Chute Release

Discussion in 'Recovery' started by Greg Furtman, Aug 17, 2019.

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  1. Oct 21, 2019 #151

    billdz

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    Wallace, in your other thread, when asked about monofilament, you replied that you had "been experimenting with different materials for a while now, this [2mm elastic bead cord] seems to work better than anything else I've tried." Could you tell us what other materials you have tried? The 2mm elastic cord has worked fine for me but I'm guessing 1mm would be as good or even better, and some are even thinking about 0.5mm elastic.
     
  2. Oct 21, 2019 #152

    Wallace

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    I've basically attempted hair bands, mono filament fishing line, rubber bands and differing diameters of elastic. The 2mm beading cord worked best, so that's pretty much where I stopped. It's a compromise between how much bundle holding power you're comfortable with/have confidence in, and ease of cut (i.e. release).
     
  3. Oct 21, 2019 #153

    billdz

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    Thanks for the reply. The 1mm beading cord looked strong enough to me to keep the chute bundled, but if there's any doubt we should avoid it. I'll be interested to hear how Greg's tests of the 0.5mm cord work out.
     
  4. Oct 21, 2019 #154

    Charles_McG

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    For your tests, did you use only one material at at time? Have you tried 2 materials (like my rubberband with a monofilament fusible link.)?

    I'm starting to think how I might implement my version with a nice wide fabric elastic band with a ring on each end.
     
  5. Oct 22, 2019 #155

    Wallace

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    Charles: I did not, but that certainly sounds like it has potential. How about just using a sacrificial fusible link? I have a spool of it "somewhere" but I'm sure it's too large, as in 14Ga. Or, if I'm reading you correctly, a loop of ,say, monofilament to tie back a rubber band? If so, I like it.
     
  6. Oct 22, 2019 #156

    Wallace

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    Always had a thought about avoiding the elastic tension on the NiChrome wire with a spring clip of some sort also.But...Since what I was using already worked, I never pursued
    it. Well, that and the eMatch version being so simple...
     
    Last edited: Oct 22, 2019
  7. Oct 22, 2019 #157

    Wallace

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    And let's not forget the commercial product either. While obviously not an original idea, it is a good design. If you want to spend money in lieu if experimenting or designing your own device I'd highly recommend it.
     
  8. Oct 22, 2019 #158

    billdz

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    That's interesting. It is the tension that causes the nichrome to break. The glass backing and every other "tension free" setup I've tried has not worked. That's why I'm going with the high tension, single use arrangement, at least for now.
     
  9. Oct 22, 2019 #159

    Wallace

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    May very well be why I didn't go that route. Once again, the Ematch version is absolutely foolproof, no need to deal with NiChrome wire at all and can easily be made redundant. Only downside is the need for an Ematch which adds cost.
     
  10. Oct 22, 2019 #160

    Charles_McG

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    Let's see if I can attach pictures from the old (2015) post...

    I put two fishing line hardware rings on my rubberbands and tie monofilament between them.
    View attachment 275903

    In use, I double up the rubber band so it stretched sideways around the chute bundle and the monofilament makes the circle (under tension). The rubber band doesn't go all the way around.
    The nichrome gets two wraps around the monofilament and each end goes into the terminal block. No tension on the wire at all.
    View attachment 285546
     
  11. Oct 22, 2019 #161

    Wallace

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    The rings are to take the strain off the mono/rubber band junction?
     
  12. Oct 22, 2019 #162

    Wallace

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    I hate to keep reiterating, but..the eMatch/elastic system is orders of magnitude cheaper, easier, and more reliable. But I've also always been a fan of anything Rube Golbergian..
     
  13. Oct 22, 2019 #163

    Charles_McG

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    That and they give a handy place to tie a tether to, so I don’t loose the rubber band each time.
     
  14. Oct 22, 2019 #164

    billdz

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    Wallace, are you now using Ematches? You are the one who got me started with the nichrome system. I have found the nichrome to be very reliable, in single use configuration. You are right that Ematch instead of nichrome is foolproof, although if you're using both an altimeter and an Ematch why not just do traditional dual deployment?
     
  15. Jan 30, 2020 #165

    Kelly

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    In these systems you guys are building... is the altimeter exposed to the first (ejection) charge? Or is it somehow isolated in an ebay?
    What I'm concerned about, is whether exposure to the high pressure 'pulse' from the ejection charge would damage the baro sensor on the altimeter? Or do you use this just like a JLCR, and just put it (the altimeter) in the same compartment as the parachute?
     
  16. Jan 30, 2020 #166

    John Beans

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    As far as I know, all modern pressure sensors can withstand ultimate pressures waves much higher than an ejection charge in a normal rocket can produce. A rocket with press fit or even shear pin assembly cannot support a large amount of internal pressure.
     
    jim_kc, ebruce1361 and Kelly like this.
  17. Jan 30, 2020 #167

    Kelly

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    Thanks, John!
     
  18. Jan 30, 2020 #168

    Greg Furtman

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    It would probably just needed to be in a protective pouch . Here's another thread you can look at.

    https://www.rocketryforum.com/threads/quantum-based-hotwire-chute-release.141642/#post-1713016
    Watch the video.
     
