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A Physics Prof Bet Me $10,000 I'm Wrong

 
 
 
ZiprHead

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I was going to put this in the Next Level thread but I think here would be better. The math get's way more complicated than I could comprehend.

 
bilby said:
Can you give a summary of what his claim is for those who don't want to watch a video.
Click to expand...
Downwind car uses clever physics to produce movement against the wind by leveraging a lot of it against the ground.
 
Anyone who has ever heeled over a Hobie Cat knows you can go downwind faster than the wind….
 
Back when I was about 12, my best friend came up with a brilliant plan. We launched into our perpetual motion grocery cart project.

We "got" a grocery cart. He "found" a car alternator and I "found" an electric motor. All we had to do was connect the alternator to the front wheels, the motor to the rear wheels, then the alternator to the motor.
Voila! A perpetual motion grocery cart!

Our moms thought it was a brilliant plan. Kept us busy outside for a couple of days. They kept encouraging us to keep at it. They were great moms.
Tom
 
bilby said:
Jarhyn said:
bilby said:
Can you give a summary of what his claim is for those who don't want to watch a video.
Click to expand...
Downwind car uses clever physics to produce movement against the wind by leveraging a lot of it against the ground.
Click to expand...
So, he invented sailing?
Click to expand...
Producing movement against the wind by leveraging a lot of it against the ground would be inventing sailing, yes; but that's not what he's doing -- he's producing movement with the wind, but faster than the wind. Turns out that takes a lot more cleverness. This contraption is not a land sailboat, pushed by the wind. It appears to actually be a perpetual motion machine, pushed by itself, but exploiting the wind to make up for its energy losses.

Elixir said:
Anyone who has ever heeled over a Hobie Cat knows you can go downwind faster than the wind….
Click to expand...
Sure, but straight downwind? Heeled over means the wind is from the side. Most of that "faster than the wind" is in the crosswind component of your velocity vector. You can't get the downwind component of the velocity vector to reach the wind speed that way -- if you did then your boat wouldn't heel over. Getting a Hobie Cat to sail with its downwind component faster than the wind would be a very neat trick.
 
Air has kinetic energy .5*m*v^2 in watts. The sail has an area, energy into the boat in watts/m^2. The boat or land vehicle has kinetic energy.

Ball park it comparing input energy to kinetic energy of the boat or vehicle. If energy in <= kinetic energy out you have a problem somewhere or you have made an astounding discovery.

I think there was a thread a long tine back on this.
 
steve_bank said:
Air has kinetic energy .5*m*v^2 in watts. The sail has an area, energy into the boat in watts/m^2. The boat or land vehicle has kinetic energy.

Ball park it comparing input energy to kinetic energy of the boat or vehicle. If energy in <= kinetic energy out you have a problem somewhere or you have made an astounding discovery.

I think there was a thread a long tine back on this.
Click to expand...
Its more just the fact that using leverage and a force differential, something can be made to transfer the energy of the differential into a moving object.

As was stated, it is about using wind as the board at the end of the video pushes the wheel assembly.

It's not a great huge discovery, just a proof that you can do it with something less solid than a board being presented in simple and useful ways.
 
bilby said:
Jarhyn said:
bilby said:
Can you give a summary of what his claim is for those who don't want to watch a video.
Click to expand...
Downwind car uses clever physics to produce movement against the wind by leveraging a lot of it against the ground.
Click to expand...
So, he invented sailing?
Click to expand...
The windmill powers a traction drive axle. The challenge is to produce a vehicle speed faster than the wind ground speed. Considering the drive train has to make two 90 degree turns, that's a tall order.
 
When it comes to Newtonian mechanics and mechanisms I doubt there is much that has has not been thought of, tried and used before.

It is what mechanical engineers do.

I posted a link somewhere to an ancient compendium of mechanisms that were used.

Air hearings are interesting. They provide very stiff bearings for machines like laser scanners.

en.wikipedia.org

Air bearing - Wikipedia

en.wikipedia.org en.wikipedia.org

A rope is a flexible medium with which to transfer energy and power. Replacing a stiff material to transfer power with something flexible does not seem to be all tat innovative.

Rotating and linear translation machines involve relative motion and inertial frames and energy/power transfer between moving frames.

The differential in a car translates rotation of a shaft to linear motion.

Torsion in a flexible strip has been used to transfer power. Springs.
 
Bronzeage said:
bilby said:
Jarhyn said:
bilby said:
Can you give a summary of what his claim is for those who don't want to watch a video.
Click to expand...
Downwind car uses clever physics to produce movement against the wind by leveraging a lot of it against the ground.
Click to expand...
So, he invented sailing?
Click to expand...
The windmill powers a traction drive axle. The challenge is to produce a vehicle speed faster than the wind ground speed. Considering the drive train has to make two 90 degree turns, that's a tall order.
Click to expand...
Actually I believe the math is the money from the clicks >> cost of the productions.
 
Bronzeage said:
bilby said:
So, he invented sailing?
Click to expand...
The windmill powers a traction drive axle. The challenge is to produce a vehicle speed faster than the wind ground speed. Considering the drive train has to make two 90 degree turns, that's a tall order.
Click to expand...
According to the video it's not a windmill; it's a fan. The movement along the ground powers the wheels, the wheels drive the fan through the drive train, and the fan maintains the machine's movement along the ground. In still air the thing would of course slow to a stop because the force of the wheels on the fan isn't enough to create enough thrust to keep the cart going; but the tailwind reduces the amount of thrust it needs.
 
Bomb#20 said:
Bronzeage said:
bilby said:
So, he invented sailing?
Click to expand...
The windmill powers a traction drive axle. The challenge is to produce a vehicle speed faster than the wind ground speed. Considering the drive train has to make two 90 degree turns, that's a tall order.
Click to expand...
According to the video it's not a windmill; it's a fan. The movement along the ground powers the wheels, the wheels drive the fan through the drive train, and the fan maintains the machine's movement along the ground. In still air the thing would of course slow to a stop because the force of the wheels on the fan isn't enough to create enough thrust to keep the cart going; but the tailwind reduces the amount of thrust it needs.
Click to expand...
I watched the video many years ago and I don't remember the details. Did they push it to get it started?

It reminds me of the Sterling engine videos about a device powered by ambient heat in the room and produces .001 horsepower.
 
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