Scott Posted October 11, 2008 Share Posted October 11, 2008 By not sitting on the spot on a treadmill? This thread is gonna turn into a long one I can't figure out why though. The people that don't know, are the doubters. The people that do, are telling the doubters why. Yet they still doubt lol. I think Thorin summed it up nicely. Quote Link to comment Share on other sites More sharing options...
ivan Posted October 11, 2008 Share Posted October 11, 2008 Thorin, you are an evil man! Fancy starting this up all over again - you know you're only going to confuse people and get them agitated. I can do science me. Quote Link to comment Share on other sites More sharing options...
MrRalphMan Posted October 11, 2008 Share Posted October 11, 2008 He's right though Gaz. If you could create enough wind you could get any plane to take off without actually moving as long as it was anchored. he didn't mention a treadmill. Yep, the Science museum has (or had) a display like that. Plane fixed on a rod and a fan blew, up goes the plane. Quote Link to comment Share on other sites More sharing options...
miko_supra Posted October 11, 2008 Share Posted October 11, 2008 Yep, the Science museum has (or had) a display like that. Plane fixed on a rod and a fan blew, up goes the plane. You can do vertical take off in a 747 in flight sim if you have a stupid amount of headwind Quote Link to comment Share on other sites More sharing options...
Thorin Posted October 11, 2008 Author Share Posted October 11, 2008 Another one to get your head around posted in one of the comments, "What if you had a helicopter on a really big turntable?", or a hovercraft on a really big upturned vacuum cleaner? Quote Link to comment Share on other sites More sharing options...
ADL Mark Posted October 11, 2008 Share Posted October 11, 2008 The helicopter would still take off, as it would be spinning on the turntable and the blades would produce thrust down on to it regardless of whether it is moving or not? Not sure on the hovercraft one.. Quote Link to comment Share on other sites More sharing options...
miko_supra Posted October 11, 2008 Share Posted October 11, 2008 what are you saying about the helicopter though? are the blades spinning or is the whole thing sitting there spinning around on this cool turntable? Quote Link to comment Share on other sites More sharing options...
Thorin Posted October 11, 2008 Author Share Posted October 11, 2008 what are you saying about the helicopter though? are the blades spinning or is the whole thing sitting there spinning around on this cool turntable? Well I guess it could be either that the turntable is spinning in the opposite direction to the blades at exactly the same speed as them, or that the blades aren't spinning at all but the turntable is spinning around at the required speed the blades would need to turn to lift off. Quote Link to comment Share on other sites More sharing options...
Scott Posted October 11, 2008 Share Posted October 11, 2008 Helicopter wouldn't take off if it was rotating in the opposite direction and at the same rate as the blades. It would basically appear that the blades were standing still therefor generating no difference in thrust. Hovercraft wouldn't lift either as if both thrust and suction forces were equal there wouldn't be any left over to actually lift it. Quote Link to comment Share on other sites More sharing options...
miko_supra Posted October 11, 2008 Share Posted October 11, 2008 Helicopter wouldn't take off if it was rotating in the opposite direction and at the same rate as the blades. It would basically appear that the blades were standing still therefor generating no difference in thrust. Hovercraft wouldn't lift either as if both thrust and suction forces were equal there wouldn't be any left over to actually lift it. Yeah i can agree with the helicopter one. Right thats that one done and dusted. Whats next? Quote Link to comment Share on other sites More sharing options...
Scott Posted October 11, 2008 Share Posted October 11, 2008 Yeah i can agree with the helicopter one. Right thats that one done and dusted. Whats next? One from the IMOC forum. Is it possible to drive onto the back of a lorry, as in knightrider, without shooting through the back of it? If you are travelling at 40mph and the lorry is doing 30, when you get into the lorry what speed will you be doing? Quote Link to comment Share on other sites More sharing options...
ADL Mark Posted October 11, 2008 Share Posted October 11, 2008 If you've got fecking good brakes, yeh Quote Link to comment Share on other sites More sharing options...
Scott Posted October 11, 2008 Share Posted October 11, 2008 If you've got fecking good brakes, yeh Lol, thats what a lot of people on imoc thought too. It turned into quite a debate. Quote Link to comment Share on other sites More sharing options...
ADL Mark Posted October 11, 2008 Share Posted October 11, 2008 And I'm still not convinced about the helicopter one, I think it would take off regardless of how the turntable was spinning. The body of the helicopter will move with the turntable so to the blades, the effect will be that the helicopter is on still ground. Are any of our budding model helicopterists willing to give this a go with a record deck? Quote Link to comment Share on other sites More sharing options...
ADL Mark Posted October 11, 2008 Share Posted October 11, 2008 These things always do, quite good fun, but some people to get very agitated! Doesn't matter what speed the truck is doing, when the car gets in it, it will be doing the speed it was doing on the road. You'd need good brakes to stop before going through the end of the truck though. Who's up for hijacking a car transporter and giving it a crack? Nobody with J-spec brakes though please Quote Link to comment Share on other sites More sharing options...
ivan Posted October 11, 2008 Share Posted October 11, 2008 One from the IMOC forum. Is it possible to drive onto the back of a lorry, as in knightrider, without shooting through the back of it? If you are travelling at 40mph and the lorry is doing 30, when you get into the lorry what speed will you be doing?Relative to the lorry, 40mph. Relative to the road, 70mph. Quote Link to comment Share on other sites More sharing options...
