Monday, May 31, 2010

3" nose cone with avionics bay

I needed to add 22 oz of lead shot nose weight into Der Red Mix's nosecone today but only had one ($30 spendy!) tube of 3M DP 8005 adhesive. It's the only material I know of that will stick stuff to polyethylene at room temperature. [Maybe I'll try this much cheaper stuff next time]. Once you pop the adhesive tube open it also doesn't store well so I planned to use it all today. This forced me to start another project that's been sitting in my mind recently to best use the 8005.
For some time now I've had this Public Missiles Ltd. screw-cap assembly (search the page for RETAINERCAP) for their CPR3K electronics mounting system. I've been wanting to put that on a length of 38mm tubing and place the whole thing into 3" nosecone to enable electronics in a stubby 3" rocket w/54mm motor mount. That came together quite easily today and here are the progress photos.
Here I've used my bandsaw to cut off the mounting features from the nosecone base, cut a 38mm hole, and six outer holes through which to thread the Kevlar™ mounting cord. I think this pattern should add margin to an already pretty tough structure:
Here I've test-fit the retainer cap assembly on the length of 38mm BlueTube.
This shows the relative length of the two parts. The tube seats perfectly in the narrowing region of the nosecone interior:
This is what the assembly will look like when prepped for launch:
Here I've dumped 7 oz of lead shot + 8005 adhesive into the nose tip, added more 8005 to the interior, placed the tube down in there, and more 8005 at the tube/base/cone interface to hold it all together:
Everything's curing overnight now.

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