champu 1 #51 January 3, 2006 Quote2 = 80% of 9934593874? I think that's what GW would refer to as "fuzzy math" what. in the fuck. are you talking about? Quote Share this post Link to post Share on other sites
Lindercles 0 #52 January 3, 2006 Quote what. in the fuck. are you talking about? Um, ok. I said QuoteDidn't I say this about 9934593874 posts ago?? and then you said QuoteYes, but that's only true if you omit 80% of my post as you have. I interpreted that to mean "you only said that 9934593874 posts ago IF you omit 80% of my posts." The implication being that if I don't omit 80% of your posts that number would be much larger. And since you had only made 2 previous posts to the thread, it seemed pretty funny. edit: if i misinterpreted you, you have my sincere apologies. Quote Share this post Link to post Share on other sites sundevil777 94 #53 January 3, 2006 QuoteQuoteYeah, it seems pretty simple. Wheel speed doesn't have anything to do with the plane taking off. Sure it does, and here's the problem: 1 - can't generate lift without forward airspeed 2 - can't generate forward airspeed without forward groundspeed (because there's no wind) 3 - can't generate forward groundspeed without the wheels rolling (because you're resting the entire weight of the plane on the ground) 4 - if wheels roll, belt fights back 5 - can't beat the belt unless you beat friction 6 - can't beat friction unless you generate lift 7 - see 1 As they say, "You can't get there from here." Physical experiments aren't going to demonstrate this properly because a belt that can instantaniously match the speed of a wheel rolling along it is a non-causal system, and is not physically realizable. Any lag whatsoever in the feedback loop between the sensor that's measuring wheel speed and the motor control that's driving the conveyor will allow the plane to take off. But that's not what the original question is asking. The conveyor matches the speed of the plane, relative to the ground. The conveyor moving doesn't mean the plane stands still relative to the ground, just the wheels would spin faster than normal, with a little extra friction for the plane to overcome.People are sick and tired of being told that ordinary and decent people are fed up in this country with being sick and tired. I’m certainly not, and I’m sick and tired of being told that I am Quote Share this post Link to post Share on other sites FreeflyChile 0 #54 January 3, 2006 i think people are looking at this as a problem of the plane being a car with wings, where the traction and propulsion come from the contact with the ground, where in fact the forward force is generated by the contact of the props with the air. if you could create this conveyor belt that could instantly match the speed of the wheels in either direction, the plane would take off because the belt would act as a frictionless surface. essentially, for the wheels to spin you need a difference in speed between the wheel and the conveyor, which, as stated, doesnt happen -- if the conveyor instantly matches the speed of the wheel, there is no time for teh wheel to move, and the speed of the wheel would always have to = 0. therefore the plane would simply slide down the runway till it took off. even if the conveyor only moved in one direction it would still take off. for the wheel to move, there has to be an initial movement of the plane relative to the belt (because the belt MATCHES the wheel speed, and the force is provided by the plane, not the belt) and if there is forward movement of the plane, the plane can eventually take off. edited to add: sundevil said this several posts ago. it's late and i was too lazy to read all the replies. Quote Share this post Link to post Share on other sites RhondaLea 3 #55 January 3, 2006 QuoteThread killer. Okay, I take it back. This is one of the few times I've seen people keep going even after you provide the definitive answer. This thread, however, seems to have as much potential for debate as a discussion of airspeed and groundspeed. I guess conveyor belts are as interesting as tractors. rlIf you don't know where you're going, you should know where you came from. Gullah Proverb Quote Share this post Link to post Share on other sites BoostedXT 0 #56 January 3, 2006 How can you 100% conclusively say that tyhe answer is X, when Y hasnt been ruled out yet? JoeFor long as you live and high you fly and smiles you'll give and tears you'll cry and all that you touch and all that you see is all your life will ever be. Pedro Offers you his Protection. Quote Share this post Link to post Share on other sites pilotdave 0 #57 January 3, 2006 Our resident physics