Does anybody use swivels, clips or quick disconnects designed for use on key chains? Im asking in regard to mid power rockets in the two pound weight range.
Key chain swivels, clips or disconnects to attach recovery harness
- Thread starter solid_fuel
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I would not use a keychain disconnect personally, but you might get away with it in some MPR. You should look up the specs and shoot for at least 5X the amount of breaking strength as the weight of your rocket. Quick-links are simple, lightweight, easy to find and easy to use.
Ive frequently seen hard deployment forces of somewhere around 30 Gees, meaning design for at least 60 times the weight of the rocket.
If you were to replace the elastic cord in Estes rockets with a length of Kevlar, I would expect you would routinely have forces above 30G during ejection, probably on every flight. It is amazing how strong the ejection charges are on a C6-7.
Because the components are so small and light, the strength of the materials relative to their size is considerable. That is why the Estes rockets can survive the relative large ejection forces.
If you were to put the same forces on a much larger rocket, you would probably have failures more often than not. The larger sizes and weights make the margin of error much lower on larger rockets. You may not have higher forces on larger rockets, but the material strength relative to size is lower.
Because the components are so small and light, the strength of the materials relative to their size is considerable. That is why the Estes rockets can survive the relative large ejection forces.
If you were to put the same forces on a much larger rocket, you would probably have failures more often than not. The larger sizes and weights make the margin of error much lower on larger rockets. You may not have higher forces on larger rockets, but the material strength relative to size is lower.
I dont believe the size (or mass) matters. These forces accompany a chute opening a few seconds away from apogee; not due to the ejection charge, but due to rapid deceleration upon chute opening. The first time I saw it in the data was a relatively small rocket.
That is true, but you have to do more then just scale up the strength of the recovery gear. You also have to adjust and control the force of the ejection. If you don't and just scale up the strength of materials, you will probably have failures because you really can't scale up the material properties.
That's also why God punishes people who don't ground test. :wink:
How many times now have you been punished?
so I am thinking if I can put one end under my boot and pull as hard as I can on the other end it’s probably ok. If it breaks obviously don’t use it.
That is, um, proprietary information.
standard mil-spec boot.
For what it's worth, I have been using these for years, but for keys, not recovery systems. They are miniature Amflo air couplers - they work just like the full size ones. It would be interesting to test and measure their strength. That being said, quick links are hard to beat.
dr wogz
Fly caster
Key chains are less quality & unknown specs.
Using parts off a dog leash would fair better in my opinion, having had some "hi gee" dogs / have put them thru the 'skunk' test.. (Dogs luuuv skunks!!)
fishing gear is next, and with online sales, 100, 200lbs (or higher) snap swivels can be had..
then there's climbing gear, heavy lift gear, etc..
Using parts off a dog leash would fair better in my opinion, having had some "hi gee" dogs / have put them thru the 'skunk' test.. (Dogs luuuv skunks!!)
fishing gear is next, and with online sales, 100, 200lbs (or higher) snap swivels can be had..
then there's climbing gear, heavy lift gear, etc..
Actually, I've found that the split rings are really strong and tend to hold up better then other parts. They are spring steel and quite strong. I have no idea what the ratings would be, but I would trust those before I trusted the disconnect.
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