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| Mess with your minds: A wind powered craft going faster than a tail wind speed. |
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| electrodacus:
--- Quote from: fourfathom on December 24, 2021, 04:33:24 am ---There are none so blind as those who will not see. --- End quote --- I showed you where to look and you do not want to look. Check any video or speed graph on Blackbird and see how acceleration rate drops consistent with reduced available power both when below and when above wind speed consistent with a finite stored energy source. If you calculate for a few points using Derek's equation the one containing vehicle speed - wind speed you get an ever increase in acceleration rate not observed in any real test. |
| PlainName:
I think the big problem for electrodacus is that at wind speed (and faster) there seems to be no relative wind to power anything. The only way to go faster than what's pushing is via some stored energy, ergo there must be some stored energy somewhere. Where? The only possible place, given that the prop is quite important, is the prop wash. Which seems reasonable if you haven't seen this thing work, and all the explanations so far seem to run up against the problem that at wind speed there is no push (or even pull), so there is no obvious way this could be working. So... how about an alternative explanation without the maths that no-one can agree on... ISTM the most important thing to bear in mind is the prop is rotating and pushing air back. For a given rotational speed, the air will flow backwards at some derived speed - the faster the prop goes the faster the air flows back. You could use this to push the vehicle at a given speed by altering the speed of the prop, so we could say that the prop turning at xrpm is equivalent to airflow of ym/s. It works in reverse, of course - push the vehicle and the airflow will cause the prop to turn proportionally to the vehicle speed through the air. So, back to wind speed and no push. But there is a push - the prop wash is effectively a wall (albeit quite flimsy!) moving at a negative speed relative to the vehicle and tied to the vehicle. If the vehicle is moving at wind speed, the prop wash is moving backwards at some speed relative to the vehicle and thus the wind. The wind can push against the prop wash to continue pushing the vehicle a little faster. In effect, the prop wash is an infinite length of the string we see with that yo-yo. By what powers the prop? It is still the wind because it is able to be pushing the vehicle still. With the prop wash moving backwards and effectively part of the vehicle, the vehicle is not at maximum speed relative to the wind, so the wind can keep pushing it. |
| Kleinstein:
There where several expalinations given how the Backbrid vehicle can work. It is just that electrodacus repeatedly ignored them or claimed they must be wrong because they contradict his preconception. The contradiction to his claim however is not a valid agument against the calculation. It more shows that his preconception is wrong, as there is no error in the calculation. There should be no problem with math, as the only math part is simple multiply and additions. The problem is getting electrodacus to accept (or understand) the basics of mechanic, like the formula for mechanic power and the balance of forces. The whole energy storrage and aero dynamics part is more like confusiion tactics only - they are not part of the proof. There were attemps to show up the flaws in his formula / conception of wind power - but somehow the perception of walking against the wind seems to be different. At least to most reader is should be clear the the (w-v) ³ formula is nonsense. |
| Brumby:
--- Quote from: electrodacus on December 24, 2021, 12:15:56 am --- --- Quote from: Brumby on December 23, 2021, 11:33:30 pm ---I draw attention to my earlier question: --- Quote ---Are you saying that energy is stored across the entire swept area of the propeller? --- End quote --- --- End quote --- Yes the entire swept area of the propeller acts as a barrier keeping the low and high pressure volumes separate. --- End quote --- How does that work? (I think this needs a diagram.) |
| BrianHG:
--- Quote from: Brumby on December 24, 2021, 11:22:34 am --- --- Quote from: electrodacus on December 24, 2021, 12:15:56 am --- --- Quote from: Brumby on December 23, 2021, 11:33:30 pm ---I draw attention to my earlier question: --- Quote ---Are you saying that energy is stored across the entire swept area of the propeller? --- End quote --- --- End quote --- Yes the entire swept area of the propeller acts as a barrier keeping the low and high pressure volumes separate. --- End quote --- How does that work? (I think this needs a diagram.) --- End quote --- What if the propeller is spinning slower than the moving air it is cutting into? What if it is stationary? |
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