professors'll debate for hours about useless things like exit separation, but where are they now when we're talking about something that affects us all in our everyday lives?? Dave Quote Share this post Link to post Share on other sites Broke 0 #58 January 3, 2006 OK this is a little annoying here... The wheels of a plane to the best of my knowlege are not powered as they are in an automobile. That being said if the plane starts to generate ground speed it will be due to the prop or turbine causing thrust. This thrust till never generate any lift because the net ground speed is still 0, with a net speed of 0 there is no air flow over the wings it is the air flow that causes a preasure gradient which creates lift. http://www.furball.warbirdsiii.com/krod/basic-physics.html I hope that link helps I say no it will not fly.Divot your source for all things Hillbilly. Anvil Brother 84 SCR 14192 Quote Share this post Link to post Share on other sites godfrog 2 #59 January 3, 2006 you have 4 basic factors in flight. thrust vs. drag and lift vs. weight. aerodynamics 101. to get off the ground you need to generate more lift than you have weight and to accelerate you need more thrust than drag.Experience is a difficult teacher, she gives you the test first and the lesson afterward Quote Share this post Link to post Share on other sites nanook 1 #60 January 3, 2006 yes. Providing the conveyer belt is the width of the wingspan. ground effect would be the factor that would cause liftoff. as the conveyer moves forward, it pulls along the air with it due to friction. the faster the belt, the higher the air pressure. sooner or later the pressure will be enough to lift the plane. Won't be alble to leave the conveyer area though. In this case you would start the conveyer first. As the plane goes backward, you give a little thrust from the engines to keep the plane in place. So the plane stays in place, the wheels match the speed of the conveyer belt. the plane flies but doesn't leave._____________________________ "The trouble with quotes on the internet is that you can never know if they are genuine" - Abraham Lincoln Quote Share this post Link to post Share on other sites wildblue 4 #61 January 3, 2006 Then it's an impossible system to build. The plane, wheels, and belt would never get past the resting state - for that to happen, something would have to not be instantaneous. If the wheels were even able to start turning, then takeoff would be possible.it's like incest - you're substituting convenience for quality Quote Share this post Link to post Share on other sites RhondaLea 3 #62 January 3, 2006 QuoteHow can you 100% conclusively say that tyhe answer is X, when Y hasnt been ruled out yet? Joe I don't take anyone's word for anything...unless "anyone" happens to be bill. If he says it, it must be true. rlIf you don't know where you're going, you should know where you came from. Gullah Proverb Quote Share this post Link to post Share on other sites JohnnyD 0 #63 January 3, 2006 MIT answer: >Yes, the plane will still likely take off. It's doable U of I answer: >the plane's not going anywhere, at least not until the wheels explode and the plane flies off the back of the belt. Just to keep score. Quote Share this post Link to post Share on other sites azureriders 0 #64 January 3, 2006 Quotei think people are looking at this as a problem of the plane being a car with wings, where the traction and propulsion come from the contact with the ground, where in fact the forward force is generated by the contact of the props with the air. if you could create this conveyor belt that could instantly match the speed of the wheels in either direction, the plane would take off because the belt would act as a frictionless surface. essentially, for the wheels to spin you need a difference in speed between the wheel and the conveyor, which, as stated, doesnt happen -- if the conveyor instantly matches the speed of the wheel, there is no time for teh wheel to move, and the speed of the wheel would always have to = 0. therefore the plane would simply slide down the runway till it took off. even if the conveyor only moved in one direction it would still take off. for the wheel to move, there has to be an initial movement of the plane relative to the belt (because the belt MATCHES the wheel speed, and the force is provided by the plane, not the belt) and if there is forward movement of the plane, the plane can eventually take off. edited to add: sundevil said this several posts ago. it's late and i was too lazy to read all the replies. QuoteThe belt runs from Nose to Tail. Quote Share this post Link to post Share on other sites