Retaining threaded rod in plastic nose cone

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I am looking for suggestions for a way to mount/retain a threaded rod inside a 5.5 inch plastic nose cone. The threaded rod will be used for an adjustable nose weight system and possibly an avionics/GPS sled.

I have previously used John Coker's brass rod technique to retain nose weight and it worked really well.
John's Nose Cone Mods

I am wondering if John's technique could also be used to retain a threaded rod that is epoxied into the tip of the nose cone. Possibly using 4 brass rods that are spaced wider apart so the threaded rod can fit through the middle.

I have sketched what this would look like.

UBL3-Nose-Cone.png


Front end detail:
UBL3-Nose-Cone-Tip.png


Rear end detail:
UBL3-Nose-Cone-Base.png


Has anybody tried something similar or got a better idea for securely mounting a threaded rod?
 
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Please forgive my ignorance, but why? Not once in all my years have I ever put weight in the nose of my rockets.
 
I've thought about doing something like this several times, but then I think about the possibility of the rocket coming in ballistic, and nothing but a thin shell of plastic between a steel rod traveling hundreds of MPH and whoever/whatever it's pointed at, and I decide against it.

My best alternate solution to date is using large steel washers (which settle in the nose so they don't move side-to-side), and something like a pool noodle cut to length in between the washer(s) and the NC base to hold them in place.
 
I've thought about doing something like this several times, but then I think about the possibility of the rocket coming in ballistic, and nothing but a thin shell of plastic between a steel rod traveling hundreds of MPH and whoever/whatever it's pointed at, and I decide against it.
Is that really different from an aluminum tip of an FG nose cone coming in ballistic?
 
In ballistics, an important concept is "sectional density" (SD). This is the mass of the projectile, divided by its cross-sectional area. The SD, along with velocity, determines how well a projectile can penetrate. So a heavy, thin object - like a 12" long steel rod, coming in lengthwise - has a huge SD. An aluminum tip - which probably weighs much less, due to the size of the tip and density of aluminum - and has a wider cross section (well, once you get past the point!) probably has a much lower SD. But, there's people here who will claim that aluminum tips are unsafe, too; and I think there are ranges that ban them.

I don't think aluminum tips nor steel rods violate any safety codes, so I'm just stating my opinion: Steel rods in nosecones give me the willies. They're not so bad in bays, where at least you have a significant 'crumple zone' between the rod and the target.
 
Yeah, we might be debating different levels of "dead". :oops: You're not going to survive a rocket coming down on your head, whether it has steel rods or not.
But, there's also the issue of a nosecone coming down ballistic by itself - a FG NC alone might not be so bad, but with a steel rod in it, could be a different story. Land sharks come to mind also. 🤷
 
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Yeah, we might be debating different levels of "dead". :oops: Your not going to survive a rocket coming down on your head, whether it has steel rods or not.
But, there's also the issue of a nosecone coming down ballistic by itself - a FG NC alone might not be so bad, but with a steel rod in it, could be a different story. Land sharks come to mind also. 🤷

I mostly agree.

This is a 20lb rocket so if the whole thing comes in ballistic the inclusion of a single threaded rod is not going to change anything.

I guess an empty nose cone coming down ballistic by itself is "less bad", but it could still be traveling incredibly fast.

This rocket will have dual deploy with a primary and back up altimeters, so 4 chances for a chute to deploy.

The Apogee newsletter 329 has instructions for installing 2 threaded rods with an air cavity at the tip of the nose cone. This is a sort of crumple zone, but it is suggested as a way to reduce the amount of epoxy (and weight) required rather than as a safety feature.
Screen-Shot-2022-04-15-at-7-20-12-am.png
 
For those worried about a metal rod, don't use one. Use a nylon threaded rod instead. You can affix it into the nose cone the same as a metal rod (epoxy and cross rods - I don't use brass, just 16 penny nails that I drill holes for, insert, then cut off the ends with a Dremel) and can still add washers for weight and hold them in place with a nylon nut).
 
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