A great display of engineering and craftsmanship.
I was quite skeptical about this experiment
and then I thought about it for a while, did some research
, and came up with an answer that will leave me with both a good night's sleep and what little hair I have left intact.
Ice boats can travel much faster than the windspeed on a reach because they transfer lateral apparent wind
into a force parallel to the direction of travel.
Logically one can reason that on a dead downwind course there is no lateral force. Therefore as the machine speeds up, the apparent wind
decreases until equilibrium and the net sum of the forces causes acceleration to cease somewhere just shy of the wind's speed.
By jibing from one reach to another, ice boats can maintain a net DDW course made good at a speed higher than the wind. But at any moment when the boat is actually traveling DDW, the boat will decelerate.
At first I thought the treadmill test had nothing to do with DDW travel. It only demonstrated the ability of the author's device to transform the energy supplied by the electric motor
in the treadmill into an aerodynamic force strong enough to overcome the weight of the vehicle on a very small incline. I figured that the experiment
didn't account for things like aerodynamic drag or other unknown factors that invalidated the claim.
Then the light bulb in my head
The device demonstrated here CAN travel dead down wind at a groundspeed greater than the local wind speed because the propeller
blades themselves are not actually travelling dead downwind.
A thought experiment:
Pretend an ice boat is sailing not on a flat sheet of ice, but instead on the surface of a large horizontal ice cylinder that is pointed directly downwind. Also pretend for the moment that our iceboat can travel around this cylinder without falling off at the bottom. Our iceboat skipper
could maintain a broad reach indefinitely without jibing by simply sailing a straight course (like a rhumb line on a mercator projection turned on its side). At any given point the boat would be pointed on a broad reach relative to the wind. The vessel's course on the surface of the cylinder would be at an angle to the cylinder's axis. But the vessel's net velocity would be dead down wind (at up to 6 times the windspeed!!! See the link at the end)
The blades of the device depicted at the begining of this thread rotate around a central axis and act like the iceboat's mainsail
on a broad reach. They transfer the lateral apparent wind into a force that, when applied to the wheels, allows the whole device to travel dead downwind SLIGHTLY faster than the windspeed. Not a whole lot faster mind you. And as soon as the windspeed relative to the ground drops to zero, the device decelerates and eventually stops.
The motive force relies on the difference in relative velocity between the ambient air and the ground. If this difference euqals zero, then there is no potential for movement.
On the treadmill, the difference between the velocity of the ambient air (zero) and the velocity of the treadmill (something) is enough to overcome the drag from the device's wheels and allow it to travel slightly faster than the apparent winsdpeed relative to the treadmill's surface.
This is certainly not a perpetual motion machine since energy is not created from the ether. The device will certainly not accelerate indefinitely. It simply travels fast enough to briefly defy common sense.