billvon 2,435 #65 January 3, 2006 >I guess conveyor belts are as interesting as tractors. Where's my tractor, dammit? I want my tractor! Quote Share this post Link to post Share on other sites pilotdave 0 #66 January 3, 2006 Ok, hypothetically speaking (or you can go try this if you want), if we put the conveyor belt on the DZ, and towed the entire DZ with a tractor at 100 knots, and the plane did take off, how much time do we leave between groups? Dave Quote Share this post Link to post Share on other sites JohnnyD 0 #67 January 3, 2006 QuoteOk, hypothetically speaking (or you can go try this if you want), if we put the conveyor belt on the DZ, and towed the entire DZ with a tractor at 100 knots, and the plane did take off, how much time do we leave between groups? Dave You just wait till the tractor is at 45 degrees - DUH! Quote Share this post Link to post Share on other sites champu 1 #68 January 3, 2006 QuoteThen it's an impossible system to build. The plane, wheels, and belt would never get past the resting state - for that to happen, something would have to not be instantaneous. If the wheels were even able to start turning, then takeoff would be possible. This is exactly my point. If the speed of the wheels even got the slightest bit of a leg up on the speed of the conveyor you could take off. But that's not what the problem said, the problem said the conveyor would match the speed of the wheels exactly at any given moment. The video that got posted of the skateboard is nonsense, he lets the thing go and then starts pulling on the paper after it's already moving. That completely circumvents the problem. I have one final thing to say, if you take anything away from any of my posts here, take away this: This isn't even a problem of propulsion/aerodynamics. It's a problem in that the control system to keep the conveyor running at the exact same speed as the wheels is NOT STABLE. The INSTANT the wheels even attempt to move along the ground, the conveyor will accelerate out of control blowing up the landing gear before the plane goes anywhere. Quote Share this post Link to post Share on other sites RhondaLea 3 #69 January 3, 2006 QuoteOk, hypothetically speaking (or you can go try this if you want), if we put the conveyor belt on the DZ, and towed the entire DZ with a tractor at 100 knots, and the plane did take off, how much time do we leave between groups? Y'know...this post actually brought tears to my eyes. rlIf you don't know where you're going, you should know where you came from. Gullah Proverb Quote Share this post Link to post Share on other sites pilotdave 0 #70 January 3, 2006 ...and most people probably just think I'm nuts. Dave Quote Share this post Link to post Share on other sites wildblue 4 #71 January 3, 2006 So the wheels are both at rest and moving at infinite RPMs at the same time.it's like incest - you're substituting convenience for quality Quote Share this post Link to post Share on other sites Broke 0 #72 January 3, 2006 QuoteOk, hypothetically speaking (or you can go try this if you want), if we put the conveyor belt on the DZ, and towed the entire DZ with a tractor at 100 knots, and the plane did take off, how much time do we leave between groups? Dave Now if the tractor pulled this conveyor belt runway with the plane on it at 100kts it will be able to take off, because the tractor would produce enough airflow over to wings to generate lift.Divot your source for all things Hillbilly. Anvil Brother 84 SCR 14192 Quote Share this post Link to post Share on other sites FreeflyChile 0 #73 January 3, 2006 hey...i went to U of I and i said it takes off! Quote Share this post Link to post Share on other sites kallend 1,651 #74 January 3, 2006 QuoteOur resident physics professors'll debate for hours about useless things like exit separation, but where are they now when we're talking about something that affects us all in our everyday lives?? Dave having a good laugh.... The only sure way to survive a canopy collision is not to have one. Quote Share this post Link to post Share on other sites kallend 1,651 #75 January 3, 2006 I believe the plane to be a Harrier and it would indeed take off, vertically.... The only sure way to survive a canopy collision is not to have one. Quote Share this post Link to post Share on other sites Prev 1 2 3 4 5 Next Page 3 of 5 Join the conversation You can post now and register later. If you have an account, sign in now to post with your account. Note: Your post will require moderator approval before it will be visible. Reply to this topic... × Pasted as rich text. 