Moderators Travis In Austin Posted July 11, 2015 Moderators Share Posted July 11, 2015 When a person runs on a stationary treadmill, does that person feel the air blowing on their face? I don't think so, but then again, I've never run on a treadmill. The youtube video, even though the guy can't demonstrate that the plane lifts off, is a poor example for several reasons. Most significantly the model he chose to represent a real plane, the scales are completely wacked. Size versus weight, but more significantly, the ratios for the prop dia. to wing span (and depth) aren't remotely close to emulating the real condition for any plane. The ratio for prop to wing span is too large, indicating the prop alone is likely capable of moving enough air across the wing, (but none of that matters since the experiment wasn't setup to show lift) to generate lift. But what he did accomplish was to demonstrate that at times he was able to match the speed of the treadmill by playing with the throttle, and that the planes throttle control of his toy plane was significantly more responsive than the speed control of his treadmill. Sorry, but the myth-busters video is even more lame, though I'm sure they easily convinced the producer to air their $how. In their video the ultra lightweight plane clearly out-accelerates the small pick-up truck, who'd a thought? They didn't attempted to discuss the acceleration discrepancies between the vehicles (no small wonder why). And they didn't address the subject of friction between their simulated magical conveyor and the concrete (which is why the material tore from the fella prancing around on top of it). Don't know how anyone could watch the myth-buster example and walk away thinking their conveyor was even remotely close to what is interpreted for the problem........ Maybe OT is right,.... it is a poorly explained problem. Either way, I remain as unconvinced and hard headed as ever..... "No Fly" EDIT: Travis, it's time for us to take a break from this BS. Don't know about you, but I'm gonna take my girlies to canyon lake. Gonna do a experiment and test the change in acceleration while their swimming and I yell "Gar!" or "Snake!". Then I'll let'em practice falling down with a wake board on their feet. Actually, they're pretty good at it, but I need a bigger boat to generate a good wake. Cheers!! A person on a treadmill doesn't move forward relative to the tread and therefore doesn't feel air movement across their face. They run in a fixed place. Their mode of propulsion is directly linked to the tread. With the hypothetical, a treadmill long enough for an airplane to achieve flight,with propulsion independant of the tread, will begin to move down the tread, accelarate, and take off. If the airplane has a normal takeoff length of 500 feet, it will require a tread 510 feet long (usable length, topside) and it will accelerate down the tread and take off just slighty over 500 feet down the tread. If it has a normal take off length 2000 feet, it wilo require a tread of 2010 feet, and it will in fact begin to fly just over 2000 feet from the starting point on the tread. The tread doesn't change anything about the length required to take off. It doesn't shorten it, and it doesn't extend it by but a foot or two. Super-high power to weight ratio, short wings, long wings, is all irrelevant. Whatever that plane's normal takeoff length off a normal runway will be nearly identical on a tread. It can be a man powered Gossamer Albertross, a stunt plane like a Pitts Special, a 747. If the tread is longer than the normal takeoff length for that particular configuration. This is why the initial inquiry is whether the plane will move forward or not. If it stays stationary like a car or a person does on a treadmill, it would never fly. But an airplane, or any vehicle, with free spinning wheels AND a means of thrust independent of the treadmill, such as a propeller or jet propulsion, will move forward down along the length of the tread. The demo in the you tube video can be done with any type if RC model you want, if it will move forward on the ground, it will m8ve forward on the treadmill. Then it only becomes a question if you can find a long enough treadmill. Quote Link to comment Share on other sites More sharing options...
Moderators Travis In Austin Posted July 11, 2015 Moderators Share Posted July 11, 2015 When a person runs on a stationary treadmill, does that person feel the air blowing on their face? I don't think so, but then again, I've never run on a treadmill. Correct. Now, however, add a jet-pack to your back and give it some thrust. Then, what happens? Here are a few examples. Quote Link to comment Share on other sites More sharing options...
Jim Naseum Posted July 11, 2015 Share Posted July 11, 2015 Forces for flying= thrust, lift, drag. Period. None of those relate to the belt/wheels. The only force produced by belt/wheel is FRICTION. That is a small force pointing to the rear of the plane. The thrust is massive force with à net vector pointing forward and easily overwhelms the small friction force. Since thrust>friction by many times, plane accelerates forward and then flies. Force diagram shows all you need. Quote Link to comment Share on other sites More sharing options...
