BenGriffiths 0 #1 February 10, 2004 One of my university projects involves the measurement of 3-D movement of a skydiver. I am assuming the acceleration in the Z axis (vertical) will never exceed }9.81 (i.e. g). However as I'm not studying Aerospace/Physics I'm having a little more difficulty calculating the maximum acceleration in the x and y axis (horizontal). Anyone got and ideas / formulae?---------- Ben G Still Sinking :-( Quote Share this post Link to post Share on other sites
bmcd308 0 #2 February 10, 2004 You will have to get at this backwards, by looking at position data in the x and y axes over time. Note that the only real force we have is the result of air movement caused by our motion through the air in the z axis, so all other acceleration is the result of drag that is not acting on our center of gravity - I can think of no way that acceleration in any axis could exceed g, since acceleration in the x and y axes is really just borrowing some energy from the z axis. Brent ---------------------------------- www.jumpelvis.com Quote Share this post Link to post Share on other sites
Hooknswoop 19 #3 February 10, 2004 QuoteI can think of no way that acceleration in any axis could exceed g, since acceleration in the x and y axes is really just borrowing some energy from the z axis. In good track, the jumper is producing lift similar to an aircraft's wing, so there can be additional accleration. Derek Quote Share this post Link to post Share on other sites
billvon 3,090 #4 February 10, 2004 >I can think of no way that acceleration in any axis could exceed g, > since acceleration in the x and y axes is really just borrowing some > energy from the z axis. I dunno about that. With a wingsuit, I can change horizontal direction very rapidly. Never measured it but I can probably go from 60mph in one direction to 60 in the other in under 4 seconds. Quote Share this post Link to post Share on other sites
winsor 236 #5 February 10, 2004 QuoteYou will have to get at this backwards, by looking at position data in the x and y axes over time. Note that the only real force we have is the result of air movement caused by our motion through the air in the z axis, so all other acceleration is the result of drag that is not acting on our center of gravity - I can think of no way that acceleration in any axis could exceed g, since acceleration in the x and y axes is really just borrowing some energy from the z axis. You're mixing apples and oranges. (V^2)/r can greatly exceed g. Blue skies, Winsor Quote Share this post Link to post Share on other sites
The111 1 #6 February 10, 2004 I've heard that speed skydivers can pull out of a dive into a track so fast that they create a screech audible from the ground, and I've heard of minimum vertical speeds in the transition/track of 40 mph. I'd bet there is some intense horizontal acceleration at the onset of that transition...www.WingsuitPhotos.com Quote Share this post Link to post Share on other sites
rendezvous 0 #7 February 10, 2004 Not really. The acceleration is x and y coordinates would be more of a function of energy transformations e.g potential to kinetic and drag etc. The value of gravity or acceleration on the Z axis only affects the potential energy at a point on the z axis. Quote Share this post Link to post Share on other sites
Staso 0 #8 February 10, 2004 QuoteI've heard that speed skydivers can pull out of a dive into a track so fast that they create a screech audible from the ground, and I've heard of minimum vertical speeds in the transition/track of 40 mph. I'd bet there is some intense horizontal acceleration at the onset of that transition... as for audible part of speed skydiving, you're right. it makes a lot of noice and can be easily mistaken for jet. i didn't beleive until i heard myself on the video that was shot from the ground. as for 40 mph, that's i beleive is not true. my jumptrack software will beg to differ though: 40 mph dive ProTrack for that dive was placed in my helmet and most likely i turned my head while transitioning into horizontal flight. every time the speed curve is smooth, it's most likely means that ProTrack was in the shadow or in the area of high preassure and then when it gets back to normal air, it will have to compensate preasure drop/raise and it will draw this nice fake smooth line. moving ProTrack to later webbing will make it much harder to produce such fake results and the profile will look more like this: more realistic one adding another ProTrack on another side and averaging should eliminate the fake results almost completely. i usually go from full dive into track right away, without any speed bleeding and i get a lot of forward speed. how fast i'm going and what the acceleration ? i have no clue. as for deceleration, on the second profile, i go from 290 to 110 mph in 14.75 seconds, which, if my calculations are correct, should add approximately .55g to my weight, brining it from 210 to 325 pounds :) feels good ... and the curve is steeper when i start slowing down, so i could be up to 350 at that point :) funny, that after doing so many speed dives, regular track or RW feels so weird for me :) without usual high speed and pressure if feels very mushy and strange, like a ballon jump :) stan -- it's not about defying gravity; it's how hard you can abuse it. speed skydiving it is ... Speed Skydiving Forum Quote Share this post Link to post Share on other sites
The111 1 #9 February 10, 2004 Heh, you caught me Stan, I was referring to you. That's awesome that you can get such decelerations in your track, I hope to be able to do that one day...www.WingsuitPhotos.com Quote Share this post Link to post Share on other sites
Staso 0 #10 February 10, 2004 QuoteHeh, you caught me Stan, I was referring to you. That's awesome that you can get such decelerations in your track, I hope to be able to do that one day... then maybe you should check dropzone.com calendar for this event and come out and play with us -- it's not about defying gravity; it's how hard you can abuse it. speed skydiving it is ... Speed Skydiving Forum Quote Share this post Link to post Share on other sites
bobsled92 0 #11 February 11, 2004 Have you ever jumped a SkyRay? I would imagine a god drive for speed into a track the way YOU do it would genrate some lift the way the guys at SkyRay R&D did. (Thier video clip was great, you could take it up a notch)._______________________________ If I could be a Super Hero, I chose to be: "GRANT-A-CLAUS". and work 365 days a Year. http://www.hangout.no/speednews/ Quote Share this post Link to post Share on other sites
bmcd308 0 #12 February 12, 2004 >>You're mixing apples and oranges. << You are correct. Idiotic position renounced. ---------------------------------- www.jumpelvis.com Quote Share this post Link to post Share on other sites