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sundevil777 94 #53 January 3, 2006 QuoteQuoteYeah, it seems pretty simple. Wheel speed doesn't have anything to do with the plane taking off. Sure it does, and here's the problem: 1 - can't generate lift without forward airspeed 2 - can't generate forward airspeed without forward groundspeed (because there's no wind) 3 - can't generate forward groundspeed without the wheels rolling (because you're resting the entire weight of the plane on the ground) 4 - if wheels roll, belt fights back 5 - can't beat the belt unless you beat friction 6 - can't beat friction unless you generate lift 7 - see 1 As they say, "You can't get there from here." Physical experiments aren't going to demonstrate this properly because a belt that can instantaniously match the speed of a wheel rolling along it is a non-causal system, and is not physically realizable. Any lag whatsoever in the feedback loop between the sensor that's measuring wheel speed and the motor control that's driving the conveyor will allow the plane to take off. But that's not what the original question is asking. The conveyor matches the speed of the plane, relative to the ground. The conveyor moving doesn't mean the plane stands still relative to the ground, just the wheels would spin faster than normal, with a little extra friction for the plane to overcome.People are sick and tired of being told that ordinary and decent people are fed up in this country with being sick and tired. I’m certainly not, and I’m sick and tired of being told that I am Quote Share this post Link to post Share on other sites
FreeflyChile 0 #54 January 3, 2006 i think people are looking at this as a problem of the plane being a car with wings, where the traction and propulsion come from the contact with the ground, where in fact the forward force is generated by the contact of the props with the air. if you could create this conveyor belt that could instantly match the speed of the wheels in either direction, the plane would take off because the belt would act as a frictionless surface. essentially, for the wheels to spin you need a difference in speed between the wheel and the conveyor, which, as stated, doesnt happen -- if the conveyor instantly matches the speed of the wheel, there is no time for teh wheel to move, and the speed of the wheel would always have to = 0. therefore the plane would simply slide down the runway till it took off. even if the conveyor only moved in one direction it would still take off. for the wheel to move, there has to be an initial movement of the plane relative to the belt (because the belt MATCHES the wheel speed, and the force is provided by the plane, not the belt) and if there is forward movement of the plane, the plane can eventually take off. edited to add: sundevil said this several posts ago. it's late and i was too lazy to read all the replies. Quote Share this post Link to post Share on other sites
RhondaLea 3 #55 January 3, 2006 QuoteThread killer. Okay, I take it back. This is one of the few times I've seen people keep going even after you provide the definitive answer. This thread, however, seems to have as much potential for debate as a discussion of airspeed and groundspeed. I guess conveyor belts are as interesting as tractors. rlIf you don't know where you're going, you should know where you came from. Gullah Proverb Quote Share this post Link to post Share on other sites
BoostedXT 0 #56 January 3, 2006 How can you 100% conclusively say that tyhe answer is X, when Y hasnt been ruled out yet? JoeFor long as you live and high you fly and smiles you'll give and tears you'll cry and all that you touch and all that you see is all your life will ever be. Pedro Offers you his Protection. Quote Share this post Link to post Share on other sites
pilotdave 0 #57 January 3, 2006 Our resident physics professors'll debate for hours about useless things like exit separation, but where are they now when we're talking about something that affects us all in our everyday lives?? Dave Quote Share this post Link to post Share on other sites
Broke 0 #58 January 3, 2006 OK this is a little annoying here... The wheels of a plane to the best of my knowlege are not powered as they are in an automobile. That being said if the plane starts to generate ground speed it will be due to the prop or turbine causing thrust. This thrust till never generate any lift because the net ground speed is still 0, with a net speed of 0 there is no air flow over the wings it is the air flow that causes a preasure gradient which creates lift. http://www.furball.warbirdsiii.com/krod/basic-physics.html I hope that link helps I say no it will not fly.Divot your source for all things Hillbilly. Anvil Brother 84 SCR 14192 Quote Share this post Link to post Share on other sites
