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| Mess with your minds: A wind powered craft going faster than a tail wind speed. |
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| fourfathom:
--- Quote from: electrodacus on December 18, 2021, 02:33:56 am ---What do you mean by stationary vehicle ? Vehicle before it touches the treadmill ? if yes then of course there is no stored energy. --- End quote --- No. By "stationary" I mean the vehicle is being held stationary on the treadmill. The wheels are in contact with the treadmill, turning, and the propeller is spinning. The vehicle speed and the windspeed are equal. This is exactly equivalent to a vehicle traveling directly downwind at the speed of the wind. And no matter how long you hold the vehicle stationary, when released the vehicle will accelerate. You claim there is no available energy when the vehicle is stationary, since "windspeed - vehicle speed = 0". Even if we ignore your equation, and at windspeed there is stored energy in a pressure differential (which I dispute -- I claim there is no stored energy adequate for even a brief burst of acceleration), how long do you think this stored energy will persist before dispersing into the surrounding environment? There is measurable stored kinetic energy in the spinning propeller, and rotating wheels, and the mass of the vehicle itself, but unless you have some sort of gearshift or prop-feathering (which the treadmill vehicle does not) none of these will cause the vehicle to accelerate, they will only slow the rate of friction-caused deceleration. And yet, the vehicle accelerates. |
| electrodacus:
--- Quote from: fourfathom on December 18, 2021, 03:20:09 am --- --- Quote from: electrodacus on December 18, 2021, 02:33:56 am ---What do you mean by stationary vehicle ? Vehicle before it touches the treadmill ? if yes then of course there is no stored energy. --- End quote --- No. By "stationary" I mean the vehicle is being held stationary on the treadmill. The wheels are in contact with the treadmill, turning, and the propeller is spinning. The vehicle speed and the windspeed are equal. This is exactly equivalent to a vehicle traveling directly downwind at the speed of the wind. And no matter how long you hold the vehicle stationary, when released the vehicle will accelerate. You claim there is no available energy when the vehicle is stationary, since "windspeed - vehicle speed = 0". Even if we ignore your equation, and at windspeed there is stored energy in a pressure differential (which I dispute -- I claim there is no stored energy adequate for even a brief burst of acceleration), how long do you think this stored energy will persist before dispersing into the surrounding environment? There is measurable stored kinetic energy in the spinning propeller, and rotating wheels, and the mass of the vehicle itself, but unless you have some sort of gearshift or prop-feathering (which the treadmill vehicle does not) none of these will cause the vehicle to accelerate, they will only slow the rate of friction-caused deceleration. And yet, the vehicle accelerates. --- End quote --- You are confusing power with energy. What I say is that a vehicle power only by wind and that is at same speed as the wind directly downwind has no wind power available. What that vehicle has is stored energy in pressure differential created by the propeller and that energy can allow the vehicle to exceed wind speed but only for a limited amount of time depending on amount of stored energy and vehicle friction losses. The treadmill model is not quite the same thing until you release the vehicle as by changing the frame of reference the vehicle has no kinetic energy at that starting point so all friction losses on the vehicle will be provided by the treadmill and what you have there is just an inefficient fan powered by treadmill motor. As soon as you release the vehicle from your hand the vehicle will simulate fairly well what happens with direct down wind blackbird from the wind speed forward. At release there will be energy stored in pressure differential (propeller will have a constant speed until release and thus stored energy will stay the same no matter how long you keep the vehicle there). When vehicle is released the pressure differential will start to drop as it will supply both vehicle losses as well as the energy needed to increase speed basically increasing kinetic energy of the vehicle. The treadmill no longer helps the vehicle in any way once released from the hand and as soon as all the pressure differential is used up the vehicle will start to slow down but because the treadmill is so short you will not be able to see that. What you can see if you take a video from the side is the decrease acceleration rate and that will not correspond to Derke's or anyone else's prediction. Wind speed will need to be higher than vehicle speed in order to be able to power the vehicle and since that is not the case vehicle can only accelerate if it has an energy storage device. A sail vehicle while more efficient in converting wind power to kinetic energy has no energy storage device thus can never exceed wind speed but Blackbird due to the use of a propeller fan has the pressure differential energy storage and that is what it allows it to exceed for a limited amount of time (few minutes depending on design and wind speed) the wind speed. The crazy explanation that vehicle when above wind speed directly down wind will take power from the wheel to supply the propeller is exactly like saying a motor and generator connected together with a belt are a free energy generator. That is because when you take energy from the wheel that is directly taken out of the vehicle kinetic energy Ws or Joules and since propeller is maybe at best 70% efficient can only put back 70% of that back in to kinetic energy and so vehicle will have lower speed. Luckily there is that pressure differential to cover all losses and accelerate the vehicle until it will be used up. |
| fourfathom:
Pressure differential energy storage? No. But I am slowly backing away from this apparently futile discussion for a while. |
| Kleinstein:
--- Quote from: electrodacus on December 17, 2021, 09:59:01 pm ---Also my point is that no vehicle can exceed wind speed directly downwind unless it has an energy storage device. --- End quote --- And that is wrong and there is no sense in repeating this all over !. :horse: :horse: :horse: :horse: --- Quote from: electrodacus on December 18, 2021, 12:59:20 am ---I'm very confident that online calculator that I liked is accurate in describing pressure on either a wall or a sail directly downwind. --- End quote --- Very confident is has to be seen with a grain of salt: The calculator is for a different problem: the force a wall has to withstand, when close to an edge (kind of clif if you want). The Zones are not the place where the pressure in the air is measured, but the distance of the wall from the edge. Close to the edge there is some concentration of the wind - so the real value to compare is the one far away from the edge. The calculated force is not that impressive to support the claimed high power from a sail. So I am glad you are confident in a calculator that contradicts your claims. Better have more confidence in the calculator for the bicycle power that showed that it is possible to drive with relatively low power against an head wind. |
| Labrat101:
@electrodacus A Bumblebee can't fly .!! Same as electrodacus can't believe a simple Solution. That if everyone says the 🌎 is round . He would argue its flat because my spirit level says so .. :palm: So if everyone here has proven it does work . Plus there has been a video showing it works . There for Bumblebee can fly also faster the tail wind . Your ideas of what is true and false , was is, and what can . Maybe beyond your comprehension . It wouldn't matter if Albert Einstein could tell you that your wrong . You are living in some sort of self denial. Get over it and except that it can and does work. |
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