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Payload bay nosecone positive retention methods

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Joshua F Thomas

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I launched my new Blue Phoenix Jr. kit this past weekend, on an F42T. The flight was great, with one exception: The nosecone, friction fit to the payload bay, came off and was lost. No recovery.

I had fit that sucker on tight, too. Took some elbow grease to get it on and off. Apparently ejection forces can be enough to drive it lose, so I am now looking into options for securing nosecones to a payload bay that still allow you to remove the nosecone from the payload bay. Any suggestions?

My current thought is to drill two small holes in the far bulkhead of the bay (where it has an anchor for the shock cord) and run another, smaller shock cord through there, with a quick link attachment to the hook on the nosecone.
 

K'Tesh

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A surprising problem for rockets that use a balsa nose block to join the payload section to the body tube is that the gasses of the ejection can flow through the balsa and blow the nosecone off if the balsa is too tight inside the body tube. To remedy this, I glue a piece of paper with my name and email address to the balsa block, then screw in my eyebolt, then back the eyebolt out, give the hole a squeeze of white glue to form the bond with the eyebolt, and seal everything in with super thin CA glue.

To secure balsa nose blocks to plastic payload sections, I use self adhesive paper labels applied to the inside of the plastic payload section, then use white glue to form the bond.
 
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lakeroadster

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I launched my new Blue Phoenix Jr. kit this past weekend, on an F42T. The flight was great, with one exception: The nosecone, friction fit to the payload bay, came off and was lost. No recovery.

I had fit that sucker on tight, too. Took some elbow grease to get it on and off. Apparently ejection forces can be enough to drive it lose, so I am now looking into options for securing nosecones to a payload bay that still allow you to remove the nosecone from the payload bay. Any suggestions?

My current thought is to drill two small holes in the far bulkhead of the bay (where it has an anchor for the shock cord) and run another, smaller shock cord through there, with a quick link attachment to the hook on the nosecone.
(3) Small wood screws.. through the payload bay, into the nose cone, spaced 120 degrees apart.
 

K'Tesh

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If a person were terribly clever, they could use those self adhesive paper labels (attached to the cone, and the inside of the payload bay tube) to form a kind of twist lock.
 

Joshua F Thomas

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Note: The nosecone on this particular rocket is solid plastic. 100g heavy. I'm not sure rivets or screws are going to be a solution here, I'd have to drill into the tough plastic...
 

lakeroadster

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Note: The nosecone on this particular rocket is solid plastic. 100g heavy. I'm not sure rivets or screws are going to be a solution here, I'd have to drill into the tough plastic...
Shouldn't be an issue. Think of them as shear pins. The friction fit of the nose cone into the payload bay really holds the sub-assy. Their sole purpose is to prevent axial movement.
 

JoePfeiffer

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I use either 4-40 screws with a t-nut, or #4 sheet metal screws, holding fiberglass nose cones to payload bays. I don't imagine drilling your plastic nose cone will be an issue.
 

Joshua F Thomas

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The screws are sounding like a good general solution. If I did it right I could get flush ones to reduce drag on the body surface.
 

Jay Dub 4009

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I usually use threaded inserts that get set with epoxy with set screws or counter sunk / pan head screws or sometimes tnuts with screws
 

Brian Johnson

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I launched my new Blue Phoenix Jr. kit this past weekend, on an F42T. The flight was great, with one exception: The nosecone, friction fit to the payload bay, came off and was lost. No recovery.

I had fit that sucker on tight, too. Took some elbow grease to get it on and off. Apparently ejection forces can be enough to drive it lose, so I am now looking into options for securing nosecones to a payload bay that still allow you to remove the nosecone from the payload bay. Any suggestions?

My current thought is to drill two small holes in the far bulkhead of the bay (where it has an anchor for the shock cord) and run another, smaller shock cord through there, with a quick link attachment to the hook on the nosecone.
I use scotch tape easy peel type
20191104_133329.jpg

notice the tape on the red Ascender I've also built a 2.26 beta testing rocket with loc components it has an electronics bay for all the fun stuff nose cone is in as tight as possible and will be taped. It will test the tape method using G80 motor. Remember one test is better than hundred opinions. Hope you have a go day soon!
 
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Kelly

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Set screws, driven through the nosecone and into the bay wall, driven flush with the surface.
 

