Snap Swivel Strengths, Gases

[SFenix]

Went and bought some snap swivels today, rated for 15lbs... they'll only be used on smaller rockets 1/x A-C engines.. What's the expected amount of pressure that will be put on a small rocket when the chute deploys? I cant imagine it'll be all that much..

Also.. doing some reading in other threads. When the ejection charge "goes off", it's hot gases and hot solids that can damage the system right? About how much pressure do they exert? Reason I ask, what about the idea of putting a kevlar (or similar material) "bag" on the side of the inside of the body tube. Stuff the parachute in there, with a shockcord attached to the bag.

Gases go up, and if the bag is in correctly, there should plenty of room for them to go around the bag, pop the nose cone, which will pull out the chute and from there go like normal..

Thoughts/experiences with something like this? It's probably been though of before.. but oh well

 

[cydermaster]

Originally posted by SFenix
Thoughts/experiences with something like this? It's probably been though of before.. but oh well

Nomex(R) heat shields do, basically, what you have thought of. You attach them to the shock cord, and 'cradle' the packed parachute in it; partially encasing the parachute, and shock cord.

I got a pack off Nomex(R) heat shields, from an e-bay auction, and I am most impressed by it. It doesn't eliminate the need for wadding, but I find it lets me half the amount I would usually use.

Thrustline Aerospace, run by our own flying_silverad(o), sell them. I've not tried Thrustline's heat shields personally, but if they are anywhere near the quality of their parachutes and kits, they'll be top-notch.

 

[SFenix]

Thanks! adds to favorites

I'd seen the heatshields, it's what gave me the idea. The heatshields popout too though right? This would be a more permament, I would think.. Probably only work on larger diameter BTs though..

 

[rbeckey]

I don't see why you couldn't afix a chute bag to the inside of a rocket and let the NC pull it out. It would have to be a fairly large rocket with a chute that could be packed real small. The pro chute makers have bags for their chutes.

https://www.the-rocketman.com/econo_bag.html

 

[trogdor]

Tim van Milligan's (Apogee) book shows a similar idea but he uses a centered central tube to contain the chute with passages all around for ejection to blow the nose off. Then nose pulls out chute, like your idea... seems like yours will work also but the complexity seems not worth it....

i.e. little things can always go wrong, I'd go with regular wadding or nomex... like chute can get caught up because of how you folded it... I've had little pieces of extra wire (cable shock inside tube..) work fine 20 flights then hang up the chute one day.. weird little things always happen...

oh and the 15lbs I think is only a measure of the total force it can take... and I've had ejection charges from an Estes C11 snap a swivel in half with a long (5 ft!) Kevlar only cord...
so those quick impact high G kinda forces are more than you think sometimes from even Estes motors. But I guess with a little bungee action inline you're much better off, maybe only 1 ft at the end of long kevlar... I'm just thinking out loud now.,,

 

[Rocketman248]

If you're going to have the nosecone pull the parachute out, makesure you have a small pilot chute on the nosecone. If not, the main chute probably won't come out. I failed my level 3 because I didn't have a pilot chute.

 

[SFenix]

Thanks guys. For the most part, I think you all confirmed what I'd thought. Oh well.

rocketman, sorry to hear that, hope the Blue Angel can be repaired to flying condition, and soon, the thing was a monster!