Aero Pack Tailcone question

[duodenumnums]

Hello, I’m about to build a 3” Wildman Shapeshifter with the Aero Pack tailcone (TA5430). The instructions say to protrude the MMT 0.740” but when dry fitting everything, the tailcone won’t screw in completely if I protrude it by that much. Is this going to be an issue? With the tailcone fully screwed in it looks like the MMT should protrude just under 1”.

 

[MolarM]

I am curious of this too (I’m beginning a 3” Darkstar). And what is the narrow ring that sits between the motor mount and the tailcone used for? I don’t have the 54 AT motor case yet, maybe it will make sense when I’ve got all the parts

 

[heada]

Test fit with the motor installed and then glue in at that length. Watch centering rings and through the wall fins so that you don't get unwanted interferences.

There is a lip on the tailcone that should fit inside the aft end of the body tube, watch for that too.

 

[OZRoc]

And what is the narrow ring that sits between the motor mount and the tailcone used for?

Different sized thrust rings on different manufacture motors.

Test fit with the motor installed and then glue in at that length. Watch centering rings and through the wall fins so that you don't get unwanted interferences.

There is a lip on the tailcone that should fit inside the aft end of the body tube, watch for that too.

+1
Cheers

 

[Ronz Rocketz]

Just had dinner with Jim and Becky. I'll forward your post to them. @heada probably answered right.

 

[mtnmanak]

Agreed - you can't just rely on the generic measurements - you need to fit the tailcone retainer to your rocket. I have used these in a few builds. I talked about it a bit in these two:

https://www.mountainmanrockets.com/...-series-builds/4-inch-wildman-darkstar-build/
https://www.mountainmanrockets.com/...r-series-builds/3inch-wildman-darkstar-build/

From that build (photos in the link), here is a checklist of how I fit the retainer to a rocket:
- I tape the retainer body securely to the end of the MMT and then carefully screw on the tailcone cap
- Line the edge of the cap up against the end of the body tube and measure the proper distance to your CRs (to the edges of the fin slots)
- This is the time to ensure your MMT is long enough. MMTs from Wildman come in all different lengths (probably from left over stock in the shop, I would imagine) - sometimes, if they are kind of short, there may not be enough tube length to accommodate the tailcone retainer - determine that now, before you start gluing things and realize the MMT won't reach the end of the fin slots!
- Mark your motor mount tube and tack your CRs in place with a couple drops of CA. This should ensure you have the spacing right, but give you the option to easily break the CRs free if any of your measurements didn't add up.

All are correct on the spacer - it is to accommodate different motor types. However, as long as the tailcone cap engages the motor retainer threads securely, it will work to retain the motor, with or without the spacer. In other words, functionally, the retainer will do its job regardless of whether there is a small gap between the retainer cap and the body tube or if the retainer cap doesn't screw all the way on to the retainer body (but does engage the threads securely). The only time I could see a gap possibly being an issue is perhaps in super-sonic flight, but, even then, it probably would not be an issue (this retainer is not used for minimum diameter flights that go extremely fast). The point of this paragraph is, use the spacer for motors that need it, but, if you find yourself at the field without the spacer, don't worry about it too much - the retainer will still work fine.

 

[duodenumnums]

Agreed - you can't just rely on the generic measurements - you need to fit the tailcone retainer to your rocket. I have used these in a few builds. I talked about it a bit in these two:

https://www.mountainmanrockets.com/...-series-builds/4-inch-wildman-darkstar-build/
https://www.mountainmanrockets.com/...r-series-builds/3inch-wildman-darkstar-build/

From that build (photos in the link), here is a checklist of how I fit the retainer to a rocket:
- I tape the retainer body securely to the end of the MMT and then carefully screw on the tailcone cap
- Line the edge of the cap up against the end of the body tube and measure the proper distance to your CRs (to the edges of the fin slots)
- This is the time to ensure your MMT is long enough. MMTs from Wildman come in all different lengths (probably from left over stock in the shop, I would imagine) - sometimes, if they are kind of short, there may not be enough tube length to accommodate the tailcone retainer - determine that now, before you start gluing things and realize the MMT won't reach the end of the fin slots!
- Mark your motor mount tube and tack your CRs in place with a couple drops of CA. This should ensure you have the spacing right, but give you the option to easily break the CRs free if any of your measurements didn't add up.

All are correct on the spacer - it is to accommodate different motor types. However, as long as the tailcone cap engages the motor retainer threads securely, it will work to retain the motor, with or without the spacer. In other words, functionally, the retainer will do its job regardless of whether there is a small gap between the retainer cap and the body tube or if the retainer cap doesn't screw all the way on to the retainer body (but does engage the threads securely). The only time I could see a gap possibly being an issue is perhaps in super-sonic flight, but, even then, it probably would not be an issue (this retainer is not used for minimum diameter flights that go extremely fast). The point of this paragraph is, use the spacer for motors that need it, but, if you find yourself at the field without the spacer, don't worry about it too much - the retainer will still work fine.

Thanks everyone!

 

[Ronz Rocketz]

Becky Green said the answers to the question of the AeroPack tailcone are correct. You really need to have your motor case first, do a dry fit and use those measurements. The spacer is needed if you're using an Aerotech motor. It should fit like glove when you're done.