Page 1 of 1

CTI 38mm Tailcone

Posted: Sun Aug 16, 2020 1:48 pm
by SpaceManMat
There was a thread on TRF where a claim has been made for a I record. One of the things I noticed was the addition of a TC to the 38mm CTI I216 motor. I posed the question as to if this could be considered a motor modification under TRA rules, so I’ll ask here as well for an AMRS clarification.

https://www.rocketryforum.com/threads/e ... st-2032965

It looks to me that there are 3 parts to this modification:
1. Extension to the thrust cone
2. Addition of tail cone
3. Reduction of the OD finger tightening knobs.

It’s the first part that I’m particularly concerned about.

Re: CTI 38mm Tailcone

Posted: Sun Aug 16, 2020 5:03 pm
by Aquaman33
I'm not familiar with the rules, but if I was writing the rules I would say that bonding anything to a motor closure is a motor modification.

But its a great rocket.

Re: CTI 38mm Tailcone

Posted: Sun Aug 16, 2020 5:54 pm
by SpaceManMat
Aquaman33 wrote:I'm not familiar with the rules, but if I was writing the rules I would say that bonding anything to a motor closure is a motor modification.

But its a great rocket.

The major concern is does it effectively de-certify the motor. This could be a safety issue it could also potentially alter the thrust of the motor, making it experimental under TRA rules, but illegal in Australia.

Re: CTI 38mm Tailcone

Posted: Tue Aug 18, 2020 4:36 pm
by drew
If you do a bit of digging in TRF looking at posts from Crazy Jim on this topic he and Charlie Ogino did this YEARS ago (2015?) and it was a "certified" modification in CTI's eyes. IIRC that would have been the rocket you can just see on the Tripoli Single motor altitude records page, entry 43.

I can't recall the specifics but yea, it wasn't considered a show stopper then.

*Edit* now that I've actually read that guys post I actually think this is a better approach when compared to what Crazy Jim and Charlie did with Charlie's I record flight. They sanded down the OD finger knobs until they were uniform with the rest of the tailcone and sanded it to a taper. This most recent modification seems to add more nozzle but doesn't appear to have cut significantly into the disposable rear closure. I can't think it's much different from what Nic L. did on his O record flight as it's effectively an addition of a tailcone on an already stock rear closure.

Re: CTI 38mm Tailcone

Posted: Tue Aug 18, 2020 5:01 pm
by Steve Shannon
SpaceManMat wrote:
Aquaman33 wrote:I'm not familiar with the rules, but if I was writing the rules I would say that bonding anything to a motor closure is a motor modification.

But its a great rocket.

The major concern is does it effectively de-certify the motor. This could be a safety issue it could also potentially alter the thrust of the motor, making it experimental under TRA rules, but illegal in Australia.

I don’t believe bonding something to the aft closure would be considered a modification. It doesn’t weaken the aft closure.


Sent from my iPad using Tapatalk