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# Wheel-Impelling Propellers

wind-assisted bike
 (+2) [vote for, against]

These bicycle wheels will give you an added boost with every lateral gust. They're just like carbon fiber disc wheels, except these have eight narrow, radially arrayed, triangular excisions.

A flap, hinged at its leading edge, fills each cutout. Depending on the bike’s speed and the direction and velocity of the side wind, when sufficient lateral pressure is applied, the flaps open to their maximum angle to act as blades of a wind turbine. As the wind rushes through the wheels, their blades increase wheel rotation, speeding you up while easing pedaling.

At this point, wheel air resistance in the direction of travel is negligible. Also, stability, a serious problem with disc wheels, is greatly improved.

 — FarmerJohn, Mar 31 2003

Whike http://www.whike.com/
Recumbent tricycle with a sail [Pellepeloton, Aug 11 2009]

dang you FarmerJohn Bicycle_20Vaned_20Spokes
[mfd] <sniff> [FlyingToaster, Aug 11 2009]

Picture?
 — DrCurry, Mar 31 2003

.r_T
ÔVÔ
 — FarmerJohn, Mar 31 2003

 *applause*

I wonder though... will these flaps open against you when you're driving into the wind?
 — waugsqueke, Mar 31 2003

It would make a lovely exhibit in the museum of fanciful devices. It wouldn't actually have to work. But that's not all that important here, right?

A few of many things to think about:
the wind direction through the wheel is a result of combining the forward and lateral velocities. (Fly a flag from the bike. Bike goes at 20 kph, no wind. Flag is straight back--air flow relative to wheel 20 kph 0 degrees.)
(Now add 20 kph wind gust perpendicular to bike. Flag flies at 45 degree angle, showing angle of air flow through wheel -upwind.) The wind rushing through the wheels is not, at that vector, able to apply much rotational force to the blades.

The proposed rotor design is the least efficient turbine possible, short of nothing (solid disc with 8 narrow cut-outs), and even under best conditions could generate relatively little if any torque. Best would be an open wheel with only three blades/spokes.

If air pressure is all that establishes the attack angle of the blades, you are cancelling out force.

Even so, you'd have a hard time getting to any combination of bike velocity, wind velocity and angle, and attack angle of the blades that wouldn't result in a stall condition (zero rotational force).

That's probably why they never invented sail-bikes. Just bike downwind only, and you can hoist a spinnaker.
 — roby, Mar 31 2003

 waugs: A strong head wind coming slightly from the side could open flaps at the bottom of the wheel, but they're not traveling that fast (forward) near the ground.

roby: The flag is a good analogy. Yes any added force would not be great, more psychological. Maybe it should be called Placebo Power.
 — FarmerJohn, Apr 01 2003

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