Small Bulge in rocket motor casing

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Wayco said:
Since CTI has been aware of this problem for years now, and all they have done is add an O-ring, (Which doesn't seem to fix the problem) the only way to fix it would be to get the word out, either by word of mouth, or on the forums.
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This was being discussed at the time of the accident, which put an end to the discussion at that time. Their position was that the problem was due to an incorrect liner size and that they had dealt with the problem. I think it would be relevant if there are problems with motors made more recently.

Jim
 
Wayco said:
  • CATO, an acronym used in rocketry, for Catastrophe At Take Off—the catastrophic failure of a rocket engine.
  • The Malfunctioning Engine Statistical Survey (MESS)

There was no catastrophe, and the motor did not malfunction. It operated nominally throughout the flight.



I went to the motorcato site and looked at what they wanted. It was all about motor malfunctions. No mention about problems with instructions. If I had a problem understanding instructions, I would post up here on TRF.
Problems with delays? Use an altimeter.
There are only six items addressed in the "Manufacture Notifications and Modification Announcements" since 2011. Maybe if everyone reported this to MESS, CTI would announce a modification? Since CTI has been aware of this problem for years now, and all they have done is add an O-ring, (Which doesn't seem to fix the problem) the only way to fix it would be to get the word out, either by word of mouth, or on the forums.
In the hope that someday, CTI will announce a modification, I filed a MESS report, but the skeptical side of me thinks that even it that happens, how many people will read about it on the motorcato site?
This thread has a much better chance of dealing with the problem.
Click to expand...

The motor did malfunction; any time a case is damaged as a result of the motor being used, that’s a reportable malfunction. Perhaps this thread will reach more users, but the certification authorities work with the data that’s turned in using MESS reports, not social media. We (TRA, NAR, and CAR) will be working hard to get more people to report all problems, even those they think are their own fault. We realize that it’s a two way street and people need to see results as well.
 
Wayco said:
  • CATO, an acronym used in rocketry, for Catastrophe At Take Off—the catastrophic failure of a rocket engine.
  • The Malfunctioning Engine Statistical Survey (MESS)

There was no catastrophe, and the motor did not malfunction. It operated nominally throughout the flight.
Click to expand...
A CATO this was not. The primary function of a motor is to push the rocket, which it did.

However, the function of the case in a reusable motor system is to contain the pressure of burning propellant and to be reusable, which makes this an undeniable failure.
 
kjkcolorado said:
Well, I’m a few days too late to have seen this thread. Flew a CTI K260 long burn this past weekend. Everything looked nominal with the flight. Recovered and returned to camp only to find I couldn’t pull my 6 grain case out of the rocket. Removed the rear closure and slid it out from the top to find a substantial bulge in the case between 1-2” from the end. Sorry, no pics. Vendor swapped me out immediately on the spot.

One, I feel lucky nothing ‘blew’. Two, I’m happy this didn’t happen in the other rocket I had that can fit long 54s.... it has a zipperless coupler. Would have had to cut it out. A fellow flyer saw the bulged case and mentioned he had read about this problem on the forum and also mentioned using epoxy to glue in the forward closure. I haven’t flown many 4+ grain 54s yet. Glad I know about this now!
Click to expand...

That was me on the flightline at NCR. Nice to meet you on the forum! The L935 that I flew that weekend worked perfectly. There was no bulge in the motor casing. I epoxied it using west systems epoxy, just a thin layer over the lower O-ring on the forward bulkhead. No buldge or damage to the case. Sadly my 2.6" Screech only went to 14,400 feet due to the FG layup I did on the fins failed and the paint flaked off. The next logcal step? Build an even smaller minimum diameter rocket with a chute release and avbay in the NC. Current design is simming to 29,500 if I get a nice finish. Buying a spraygun to get a really smooth finish.
 
mperegrinefalcon said:
That was me on the flightline at NCR. Nice to meet you on the forum! The L935 that I flew that weekend worked perfectly. There was no bulge in the motor casing. I epoxied it using west systems epoxy, just a thin layer over the lower O-ring on the forward bulkhead. No buldge or damage to the case. Sadly my 2.6" Screech only went to 14,400 feet due to the FG layup I did on the fins failed and the paint flaked off. The next logcal step? Build an even smaller minimum diameter rocket with a chute release and avbay in the NC. Current design is simming to 29,500 if I get a nice finish. Buying a spraygun to get a really smooth finish.
Click to expand...

