251–260 of 263 posts
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Sounds to me like it improves efficiency rather than consumes more
Same could be said for a turbocharger but we just happen to set the fuel mixture dynamically.
EDIT it’s more like gearing.
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Why would you consider those two scenarios analogous? In one scenario, the wind is “giving it a push” constantly, and in the other scenario, you’re giving it a push for only a brief moment.
When it is moving faster than the wind, is the wind still giving it a push?
I think this explains it conceptually best: https://www.youtube.com/watch?v=k-trDF8Yldc I'm surprised people have such trouble with this.
in this case though, it's not the ground that provides the motion but the wind. The mental equivalent of this with wind is not straightforward
The propeller is being used a forward motion compensator. At a standstill, the wind just acts on the entire vehicle including the stationary propeller, and sets the whole thing in motion. Without the propeller, going directly downwind would be limited by the speed of the wind acting directly on the vehicle which otherwise lacks any relevant moving parts for the wind to act on. By adding the propeller, driven by the f…
I wonder how one would go about making such machine that would work in zero gravity. Without friction, something else would have to convert part of the wind force to propeller torque. Maybe small turbines could be added that would spin according to apparent wind (forward or backward) and spin the propeller to generate additional lift.
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I wonder how one would go about making such machine that would work in zero gravity. Without friction, something else would have to convert part of the wind force to propeller torque. Maybe small turbines could be added that would spin according to apparent wind (forward or backward) and spin the propeller to generate additional lift.
Fun thought exercise, but are there any practical scenarios where one has wind but no gravity?
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Fun thought exercise, but are there any practical scenarios where one has wind but no gravity?
solar wind
Release the Blackbird from rest. It’s easy to visualize what happens: the wind turns the propellers, which turns the wheels, and the Blackbird rolls forward.
While the Blackbird is going slower than the wind, this is a straightforward system.
What happens when the Blackbird is going the same speed as the wind?
In that case, the wind is no longer pushing the rotor, since there’s no difference in speed. However, the rotor is still spinning! So now it acts like a propellor — pushing against the wind.
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It’s really not that complicated - wind speed is not the same as energy. The propellor is a device that pushes against the air to move forward, it takes energy from the wind, produces a force, and the force produces momentum in the vehicle. We know that a stationary turbine can continually take power from the wind. When that wind energy is stored in a battery it can power your car much faster than the wind. This just…
This does not explain the most obvious issue (or at least my most obvious issue): when going as fast as the wind, there is no wind anymore. The answer: at that point, your wheels are turning, and so you can get energy from your turning wheels, but not directly from the wind. This is how I explain it in my head: 1. When going slower than the wind, the wind pushes you forward. Propeller at this point is useless. 2. Whe…
IMO it is just positive feedback: the faster you go the more wind is being pushed back by the propeller. At some point the system reaches a state of saturation or equilibrium (the wheels turning no longer can speed up the propeller enough to generate more push). This equilibrium is going back and forth between phases 2 and 3 as you described it.
The thing that makes it a little bit hard to reason about is that all three components (wind, wheel, propeller) are interdependent and influence each other in a more or less fluid way. To me it feels similar like reasoning about active filter topologies.
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This does not explain the most obvious issue (or at least my most obvious issue): when going as fast as the wind, there is no wind anymore. The answer: at that point, your wheels are turning, and so you can get energy from your turning wheels, but not directly from the wind. This is how I explain it in my head: 1. When going slower than the wind, the wind pushes you forward. Propeller at this point is useless. 2. Whe…
> 3. When going faster than the wind, all your energy will come from the turning wheels. But why do the wheels keep turning in this scenario? Is there somehow a net-force on the back-side of the vehicle from the wind?