speedy 0 #1 April 19, 2007 It seems I am not only crap at physics and maths but also at searching the forums. Can anyone give me a ball park figure as to what a 1kg (2 lbs) helmet with video effectively weighs during deployment? I know it all depends on how quickly the canopy opens. But lets take a distance of 150 meters (500 ft) for the opening distance. That's 172 feet per second down to 32 feet per second over that distance. I just like some figure like the camera gear weighs xx Kilos during deployment. More if the canopy opens fast, less if it opens slowly. Can someone help? Dave Fallschirmsport Marl Quote Share this post Link to post Share on other sites
The111 1 #2 April 19, 2007 Quote Can someone help? Sure. At a 1G load it weighs one times its weight. At a 2G load it weight two times its weight. Etc. This kind of precise number chasing is not well served in skydiving applications, IMO. What IS an important thing to consider though is that the weight of your camera helmet alone is not the primary factor in how much your opening can hurt your neck. Much more important than weight is (1) distance from the base of your neck and (2) position of your head relative to opening direction. I say relative to opening direction, rather than vertical, since in a wingsuit (which I am 99% of the time) opening is not straight down. If you keep the camera, your neck, and your spine in line with the opening direction, you will only feel compression load on your neck, which is much preferable to the alternative, bending load. To do this requires (1) a nice weight distribution on the helmet and (2) a nice head position on opening. My helmet is about 7 lbs and some people act like that's crazy. But I've heard of certain pros using 20-30lb setups. Now that's heavy duty.www.WingsuitPhotos.com Quote Share this post Link to post Share on other sites
speedy 0 #3 April 19, 2007 Quote This kind of precise number chasing is not well served in skydiving applications, IMO. I agree with you entirely. I am not looking for a precise number. It's a bit like - "you think you can hold onto a baby in a 30 mph crash? It weighs nearly 3 tons at the moment of impact". Usless info but it does sort of make you think, maybe the seatbelt is better. So how many G's does a normal opening exert on the jumper? Thanks for your other comments though. Dave Fallschirmsport Marl Quote Share this post Link to post Share on other sites
Calvin19 0 #4 April 19, 2007 on the same note... i have done some SkiBASE jumping with a older HD camera and a HUGE FREAKING LENSE. it was for a production crew, we got 'paid' to do it. and we had to use their 'professional' cameras on our helmets. the camera itself was bigger than a normal video cam, and the lense must have been 4 lbs. and it was sticking out 6" in front of our helmets. and still... double backflips were performed... slider down BASE openings as well. i think a persons neck can take a lot. as long as they are ready for it. Quote Share this post Link to post Share on other sites
velocityphoto 0 #5 April 20, 2007 Norm kent told me his light helmet is 17 and his heavy film camera is 34 i believe ... A friend will bail you out of jail , a REAL friend will be sitting next to you in the cell slapping your hand saying "DUDE THAT WAS AWSUM " ................ Quote Share this post Link to post Share on other sites
LouDiamond 1 #6 April 20, 2007 QuoteSo how many G's does a normal opening exert on the jumper? This is another huge variable thats hard to quantify consistently. John Sherman talked about this at PIA and showed the G forces measued by the PDAS system they use to gather this kind of information. Bottom line , there are several different G forces "felt" during the opening, the snatch force was rather low however, the higest was during the inflation of the canopy. The number of Gs felt depended on the canopy make and model and was subject to anomolies such as packing techniques."It's just skydiving..additional drama is not required" Some people dream about flying, I live my dream SKYMONKEY PUBLISHING Quote Share this post Link to post Share on other sites
ltdiver 3 #7 April 20, 2007 Quote What IS an important thing to consider though is that the weight of your camera helmet alone is not the primary factor in how much your opening can hurt your neck. Don't forget the weight of your head as well. The weight of a human head factors in in any whiplash injury as well. Think about it, people in cars normally don't wear helmets and yet, with the force of being hit from behind their neck can be screwed up for life. [therapist's voice]>[/therapist's voice] ltdiver Don't tell me the sky's the limit when there are footprints on the moon Quote Share this post Link to post Share on other sites
dragon2 0 #8 April 20, 2007 My neck muslcles usually complain the most after an opening with a fast turn in it when the copy is not fully open. Getting whipped around hurts more than a harder opening straight on. ciel bleu, Saskia Quote Share this post Link to post Share on other sites
dorbie 0 #9 April 24, 2007 Camera weight = deployment G-forces * mass Assuming you include 1 for gravity in deployment Gs It's also worth considering the 'moment' about the neck during deployment. The distance the camera is from the fulcrum (the higher it is on your head) the greater the bending load on your neck. Think of your head and helmet as a lever against your neck (the moment arm). The longer the lever the greater the bending load on your neck. Mounting your camera higher on your head is generally a bad thing unless the load is applied straight down through your neck. If you're on your belly and you take a whack the bending load your camera will add to your neck increases with (is multiplied by) the distance above your head. If you want to intuitively understand this imagine using a wrench to turn a bolt. Your vertebrae is the bolt, your neck, head & helmet is arm of the wrench and your camera under G-load is the hand pushing on the wrench. The longer the wrench the easier it is to snap the bolt. (simpified of course because everything on your head generates load under Gs). http://en.wikipedia.org/wiki/Moment_%28physics%29 Quote Share this post Link to post Share on other sites
champu 1 #10 April 24, 2007 A picture is worth a thousand words... Quote Share this post Link to post Share on other sites
dorbie 0 #11 April 25, 2007 Cool, in that diagram you're also accounting for the angle of the head relative to the force vector in calculating the moment. The sin theta term. There's a shear force too, sin theta instead of cos theta in the compression equation, if you're interested. Quote Share this post Link to post Share on other sites
champu 1 #12 April 26, 2007 Quote There's a shear force too, sin theta instead of cos theta in the compression equation, if you're interested. Yeah, a couple notes about that drawing... 1) I'm treating the complex structures of the human cervical vertebrae as a single pivot point, which my sister (an orthopedic surgeon) would have my ass for, but I don't really care. 2) It's important to note that while the junction between the three rings and the risers is at your shoulders, and you may think of it as a reference when orienting your neck to reduce the torque it experiences, it should be understood that your deceleration begins at the legstraps, and the orientation of your entire back during deployment should be considered whether or not you are strapping bowling balls to your head. /edited to add: "I do vector calculus just for fun. Ain't got a gat, but I got a soldering gun." Quote Share this post Link to post Share on other sites
