Modular Avionics Bay for 4-inch Nose Cones

I created this av-bay system for the nose cone on my 4-inch Mega der Red Max - a recreation of the Estes rocket.

It has a robust hasp for taking a shock cord (though the pictured attachment is just a leash - my cone is rigidly attached to the top of its body tube with 1/4-inch removable plastic push-rivets.

This system includes sleds for the EggFinder Mini GPS Tracker, the Eggtimer Quark 2-event Altimeter, and the Eggfinder TRS flight computer (which puts the GPS and Altimeter on one board). There's also a blank plug, which you can also use as a starting point for your own devices.

I've provided a cut-sleeve guide, for removing the original bottom of your nose cone, and a drill guide, for drilling your cone for the attachment screws.

I printed with PETG, and try to print to use the minimum of support. I like to use M3 allen screws for board-to-sled attachment, where I can. This design does not include screw inserts: you're cutting your M3 threads in the plastic. A washer set is provided in the STLs for some handy parts for fitting. The hasp attaches to the base with machine screws, and I use flat-head screws to attach the base to the nose cone.

You can use the cut sleeve on the base of the cone to mark the cone for cutting. Slide the sleeve on, press it to the shoulder, and draw a line around the bottom of the cut-sleeve, where you'll cut off the bottom. This sleeve was designed particularly for the Estes Mega Der Red Max nose cone. You may have to modify, or tape-down the cut sleeve on your cone.

Once you've cut the cone and printed that base, you'll need to drill the bottom of the cone for attaching flat-head screws. Place the av-bay base in the cone, and slip the drill guide over the bottom of the cone, lining up the points of the triangles on the drill guide with the notches in the av-bay base. Then, after making sure your drill guide and av-bay base are aligned exactly as you want, mark each place where a screw hole needs to be drilled, using a Sharpie or pencil, as you prefer.

Print the sled mount(s) that you want to use, or use the sled plug to design a new sled.

Be careful in designing a sled, that you leave enough clearance to get the complete board through the hole, and snapped in place. The fit can be unexpectedly tight, especially if you accidentally design a sled that would need to be bent to actually fit inside. Good luck!