Gilbert Posted July 12, 2015 Share Posted July 12, 2015 (edited) I think Coytee deserves a vasectomy for bumping this thread. A person on a treadmill doesn't move forward relative to the tread and therefore doesn't feel air movement across their face. They run in a fixed place. Their mode of propulsion is directly linked to the tread. I completely understand your argument, long before you ever considered writing this reply. It's wrong. Again, Turbine, Prop, Squirrel, Hamster, it doesn't matter. Watch your own youtube video, what happens with the plans speed matches perfectly the speed of the treadmill...... No Forward Movement. Might I suggest a stiff drink and grilled steaks and lamb chops? That's what I'm gonna be grilling right after this. Jeff Matthews, on 11 Jul 2015 - 2:46 PM, said: Gilbert, on 11 Jul 2015 - 2:21 PM, said: When a person runs on a stationary treadmill, does that person feel the air blowing on their face? I don't think so, but then again, I've never run on a treadmill. Correct. Now, however, add a jet-pack to your back and give it some thrust. Then, what happens? Jeff, As a kid, did you ever try running up a downward moving escalator. I have, and I made it to the top without a jet pack. What's your point? In both to the two lameass examples (youtube and nutbusters), they each demonstrated that neither of them considered the concept of relative (differential) acceleration. I expected as much from the numbnuts in the youtube video, but expected an approach that could have at least been considered scientific (oh my god, I sound like MD, I'm fk'ed). Instead, the nutbuster duo gave us small pickup truck dragging an extraordinarily long burlap sack across the pavement..... Did anyone in here consider the mythbusters' conveyor ideal or even remotely similar to the magical speed matching conveyor in the problem?.... didn't think so, I didn't either. Forces for flying= thrust, lift, drag. Period. None of those relate to the belt/wheels. The only force produced by belt/wheel is FRICTION. That is a small force pointing to the rear of the plane. The thrust is massive force with à net vector pointing forward and easily overwhelms the small friction force. Those are the main force components that everybody will agree on. The only component of "drag" I'm concerned with is that resulting from the weight of the plane and the coef. of friction acting on each wheel (bearing and contact patch). Those force components keep the plane on the ground when stationary, the magical conveyor prevents the craft from obtaining a forward "ground speed", relative to fixed earth (yes I know the world rotates, but lets keep it simple). Even a person that has never done the analysis, can watch the bozo in the youtube video. Bozo clearly demonstrates that his model plane will ALWAYS moves backwards when he fails to maintain adequate thrust. It happens so many times, that it should have screamed out at me (and all of you) during the first viewing. The ONLY time his plane moves forward is when he out accelerates (applies too much thrust) the speed of the treadmill (and forces due to drag). That he failed to mention or even consider the relative accelerations, means he should be neutered and prevented from entering his candidacy for the Nobel Prize for Science. Edited July 12, 2015 by Gilbert Quote Link to comment Share on other sites More sharing options...
Coytee Posted July 12, 2015 Author Share Posted July 12, 2015 I think Coytee deserves a vasectomy for bumping this thread You have to admit, it is an entertaining thread. 1 Quote Link to comment Share on other sites More sharing options...
Gilbert Posted July 12, 2015 Share Posted July 12, 2015 I think Coytee deserves a vasectomy for bumping this thread You have to admit, it is an entertaining thread. I'm gonna cut your nutsack. Quote Link to comment Share on other sites More sharing options...
BigStewMan Posted July 12, 2015 Share Posted July 12, 2015 send it to myth busters. Quote Link to comment Share on other sites More sharing options...
Moderators Travis In Austin Posted July 13, 2015 Moderators Share Posted July 13, 2015 (edited) It is an imaginary conveyor belt. The coefficient if friction of the bearings is all that matters, the contact point/patch of the tires are irrelevant because the coefficient of the bearings/wheels is significantly less than the tires, just as it is with every automobile. The contact point of the tires would only be relevant if it were an exercise in braking, which it isn't. The thrust generated by the propeller acts on the plane every bit the same as attaching a cable to the front of a vehicle in neutral and pulling it with a winch. Both are pulling the vehicle in a horizontal direction from a source independent of the treadmill. The fact that one is generating pull from a fixed point, and the other is oulling through a fluid does not matter, they pull forward, accelerate, and do so regardless if the speed of the treadmill. Edited July 13, 2015 by dwilawyer Quote Link to comment Share on other sites More sharing options...