Hey there! Since you mentioned you read about the bulge issue on TRF I was wondering if you would see this and chime in. Good to meet you at NCR. Thanks for the ‘heads up’ on the epoxy fix/prevention.
 
Well, I'm unfortunately a member of the bulged-54mm-6xl case club. I flew a K1440 this past weekend at MMMSC, and just noticed that my case has a substantial bulge. You can see at the junction of the liner and forward closure where the gas came through. As per the advice in this thread, I HAD epoxied in the forward closure with rocketpoxy, though perhaps I was too judicious in my application?

I'll file a MESS report.

Should I expect just a new casing, or a new casing and a new reload? The flight was perfect other than this...

In other bad news, another flyer this weekend at the club had an immediate CATO on a K1440 that destroyed their rocket. They had not epoxied in the forward closure.


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kLntJye0ptLSuQ1Oc5fVULWwp4mVQgg4czglCFqXaEdFzxroNjKkWCm3XRxao4wwg0frZuaQ4d0vNrbaFPqm1J5aHgJuPPkTLL6XzV8DPKJtjeaILfXRCnB8zibs8UJRDYFFq38EmYf723AbfSeMxzKsHNuCKynrgLpKic24EILgor5NMCxpWbY1ad1fHbxXBjOVGxKhs9MV8TGe_0eYDoL19tMnhS46wSku6yYv13F49HbsP4nbziZUUZo7q6ded6FuH2VwsniZp7XQiSkYr-xkBoxiqHf-B0IpMjb8E91kQIVienUkD3dS-qBZeRGVTPQ3adONVaeeUJeK7CmZLwkvtl0rOmG7_Ek0VYXafD-OvrKQ4D0jdWuXDnpCA8eM0TcQLY_-J-jlGpgofi5tWlPgRRDN7ueTEzEQCyH8lU9ORnUAPa9svv8MTnSfrRgJum9JgWYfPKOeg7vaenD017PoDbetmza_5_5EBT4dbEiMaFPJ5ypNScagZ_XvUKjU5-ejcQPFXGjesIrCFW4RDJp-PFv08XSlVKtrxi5BE5kcYx5h29Vm9pLclDIQivnaMMJxPI07zpIA2BC91Gv-PJWTP27SpRKe5PspCcaP=w2410-h1808-no
 
I was given new case from our on site vendor. I’d imagine since flight was successful you won’t get another motor.
 
timbucktoo said:
I was given new case from our on site vendor. I’d imagine since flight was successful you won’t get another motor.
Click to expand...
That seems only fair. It hadn't occurred to me until I saw this thread that a new load would even be considered (I already emailed my vendor and asked about just getting a case replacement).
 
Is this only a concern with 4grain and longer 54mm? I have a 2 grain that was quite new (March 21, 2018) and the fwd closure did NOT have any type of o-ring on the closure that went into the liner. It did seem to fit quite loose in there. I had heard Jim Jarvis mention this before so I did put a very thin layer of 5-min epoxy into the lip of the liner and then put the closure in and set it upside down on the fwd closer to hold it until it dried. I’m wondering if I put enough now.
 
jqavins said:
Tsk tsk. You're only owed a case.
Click to expand...
No need to tsk tsk... :)

I agree that replacing the case only is the fair thing (and that's what I emailed the vendor and asked for before I wrote anything on this thread), but there seemed to be some debate earlier in the thread about this so I was just curious.
 
