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| homedepotpro |
 Posted: 12/02/2007 21:09 PM Post subject: |
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Lieutenant Colonel
Joined: 26 Nov 2006
Posts: 446
450.72 Spud Bux
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| when i put it into ggdt awhile back it said 140 g's i think, that a ballpark estimate. |
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| BigGrib |
| Posted: 12/02/2007 21:16 PM Post subject: |
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GribNation Founder
Joined: 01 Oct 2007
Posts: 627
220.47 Spud Bux
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| what velocity is that and what psi and volume of air and blah blah blah cause all of those factors need to be taken into account right so how did you come up with 93 and 186 i mean aside from your hypothesised accelertation time and psi you dont know the barrel length and the mass of the golf ball and all that stuff |
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| paaiyan |
| Posted: 12/02/2007 21:22 PM Post subject: |
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Ascendant Defenestrator
Joined: 27 Dec 2006
Posts: 2056
2624.44 Spud Bux
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The mass and all that stuff doesn't really matter. The g-forces experienced are independent of mass, all that matters is the change in velocity and the amount of time that change took. 300 fps is about 91 meters per second. Divide that by the estimated .1 seconds for the time of acceleration and you get 914.6 meters per second squared. The gravitational constant is 9.8 meters per second squared. Divide your 914.6 by 9.8 and you have 93.3. That's 93.3 times the gravitational constant, the force of gravity. Technically you subtract 1 for vertical acceleration, and the calculations for horizontal are a bit more complex due to the not quite horizontal gravitational effect, but they yield nearly the same result anyway.
Side note, the record for g-forces survived by a human is approximately 180. That was only instantaneous though. |
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| hubb017 |
| Posted: 12/02/2007 21:33 PM Post subject: |
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Sarcasmo
Joined: 28 May 2007
Posts: 1477
587.45 Spud Bux
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Well, since the g-force will affect the camera, it would seem fair to say that one may need to figure some kind of way to eliminate / reduce the g-forces going up.
I'm not too sure on how to do this but some sort of cushioned sabot comes to mind, one that will break away when the camera reaches its maximum height and begins to come down. |
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| paaiyan |
| Posted: 12/02/2007 21:34 PM Post subject: |
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Ascendant Defenestrator
Joined: 27 Dec 2006
Posts: 2056
2624.44 Spud Bux
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| Going up isn't the problem. Starting to go up is. Potato guns naturally have near instantaneous acceleration, there's nothing you can do about that. |
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| windshrike |
| Posted: 12/02/2007 21:53 PM Post subject: |
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Sergeant Major
Joined: 28 Jun 2007
Posts: 178
444.10 Spud Bux
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I say to start at minimal pressures(i.e. 5 psi) and work your way up until the camera no longer works. Of course, if you still want your camera after, make sure you stop when it still works but is going too fast to see easily.
About the parachutes: Test a few methods of folding them, but there is nothing foolproof. |
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| Ragnarok |
| Posted: 12/02/2007 21:59 PM Post subject: |
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Lord of Karma
Joined: 19 Dec 2006
Posts: 2668
7312.17 Spud Bux
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... Except very low pressures and a longer barrel.
Cameras like that aren't designed to stand more than light knocks, a few G at most, not several hundred. Most of the time the cameras are torn apart by the acceleration.
If you could get all parts accelerating at precisely the same rate, then it would be fine, but a spudgun can't do that.
If you could create a stable gravity pulse with positive feedback shielding, then it would be a pittance, but even I'm having trouble with that one. The rotating superconductors keep heating above their transition temperature, and it's all going wrong.
I still think just putting the camera on the RC heli is the best move.
P.S: I get about 2000 G peak acceleration for a golf ball at 100 psi.
0.1 seconds is a very long time for anything to be in the barrel.