Scott Posted October 11, 2008 Share Posted October 11, 2008 And I'm still not convinced about the helicopter one, I think it would take off regardless of how the turntable was spinning. The body of the helicopter will move with the turntable so to the blades, the effect will be that the helicopter is on still ground. Are any of our budding model helicopterists willing to give this a go with a record deck? Think about it. If you take a helicopter and spin it anticlockwise at 1000rpm and then spin the blades clockwise at 1000rpm to your eye the blades won't move but the helicopter will still be spinning anticlockwise at 1000rpm. Doesn't need a test Trust me, i'm a well erm... an engineer? Quote Link to comment Share on other sites More sharing options...
Gazboy Posted October 11, 2008 Share Posted October 11, 2008 One from the IMOC forum. Is it possible to drive onto the back of a lorry, as in knightrider, without shooting through the back of it? If you are travelling at 40mph and the lorry is doing 30, when you get into the lorry what speed will you be doing? It's a 10mph difference so given that our cars can do 60-0 in 109 feet so a 25 foot trailer shouldn't be much of an issue from ten mph, but wouldn't you break something in the drivetrain in the transfer phase??? Helicopter is a good one Quote Link to comment Share on other sites More sharing options...
Scott Posted October 11, 2008 Share Posted October 11, 2008 It's a 10mph difference so given that our cars can do 60-0 in 109 feet so a 25 foot trailer shouldn't be much of an issue from ten mph, but wouldn't you break something in the drivetrain in the transfer phase??? Helicopter is a good one Yeah 10mph is the answer. THe drivetrain wouldn't be an issue as long as you dropped it out of gear or dropped the clutch (not sure how they did it with the auto). Quote Link to comment Share on other sites More sharing options...
Swampy442 Posted October 11, 2008 Share Posted October 11, 2008 OMG How do you think a sea plane takes off? FFS the same way as all other planes do, by moving forward at speed into oncoming air. Said air passes over the aerofoil shape of the wing, with the air on top of it travelling further than air on the bottom, therefor creating a low pressure area over the wing, causing lift Hi 5 for Scotster lol. Plus if the chopper was spinning on Mikos cool turntable at 360 rpm the pilot will be in no fit state to fly anyway! 17 years working on planes and helicopters has taught me a thing or 2 lol. Also if it was possible why has nobody built a plane sized treadmill to test it... Quote Link to comment Share on other sites More sharing options...
Scott Posted October 11, 2008 Share Posted October 11, 2008 Relative to the lorry, 40mph. Relative to the road, 70mph. relative to lorry 10mph relative to road 40mph Won't quite be 10 or 40 though as you have to actually make it up the ramp. I think in most cases the 10mph would be lost on the way up the ramp so the car would have to either be driven up the ramp or the speed would have to be increased to make it accurate. Quote Link to comment Share on other sites More sharing options...
Thorin Posted October 11, 2008 Author Share Posted October 11, 2008 Yeah 10mph is the answer. Is it? Also if it was possible why has nobody built a plane sized treadmill to test it... Mythbusters did Quote Link to comment Share on other sites More sharing options...
Swampy442 Posted October 11, 2008 Share Posted October 11, 2008 Touche lol. Ok, why has nobody built a life sized plane treadmill to test it Quote Link to comment Share on other sites More sharing options...
OhGod Posted October 11, 2008 Share Posted October 11, 2008 Think of it like a boat in the ocean. If you put a boat into a current it will move the boat the way the current is going. If you raise the sail and the wind is blowing the other way all you need is the amount of force created from the wind (thrust) to be greater than the amount of force created by the ocean (friction) and the boat will move forward. Yes but the original problem states that - to continue your boat analogy - as the wind picks up, the current also picks up to compensate, so the boat remains stationary. It doesn't matter how hard the wind blows, the current matches speed to counter any forward movement of the boat. The problem was not about whether a plane could take off from a treadmill running at a constant speed - which is why the oft quoted Mythbusters episode is moot; it can, it'll just need to generate more thrust than usual to counter the reverse action of the treadmill. So back to the plane; as the engines produce thrust the treadmill increases speed so that - via friction or whatever - the reverse forces on the plane are the same as produced by the engine. As such, the plane remains stationary as the treadmill and wheels spin at silly speeds until the wheels overheat and fall apart! I think there was some confusion over whether the treadmill countered the plane speed or the wheel speed. I saw it as the former. Quote Link to comment Share on other sites More sharing options...
Thorin Posted October 11, 2008 Author Share Posted October 11, 2008 More stupid people reveal themselves. Well, it appears that my work on this planet is finished, so I must now return to my home planet of Zarquon. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
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.