BryRocket said:
Is this only a concern with 4grain and longer 54mm? I have a 2 grain that was quite new (March 21, 2018) and the fwd closure did NOT have any type of o-ring on the closure that went into the liner. It did seem to fit quite loose in there. I had heard Jim Jarvis mention this before so I did put a very thin layer of 5-min epoxy into the lip of the liner and then put the closure in and set it upside down on the fwd closer to hold it until it dried. I’m wondering if I put enough now.
Click to expand...
I glue all pro54 motors since I don't really know which are affected and which are not. I put a generous coating of epoxy on the lip of the liner so that when the closure is inserted, a fillet will form to protect the gap. I haven't had any failures while doing this, but there is no official blessing of the technique.

Jim
 
rocketsam2016 said:
No need to tsk tsk... :)

I agree that replacing the case only is the fair thing (and that's what I emailed the vendor and asked for before I wrote anything on this thread), but there seemed to be some debate earlier in the thread about this so I was just curious.
Click to expand...
Fair enough.
 
Just reviving this thread to report what appears to be have been the same problem the weekend before last - CTI K630 in a 4G casing:
cato detail.jpg
 
markkoelsch said:
First, did you fill out a mess report?

Secondly, have you contacted CTI about this?
Click to expand...
The MESS report form is only for NAR, TRA or CAR members - there's nowhere for UKRA members to list their membership details. The club vendor took all necessary details and has lodged a claim with CTI.
 
Tim51 said:
The MESS report form is only for NAR, TRA or CAR members - there's nowhere for UKRA members to list their membership details. The club vendor took all necessary details and has lodged a claim with CTI.
Click to expand...
The motor certification people need the information from the MESS report. They do not receive any information from the manufacturers when claims have been submitted. Where it asks for NAR, CAR, or TRA number, write UKRA followed by your UKRA number. They are just text fields so you can literally put anything, or even leave them blank. That’s not the important information.
Thank you!
 
Steve Shannon said:
The motor certification people need the information from the MESS report. They do not receive any information from the manufacturers when claims have been submitted. Where it asks for NAR, CAR, or TRA number, write UKRA followed by your UKRA number. They are just text fields so you can literally put anything, or even leave them blank. That’s not the important information.
Thank you!
Click to expand...

Thanks Steve. On previous occasions I have tried to input 'UKRA = number' but it won't accept it. I suspect most of us outside of North America don't fill out MESS reports because of that. Anyway, I'll try emailing the site directly.
 
Tim51 said:
Thanks Steve. On previous occasions I have tried to input 'UKRA = number' but it won't accept it. I suspect most of us outside of North America don't fill out MESS reports because of that. Anyway, I'll try emailing the site directly.
Click to expand...

Tim, I sent you a private message about this. Read it, and if it does not work per Steve’s reply email me the info and I will enter it in your behalf.
 
So this past weekend at LDRS, I experienced a CATO on a CTI L265 54 XL. The forward closure blew out about a second after motor lit off. MESS report filed. I epoxied the FWD closure with a 10 minute epoxy a few days before. Apparently not the answer. I spoke with Jim Jarvis afterwards & he recommends longer curing epoxy such as West Systems or Aeropoxy. Good news is Chris Short warrantied motor/casing on site. Bad news shown below:IMG_4865.JPG
 
Oh man, this was the sustainer of your 2-stager huh? Sorry to see that.

That’s the long burn Mellow propellant correct?

I’ve used 5 minute epoxy on all my 38 and 54 cti loads. Guess I’ll consider something more substantial. Crazy it went almost immediately.
 
Yep. That’s the one and it was the long burn Mellow. I saw it light and like you said, within a second, ouch!
 
My condolences.

You going to wack that burnt end off, throw a coupler in it and repair?
 
I posted up about this on another thread, but it's relevant to this one too.
I spent a couple hours removing a 98mm 6XL casing from my Ultimate Darkstar today. Flew it to 21,000 ft. at LDRS 38 Sunday on an O3400.
I kinda knew what I would find, a small bubble at the top of the casing:
IMG_2064.jpg


After I yanked and twisted it half way out, I resorted to a long piece of 2" PVC pipe and a sledge hammer. Now I have a swollen knuckle and a brand new GEN 2 casing I will never use again.
 

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