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| Mess with your minds: A wind powered craft going faster than a tail wind speed. |
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| Brumby:
--- Quote from: Psi on September 04, 2021, 11:54:54 am ---.... not everyone agrees that a treadmill is a valid analog. --- End quote --- Those people do not understand "frames of reference". This fundamental lack of understanding of a very simple principle within physics and perfectly applicable to Newtonian mechanics means they are handicapped in comprehending what is going on. I would go so far as to say some would be incapable of allowing the possibility and could actively engage in presenting arguments attempting to disprove (something that has already been demonstrated). When such arguments come from those who cannot understand fundamental principles, their process is bound to be flawed and their conclusions will be of no value to anyone but their delusion. (Now why does that seem familiar? Oh... yeah.) |
| Kleinstein:
Compare the film of the experiment on the treadmill with the film made from the car driving at the speed of the wind. In both films the air is essentially stationary and the ground is moving relatively fast. So the Treadmil is kind of wind tunnel to test the vehicle at a speed very close to wind speed. The only thing really missing to make this a wind tunnel is the fan to produce zero wind speed. The belt drags some air with it, but so does the wall in a wind tunnel and in real world the wind is also different at different hights. So the concept of 1 wind speed is an approximation only. The points that could have been done better in the treadmill experiments could be using a string and force meter to hold the vehicle and to show the direction of the air flow produced by the prop. It was already quite instructive that they showed the failed attempt with the prop with too much pitch / too small wheels. |
| Alex Eisenhut:
For someone just starting to read all these posts, I think this would be the right song to play in the background |
| Labrat101:
--- Quote from: Brumby on September 04, 2021, 01:03:04 pm --- --- Quote from: Labrat101 on September 04, 2021, 12:28:19 pm ---. There seems to be a fixation on treadmills etc. --- End quote --- That's because a treadmill is a convenient mechanism to demonstrate the principle. This is because of the validity of the concept of "Frames of reference". --- Quote ---I will give a just a few reasons why they are not used other than exercising the Dog . --- End quote --- This will be entertaining.... Answer You have No idea of what the difference between a treadmill that you have in your house and a wind tunnel --- Quote ---First they have a very high friction as the belt runs over the rollers the surface gets warm to hot . --- End quote --- So? How does that affect things? Answer The Added Friction will give bad results .. --- Quote ---the bottom of the belt that hangs down at the bottom has to be loose . So it flaps . --- End quote --- So? How does that affect things? Answer You are really Funny that you don't know why, Must have slept thought entire physics lesson --- Quote --- Having to moving surfaces running in parallel in opposite directions causes side air distortion and turbulence. . --- End quote --- So? As a factor that is somewhat minimal, how does that affect things? Answer : OMG somewhat minimal :palm: If this was your oscilloscope giving these error would you except it --- Quote ---Even at airports they did away with this due to belts getting hot . Now they use just rolling beds .. Belt-less. In other places the belts were replaced with slated belts that were self cooling .. --- End quote --- So? The temperature of belts is not going to affect the experiment unless they've burst into flames or gone so tacky as to be unable to allow rolling. This is a non-argument. Answer it proves that the industry has excepted they are a waste of energy and useless --- Quote ---The aerospace industry , Lockheed , NASA , and all the others . Don't use this in a wind tunnels or for replacing the use of a wind tunnel due to there significance and disturbance in testing. --- End quote --- Don't see this being significant for the scale of test we are talking about. Answer the smaller the item being tested the greater the accuracy has to be --- Quote ---The test item in a wind tunnel is usably suspended . in the car test rollers are used and the wheels are placed between 2 controlled rollers . 2 at the front and 2 at the back . and are computer controlled . The rollers are covered by a plate so no other side effects mess with the final tests . --- End quote --- OK. Fine. The rollers are a perfect analogy for travelling over the ground (Just as a treadmill belt is, BTW) - but the only thing is that they constrain the movement of the wheels. In such an experiment, the rollers would need to be programmed to increase speed to match the performance of the vehicle, while the wind speed remains constant. Do that and you'll find the Blackbird does work. Oh now you agree with me .. what's this .. I said " computer controlled " your remark "would need to be programmed " has to be spiting hairs --- Quote ---Treadmills etc work great on paper and for demonstrating science projects . And not to for get the GYM . or moving lots of odd shaped stuff from containers etc . So Please get over the treadmill . .. hamsters likes them . --- End quote --- OK - a dismissive wave of the hand and it all goes away...? That is classic denial. answer :-DD By whom --- End quote --- I am sorry and not being rude but you have not got any idea in real world industrial physics If this had been your own personal project Then you would look at it differently and in that case I would not have cared . This a wind tunnel from a car manufacture .. If they could do this on a Treadmill, That are relatively cheap . . NO.. They go too all that trouble in building a wind tunnel that costs $ Millions . :scared: They could have just got a Treadmill from BangUgood for $200 . Enjoy the video . |
| Kleinstein:
The interesting part for the prop powered vehicle is at a speed very close to the speed of wind and especially the case with the vehicle at the speed of wind. This means the case where the vehicle does not see any external wind and only the ground is moving. So in a wind tunnel with the vehicle fixed this would be zero wind speed. >:D The treadmill is perfectly fine to produce zero wind speed, especially for a more hobby / fun project and basic demonstration. This is not about a precision measurement but demonstration of the principle workings. |
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