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Re: MC aerodynamics

To: "JAMES CANNON" <dr.piston@worldnet.att.net>
Subject: Re: MC aerodynamics
From: john robinson <john@engr.wisc.edu>
Date: Mon, 12 Feb 2001 12:12:04 -0600
Howdy,
         I considered that, but the amount of wing area is pretty small, 
not more than 18-20  inches length total, including forks and rear of front 
fender, the "disc" of the wheel is many times larger(when talking about 
aero), all the aero forces are behind the point of contact of the tire, 
causing the wheel to "fly" straight, at speed the steering input is small, 
"leaning" the bike probably produces more drag than turning the wheel, to 
say nothing of the amount of flywheel effect the wheel imposes on the bike 
steering. I don't think the wing area is going to affect the steering of 
the bike to any appreciative amount, but I don't know, that's why I'm 
asking for input.

At 11:55 AM 2/12/01, you wrote:
>I've wondered also but was afraid it may act like a rudder.
>
>J.C.
>-----Original Message-----
>From: john robinson <john@engr.wisc.edu>
>T
> >Howdy,
> > As I look at pictures of bikes that are racing at Bonneville Salt Flats,
> >(and any road race bike in the last 30 years or so), I notice all bikes do
> >not have any aero fairing on the lower fork legs; as this is a known
> >smoother of air, by making the rear of any round tube pointed, how come no
> >one is modifying the lower legs for more speed? It can't be because it's
> >too hard to do, some of the work I've seen done is incredible....why? Is it
> >that  the pattern of air that is flowing around the front forward edge of
> >the tire and the disruption of air by the spokes that causes the aero
> >advantage to be negated? somebody try it before and it didn't work, too
> >much unsprung weight? anybody seen any wind tunnel data that I could read?
> >For straight line speed, as at the Salt, how come no one has made the back
> >of the front fender more fair the same way, with a pointed tail section?
> >How about gathering the air, as most bikes do now, at the front of the
> >engine, direct it in a closed tube through the bike and vent it via
> >converging diverging vents aimed at the hole in the air above and behind
> >the rider? Bikes punch a fairly dirty hole in the air, any cleaning up
> >results in more speed, doesn't it? anybody got books that I can go to for
> >bike aerodynamics?  or is it a black art, secrets for the manufacturers
>only?


              John Robinson, Mechanician
   Mechanical Engineering University of Wisconsin
                 1513 University Ave.
                  Madison, Wi. 53706
                     608-262-3606
                   FAX 608-265-2316
        Current World Land Speed Record Holder
                 Bonneville Salt Flats
            H/GCC 92 cu.in. 1980 Dodge Colt
                   131.333 MPH set 1995
                   136.666 MPH set 1996
                   140.292 MPH set 2000
                   144.396 MPH set 2000

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