godfrog 2 #59 January 3, 2006 you have 4 basic factors in flight. thrust vs. drag and lift vs. weight. aerodynamics 101. to get off the ground you need to generate more lift than you have weight and to accelerate you need more thrust than drag.Experience is a difficult teacher, she gives you the test first and the lesson afterward Quote Share this post Link to post Share on other sites
nanook 1 #60 January 3, 2006 yes. Providing the conveyer belt is the width of the wingspan. ground effect would be the factor that would cause liftoff. as the conveyer moves forward, it pulls along the air with it due to friction. the faster the belt, the higher the air pressure. sooner or later the pressure will be enough to lift the plane. Won't be alble to leave the conveyer area though. In this case you would start the conveyer first. As the plane goes backward, you give a little thrust from the engines to keep the plane in place. So the plane stays in place, the wheels match the speed of the conveyer belt. the plane flies but doesn't leave._____________________________ "The trouble with quotes on the internet is that you can never know if they are genuine" - Abraham Lincoln Quote Share this post Link to post Share on other sites
wildblue 4 #61 January 3, 2006 Then it's an impossible system to build. The plane, wheels, and belt would never get past the resting state - for that to happen, something would have to not be instantaneous. If the wheels were even able to start turning, then takeoff would be possible.it's like incest - you're substituting convenience for quality Quote Share this post Link to post Share on other sites
RhondaLea 3 #62 January 3, 2006 QuoteHow can you 100% conclusively say that tyhe answer is X, when Y hasnt been ruled out yet? Joe I don't take anyone's word for anything...unless "anyone" happens to be bill. If he says it, it must be true. rlIf you don't know where you're going, you should know where you came from. Gullah Proverb Quote Share this post Link to post Share on other sites
JohnnyD 0 #63 January 3, 2006 MIT answer: >Yes, the plane will still likely take off. It's doable U of I answer: >the plane's not going anywhere, at least not until the wheels explode and the plane flies off the back of the belt. Just to keep score. Quote Share this post Link to post Share on other sites
azureriders 0 #64 January 3, 2006 Quotei think people are looking at this as a problem of the plane being a car with wings, where the traction and propulsion come from the contact with the ground, where in fact the forward force is generated by the contact of the props with the air. if you could create this conveyor belt that could instantly match the speed of the wheels in either direction, the plane would take off because the belt would act as a frictionless surface. essentially, for the wheels to spin you need a difference in speed between the wheel and the conveyor, which, as stated, doesnt happen -- if the conveyor instantly matches the speed of the wheel, there is no time for teh wheel to move, and the speed of the wheel would always have to = 0. therefore the plane would simply slide down the runway till it took off. even if the conveyor only moved in one direction it would still take off. for the wheel to move, there has to be an initial movement of the plane relative to the belt (because the belt MATCHES the wheel speed, and the force is provided by the plane, not the belt) and if there is forward movement of the plane, the plane can eventually take off. edited to add: sundevil said this several posts ago. it's late and i was too lazy to read all the replies. QuoteThe belt runs from Nose to Tail. Quote Share this post Link to post Share on other sites
billvon 2,435 #65 January 3, 2006 >I guess conveyor belts are as interesting as tractors. Where's my tractor, dammit? I want my tractor! Quote Share this post Link to post Share on other sites
pilotdave 0 #66 January 3, 2006 Ok, hypothetically speaking (or you can go try this if you want), if we put the conveyor belt on the DZ, and towed the entire DZ with a tractor at 100 knots, and the plane did take off, how much time do we leave between groups? Dave Quote Share this post Link to post Share on other sites
JohnnyD 0 #67 January 3, 2006 QuoteOk, hypothetically speaking (or you can go try this if you want), if we put the conveyor belt on the DZ, and towed the entire DZ with a tractor at 100 knots, and the plane did take off, how much time do we leave between groups? Dave You just wait till the tractor is at 45 degrees - DUH! Quote Share this post Link to post Share on other sites
