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#11
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In article , Bob Fry
wrote: "BC" == Byron Covey writes: BC You can't do a roll and retain 1 G positive throughout the BC roll. BJC There's supposed to be a video of the great Bob Hoover doing a barrel roll with a glass of water on the panel...not a drop spilled. If anybody knows where a copy of the video is (or if it even exists) that would be a worth addition to Jay Honeck's collection. All that shows is that he maintained positive G's and coordination. |
#12
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David O wrote:
Chris W wrote: Do we have any who is a math whiz here? I want to find a formula to calculate the position of an airplane throughout a 1G roll. The reason I'm doing this is so I can build a "roll track" for a remote control car so the car will alway have a positive g force on it to keep it on the track. Anyone have any ideas? So far my attempts have have all come up short. They don't pass what my college calculus instructor called the "warm and fuzzy" test. I think it has been too long since I took those classes. Chris, I suggest that you forget about trying to model the path of an airplane in a 1 G roll and, instead, make your car track a simple helix. With a simple helix you should be able to keep your car's front wheels straight as the car goes through the helix. Now for the details... Why didn't I think of that. That is a much simpler solution. I can even do those calculations but thanks for doing them for me. If I get a 3d model going I will send you an image. -- Chris W Gift Giving Made Easy Get the gifts you want & give the gifts they want http://thewishzone.com |
#13
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Chris W wrote:
If I get a 3d model going I will send you an image. Yes, please do. David O -- email: David at AirplaneZone dot com |
#14
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A properly performed barrel roll is a 1G manuever. The aircraft's
flight path describes a helix, as David described below. An aileron roll is a variable-G operation, since you feel -1G while inverted. |
#15
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CB wrote:
A properly performed barrel roll is a 1G manuever. Nope. It's a small amount of positive G's but it's not a constant 1G. Did you actually read David's post? |
#16
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"CB" wrote
A properly performed barrel roll is a 1G manuever. The aircraft's flight path describes a helix, as David described below. An aileron roll is a variable-G operation, since you feel -1G while inverted. Check the following web sites, they all contain the same paragraph. Care to give us your references for the definition of a barrel roll. http://www.iac.org/begin/figures.html#Barrel%20Rolls http://acro.harvard.edu http://web.winco.net/~efildes/slowroll/barlroll.html The Barrel Roll is a not competition maneuver. The barrel roll is a combination between a loop and a roll. You complete one loop while completing one roll at the same time. The flight path during a barrel roll has the shape of a horizontal cork screw. Imagine a big barrel, with the airplanes wheels rolling along the inside of the barrel in a cork screw path. During a barrel roll, the pilot experiences always positive G's. The maximum is about 2.5 to 3 G, the minimum about 0.5 G. Bob Moore |
#17
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"CB" wrote in message
A properly performed barrel roll is a 1G manuever. The aircraft's flight path describes a helix, as David described below. No. An aileron roll is a variable-G operation, since you feel -1G while inverted. No. Ever done one? moo |
#18
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OK, folks, brace yourselves, you don't often see this on RAH....
I was wrong. That's what I get for relying on an aging memory rather than looking it up. CB |
#19
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On Sun, 19 Jun 2005 11:04:39 -0500, Chris W wrote:
4 Groups? Do we have any who is a math whiz here? I want to find a formula to calculate the position of an airplane throughout a 1G roll. The reason At any rate, do you want to maintain 1G, or just positive G? it's a big difference. You can do a barrel roll and maintain positive G all the way around. It's a very simple maneuver and very easy to do. It's also probably one of the easiest to screw up. I'm doing this is so I can build a "roll track" for a remote control car Remember that in straight and level flight you are pulling 1G. If you start a roll you will have to start adding nose up stick to maintain 1G to the point of 1G when inverted. " "Theoretically" as you rolled past inverted you would start reducing back pressure until you were back wings level. At this point it takes some one much more versed in aeronautic theory (and practice) than I, but... A barrel roll comes the closest to what you are asking. It, however starts out at more than 1G. Typically 2Gs and it can be more. With a 2G pull up at the start, you will be pulling 1G when passing inverted. Remember you started out in a nose high attitude to get to this point. So in the theoretically description you would most likely be way nose low at the 180 degree inverted position and I think you will probably get well past 2 Gs getting back to the wings level position. so the car will alway have a positive g force on it to keep it on the But, if it's just the positive Gs you need, shape the track like the path a plane would take through a barrel roll. It would go up and curve to the right forming a corkscrew shape with the end right back at the same level as the beginning. You can add turns as well "as long as the car is changing direction in relation to *its" own vertical axis. For example if the car is on its right side the track needs to be curving right, if on its left then the track needs to be curving left. If the car is inverted the track needs to be curving down. Remember too that the car has to be going fast enough to maintain the desired G forces and traction. Slow down and it'll just fall off. Roger Halstead (K8RI & ARRL life member) (N833R, S# CD-2 Worlds oldest Debonair) www.rogerhalstead.com track. Anyone have any ideas? So far my attempts have have all come up short. They don't pass what my college calculus instructor called the "warm and fuzzy" test. I think it has been too long since I took those classes. |
#20
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My take on this is that an airplane in a 1G roll would follow the same
path as any other object. Imagine your in space. A 1G roll would be a perfect circle with a constant 1G acceleration. Now bring that path into the Earth's gravity well. Now the 1G roll is all messed up by the Earth's 1G. How can we fix that? Just like the Vomit Comet does, by accelerating down at 9.8m/s^2. Superimpose a roll on top of a parabolic descent and you have the path of a theoretical airplane in a 1G roll. I don't think there is a plane that could actually perform this maneuver in reality. -- This is by far the hardest lesson about freedom. It goes against instinct, and morality, to just sit back and watch people make mistakes. We want to help them, which means control them and their decisions, but in doing so we actually hurt them (and ourselves)." |
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