Estes Doorknob/Big Daddy Nosecone with integrated Ebay

The 3-in Doorknob Nosecone Ebay Upgrade!

Introduction:

This model is an upgrade to the Estes 3-in Doorknob and to my 3-in Doorknob Builders Kit.  It includes the ring that will fit inside the shoulder of the nosecone, the ebay sled, and as a bonus… a replica Doorknob nosecone with the ring integrated.

Each model was build using Fusion360 and was inspired by the IPL 4-in version.  I now use this on every one of my models from BT60 to 4-in.  It's a brilliant design.

The nosecone was inspired by the model by Arogen67's Big Daddy Nosecone model.  

Usage:

• To use the ebay and ring in an existing nosecone, use the body tube as a guide and slip the nosecone down until the sides no longer slant.  you won't need the shock cord mount. 
• Mark the circumference of the shoulder with a sharpie or pen.
• Using a band saw, hack saw, or dremel, cut the bottom part of the nosecone off and discard.
• Take the printed ring and insert it into the new opening.  The fit will be snug.
• Glue with epoxy - CA Glue is garbage for shearing strength and this is where the shock from parachute inflation and the ejection will take place.  
• Rough up the inside of the nosecone and the outside of the ring with 120 grit and glue in place
• The epoxy may squeeze out, so either coat the ring threads with grease/oil or be sure to clean it off with IPA.
• The middle hole on the bottom of the ebay sled is 6mm so a ¼-in x 20 eyehook will fit perfect
• The two lateral holes are for venting and/or routing e-matches for electronic deployments 
• This is a ¼-in hole on the top of the sled.  You can use this to hang additional items off the sled.  I attached all thread to it and added weight so I could adjust the Center of Gravity to my specified configuration.
• The included nosecone already has the ring integrated in it, so you don't have to chop up your Estes nosecone.  

I printed mine in PETG at 0.2 resolution on a 0.4 nozzle with 100% infill.  It adds a bit of weight to the model but the weight is in the right place, and since the shock cord will be attached to the sled, I wanted mine to be very strong.  In fairness, you could probably get away with 50% infill but your mileage may vary.

Please feel free to download, print, modify, remix this as you see fit.  Just please provide attribution if you publish it.

This model will only fit Estes 3-in tubes unless you modify them in your slicer.  While I have flown this model several times, and have tested its durability and usage,  I am in no way responsible if things go south for you.  Please use caution and ask for help if you are not absolutely sure of what you're doing.

Hobby Rocketry is a fun and exciting hobby but it's still rocket science.  Have fun and be SAFE