Nytrunner

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Note: The nosecone on this particular rocket is solid plastic. 100g heavy. I'm not sure rivets or screws are going to be a solution here, I'd have to drill into the tough plastic...
Your 100g cone is peanuts compared to a lot of rockets around here. You'll have to drill for any sort of positive retention. What I wouldn't do is rely on a friction arrangement of any sort.

3 removable rivets like apogee sells (and mcmaster for better pricing) are more than enough to restrain the nose, and you dont have to use a screwdriver to install/remove.

Since the cone (and I assume shoulder) is solid, the above recommendation of some sort of threaded insert is good too. If your plastic is solid, you could potentially just tap the cone itself. Either direct tapping or threaded inserts will require a screwdriver for install/removal, which is one more thing to cart around
 

Joshua F Thomas

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How do the rivets work exactly? You drill into the nosecone and put the rivet holder in that side, and drill through the body tube and use a rivet to hold the two together?
 

Banzai88

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You drill a hole through both parts, then the rivet goes through BOTH pieces from the outside. As the central stem gets pressed down, the 'fingers' expand and friction lock the whole assembly together. To remove, pull the stem, the 'fingers' retract, and you pull the last part out and it all comes apart.

See the pictures and video here: https://www.apogeerockets.com/Building_Supplies/Misc_Hardware/Removable_Plastic_Rivets
 

Joshua F Thomas

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You drill a hole through both parts, then the rivet goes through BOTH pieces from the outside. As the central stem gets pressed down, the 'fingers' expand and friction lock the whole assembly together. To remove, pull the stem, the 'fingers' retract, and you pull the last part out and it all comes apart.

See the pictures and video here: https://www.apogeerockets.com/Building_Supplies/Misc_Hardware/Removable_Plastic_Rivets
So if the bottom item is solid (like my nosecone is) does this still work, or do you have to use a different method? Do the rivets only work if you're drilling completely through two objects?
 

Nytrunner

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So if the bottom item is solid (like my nosecone is) does this still work, or do you have to use a different method? Do the rivets only work if you're drilling completely through two objects?
Normally itd go through 2 relatively thin layers like the tube and shoulder, but I'd bet you could still use them by drilling the normal shank hole in tube and shoulder then expanding the shoulder hole just large enough for the expanded fingers of the rivet.

Alternatively, see my previous post about threaded options
 

bobbyg23

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I use 3 screws on my LOC 4" nosecones. This is my 72" long level 2 rocket.
16066880039604086501733602006923.jpg
16066880301902912389645170779523.jpg
 

RocketTree

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I always use a small shock cord backup on friction fitted sections in case of unanticipated separation.
 

Joshua F Thomas

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So assume that I want to use threaded inserts. What am I looking for? I've not used threaded inserts before. If I was going to use a bolt I'd be looking for something like a 4-40 to be the right size. How do I find the right threaded inserts for those?
 

Nytrunner

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There is about 10 million different options, which is why I came here, to ask people who have done it before :rolleyes:

Knurled? Self-tapping? Brass? Steel? Helical? Tappered?
I misread, it sounded like you were struggling to find inserts that would fit 4-40 threads.

To be honest, just pick one. Do you want lighter weight? pick the one that's lighter material. Don't want to tap? do self tapping, or knurled.

Drill a 4-40 hole through the airframe into the shoulder, drill out the shoulder hole to receive the insert, tap or don't tap depending on what you get, dip in some epoxy, install the inert, let it cure, and you're done.
 

Joshua F Thomas

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I misread, it sounded like you were struggling to find inserts that would fit 4-40 threads.

To be honest, just pick one. Do you want lighter weight? pick the one that's lighter material. Don't want to tap? do self tapping, or knurled.

Drill a 4-40 hole through the airframe into the shoulder, drill out the shoulder hole to receive the insert, tap or don't tap depending on what you get, dip in some epoxy, install the inert, let it cure, and you're done.
My shoulder is plastic (solid urethane). Does this change the type of insert required? From my reading, the knurled are installed via heat application with a soldering iron?
 

Nytrunner

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Where did you get this solid urethane cone? Definitely not a common item

That's a thermoset material, so you'd probably want a press in or self tapping (or tap and use a threaded)
(which also came from a quick google)
 

Joshua F Thomas

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The solid urethane cone is part of ARR's Blue Phoenix / Blue Phoenix Jr Kit. The 38mm size masses about 125g.

Thanks for the info.
 
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