I posted a bunch of related resources here:
http://www.7gen.com/book/revivifying-lectra-motorcycle/cabin-scooter-design-resources-around-internet/23570
and
http://www.7gen.com/website-categories/aerodynamics
One interesting thing I've found is there are "ecomodders" who are
modifying their gas cars for more efficiency. One thing they've done is
some simple aerodynamic improvements like mounting a boat-tail-like rear
end, mounting a nosecone, mounting covers over wheel wells, and moving
side mirrors inside the cabin.. and one of them is claiming 90+
miles/gallon with a normal honda civic.
A couple weeks ago I did some baseline measurements.. I found a
technique on instructibles.com to estimate drag coefficient by measuring
the time it takes to coast from 45 miles/hr to 0 miles/hr. There are
many more variables in the coast-down time than just aerodynamic drag,
because it is including road resistance and rolling resistance.
It seems to me -- that setting aside all measurements like Cd -- if you
make a modification and it improves efficiency, that's a good thing,
even if you can't put your finger on exactly why it improved efficiency.
- David Herron
john fisher wrote:
don't know bidwell's calcs.
2-3 X qualifies as "substantial" to me, while 30% does not.
Vetter used to be interested in LSR racing. Those designs aren't usable for
street or track.
CD is not the only factor in aero calcs - its wildly misused all over the
internet. In fact most say the tail is more
important than the nose. The thing *I* think its important to remember is you
can't calculate the actual drag without
either 1) a cad model and major-league software on huge hardware, or 2) a wind
tunnel that lets you test the bike at
lean. You can mount the bike on a trailer and get some idea, but my point is,
its really hard to measure aero effects.
That said, everybody guesstimates based on previous designs.
theres some other good, trustworthy links out there, I'll look tonight.
Wikipedia may be pretty good on this by now.
dale henderson wrote:
i got my results from the equation found in biddwells [spelling] "EL CHOPPER".
i've found the equation works very well for my current bikes, so i just tried reducing
the Cd, i even tried 0.1,