champu 1 #68 January 3, 2006 QuoteThen it's an impossible system to build. The plane, wheels, and belt would never get past the resting state - for that to happen, something would have to not be instantaneous. If the wheels were even able to start turning, then takeoff would be possible. This is exactly my point. If the speed of the wheels even got the slightest bit of a leg up on the speed of the conveyor you could take off. But that's not what the problem said, the problem said the conveyor would match the speed of the wheels exactly at any given moment. The video that got posted of the skateboard is nonsense, he lets the thing go and then starts pulling on the paper after it's already moving. That completely circumvents the problem. I have one final thing to say, if you take anything away from any of my posts here, take away this: This isn't even a problem of propulsion/aerodynamics. It's a problem in that the control system to keep the conveyor running at the exact same speed as the wheels is NOT STABLE. The INSTANT the wheels even attempt to move along the ground, the conveyor will accelerate out of control blowing up the landing gear before the plane goes anywhere. Quote Share this post Link to post Share on other sites
RhondaLea 3 #69 January 3, 2006 QuoteOk, hypothetically speaking (or you can go try this if you want), if we put the conveyor belt on the DZ, and towed the entire DZ with a tractor at 100 knots, and the plane did take off, how much time do we leave between groups? Y'know...this post actually brought tears to my eyes. rlIf you don't know where you're going, you should know where you came from. Gullah Proverb Quote Share this post Link to post Share on other sites
pilotdave 0 #70 January 3, 2006 ...and most people probably just think I'm nuts. Dave Quote Share this post Link to post Share on other sites
wildblue 4 #71 January 3, 2006 So the wheels are both at rest and moving at infinite RPMs at the same time.it's like incest - you're substituting convenience for quality Quote Share this post Link to post Share on other sites
Broke 0 #72 January 3, 2006 QuoteOk, hypothetically speaking (or you can go try this if you want), if we put the conveyor belt on the DZ, and towed the entire DZ with a tractor at 100 knots, and the plane did take off, how much time do we leave between groups? Dave Now if the tractor pulled this conveyor belt runway with the plane on it at 100kts it will be able to take off, because the tractor would produce enough airflow over to wings to generate lift.Divot your source for all things Hillbilly. Anvil Brother 84 SCR 14192 Quote Share this post Link to post Share on other sites
FreeflyChile 0 #73 January 3, 2006 hey...i went to U of I and i said it takes off! Quote Share this post Link to post Share on other sites kallend 1,651 #74 January 3, 2006 QuoteOur resident physics professors'll debate for hours about useless things like exit separation, but where are they now when we're talking about something that affects us all in our everyday lives?? Dave having a good laugh.... The only sure way to survive a canopy collision is not to have one. Quote Share this post Link to post Share on other sites kallend 1,651 #75 January 3, 2006 I believe the plane to be a Harrier and it would indeed take off, vertically.... The only sure way to survive a canopy collision is not to have one. Quote Share this post Link to post Share on other sites Prev 1 2 3 4 5 Next Page 3 of 5 Join the conversation You can post now and register later. If you have an account, sign in now to post with your account. Note: Your post will require moderator approval before it will be visible. Reply to this topic... × Pasted as rich text. Paste as plain text instead Only 75 emoji are allowed. × Your link has been automatically embedded. Display as a link instead × Your previous content has been restored. Clear editor × You cannot paste images directly. Upload or insert images from URL. Insert image from URL × Desktop Tablet Phone Submit Reply 0
kallend 1,651 #74 January 3, 2006 QuoteOur resident physics professors'll debate for hours about useless things like exit separation, but where are they now when we're talking about something that affects us all in our everyday lives?? Dave having a good laugh.... The only sure way to survive a canopy collision is not to have one. Quote Share this post Link to post Share on other sites
kallend 1,651 #75 January 3, 2006 I believe the plane to be a Harrier and it would indeed take off, vertically.... The only sure way to survive a canopy collision is not to have one. Quote Share this post Link to post Share on other sites
