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LOC Vulcanite - failed ground test.

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DavidMcCann

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Well. That's one way to skin a cat.

3 2-56 nylon shear pins.
3 rivets, without push pins installed. <--- failure.




[YOUTUBE]Ix8nnMiE36M[/YOUTUBE]


So, gonna recut a new payload tube and try that with a friction fit nose and the pins installed. That's 1g BTW, and seemed fairly stout.
 
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astrojase

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Well. That's one way to skin a cat.

3 2-56 nylon shear pins.
3 rivets, without push pins installed. <--- failure.
Sorry to see that happen, it is why we ground test though! IMHO your failure analysis should be the other way around, that is, the 3 shear pins in the nosecone probably caused the failure - not sure you need that many, in fact, I reckon you could get away with friction fitting something that size. I regularly fly four and six inch fibreglass airframes and have only ever needed 1 shear pin in the nosecone.
 

DavidMcCann

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Sorry to see that happen, it is why we ground test though! IMHO your failure analysis should be the other way around, that is, the 3 shear pins in the nosecone probably caused the failure - not sure you need that many, in fact, I reckon you could get away with friction fitting something that size. I regularly fly four and six inch fibreglass airframes and have only ever needed 1 shear pin in the nosecone.
Well, had I fully installed the rivets, the shear pins may have popped. But looking at it now, I agree. little tape on the nose and it'll be good to go.


Why didn't I install the pins? Yea, i'm wondering that too. We'll go with stupid and lazy for now.
 
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Buckeye

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I love the audible sigh at the end of the video.
 
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cbrarick

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I fly the same rocket - a lot. I just use friction fit, even with the J600.
 

ksaves2

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One gram of powder? Wow. I epoxy a thin little steel plate on the forward end of the shearpin hole in the thin walled cardboard tube to assist with "shearing"
and tailor the NC shoulder to allow for it. Two should be enough.

The deal with the NC shearpins is one wants to prevent an apogee deployment of the main recovery laundry of a high flying rocket period. If the apogee charge
is a little "robust" and the recovery package slides easily in the tube, the momentum of the drogue/apogee deployment could cause the main chute to push off the nosecone.

All's you have to do is lose one pricey rocket with a lot of hardware to an unintended apogee main deployment and you'll rethink your strategy.

I heard many a lamentation from fliers who lost rockets in that fashion and I started with shearpins early on when I started out.

Sure, if you have a DD that doesn't go that high, can normally see all the events and you can "tolerate" a main at apogee, by all means friction fit.
If you can tolerate a farther walk to recover, fine. If your DD rocket is going up to "outta sight" land for a bit of time, don't have a tracker and count
on being able to get a visual as it's coming down fast, you could lose it as it starts drifting and you can't get a visual on it if it's main at apogee time. You got a tracker? ok that'll help. If it's a GPS tracker you'd be in a better position especially if following the rocket on a real time map. Then again, could end up to be a long drive. Better to prevent an adverse event than have to resort to a backup and perhaps laborious tracking plan.
Kurt
 

cbrarick

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All's you have to do is lose one pricey rocket with a lot of hardware to an unintended apogee main deployment and you'll rethink your strategy.

I heard many a lamentation from fliers who lost rockets in that fashion and I started with shearpins early on when I started out.

Sure, if you have a DD that doesn't go that high, can normally see all the events and you can "tolerate" a main at apogee, by all means friction fit.
If you can tolerate a farther walk to recover, fine. If your DD rocket is going up to "outta sight" land for a bit of time, don't have a tracker and count
on being able to get a visual as it's coming down fast, you could lose it as it starts drifting and you can't get a visual on it if it's main at apogee time. You got a tracker? ok that'll help. If it's a GPS tracker you'd be in a better position especially if following the rocket on a real time map. Then again, could end up to be a long drive. Better to prevent an adverse event than have to resort to a backup and perhaps laborious tracking plan.
Kurt
Golly, sorry the friction fit camp got you upset. It does work, though. just like using sheer pins you gotta know what you're doing to get good results.
I've never put mains at apogee on that rocket, even with the J600 or the J530. Of course I've only gotten that rocket up about 7600 feet.

My main point is to follow your bliss, just be good at it before you go very high.


ps your use of metal to help is a well thought out plan and I'm sure you get the same result every time. That's the important thing. on my bigger projects where I feel compelled to use sheer pins I tend to put the hole thru the metal & I use aluminum flashing. just a little different technique, same results :>
 

cbrarick

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Just noticed....Hey Dave, why is there blue tube on a LOC kit??????
 

ksaves2

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Golly, sorry the friction fit camp got you upset. It does work, though. just like using sheer pins you gotta know what you're doing to get good results.
I've never put mains at apogee on that rocket, even with the J600 or the J530. Of course I've only gotten that rocket up about 7600 feet.

My main point is to follow your bliss, just be good at it before you go very high.


ps your use of metal to help is a well thought out plan and I'm sure you get the same result every time. That's the important thing. on my bigger projects where I feel compelled to use sheer pins I tend to put the hole thru the metal & I use aluminum flashing. just a little different technique, same results :>
No, friction fit doesn't have me in a "foul" mood. One simply needs to assess what risk they are willing to take. Agree with you on that point. When someone loses $700.00 worth of hardware from a friction fit failure you have to consider if you feel lucky about it for the project at hand.

I had a friction fit failure that saved a fincan on a single deploy rocket. Grease oozed into the ejection charge well unbeknownst to myself and the scratch
four inch diameter LOC tubed rocket was coming in ballistic nose down. The Covert parachute slid down inside, knocked the nosecone off, chute came out,
exploded to shreds, zippered a fair portion of the body tube and knocked the fincan sideways. Rocket landed horizontally flat in mud and the fincan was nicely
intact. Did a coupler repair, constructed an ebay, main chute bay and the rocket lived on as a dual deploy. Kurt
 

ksaves2

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Just noticed....Hey Dave, why is there blue tube on a LOC kit??????
Not Dave here but perhaps the OP substituted materials to try it out? Mild kit bash? Kurt
 

DavidMcCann

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Had a bluetube av bay for some reason.... wound up on this by being available. fit is good to the booster. The spare 54mm tube I got for the payload is a little wobbly.
 
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