Extended AFT Closure Idea.

[TimothyG]

I've been frustrated with the aft closure on CTI 54mm motors due to my inability to think of a way around the externally threaded tube with the closure I can't make work without a thrust ring. I had an idea for an extended AFT closure that I thought I'd propose and let others take the idea and run. What if a Stepped closure was created that turned a 6 grain into a 6XL or a 5 into a 6 or 6XL. The idea is that the after closure be made to still possess the thrust ring and thread onto existing casings, however, now there's a step-down zone to motor diameter that can be utilized as an interstage matting device. This would allow for some very efficient flights using CTI's big long burn motors in 54mm with an efficient and lightweight mating system. I'll have a drawing of what I'm proposing in the next couple of days but hopefully, this gets some people thinking about a really cool aft closure that opens CTI 54mm hardware up to some pretty crazy two-stage projects.

 

[TimothyG]

Something like this that replaces the aft closure basically extending the usage of a shorter case to a longer motor. In combination, you end up with a wonderfully consistent surface to join the interstage to the sustainer on CTI's long burn motors.

 

[PayLoad]

Idea is valid, but Unfortunately, you would then have a non-approved, experimental motor.

 

[cerving]

I've seen people turn down the thrust ring to make the motor case act as a coupler... don't know if that makes it EX, though. I've heard that it does not; and gluing a switch band to the outside of a motor case is definitely an allowed "modification", similar to adding a masking tape thrust ring.

 

[TimothyG]

I've seen people turn down the thrust ring to make the motor case act as a coupler... don't know if that makes it EX, though. I've heard that it does not; and gluing a switch band to the outside of a motor case is definitely an allowed "modification", similar to adding a masking tape thrust ring.

That's a helpful solution for another one of my projects but CTI's 54mm aft closure precludes the use of a turned down closure in this manner. It's a shame because they have a wonderful selection of high-performance long burn motors and I have a strict policy of not exceeding 20G's of acceleration on my sustainer.

 

[cerving]

Yeah, that outside threads pretty much make that a no-bueno. It works with their other hardware, though... and with all of the AT hardware.

 

[jimzcatz]

I'm having a hard time understanding exactly what you want to do and why you can't.

 

[TimothyG]

I'm having a hard time understanding exactly what you want to do and why you can't.

I make the sustainer motor extend out of the airframe and use the motor as my interstage connection point for min dia two stages.

 

[jimzcatz]

Ahh, got it.

 

[T34zac]

It’s an interesting idea, and might be doable if you have a place to fly EX.

However you’d need to seal those threads so the motor doesn't leak at all. Your design puts the o-ring from the nozzle carrier past the threads and therefore turns those threads into a potential problem zone.

 

[blackjack2564]

You mean like this...

6xl clone with recessed closures and head end ignition.
It was easier just making the whole shebang, than modifying existing.
For a 54 minimum sustainer to 75mm booster, based on same type closures they use on CTI 75's and 98's. If u can make the extension, u certainly can make a new motor case.