Changes in CTI Pro54 plugged forward closures

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plugger

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As mentioned in a previous thread a couple weeks ago I flew a L935 which uses a Pro54 6-GXL casing. All Pro54 6-GXL reloads are listed as plugged on CTI's website. That said, the CTI Pro54 L935 motor I flew, whilst being labelled as a plugged motor, actually WASN'T plugged, much less threaded. Historically CTI Pro54 plugged forward closures had a threaded insert for positive motor retention and were plugged (as in, the forward closure was fully sealed from the combustion chamber).

The forward closure that came with my L935 had a circular cardboard insert with the letter "P" written on it over what should have been the threaded insert. I carefully removed the cardboard insert and was quite shocked to see an empty charge well and the top of the smoke grain. I was able to work around this and effectively threaded the forward closure to my motor retention point but I thought this might be something worth mentioning to the community. For the record it also appears that CTI have added a second O Ring to the forward closure of some of their 54mm motors. Maybe this is due to the K300 CATO issues? Regardless, ideally I would prefer to know about these changes before I'm on the flight line. Is this sort of thing documented anywhere?
 
As mentioned in a previous thread a couple weeks ago I flew a L935 which uses a Pro54 6-GXL casing. All Pro54 6-GXL reloads are listed as plugged on CTI's website. That said, the CTI Pro54 L935 motor I flew, whilst being labelled as a plugged motor, actually WASN'T plugged, much less threaded. Historically CTI Pro54 plugged forward closures had a threaded insert for positive motor retention and were plugged (as in, the forward closure was fully sealed from the combustion chamber).

The forward closure that came with my L935 had a circular cardboard insert with the letter "P" written on it over what should have been the threaded insert. I carefully removed the cardboard insert and was quite shocked to see an empty charge well and the top of the smoke grain. I was able to work around this and effectively threaded the forward closure to my motor retention point but I thought this might be something worth mentioning to the community. For the record it also appears that CTI have added a second O Ring to the forward closure of some of their 54mm motors. Maybe this is due to the K300 CATO issues? Regardless, ideally I would prefer to know about these changes before I'm on the flight line. Is this sort of thing documented anywhere?

Not that I know of. NFPA 1125, requirement 8.1.6, requires manufacturers to report any post-certification changes to a motor’s design or chemical composition (which exceed manufacturing tolerances) to the testing organization that certified it. We have been emphasizing this lately and more changes have been reported. None of the changes that have been reported should have triggered re-testing.
I could understand a manufacturer arguing the the inclusion or exclusion of a threaded insert in the forward closure would have no effect on the performance of the motor.
 
AFAIK some of the 6XL plugged motors have never included the threaded insert. I've only ever seen the insert on K300s but I haven't flown one in several years.
 
AFAIK some of the 6XL plugged motors have never included the threaded insert. I've only ever seen the insert on K300s but I haven't flown one in several years.
Interesting, thanks Mike. From my perspective I have seen K300s both with and without the threaded insert. I flew one ~6 years ago at Balls23 and it didn't have the threaded insert and I instead used an AeroPack internal motor retainer CTI adaptor for that flight. I flew another a few years ago (that CATOed) and it did have the threading.

That said the spare/unused threaded plugged forward closure I have was bought from Wildman as a stand alone unit after that Balls23 experience. Briefly I considered swapping out the closure on my L935 with my spare until I noticed the new (to me) second O-ring in a groove that the previously purchased closure didn't have. That's what made me stick with that forward closure instead of swapping over to the threaded one I still have that's never flown.
 
I had an L935 closure blow-by completely destroy one of my favorite rockets a few years ago, so if they added an O-ring that's OK with me and you were right not to mess with it.

There's a Crazy Jim post somewhere around indicating that threading an eyebolt into the closure hole is a standard acceptable practice for CTI Pro54 motors for retention, so one should plan on doing that. I know that L990s and L265s made in the past couple of years didn't have the insert and for all I know CTI has quit using the insert entirely.
 
I have reposted my original post from Ausrocketry for information dissemination.

I have used a lot of CTI 54mm reloads and there has never been a plugged one that I have found. Each time I used the adaptor (Aeropack?) and threaded that into the charge well. I am fairly certain I have burned an L935 along the way and don't remember finding anything different to what I normally expect.

FWIW I have also taken to bonding the forward closure to the liner with epoxy before flight, as a precaution due to the catos that have been observed.

Nice flight BTW
icon_smile.gif
 
Be careful when buying an extra threaded closure. There are 2 sizes, one for the K-300 ....it is for the extra thick liner [long burn]. That one if placed on a regular motor will be a loose fit in the liner!
I just epoxy ALL my forward closures to be safe from blow by.

By the way even if using a closure with threaded insert, you should thread a bolt or eyebolt into it anyway if not planning on using it for recovery attach.
The threaded insert if not plugged is just open like the touch hole version!

I have been gluing E-bolts into my closures for years. They are tapered and a 3/16 drill bit hand turned in the touch hole to "straighten it" will allow a standard 1/4 E-bolt to self tap into the touch hole. [for 54mm]
After gouging the sides of BP well to help adhesion I simply fill with 10 minute epoxy.
For 38mm a #10 [3/16] eyebolt fits perfectly and also self taps.