0.01s to 0.02s is more likely. |
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| paaiyan |
| Posted: 12/02/2007 22:00 PM Post subject: |
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Ascendant Defenestrator
Joined: 27 Dec 2006
Posts: 2056
2624.44 Spud Bux
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| Ragnarok wrote: |
P.S: I get about 2000 G peak acceleration for a golf ball at 100 psi.
0.1 seconds is a very long time for anything to be in the barrel.
0.01s to 0.02s is more likely. |
Hey, if you think your time for acceleration is more accurate, have at it man. I was guesstimating, and made no assertions of fact. |
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| windshrike |
| Posted: 12/02/2007 22:00 PM Post subject: |
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Sergeant Major
Joined: 28 Jun 2007
Posts: 178
444.10 Spud Bux
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| I just thought of something: make this parachute round, but rig the RC helicopter to drop it in mid-air. That would make a nice video. |
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| BigGrib |
| Posted: 12/02/2007 22:54 PM Post subject: |
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GribNation Founder
Joined: 01 Oct 2007
Posts: 627
220.47 Spud Bux
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| ok so the barrel length is 36" to mid-diameter and the ball will be traveling at a blazing 300 fps, which means that ball will exit the barrel at full velocity @ .01 seconds, do all the math on that sucker and you get exatctly 928.57 G's bingo slam dunk yahtzee, thank you and goodnight |
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| jackssmirkingrevenge |
| Posted: 12/02/2007 23:08 PM Post subject: |
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space monkey
Joined: 15 Mar 2007
Posts: 7098
11428.06 Spud Bux
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There's a few good ideas on this thread - I also liked this idea by dewey-1 which he claims functioned reliably:
Looking at the camera system, it looks like it could easily shed a few grams - shorted the wire and hook up the battery directly without a connector, strip the metal casing of the 9 volt etc.
Make sure the camera is well packed to be able to resist the acceleration forces, perhaps mounting it on a spring-loaded base would be a good idea. |
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| Carlman |
| Posted: 12/03/2007 1:36 AM Post subject: |
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The Aussie
Joined: 24 Nov 2007
Posts: 1171
376.06 Spud Bux
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WOW!, thts alot of replies for a short amount of time lol
it kinda went off topic thn righted itself again so its all good
anyway, ive been searchin on the net and contemplating a few ideas, nd thnx go out to JSR for directing me to that other thread. 
thnx for all the replies guyz, i WILL make this work... |
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| BigGrib |
| Posted: 12/03/2007 1:59 AM Post subject: |
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GribNation Founder
Joined: 01 Oct 2007
Posts: 627
220.47 Spud Bux
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| actually we were figuring out how much g forces you need to make your camera rig be able to withstand, you should absolutely mount the camera on some sort of slide mount with a nice stiff spring backing it up, and if you were good with micro electronics so you have a gravity switch that when it starts to decend it triggers a co2 cartridge or some sort of charge to blow the chute, i relly dont think weight would be too much of an issue as long as you dont go hog ass wild with it, heck you coud run the gravity switch off the 9v running your camera. |
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| BigGrib |
| Posted: 12/03/2007 2:21 AM Post subject: |
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GribNation Founder
Joined: 01 Oct 2007
Posts: 627
220.47 Spud Bux
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| here's another idea, if you were to take a model rocket and make it a nice fit in your barrel, maybe with fold out fins once it comes out of the barrel, and have your camera mounted in the nose cone and run your ignitor wire up and out the barrel, oh i forgot to mention you will need a combustion with at least a chamber fan in it, but use that model rocket to ignite the propane in your chamber to give it that kick out of the barrel before the model rocket fully ignites. there ya go |
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| hubb017 |
| Posted: 12/03/2007 4:38 AM Post subject: |
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Sarcasmo
Joined: 28 May 2007
Posts: 1477
587.45 Spud Bux
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| jackssmirkingrevenge wrote: | | Make sure the camera is well packed to be able to resist the acceleration forces, perhaps mounting it on a spring-loaded base would be a good idea. |
That's what I meant in my above thread. |
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