Aero Pack tailcone retainer questions

Gentledudes,

I'm building a Wildman Extreme for my L3 project (4" body/75mm motor). I am planning on using the Aero Pack tailcone retainer (because it looks so bitchin') and have a couple of questions before I break out the JB Weld

(1) I'd like the option to fly 54mm motors to keep the altitudes reasonable for our regular field. Aero Pack makes a 75-54 adapter, but they weren't specific about whether it would work with the tailcone retainer. Does anyone have experience with this?

(2) If it is possible to use the adapter with the tailcone, could I also use it along with my 75mm CTI cases to dry-fit the tailcone to the motor tube before I glue it up? I left the motor tube a bit long and will trim it to the proper length when I've got a motor (or motor/spacer combo) to make sure it fits properly. I would like to avoid buying the 75mm case (and motor in a cert special) until this summer, when I can get to fields where M's make sense in this rocket.

Any/all advice appreciated, thanks!

Yes it will work. I can attach some photos tomorrow showing exactly what it looks like on one of my rockets.

First, the adapter works perfectly with the tail cone.

Secondly, I very strongly recommend mocking it all up with the case. I did mine without, and i needed to massage the spacer ring a little.

I don't have exactly the same hardware (38mm to 3" tailcone retainer with a 29mm adapter), but at least in the size I do have the adapter works just fine with the tailcone. I dry fitted with my 29mm case in the adapter, since I didn't have the 38mm stuff yet at that time. I dry fitted the retainer such that I could set the tailcone installed depth, so that I made sure it came up flush with the rear of the body tube while I was installing the motor mount. Once that was set, I pulled the dry fit parts off so I could install the fins and so forth. I'm not sure how helpful that is, but at least indicates that what you'd like to do should work...

I second everything said. Be sure to mock up before building to ensure proper depth of MMT

The 4" to 75mm tailcone needs careful measuring / alignment, because the screw on tailcone also acts as a thrust ring, snugging up to the outer airframe. Second, the 75 to 54 mm adapter is completely different than the smaller 38 to 54 mm design. If you build with a 75 mm case for alignment it will be fine.

I'll add to the chorus of your adapter will work. I have a 4" to 54mm tailcone and adapt it down to 38mm no problem.

I posted some general tailcone info here: https://www.rocketryforum.com/showthread.php?130923-Woferry-you-asked-about-Aeropack-tail-cones

Worsaer said:

The 4" to 75mm tailcone needs careful measuring / alignment, because the screw on tailcone also acts as a thrust ring, snugging up to the outer airframe. Second, the 75 to 54 mm adapter is completely different than the smaller 38 to 54 mm design. If you build with a 75 mm case for alignment it will be fine.

Click to expand...

What Bill said is exactly right. I wrap the motor and thrust ring/aft closure on the motor with tape until it fits snugly into the male portion of the retainer so they are completely concentric with each other.


Steve Shannon

At the risk of providing way too much information, here is how it all fits together.


First of all, the 4" to 75mm tail cone is indeed very cool. I went with this as a natural choice for my scratch Black Brant II.


Here is the base adapter with adhesive on the 75mm motor mount tube.





Notice there is a small lip on the tail cone that will mate with the body tube as you tighten it down. This is where the tolerance / length of your motor mount is key. If it's too long, your thrust will not be conveyed to the body tube, and you'll have an awkward gap. Too short, and you may not engage the threads sufficiently.




Here is it fully seated...




Now for the 75mm to 54mm AeroPack adapter. As you can see, you get three pieces. One slides over the motor and snugs down as a clamp with an allen key. The second also slides over the motor, and engages the aft closure. The last one is a fancy washer that engages the aft motor closure in the retainer cap (in this case the tail cone cap.)


A close up of the split ring that uses an allen key to tighten on the motor case.



Here's an exploded view of how it goes together on a 54mm case.


And finally a view of the aft end with the 54mm motor and adapter installed.

Awesome info, thanks everybody! And especially to Bill for those pics.