Anyone ever use 550?

[11bravo]

***NOTE: Before you go any further, as I wrote (am writting) this it is quite late in a very long day, and it rambles and wanders, but still gets to the question.***

For recovery systems on rockets?
Not sure what else it maybe called.
It is the line from which shroud lines on (at least) military parachutes are made.
It is tubular, about 1/8 inch, and green; inside are 7 strands of white line.
Each complete strand is rated at 550 pounds static load.
Anyway, I was just tinkering around with some. I pulled out the inner strands and formed a loop using the method here-
https://www.geocities.com/rdh82000/Tips/kevlar.htm

Instead of a brass tube, I used a bit of shrink tube over the loose end and made the insertion hole about 5 inches from the end.

Not being of sound, when I had a loop roughly 1.5-2 inches long when laid flat (3- <4) inches round trip, there was a lump (the shrink tube) about 6 inches upstrand of the hole so I figured I had about that much of the running end stuffed up in the strand end. Well, what had actually happened was that I got a little over an inch of the running end inside and the shrink tube slipped off and I just worked the empty shrink tube up into the strand.
BUT... I did not realize this ('cuz its been a lond day and the 3-4 inches of still exposed cord and the roughly 6 inches inside the other part added perfectly well up to the 5 inches I started with) and pulled on the loop and it did not move! And that was with only a small fraction of what I thought was holding it.

Anyway, I'm not sure how it would deal with high temps involved in ejection charges, but would think that the high temp durations would be rather short and that it may hold up.

Any thoughts from folks that are familiar with the material?

It runs about $5-6 for a hundred foot coil so it is fairly cheap if it would work well.

Greg

 

[MetMan]

11B--

I've used 550 cord a few times as shock cord. I've either attached it to a kevlar leader or epoxied it directly to the body tube. Either way has worked just fine.

Just make sure you use plenty to take the "shock" out of the shock cord...

MetMan
Former 12B in a another life...

 

[MarkABrown]

With a little 550 cord and some Hundred Mile an Hour tape, one can rule the world!

{Former 11B}

 

[11bravo]

IIRC, that's the MOS that blows things up!
That could have been fun too.
You haven't transferred any of that knowledge over to rocketry, have you?
I actually suspected that the 550 would work just fine, just wondered if there was any experience with it.
Thanks for the reply, and a big hairy
HOOAH! to you,

Greg

P.S. How big of rockets are you talking?
Model rockets, scratch built mid-powers, flying Volkswagons?

 

[11bravo]

Originally posted by MarkABrown
With a little 550 cord and some Hundred Mile an Hour tape, one can rule the world!

{Former 11B}

SING IT, BROTHER!!!

Greg

 

[11bravo]

 

[MetMan]

Originally posted by 11Bravo
IIRC, that's the MOS that blows things up!
That could have been fun too.
You haven't transferred any of that knowledge over to rocketry, have you?

P.S. How big of rockets are you talking?
Model rockets, scratch built mid-powers, flying Volkswagons?

Actually, the one thing I remember is the field expedient formula for the amount of explosives you need to blow something up: P. That's it, P. It stands for plenty!

And of course I haven't transferred any knowledge over to rocketry--rocket motors aren't explosives.

The rockets I've used 550 on have been mid-power--a 4XD Big Daddy cluster and a 29mm Estes AMRAAM.

MetMan

 

[DynaSoar]

Originally posted by 11Bravo
Anyway, I'm not sure how it would deal with high temps involved in ejection charges, but would think that the high temp durations would be rather short and that it may hold up.

Any thoughts from folks that are familiar with the material?

It runs about $5-6 for a hundred foot coil so it is fairly cheap if it would work well.

Greg

Shrink tube? Don't know about many repeated ejections, but seems to me it should tighten up until it's as tight as it gets, then just stay that way. I mean, it takes the heat shrinking it. That doesn't ruin it.

As far as the cord, if that's the stuff they use for flares, it should handle the heat fine. Those thing descend through their own "exhaust". The seven lines makes me think it is.

At that price seem like a cheap enough experiment.

 

[11bravo]

I just used the shrink tube to hold the loose (I'll call them) fibers on the end being inserted into the other part.
In the top pic on this page-

https://www.geocities.com/rdh82000/Tips/kevlar.htm

replace the tape and brass tube with my shrink tube.
It also gave something to feed along inside, kind of like a safety pin when trying to feed a drawstring through a sweatshirt hood.

Not sure if that really cleared up what I meant.

Otherwise, trying to push the fast fraying end back into the other part would be like playing pool with a rope cue.

Greg

Edit:
Maybe this describes it better:
In the top pic on the page linked to above, replace the tubular kevlar with 550 cord that has had the seven inner strands removed, the red pen with a golf tee, and the tape and brass tube with the shrink tube.
He fed the brass tube back out, removed it and tucked the loose end back in, I just left it inside. Gotta lump.