Jim Naseum Posted July 13, 2015 Share Posted July 13, 2015 I think Coytee deserves a vasectomy for bumping this thread. A person on a treadmill doesn't move forward relative to the tread and therefore doesn't feel air movement across their face. They run in a fixed place. Their mode of propulsion is directly linked to the tread. I completely understand your argument, long before you ever considered writing this reply. It's wrong. Again, Turbine, Prop, Squirrel, Hamster, it doesn't matter. Watch your own youtube video, what happens with the plans speed matches perfectly the speed of the treadmill...... No Forward Movement. Might I suggest a stiff drink and grilled steaks and lamb chops? That's what I'm gonna be grilling right after this. Jeff Matthews, on 11 Jul 2015 - 2:46 PM, said: Gilbert, on 11 Jul 2015 - 2:21 PM, said: When a person runs on a stationary treadmill, does that person feel the air blowing on their face? I don't think so, but then again, I've never run on a treadmill. Correct. Now, however, add a jet-pack to your back and give it some thrust. Then, what happens? Jeff, As a kid, did you ever try running up a downward moving escalator. I have, and I made it to the top without a jet pack. What's your point? In both to the two lameass examples (youtube and nutbusters), they each demonstrated that neither of them considered the concept of relative (differential) acceleration. I expected as much from the numbnuts in the youtube video, but expected an approach that could have at least been considered scientific (oh my god, I sound like MD, I'm fk'ed). Instead, the nutbuster duo gave us small pickup truck dragging an extraordinarily long burlap sack across the pavement..... Did anyone in here consider the mythbusters' conveyor ideal or even remotely similar to the magical speed matching conveyor in the problem?.... didn't think so, I didn't either. Forces for flying= thrust, lift, drag. Period. None of those relate to the belt/wheels. The only force produced by belt/wheel is FRICTION. That is a small force pointing to the rear of the plane. The thrust is massive force with à net vector pointing forward and easily overwhelms the small friction force. Those are the main force components that everybody will agree on. The only component of "drag" I'm concerned with is that resulting from the weight of the plane and the coef. of friction acting on each wheel (bearing and contact patch). Those force components keep the plane on the ground when stationary, the magical conveyor prevents the craft from obtaining a forward "ground speed", relative to fixed earth (yes I know the world rotates, but lets keep it simple). Even a person that has never done the analysis, can watch the bozo in the youtube video. Bozo clearly demonstrates that his model plane will ALWAYS moves backwards when he fails to maintain adequate thrust. It happens so many times, that it should have screamed out at me (and all of you) during the first viewing. The ONLY time his plane moves forward is when he out accelerates (applies too much thrust) the speed of the treadmill (and forces due to drag). That he failed to mention or even consider the relative accelerations, means he should be neutered and prevented from entering his candidacy for the Nobel Prize for Science. Ground speed does not matter,... Only airspeed. The planes flight is relative always to air, not to ground. Thrust force is opposition to air not ground. Other than small friction force, ground and belt are irrelevant to the airspeed. Air mass is independent of ground mass. Plane is operating against airmass. Plane is not motivated by its wheels. They only support the weight until lift overcomes weight. Fisics is fun lol!!! Quote Link to comment Share on other sites More sharing options...
cradeldorf Posted July 13, 2015 Share Posted July 13, 2015 Other than the wheels would be spinning twice as fast as a normal takeoff yep it'll fly. 1 Quote Link to comment Share on other sites More sharing options...
sputnik Posted November 7, 2017 Share Posted November 7, 2017 Just wondering if Gilbert has come to his senses by now. 1 Quote Link to comment Share on other sites More sharing options...
oldtimer Posted November 7, 2017 Share Posted November 7, 2017 There's a guy on here who would call that trolling. Luckily the rest of us have a sense of humor. Quote Link to comment Share on other sites More sharing options...
sputnik Posted November 7, 2017 Share Posted November 7, 2017 Trolling? Me? Quote Link to comment Share on other sites More sharing options...
oldtimer Posted November 7, 2017 Share Posted November 7, 2017 Never. Quote Link to comment Share on other sites More sharing options...
CECAA850 Posted November 7, 2017 Share Posted November 7, 2017 Gilbert trolls with his fly down. 1 Quote Link to comment Share on other sites More sharing options...
BigStewMan Posted November 7, 2017 Share Posted November 7, 2017 This thread has been around quite some time. I’m going to say that if the plane hasn’t taken off by now -- it won’t. Quote Link to comment Share on other sites More sharing options...
oldtimer Posted November 7, 2017 Share Posted November 7, 2017 It took off a long time ago. Quote Link to comment Share on other sites More sharing options...
CECAA850 Posted November 7, 2017 Share Posted November 7, 2017 5 minutes ago, oldtimer said: It took off a long time ago. Unfortunately it was Air Malaysia. Quote Link to comment Share on other sites More sharing options...
oldtimer Posted November 7, 2017 Share Posted November 7, 2017 Shot down by the Russians? Quote Link to comment Share on other sites More sharing options...
BigStewMan Posted November 7, 2017 Share Posted November 7, 2017 or it was Delta and landed at the wrong forum. Quote Link to comment Share on other sites More sharing options...
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