DSCN3440.jpg DSCN3806.jpg
 
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I had an L935 closure blow-by completely destroy one of my favorite rockets a few years ago, so if they added an O-ring that's OK with me and you were right not to mess with it.
Yea, I had a K300 CATO destroy a half scale AMRAAM (my profile pic btw) and I agree completely.

There's a Crazy Jim post somewhere around indicating that threading an eyebolt into the closure hole is a standard acceptable practice for CTI Pro54 motors for retention, so one should plan on doing that. I know that L990s and L265s made in the past couple of years didn't have the insert and for all I know CTI has quit using the insert entirely.

As can be seen below he's been kind enough to replicate that post in this thread. :D And while your comment about CTI no longer using the threaded insert is pretty much what I'm curious about as it doesn't seem any of this is documented online in an easily found manner. Hence my questions.

Finally, after thinking about it a bit more I do believe I've only seen the CTI made threaded insert on K300s. I'm not 100% on that though.
 
I have reposted my original post from Ausrocketry for information dissemination.

I have used a lot of CTI 54mm reloads and there has never been a plugged one that I have found. Each time I used the adaptor (Aeropack?) and threaded that into the charge well. I am fairly certain I have burned an L935 along the way and don't remember finding anything different to what I normally expect.

FWIW I have also taken to bonding the forward closure to the liner with epoxy before flight, as a precaution due to the catos that have been observed.

Nice flight BTW
icon_smile.gif

And for the sake of information dissemination here's the response I wrote there to your post.

OverTheTop said:
I have used a lot of CTI 54mm reloads and there has never been a plugged one that I have found.

Excluding two "White - Longburn" reloads all of the plugged reloads leverage the 54-6GXL casing. Have you flown lots of them? IIRC I've flown 4 54-6GXL reloads; one L1030, two K300s, and one L935. I do believe each one has has a slightly different forward closure than the last. In order of burning.

1st - L1030 (Balls 22) - No threading in the forward closure
2nd - K300 (Balls 23) - Threaded forward closure
3rd - K300 (WARS - Grass Valley 2016) - Threaded forward closure (CATOed)
4th - L935 (Thunda 2019) - No threading in the forward closure, new O-Ring groove and additional O-Ring

I'll reach out to Blake soon, I should hopefully have a warranty replaced K300 from the one that CATOed on me in 2016. I'm curious to both count the number of O rings on the FC as well as see if there's a threaded insert.

FYI here's what I'm talking about when I refer to threaded closures; this is a completely unmodified Pro54 Forward Closure.

mavSF1g6z1xED5Hd1d01LegFNwYA0CvFcaY6bsAm31k0B_jRaZxoUbOUZ_Uf25NMjDIdnBIAzC_zeOxTXzanqCUPCi6j9bzgun7L5rY9fYCufqIg2SaPx2VayW7jXcnOu5dAjCW_G64Wt860iYVx_ROXL0_kx37cFWRct_Jw1h06PNQayLrZcENYU4Gj9C1kDKdFvnaTc2hUcGTa9mKFyK246c5BxcFqH2eSz0tBhYj2j6pXZTPUHrK9xBdv_4GqUDhv2a7g1Q4BU1VTDtvS463ZqDMuaac91aZwwJVQorUF2kJRBA_pKgCP9HSdfCydALTAMbdYIRuF3IYX5xLmcsIOLY8ifWrFf27jnpImHPPdVkI1EJrDRVEiIeKibzjrwcKeC5Xaq7hNRDt4AQtmN0aq3_phRfa5c7BraHtyIENkgavVtum2im0VgjIUnpAcBCZdfDIpZMRlKdzZLbJD62UsjMy9z3SBYBHTJxTnbOVtKezZKg_2nTeNglT6C-Cu1ihppeB-VPbJwKWrznPTKDXDETC6xSqGk2aMKCcKpaResiC37FCLATVeOlG6KGo5LyAXDtn48ZYSzR-o09v0pPCw3v9nHGDtj5bOsQ_0CLZ8V5tg1xTFNnABaCSfHp5P-dIYX9OcryZD3rcMU5mFEcLr6q9KCnTwS9siM2r7l59VIOMjINbWrJribce1iDP0lgm5u20HV18gjSU3OEfnE24tIw=w981-h961-no


And from the post CJ made over on TRF it appears that there are two variants of this threaded closure (or were). One for the K300 due to the thicker liner, the other I assume for the rest of the line. But this is the point, to my knowledge none of this is actually documented in a public way or at least I've not found it. Hence my questions, I'd like to have a better understanding of these variations.

OverTheTop said:
Each time I used the adaptor (Aeropack?) and threaded that into the charge well. I am fairly certain I have burned an L935 along the way and don't remember finding anything different to what I normally expect.

I own the AeroPack adaptors, both the 38mm and 54mm variants. I used one on my K300 flight at Balls as I was using internal motor retention and at that time I had yet to see a threaded forward closure. Of course my K300 did have a threaded closure but I wasn't aware it would so my design was incorporating the AeroPack adaptor. I had to use it as my internal threaded rod point wasn't deep enough to engage the threads on the FC as I had designed it to mate with the AeroPack adaptor sitting on top of the FC.

