. And the rider doesn't fly headfirst in a wreck. All VERY GOOD things. Still, I didn't see much bragging about MPG in the FF scene. I did see bragging about top speed. Of course a fairing goes faster. But, c'mon, zero practicality, people! The main bennie of moto fairings is MPG...and style...and then acceleration. But top end? Get real.

Here's Ian Pegram's faired FF project, the Genesis, that gets 110mpg:





I notice quit a bit of fussing being done in the project and company webpages over *landing gear* for fully-faired FF designs. Why not just use slotted soft side material in the foot area? Or just let foot-holes stay open? Or use hardshell "bomb bay" bungie retracting flaps like HPV bikes do? It looks like so many of these rigs put tons of weight and effort into landing gear when an everyday vehicle probably doesn't need them to get 90% of the gains of fairings. To me this only belongs on max-speed bikes or on car-bikes. Here's a nice faired FF, altho it has to rely on landing gear:



Anyway, there's some super work being done out there. Some neat characters who've been inventing away for decades. (All hail Royce Creasey!) As is sadly typical for good ideas, it seems like there hasn't been much market backing. It's rather shocking, given the multimillion$ scope of the moto-accessory market. (Well, Vetter did great with his Windjammer fairings and others.) What about the billion$ moto industry outright? These fairings should be coming stock on some models. Just think of the MPG gains that could be so readily had from any of the hundreds of companies that churn out molded fiberglass stuff.

ComfortMax FF faired moto: www.bikeweb.com/node/855

www.angib.pwp.blueyonder.co.uk/tmax/tmax00.htm



ECO Mobile and MonoTracer: www.peraves.ch/



A good forum thread: www.bikernewsonline.com/2005/01/ecomobile-motorcycle-for-cagers.htm

Julian Bond's Best Feet Forward: www.voidstar.com/bff/ffoneoff.html

The World of Royce Creasey: www.hightech.clara.net/

Here's an early Royce creation that's still going strong:



Bad things happen to good bikes. This pic shows how a FF with a crumple zone works, instead of pitching the rider:



Dan Gurney's Alligator: www.allamericanracers.com/alligator/alligator_tech.html

Gurney was a top car racer and designer (I think) and a very tall person. He felt his center of gravity was too high on motorcycles so he recently launched a line of bikes that he thinks are cooler, safer, faster...





Thanks to the wondrous BikeWeb.com site, I discovered that back in the day Audi used to build bikes and motos. They had a designer, Baumm, who went nuts for aero. He made a faired moto that got a dozen world records, mostly for small engines like 50cc and 100cc. It's built like many faired bikes are built today. They say his records are still unbroken but they don't say what they are. However, I did see 200mph for 40hp mentioned, probably a bigger engine, huh? Here's Baumm's famous NSU Hammock or Deckchair...sad nicknames for a sweet lookin' ride:







So how about that? An amazing scene, huh? Oneathese days I'm going to get me a sippy car or slippery moto and save more gas than I already do (by working at home).

Related Articles & Good Stuff

Views From a Wider Range of OYB

Steve - , posted on Jul 09, 2006
Great article Jeff!

Per Vetters website, I think you are wrong regarding Harleys. Note that with only changes to gearing and a Vetter fairing, he had a winner with close to 100 mpg in his first mileage contest back in 1980 or so.

I would guess a stock Harley would be around 30-40 mpg at least. As you know, the problem with motorcycles is the horrible aero. Most are stuck around 40 mpg. I checked my 1990 Yamaha XT 600 and it gets about 45 mpg.

You also noted that frontal area is very important for aero. I think we need to look at cars that are longer and narrower than what we have now. I am looking at a design for two people riding in tandem rather than side by side. I think we need to go to four wheels to make these things year round capable. Riding a motorcycle on ice and snow is not going to work.

Thanks for the inspiration.

PS: For a really slick looking 157 mpg (4) passenger car, Google Loremo. They are a German company looking to 2009 for production at $13,000.
JeffOYB - Williamston, MI, posted on Jul 09, 2006
Thanks for the heads-up. I stand corrected on the Hog mpg. Still, there's trouble in mpg-city.

Yeah, a longer, narrower car is far better. But I think we can make HUGE gains with rather familiar configurations. Install a half-size engine (I don't need to go 100mph.) Install a tranny with mpg-optimal gearing. Harder, narrower tires. All those aero features. One could likely do this to an existing Civic and hit, what, 75mpg. A slightly revised car could probably be just 6" longer and 6" narrower in back axle than front and be largely helped---like the old Citroen DS. But probably a car would have to go tandem to readily beat 100mpg. It's interesting to me how much more aero a car is than a typical moto---well, motos shouldn't just take that laying down (or maybe they should! recumbent moto ahoy!) --JP
bobwreford - , posted on Jul 14, 2006
Good article Jeff!

I have gradually improved the fuel consumption on a Honda VT600 Shadow from 45 mpg to 55mpg then to 70 mpg (all at the double nickel 55 mph average cruising speed.).

Pic at

http://www.bikeweb.com/node/798

I am in the UK so our gallons are bigger than the US ones by a factor of 6 to 5 when comparing consumption figures.

I chose the bike because it was narrow and cheap ($550), the fairing at the front was made in 1885 by a guy called Jack Difazio who majored in non telescopic front ends:-

http://www.bikeweb.com/node/1142

I find if you recline the seating too much the bumps clout your spine - 24 inches and up is fine.

Adding the brackets to support fibreglass panels adds a lot of weight, over 100 pounds to my bike, but the momentum down the hills helps get you over short uphill bits hopefully.

Craig Vetter has been very encouraging of my project, great guy!
bobwreford - , posted on Jul 14, 2006
Guess that should be 1985 for the year of my fairing!

Got excited that time......
boatbuilder - , posted on Jan 23, 2007
In the mid '80s a Brit named Tony Foale, who was famous for his motorcycle frame designs, worked on a couple of faired bikes too.

If you are interested check out the 'Articles' page on his website, and look for QL and Q2.

http://www.tonyfoale.com/

brunojlb - , posted on Jan 24, 2007
I'm actually interested in the 40mph bike! Anyone have any links or info about these machines esp homebuilt versions?

Please send me any links or info to sterbater@gmail.com

Thanks!
brunojlb - , posted on Jan 24, 2007
I'm actually interested in the 40mph bike! Anyone have any links or info about these machines esp homebuilt versions?

Please send me any links or info to sterbater@gmail.com

Thanks!
jbbishop2 - , posted on Jan 24, 2007
You might also be interested in Jory Squibb's homebuilt 100 mpg Moonbeam microcar, made from a couple of Honda Helix scooters. "How to Build" journal is at
http://mysite.verizon.net/vze6omtd/jorysquibb/id1.html