Build Your Own Wind Tunnel

Foilsim - Basic Aerodnamics software - freeware

Applied Aerodynamics:A Digital Textbook

Bicycle Aerodynamics

NACA ducts

Aero Design Team Online

The Incomplete Guide to Airfoil Usage


The aerodynamics of bicycles

Scientific American's article: Caught in a Wind Tunnel

Bicycle Aerodynamics


I had an interesting day out yesterday at the Manchester University aeronautical facility, testing stuff in their wind tunnel . We had been invited by a production company making a series of science programmes for the BBC, hosted by Adam Hart-Davis. Adam is a well known personality best known for his series "What Did The Romans Do For Us?", he also happens to be Windcheetah owner..... Anyway, his new programme, Science Shack, covers a wide range of topics . The show we were involved with is due to be broadcast in late November and covers the subject of aerodynamics and wind resistance. To demonstrate certain points the wind tunnel was used to compare the drag created by1] a bicycle 2] a part faired recumbent and 3] a fully faired recumbent. The figures were very interesting which is why I thought The List might wish to share in the information. A number of readings were taken across a wind speed range of 20 to 50mph and the drag expressed as Newtons. Heres a sample of some of the readings, the figure under each heading is the drag measured in Newtons.

Speed Bicycle Part -faired trike Fully faired trike
20mph 16.0 8.03 5.3
30mph 36.0 15.52 8.31
40mph 64.0 31.0 15.73

It`s interesting to note that a part faired trike [ nose cone and rear fairing, plus wing mirror, but no mudguards or wheel fairings] is generating only half the drag of a conventional upright, this figure gets even better as speed is increased. Even more impressive is the fully faired trike which is half the drag of a part faired trike,therefore a quarter of the drag of a conventional upright bike. The fully faired trike was totally enclosed, with wheel fairings and small side ventilation apertures. Just to bring us back down to earth we should remember that tyre rolling resistance doesn`t form any part of these calculations,in theory the bicycle should roll easier than a trike. The tests were also done in the usual rush that all TV companies operate, so they should only be taken as broad brush examples as opposed to absolutely accurate figures, even so it makes fascinating reading . Just for the record the bike was a mono-forked mountain bike, and Adam sat on/in each machine for the tests. The part faired trike was my own Windcheetah and the fully faired trike was Mike Burrows own Windcheetah racer. It`s a sobering thought that the drag on Mikes racer at 40mph is still less than the upright at 20mph. The tunnel is an old RAF facility capable of generating 150mph wind forces.




Thursday, 29 January 2009