Thorin Posted October 10, 2008 Share Posted October 10, 2008 Original thread http://www.mkivsupra.net/vbb/showthread.php?t=139595 I now have the definitive answer, if only this had been posted back then. http://blag.xkcd.com/2008/09/09/the-goddamn-airplane-on-the-goddamn-treadmill/ The practical answer is “yes”. A 747’s engines produce a quarter of a million pounds of thrust. That is, each engine is powerful enough to launch a brachiosaurus straight up (see diagram). With that kind of force, no matter what’s happening to the treadmill and wheels, the plane is going to move forward and take off. Proof : Quote Link to comment Share on other sites More sharing options...
jamesmark Posted October 10, 2008 Share Posted October 10, 2008 But what if the treadmill was designed to equal the force of the 747's engines? Quote Link to comment Share on other sites More sharing options...
RobSheffield Posted October 10, 2008 Share Posted October 10, 2008 But what if the treadmill was designed to equal the force of the 747's engines? Dont start Just Dont Quote Link to comment Share on other sites More sharing options...
jim_supra Posted October 10, 2008 Share Posted October 10, 2008 Dont start Just Dont Too late Rob, I can see another long thread coming. Quote Link to comment Share on other sites More sharing options...
Gaz6002 Posted October 10, 2008 Share Posted October 10, 2008 Quote Link to comment Share on other sites More sharing options...
michael Posted October 10, 2008 Share Posted October 10, 2008 Does the treadmill have a fan built into the console? Quote Link to comment Share on other sites More sharing options...
Ian C Posted October 10, 2008 Share Posted October 10, 2008 Don't make me side with Matt H again you bastard Quote Link to comment Share on other sites More sharing options...
Charlotte Posted October 10, 2008 Share Posted October 10, 2008 I like dinosaurs. Quote Link to comment Share on other sites More sharing options...
michael Posted October 10, 2008 Share Posted October 10, 2008 Quote Link to comment Share on other sites More sharing options...
Gazboy Posted October 10, 2008 Share Posted October 10, 2008 But what if the treadmill was designed to equal the force of the 747's engines? Then you have a very expensive treadmill spinning it's nuts off as the plane buggers off into the sky. Quote Link to comment Share on other sites More sharing options...
jamesmark Posted October 10, 2008 Share Posted October 10, 2008 Then you have a very expensive treadmill spinning it's nuts off as the plane buggers off into the sky. But does it? Bugger off into the sky..... Quote Link to comment Share on other sites More sharing options...
MrRalphMan Posted October 10, 2008 Share Posted October 10, 2008 Yes Quote Link to comment Share on other sites More sharing options...
miko_supra Posted October 10, 2008 Share Posted October 10, 2008 of course it's not going to fly?! Wings need air flowing over them to produce lift and the only air flowing is that being sucked into the engines Quote Link to comment Share on other sites More sharing options...
MrRalphMan Posted October 10, 2008 Share Posted October 10, 2008 he he he.... This is going to fill the ol mail box up... Have you seen what it did to the Dinosaur... wow. Quote Link to comment Share on other sites More sharing options...
jamesmark Posted October 10, 2008 Share Posted October 10, 2008 Yes I am not convinced. Quote Link to comment Share on other sites More sharing options...
Havard Posted October 10, 2008 Share Posted October 10, 2008 of course it's not going to fly?! Wings need air flowing over them to produce lift and the only air flowing is that being sucked into the engines Is this really happening?? Quote Link to comment Share on other sites More sharing options...
Gaz6002 Posted October 10, 2008 Share Posted October 10, 2008 Is this really happening?? Nope you're imagining it mate Quote Link to comment Share on other sites More sharing options...
ADL Mark Posted October 10, 2008 Share Posted October 10, 2008 I can understand how people don't think it will take off, they see that the moving runway will stop the plane from going forwards and therefore not getting any airflow past the wings to give lift. Took me a little while to work it out, but it wouldn't matter how fast or in which direction the runway was moving, the planes engines will push it forwards because they are pushing on the air. The wheels on the plane are just there to allow it to move around on the ground, they're not powered so are not used to get it up to speed for take off, just the thrust of the engines. Quote Link to comment Share on other sites More sharing options...
SupraStar 3000 Posted October 10, 2008 Share Posted October 10, 2008 missed the original thread so i'll post here Now, I dont know much about anything, but I do know a plane needs to generate forward motion to achieve lift. The reason is correctly air pressure creating lift over the wings. The idea of the engine carrying the aircraft vertically is stupid. The harrier was built to achieve vertical flight and can only just manage it for short periods at a time. A 747 stands no chance. Quote Link to comment Share on other sites More sharing options...
Scott Posted October 10, 2008 Share Posted October 10, 2008 I only just saw this and the other thread and i honestly can't see the debate. Either i am favourably informed or you guys have no idea what thrust is. The momentum of an aeroplane comes from the engine pushing/pulling the air around it, its got nothing to do with the wheels. At the time of takeoff, if it was on a conveyor the wheels would be turning at twice the speed they normally would but the plane would still be moving forward at the same speed as it would be during normal takeoff, take away a tiny bit for the extra resistance in the wheels. Edit, here's a scenario you can play through your mind. Imagine you had powered rollerskates on and you went onto a treadmill. If you equal the speed of the skates to the treadmill then u won't move. Now, take freewheeling skates and put on a jetpack. Imagine that you had already been on a runway and found out the speed that the jetpack powered skates would go on a flat and set the treadmill to that speed. Turn on the jetpack. Regardless of how fast the skates are turning the force from the jetpack is pushing the air behind you via exhaust gas. This would create an equal and opposite reaction pushing the jetpack forward from its current position..... regardless of where the skates are. Quote Link to comment Share on other sites More sharing options...
bigbloodyturbo Posted October 10, 2008 Share Posted October 10, 2008 the 747 would take off, the speed the treadmill is travelling would have no bearing on the forward speed of the aircraft. If the engines where turning the wheels then yes, the aircraft would not be able to travel forwards as they would have to overcome the speed of the treadmill before accelerating the aircraft however, thrust is acting on the airframe not the wheels. The only limiting factor is how much rpm the wheels could take before the bearings burnt out and seized. Quote Link to comment Share on other sites More sharing options...
Scott Posted October 10, 2008 Share Posted October 10, 2008 the 747 would take off, the speed the treadmill is travelling would have no bearing on the forward speed of the aircraft. If the engines where turning the wheels then yes, the aircraft would not be able to travel forwards as they would have to overcome the speed of the treadmill before accelerating the aircraft however, thrust is acting on the airframe not the wheels. The only limiting factor is how much rpm the wheels could take before the bearings burnt out and seized. Either ur a good parrot, or a bad ventriloquist dummy Quote Link to comment Share on other sites More sharing options...
bigbloodyturbo Posted October 10, 2008 Share Posted October 10, 2008 Either ur a good parrot, or a bad ventriloquist dummy i was typing when you where typing but trying to eat waffles at the same time, hence me being slower;) Quote Link to comment Share on other sites More sharing options...
Pete Posted October 10, 2008 Share Posted October 10, 2008 Oh no not again! I've only just got over the embolism brought on from thinking about this last time. Quote Link to comment Share on other sites More sharing options...
ADL Mark Posted October 10, 2008 Share Posted October 10, 2008 The idea of the engine carrying the aircraft vertically is stupid. The harrier was built to achieve vertical flight and can only just manage it for short periods at a time. A 747 stands no chance. I think you've kind of missed the point Ed Quote Link to comment Share on other sites More sharing options...
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