38 CTI motor fail this one is a mystery. Help

[SpaceManMat]

Ive seen a similar over pressurisation issue before on a CTI 38mm, not sure which motor. I’ll try and track it down.

Actually it was a CTI 29mm case with 2 spacers. The reload was a F31, it managed to push the forward closure past the first spacer and into the second only stopping when it hit the top lip of the case. Case and both spacers where damaged.

 

[JARED S JAYNES]

Since no one else has asked, what igniter did you use? Was it the CTI e-match? Or something else?

supplied CTI blue and grey wire ignitor

 

[JARED S JAYNES]

if the ignitor had grey and blue wires, then it's an oddity
If not, then you probably - note probably had a forward closure that should have been replaced. There are specific date stamps, which your photo doesn't show because it's too tight - to verify this.
If you buy it from me I'd have replaced the forward closure if it had the old, yellow wired ematch. Just because it's better safe then sorry. Of course, the only ones that have to be replaced is the ones in the effected date range. My problem is that I'm not that smart.....

its weird the date stamp on the cardboard tube says march 2018, i have emailed tim at apogee, what do i do with the rest of my reloads send them back they all look like they are from the same batch. not to mention the damaged cti case and spacer... only silver lineing is that the rocket, and all the electronics in the nose were undamaged. bummed i just finished 3 scratch builds all running on 38mm motors for uroc upcoming launch.

 

[Nytrunner]

You had a really unlucky experience. If at all possible, don't let this color your perception of the ProX motors, they're really good a vast majority of the time.

(see what I did? I just vouched for them, transferring the bad juju from your reloads to mine!)

 

[Steve Shannon]

its weird the date stamp on the cardboard tube says march 2018, i have emailed tim at apogee, what do i do with the rest of my reloads send them back they all look like they are from the same batch. not to mention the damaged cti case and spacer... only silver lineing is that the rocket, and all the electronics in the nose were undamaged. bummed i just finished 3 scratch builds all running on 38mm motors for uroc upcoming launch.

This is probably not something easily repeatable. I would not be afraid of the other motors in that batch.

 

[jahall4]

... the ejection charge shot up thru the rocket the motor destroyed the areo pack retention...

Maybe I overlooked where you mentioned, but where you using forward closure
retention?

 

[JARED S JAYNES]

Maybe I overlooked where you mentioned, but where you using forward closure
retention?

no i was not, the motor kicked back pulling off the rear areopack motor retention ring in addition to sending the forward clowure up thru the rocket.

 

[jahall4]

no i was not, the motor kicked back pulling off the rear areopack motor retention ring in addition to sending the forward clowure up thru the rocket.

Did you inspect the forward closure per the CTI bulletin? I have not seen where that was mentioned. Even if the date code would indicate a motor that should not be affected you never know.

 

[Steve Shannon]

Did you inspect the forward closure per the CTI bulletin? I have not seen where that was mentioned. Even if the date code would indicate a motor that should not be affected you never know.

It’s obvious looking at his forward closure picture that this wasn’t the type of failure seen in the recalled motors. Zoom in and you can see that the material that separates the delay grain from the ejection well is still there.

 

[jahall4]

It’s obvious looking at his forward closure picture that this wasn’t the type of failure seen in the recalled motors. Zoom in and you can see that the material that separates the delay grain from the ejection well is still there.

That's assuming the failure followed the norm. How many 6/15/2016 bulletin failures have you seen where a spacer was used?

 

[Steve Shannon]

That's assuming the failure followed the norm. How many 6/15/2016 bulletin failures have you seen where a spacer was used?

That failure mode was defined by the delay grain being forced through the forward closure and was caused by slippery material mistakenly provided by a supplier to CTI. There’s nothing similar about this. This is a completely different failure mode. I saw a few of those CTI recall failures, some may have had spacers.

 

[jahall4]

That failure mode was defined by the delay grain being forced through the forward closure and was caused by slippery material mistakenly provided by a supplier to CTI. There’s nothing similar about this. This is a completely different failure mode. I saw a few of those CTI recall failures, some may have had spacers.

I don't see a picture of the delay grain in this thread. If he drilled out 9 seconds maybe that played a factor, but my question about inspection was to rule out the recall as a cause, not draw a conclusion. Maybe there is a mode where the dealy grain comes loose and falls into the core, seems very unlike, but...

 

[tim cubbedge]

I don't see a picture of the delay grain in this thread.

See post #1

 

[BayouRat]

Common over pressurization in these CTI reloads. Happens all the time unfortunately.

 

[jahall4]

See post #1

Where in post #1?

 

[tim cubbedge]

Where in post #1?

Surely you jest but if not it is the very first post in the thread
38 CTI motor fail this one is a mystery. Help

 

[jahall4]

Surely you jest but if not it is the very first post in the thread
38 CTI motor fail this one is a mystery. Help

There is no delay grain pictured. There is a battered and beaten forward closure, but no picture of the dealy grain that should be inside it.

