[email protected] wrote:
> On Dec 12, 6:03 pm, "Leo Lichtman" <[email protected]>
> wrote:
>> I took the change out of my left pocket and put it in my right pocket.
>> Question: what effect did that have on my net worth?
>
> Hello Leo,
>
> Lets say there is a big hole in your left pocket.
>
> Drag presented by the rider is not useful for anything, it's an
> annoyance.
>
> The surface area of the rider and the fan placed in series is not the
> same thing as when placed parallel. The drag per cm2 has it's
> maximum.
>
> It's like a screen blocking the wind. You know how a wind screen
> works.
A wind screen spares the person behind it the annoyance of having to
face into a stiff wind, but it creates a lot of drag.
> It's just like cycling behind someone or driving behind a truck.
Is it, now? Try attaching a garage door to the front of your car and
tell me if it improves your gas mileage the way drafting behind a truck
would. (Hint: It won't, because the drag on the garage door will be
transmitted to your car -- unlike a drafting situation, where the drag
on the truck in front of you is *not* transmitted to your car.)
> The rotors make drag but this drag is not slowing the vehicle down.
It most certainly is, unless the windmill is not attached to the bicycle.
> The rider is riding in the slipstream of the windmill.
But the drag on the windmill acts on the bicycle, and since the rider is
mechanically connected to the bicycle (i.e., sitting on it), it slows
the rider down too. The windmill might make it a little more comfortable
for the rider, the way a windshield would, but it won't help the rider
go any faster.
> five thousand years ago, the Egyptians made sailboats.
>
> In 1493 Giacomo Caprotti designed a bicycle.
>
> In 1790 Monsieur Sivrac made the first bicycle.
>
> In 50 Hero of Alexandria described A wind wheel operating an organ
>
> In 700 windmills were used in Iran.
>
> Everything has already been done.
I don't know about that, but I DO know that you're not the first person
to come up with this idea. It's been done to death (though as a concept
it has its pedagogical uses, namely demonstrating the laws of
thermodynamics).
> If I put the windmill on the bike. You want to pretend it stops
> working??
>
> Be specific, what stops working. The bike or the windmill?
>
> They don't just continue to work but they actually compliment another.
As another person already pointed out, if you put a windmill on the
front of a bicycle it will increase the drag on the bicycle. (For
instance, the air pressure behind the windmill will be less than in
front of it, creating a net force opposing the motion of the bicycle.)
The best you could hope to do is use some of the energy from the fan to
offset the effects of the drag. You will not, however, be able to offset
all of the drag you add, so the net effect will be that the bicyclist
will have to pedal harder to maintain the same speed as without the
windmill.
If you don't believe me, try your idea out in a wind tunnel. I guarantee
the drag coefficient increases enough to negate the energy you extract
from the airstream and then some.
> Just look at the spammers trying to obfuscate the topic. That should
> say enough.
Oh, that's an *old* chestnut -- if enough people say it doesn't work,
why then they're covering something up and it MUST work, right?
