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Mess with your minds: A wind powered craft going faster than a tail wind speed.
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gnuarm:

--- Quote from: fourfathom on December 31, 2021, 04:59:09 pm ---
--- Quote from: gnuarm on December 31, 2021, 04:27:21 pm ---Then he takes close up photos of gears nearly slipping and talking as if the micro level of energy involved in that is providing the necessary energy for faster travel.  It's pure BS.
--- End quote ---

The whole stick-slip hysteresis energy storage explanation is silly.  If there is a stick-slip cycle then energy is stored and released during the cycle.  If ED's explanation were true, the vehicle would be varying above and below windspeed at the cycle rate.  But the downwind speed of the vehicle through many of these nonexistent "cycles" remains faster than windspeed.

--- End quote ---

Exactly.  So he has to claim the storage is in the air around the propeller as if this would actually power something meaningful.  It only exists because it is continuously replenished and constantly depleted as fast as the air moves through the propeller.  So very, very little stored energy.

This guy is starting to bug me.  We call him on his crap and he pulls more crap out of his crap bag.  But I guess it's a matter of fool me once, shame on you.  Fool me 5,067 times, shame on me.  We just can't seem to stop responding to him. 

I bet it would really bug someone for the conversation to be only between others, but not directly to him.  lol
gnuarm:
If you are talking about the propeller generating thrust, that is downwind.  So the propeller is pushing the front wheels down. 

In upwind mode the prop is a windmill.  It creates drag which will tend to shift the weigh so the front wheels could lift.  The car would be better operated with the prop in the front. 

I don't follow at all about the front wheels lifting for lower drag causing the car to accelerate.  Do you mean the drag of the wheels on the road?   
fourfathom:
Here's something that had me confused:

Bicycle stopped in the wind.  Wheels are not turning.  Brakes are locked (or wheels are bolted to the ground -- same thing).  There is force, but no movement, so no power.

Now, replace the brakes with a stalled motor.  There is still no movement, just two opposing forces (just as in the previous situation).  But the motor requires power (V*A) to remain stalled.  This power is being turned into heat.  I assume that we just consider that the motor is operating at 0% efficiency?  But it is providing torque. 

Or replace the motor with an electromagnetic solenoid that holds the bicycle in place against the wind -- really the same situation as the stalled motor.  In both cases power is being consumed, but no work is being done other than heating the air?

It seems to me that some of ED's confusion is related to this.  I know I still struggle with the terms, since I always go back to the volts and amps.  ED's models using generator and motor also add to the potential (no pun intended) confusion.

bdunham7:

--- Quote from: fourfathom on December 31, 2021, 06:50:46 pm ---Now, replace the brakes with a stalled motor.  There is still no movement, just two opposing forces (just as in the previous situation).  But the motor requires power (V*A) to remain stalled.  This power is being turned into heat.  I assume that we just consider that the motor is operating at 0% efficiency?  But it is providing torque. 

--- End quote ---

For a motor, efficiency is the work done by the motor as a percentage of power input.  So if it does zero work, it is 0% efficient.  However, the motor can be made arbitrarily efficient to have arbitrarily small losses, at least theoretically.  If the motor is actually doing a certain amount of work (output) then it has to have at least that much input power, since it can't exceed 100% efficiency.  However, if it is doing zero work, as in a stalled motor, you an reduce the input power to an arbitrarily low number.  As a trivial example, lets say your motor requires 5 amps at 60 volts to provide enough torque to hold a bicycle in place with a headwind--300W.  If we assume a motor that has a torque proportional to the input current, then we can use a 10:1 gearbox so that the motor only needs 0.5 amps to hold the same bicycle against the same headwind.  IOW, the work being done by the motor (output) is simply the lower bound for input power.
IanB:

--- Quote from: fourfathom on December 31, 2021, 06:50:46 pm ---Here's something that had me confused:

Bicycle stopped in the wind.  Wheels are not turning.  Brakes are locked (or wheels are bolted to the ground -- same thing).  There is force, but no movement, so no power.

Now, replace the brakes with a stalled motor.  There is still no movement, just two opposing forces (just as in the previous situation).  But the motor requires power (V*A) to remain stalled.  This power is being turned into heat.  I assume that we just consider that the motor is operating at 0% efficiency?  But it is providing torque.
--- End quote ---

Remember that gearing can be placed between the motor and the wheels. Also, there is a property of gear trains that sometimes they can only go one way. For example, a worm drive. If you turn the input to a worm drive, the output will turn. But if you try to turn the output, it will not move. No matter how much force you apply to the output of a worm drive you cannot drive it backwards. So the vehicle will sit stationary in the wind until you turn the input to the gear train, and this will then need little power to make it move.

So once you have this situation, you can just put a really tiny motor on the input to the worm drive, and as long as the gearing is high enough, the tiny motor can move the output against an arbitrarily large force. This is just the principle of levers applied to rotation. Given a big enough lever, you can lift a mountain with the weight of a feather.
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