 

[Steve Shannon]

There is no delay grain pictured. There is a battered and beaten forward closure, but no picture of the dealy grain that should be inside it.

You should look at the second photo in that first post.

 

[blackjack2564]

One thing you learn as you gain flying experience, every now & then you get an anomaly that never gets figured out.
I call that my "offering to the rocket godz" . I hope you DO figure this issue out, but if not, just consider it your offering and you should be able to fly trouble free for a few more years till it's time for another "offering" to appease said godz! lol.
I would gamble that most of us flying over 6-7 years have had similar experiences.

Ps: for those wondering, the recall was a couple years ago, so no worries with your remaining loads according time date stamp.
The supplier of plastic used by CTI for injection molding the closures {CTI makes their own] sent a product that contains a slippery mold release. The epoxy that holds the delay grain in place would not adhere to the plastic. Once discovered, it was totally suppliers fault, simple wrong product shipped, that looked identical to correct one [but shinier ] the recall was implemented and everything became happy again in CTI motor land.

Forrest Gump said it all: "$h!t happens"

 

[SpaceManMat]

I always thought Forest Gump said: “Life is like a box of reloads, you never know which one will Cato!”

Maybe that was the remake

 

[boatgeek]

I saw an example of the recall failure with a spacer used. 2G motor in a 3G case. The aftermath looked nothing like this. In that case the delay grain, touchhole, and BP were all completely gone but the rest of the forward closure was in place.

I would hope that your vendor or CTI would replace the case as well as the reload.

 

[jahall4]

You should look at the second photo in that first post.

Again that's the forward closure, but mangled all to hell.

 

[JARED S JAYNES]

There is no delay grain pictured. There is a battered and beaten forward closure, but no picture of the dealy grain that should be inside it.

I will post a picture of the delay grain, it's intact with my drill hole from the DAT tool, this must just be a over pressure to eject the forward closure out the front of the case, looks like a unknown cause that's obvious. Ordered a new single grain case to use the rest of the reloads. Moving on.

 

[jahall4]

I will post a picture of the delay grain, it's intact with my drill hole from the DAT tool, this must just be a over pressure to eject the forward closure out the front of the case, looks like a unknown cause that's obvious. Ordered a new single grain case to use the rest of the reloads. Moving on.

Thanks! Some of us may want to dwell This failure is rather interesting and I have several minimum diameter 38mm flights in my future.

 

[JARED S JAYNES]

ok full disclosure after the failure i did try and remove the spacer and used the forward closure to pound out the motor grain. then the forward closure got stuck in the spacer and then attempted to pound it back out using a 3/4 drive socket. thats when i cut the case in half to get the components out. but here are the pics

 

[Steve Shannon]

Again that's the forward closure, but mangled all to hell.

Yes, but if you zoomed in you could see the plastic partition that separates the delay grain from the ejection charge. It was intact, proving that it wasn’t the type of failure covered by the recall.

 

[jahall4]

...and used the forward closure to pound out the motor grain

Thanks, that explains why the fore end of the forward closure looks so mangled.

 

[jahall4]

Folks, I may be seeing seeing something that is not right about the assembly of the grains...Could the forward grain be turned around and the ignition pelet, now on the aft end of the forward grain, be partially burnt away?

I'm looking at this pic primarily: https://www.rocketryforum.com/attachments/20190218_221007-jpg.375092/

In this pic we have to be looking up (aftt -to-fore) the casing and the pelet can be seen at the aft end. The pellet should of course be at the fore end of the forward grain at the very top of the core and it not:

https://www.rocketryforum.com/attachments/20190218_220948-jpg.375091/

https://www.pro38.com/pdfs/Pro38_Case_Spacer.pdf

 

[blackjack2564]

First thing I would want know....is the correct nozzle there. . I HAVE seen issue like this when there was a nozzle switch [by accident] that the throat was too small. Over pressurized=boom.

 

[SpaceManMat]

Folks, I may be seeing seeing something that is not right about the assembly of the grains...Could the forward grain be turned around and the ignition pelet, now on the aft end of the forward grain, be partially burnt away?

I'm looking at this pic primarily: https://www.rocketryforum.com/attachments/20190218_221007-jpg.375092/

In this pic we have to be looking up (aftt -to-fore) the casing and the pelet can be seen at the aft end. The pellet should of course be at the fore end of the forward grain at the very top of the core and it not:

https://www.rocketryforum.com/attachments/20190218_220948-jpg.375091/

https://www.pro38.com/pdfs/Pro38_Case_Spacer.pdf

Not sure I agree with you there. As far as I can tell the second picture shows the pellet and has the remains of the forward seal embed in it. So I would interpret this as the grain being forced upwards during over pressurisation, no doubt the forward closure lost the oring as it was forced through the spacer and then the grain ran into the oring and spacer resulting in the oring being embed into the top of the grain.