All that said I've used the adaptor since and don't plan to do so in future. I'd rather pull the FC, use a drill bit (by hand) to ensure the internal diameter of the FC will match my threaded rod, and then screw it in identically to how you would the AeroPack adaptor. I prefer this method as it's simpler, lighter, shorter, and seems robust enough to support some pretty serious performance.

OverTheTop said:
FWIW I have also taken to bonding the forward closure to the liner with epoxy before flight, as a precaution due to the catos that have been observed.

I plan to start to doing the same moving forward.

OverTheTop said:
Nice flight BTW :)

Thank you sir!
 
Be careful when buying an extra threaded closure. There are 2 sizes, one for the K-300 ....it is for the extra thick liner [long burn]. That one if placed on a regular motor will be a loose fit in the liner!
I just epoxy ALL my foot closures to be safe from blow by.

By the way even if using a closure with threaded insert, you should thread a bolt or eyebolt into it anyway if not planning on using it for recovery attach.
The threaded insert if not plugged is just open like the touch hole version!

Thanks for this post CJ, I'm entirely unsurprised that you're all over this! I had no idea there were two extra threaded closure sizes for instance.

And you're correct (and I was wrong) that even the closure with the threaded insert isn't plugged. Much like the L935 I burned there's no plugging what so ever, just an empty charge well and the top of the smoke grain. I find it somewhat confusing that CTI labels these closures as plugged when it's obvious that they're not plugged at all and instead only don't have any BP in the charge well.
 
I have flown a number of 54mm 6XL motors, and just took delivery of a newly made L935. I have also seen both the threaded and merely empty 'plugged' enclosure. The latest one just has a paper disc over the charge well.

I think the issue is really semantics. When we think of Aerotech plugged closures, it's literally a plugged closure, no charge well or touch hole. But when CTI says 'plugged', they really mean no delay - it must be flown with electronic deployment. I think most of us expect there to be parity in the two descriptions. It's implied that any AT motor with a plugged forward closure must use electronic deployment, but since CTI supplies the forward closure with the motor, they use the term 'plugged' to indicate it's not suitable for motor ejection.

I almost got burned at BALLS a few years back as I had set up a 54MD diameter rocket to use the threaded forward closure I had used on prior 6XL reloads. When I was prepping the motor I was shocked and dismayed to find it was simply the regular closure with a paper disc over the charge well. I ended up having to friction fit the motor case, which worked but was 'sub-optimal'.


Tony
 
I think the issue is really semantics. When we think of Aerotech plugged closures, it's literally a plugged closure, no charge well or touch hole. But when CTI says 'plugged', they really mean no delay - it must be flown with electronic deployment. I think most of us expect there to be parity in the two descriptions. It's implied that any AT motor with a plugged forward closure must use electronic deployment, but since CTI supplies the forward closure with the motor, they use the term 'plugged' to indicate it's not suitable for motor ejection.

I've got to disagree with that comment. Given I came from Aerotech hardware to CTI reading about plugged forward closures in CTI hardware I immediately assumed the touch hole was physically plugged. Hence my confusion. Given CTI's design I can't see any reason why you couldn't add BP to the charge well and have a backup motor ejection on their "plugged" motors. I personally wouldn't do it but I can see it easily being done with some BP and tape.

I almost got burned at BALLS a few years back as I had set up a 54MD diameter rocket to use the threaded forward closure I had used on prior 6XL reloads. When I was prepping the motor I was shocked and dismayed to find it was simply the regular closure with a paper disc over the charge well. I ended up having to friction fit the motor case, which worked but was 'sub-optimal'.

Agreed. I always try and use positive retention if at all possible.
 
Given CTI's design I can't see any reason why you couldn't add BP to the charge well and have a backup motor ejection on their "plugged" motors.
Typically because there's not a reliable delay time, or the delay is too short to be useful.
 
I've got to disagree with that comment. Given I came from Aerotech hardware to CTI reading about plugged forward closures in CTI hardware I immediately assumed the touch hole was physically plugged. Hence my confusion. Given CTI's design I can't see any reason why you couldn't add BP to the charge well and have a backup motor ejection on their "plugged" motors. I personally wouldn't do it but I can see it easily being done with some BP and tape....
Actually, I think you are agreeing with my statement. You assumed the hole was plugged because that's what it means with Aerotech hardware. But with CTI motors, 'plugged' does not mean that, it means that there is no motor ejection, whether it's by simply leaving out the BP or physically closing the hole with a screw or threaded insert. Hence my statement that it's semantics - plugged means different things with AT vs. CTI. If CTI had labeled the motors 'do not use motor ejection - no BP powder supplied', there would be no confusion as to what they mean.

It is bothersome that they don't use terminology that has become standard with all other motors. Also that they sometimes ship the 'plugged' motors with the standard forward closure, just sans BP. But AT doesn't have anything that matches the L265 or L935, so I'm happy to put up with the grief.


Tony
 
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