Sunday, March 08, 2009

The physics of Endurance Bicycles .

The physics of Endurance Bicycles .
Andre Willers
8 Mar 2009

Endurance cyclists .

I was watching the first lot of the Argus-PicknPay cycle tour (109 km) winners in Sea Point when I saw a bearded gentleman in voluminous clothes on a old-style bicycle bedecked with canvas cold-water canvas panniers cruise casually past , looking around with an amused interest .
No drop handles , lycra or intent expression . But he was in the first lot .

At first I thought he was taking the mickey out of others . Then I considered his get-up and realized that he could have easily continued on past the finish and done another 109 km without raising a sweat or a blister .

And he had probably done this as a matter of routine .
One of those Cairo-Cape cyclists .

But how ?

The main drag on a bicycle is from the vortices on the spokes of the wheels . The thickness of the wheels only matter in accelleration , not steady speed . They are the fastest moving parts . Though thin , there are a lot of them (Note solid spokes in racing cycles - the designers are well-aware of this) .

The Coanda-effect .
Thin layers of air cling to the surface . This is the basis of space-shuttles and most modern combat-aircraft .
The water-panniers hanging from both sides of his front and back wheels created a coanda-effect on the spokes . The disk of air surrounding the spokes rotated with the wheel , and did not form vortices . The minimum covering has to be calculated , but my estimate is that if half of the wheel has a covering , spoke drag would be reduced by about a factor of 6 .(It is a non-linear response) .
(You can do this with cardboard )

The guy could pedal 6 times as far as someone without it .

The handle-bar panniers .
Water panniers across old-style handle bars .
This at first seems a no-no . The cross-section is increased . But look at the drag . In conjunction with the wheel and middle-bar panniers , the rider sits in a shock-bubble .
The front-surface is smoother than the rider's irregular visage .
The net drag is lower than those drop-handle cowboys .

The water .
The panniers are canvas bags of water cooled by evaporation . Remember your father or grandfather had these on their car's bumpers . A nice , cool drink , always available . Remember , the weight does not matter much . The bicycle is the second-most efficient machine ever made .(about 98%)

The clothing .
Loose clothing like a jhellaba has evolved over about 10 000 years as the most efficient clothing to wear in hot , arid climate where moderate exertion is called for .
Far better than lycra .

The balls .
Sitting crouched over drop-handles for hours at a time with your legs going up-and-down is not conducive to a healthy sex-life .

The gearing .
He did have gears . But not very fancy ones .

My mother-in-law in the 1930's in Germany thought nothing of cycling 100 to 120 km for a Sunday picnic (+- 4hrs in the morning ) , then taking the train back in the afternoon .

The good old days . When men were men and bicycles had no gears .

Andre .

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