  19. Jan 30, 2020 #169

    Kelly

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    Yeah, protective pouch or something for sure - it definitely needs to be protected from flame, hot gases/particles, corrosive byproducts, etc. But a soft shell pouch wouldn't protect from the pressure pulse. John's info indicates these are more robust than I expected.
     
  20. Jan 30, 2020 #170

    Greg Furtman

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    And remember that the protective pouch will be above the dog barf & parachute are below it so it should be pretty well protected. :)
     
  21. Jan 31, 2020 #171

    billdz

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    Glad to see this thread has been resurrected, my device is still working (knock on wood). Greg, did you get yours working? Wallace, Charles, anything new?

    Kelly, my altimeter is enclosed in a piece of body tube, with the bushing/heating element attached to the outside of the tube, which is tethered to the chute in the same manner as a JLCR. Wallace has his altimeter in an e-bay or nose cone, and he runs wires from the altimeter down to the bushing with the heating element.
     
  22. Jan 31, 2020 #172

    Greg Furtman

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    billdz, I haven't worked on it lately. Too many other things that needed to be dealt with. I'll try to geet back on this soon.
     
  23. Jan 31, 2020 #173

    ebruce1361

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    I too, had to put my projects on hold. Mostly to accommodate the hubbub of the holidays with family visiting from out of state, etc. I actually have plans to get back to work on my electric cigarette lighter version this weekend as well as some other electronics projects with some parts I just ordered. Stay tuned!

    By the way, the video I posted a few months ago is no longer available because I moved it to a new youtube channel dedicated for rocketry. If anyone wants to check it out, my channel is called B.F.R.A (Bruce Family Rocketry Adventures). Any additional videos pertaining to this project as well as flight videos are located there.
     
  24. Jan 31, 2020 #174

    Wallace

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    I've used a simple short piece of BT taped to the shock cord a few times and it worked fine. Until I stupidly got in a hurry and grabbed the nearby roll of blue masking tape instead of walking "all the way" back to the truck for electrical tape. Never saw that setup again....
     
  25. Feb 1, 2020 #175

    billdz

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    Looks like my "knock on wood" in post #171 did not work, I've just experienced my first issue with the device. I was doing a bench test, the nichrome wire got hot as usual, but ... this time the 2mm cord failed to break! Repeated the test twice more, same result. I don't get it, it had never failed before, now 3 fails in a row (thankfully on the bench, not in flight). Maybe the cord hardens somehow over time?
     
  26. Feb 1, 2020 #176

    Kelly

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    Maybe your battery isn't putting out the same amount of juice?
    If it were me (and I think I will build one of these this summer) I would tie a piece of monofilament onto the cord, and use the nichrome to melt the monofilament, not the elastic.
     
  27. Feb 1, 2020 #177

    Greg Furtman

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    What kind of battery are you using? I know some things for me are getting harder over time. :p
     
  28. Feb 2, 2020 #178

    ThreeJsDad

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    You guys have inspired me SO much, and yesterday I had what I believe is an Epiphany. I think I have a system that will be super reliable and easy to set up. The same design can be used to cut the rubber band or to simply as a release mechanism.

    I will shoot some pics later but here is the basic concept.

    I made a charge using a Christmas bulb. I soldered my lead wires to the bulb and then cut the end off the bulb with a diamond cut off wheel. I then filled the glass tube with hand ground Pyrodex. I then wrapped the whole vial with a couple of layers of masking tape. I twisted the end of the tape to seal it off.

    This charge ended up at .25" which fits perfectly inside a tube I already have. I have another tube that fits perfectly over the first. I am sealing one end of both tubes with JB weld. The plan is to drill a hole in the end of the smaller tube for my wires, put the charge inside and put the larger tube over the smaller tube.

    If we GRIND a hole in the outer tube and the inner tube we will have very sharp cutting edges to thread our band through. When the charge fires it will cut the band quite easily. I say grind the hole as opposed to drilling because it will give us a better cutting surface. Just remember to make a tether system so the parts don't get lost.

    An alternate method would be to simply tie the band to the outer tube and the inner tube. When they separate the band opens and the chute opens. This system is easily repeatable. We could have bands made up for each of our rockets and simply move the altimeter from rocket to rocket by attaching it to the shock cord.

    The charges are stupid simple to make and can easily be made up in advance. I like the idea of the charge being self contained so they just drop into the mechanism. This removes the fuss of measuring and filling at the field. This will also make it very consistent and reliable.
     
    Last edited: Feb 2, 2020
  29. Feb 2, 2020 #179

    rcktnut

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    Do you mean something on the order of these? https://aeroconsystems.com/cart/launch-recovery/cable-cutter-by-archetype-rocketry/
    https://fruitychutes.com/buyachute/...cketry-piranha-cable-cutter-2-pack-p-280.html
    Christmas tree bulbs have been used in the past to ignite deployment charges, proving to be not the most reliable method now available.
     
    Last edited: Feb 2, 2020
  30. Feb 2, 2020 #180

    ThreeJsDad

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    Exactly !! See what happens when one leaves the hobby for a while...LOL

    The Christmas bulb did indeed prove to be problematic in my tests. I would be very interested in a home brew ignition source that is reliable.
     

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