Attempting the K and L altitude records

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mikec

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FWIW, I flew a CTI M1101 a couple of weekends ago, and the pyrogen igniter supplied with the motor had cracks, and failed to ignite it, but did blow the cap off with a fair degree of authority. Did you have the cap down on the rail/tower stop or was it free to blow off? I'm not sure it's plausible that an igniter could produce enough pressure to blow off the aft closure, but getting an overpressure right at ignition also doesn't seem likely. But who knows?
 

T34zac

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FWIW, I flew a CTI M1101 a couple of weekends ago, and the pyrogen igniter supplied with the motor had cracks, and failed to ignite it, but did blow the cap off with a fair degree of authority. Did you have the cap down on the rail/tower stop or was it free to blow off? I'm not sure it's plausible that an igniter could produce enough pressure to blow off the aft closure, but getting an overpressure right at ignition also doesn't seem likely. But who knows?
The cap was free to blow off down the tower. But that's never stopped a motor from igniting for me before.
 

T34zac

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Going to be making my next attempt at the K300 flight this weekend. Looking for Saturday before noon, or Sunday before 10am. Pretty much assembling the entire rocket on site since AMW still has my reload and case.
 

T34zac

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Went out, set it up, and motor lit with the first igniter this time! Unfortunately, roughly a second and a half into the burn the nozzle blew out again. Same failure, just later into the burn. I want to give it another go, but not until CTI fixes these motors. It's a bit ridiculous.
 

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T34zac

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A little dab of hotmelt glue will keep that JST connector in place during the launch more positively than just the friction lock. I hope your flight goes well.
Flight was attempted twice, both times the motor cato'd. The electronics connection held up fine in both, but I'll keep that in mind for the next go.
 

Banzai88

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It IS ridiculous at this point. Frequency of CTI 54mm has become alarming...
To the point where they've acknowledged it publicly several times on the CTI thread about the 54mm and have also hinted at that they're familiar with the long 38mm load problems, too. In their own words are working on data collection and a possible solution, pending them getting their data collection (presumably a motor test stand?) equipment up and running again.
 

OverTheTop

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Flight was attempted twice, both times the motor cato'd. The electronics connection held up fine in both, but I'll keep that in mind for the next go.
No worries. I find it give me a bit more confidence, and is also cleanly and easily removed with sidecutters when you need to separate the connectors.
 

manixFan

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Flight was attempted twice, both times the motor cato'd. The electronics connection held up fine in both, but I'll keep that in mind for the next go.
Did you try the epoxy seal method on either motor? Basically you run a bead of JB weld around the liner and the top of the top grain and then seat the forward closure with a twist to try and prevent blow by. It's been discussed in a number of posts about the long CTI motors. I think Jim Jarvis was the one who first figured it out. I've used it for several years now and have not had any failures, but I do know at least one flyer that had a burn through even after trying it.

I have been flying the 54mm 6XLs for years - primarily the L265 and L935, and the L640 when it was available. I have one each for the L265 and L935 on hand. I've also flown a fair number of the long 38mm motors - the J150 and J530 and also have one of each on hand. (I sense a pattern.) I've not had a failure but I've seen many of them personally, and of course have read the reports here as well. I know motors have been decertified in the past for safety issues if they failed enough, but then others, like the Estes E engines that I read a lot about, remain in service. I'm not sure what the right call here is but I feel like I'm sitting on a ticking time bomb, and it's only a matter of when, not if, I'll lose a rocket to a long CTI motor.

Once I use up what I have on hand, that's it until CTI figures something out. What kills me is the one Aerotech motor I flew as a substitute cato'd due to a cracked liner. I lost an Orangeburg 2000 LDRS case due to that.

I get rocket motors can have issues, but when an issue is as persistent as the failure mode of the longer CTI motors, it needs to be fixed, and sooner than later.


Tony
 
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mikec

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Did you try the epoxy seal method on either motor? Basically you run a bead of JB weld around the liner and the top of the top grain and then seat the forward closure with a twist to try and prevent blow by.
That solution is for blow-bys, case bubbles, etc. It won't, AFAIK, fix a CATO. The CATO seems to be something unique to the K300 (so far anyway.)
 

JimJarvis50

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Did you try the epoxy seal method on either motor? Basically you run a bead of JB weld around the liner and the top of the top grain and then seat the forward closure with a twist to try and prevent blow by. It's been discussed in a number of posts about the long CTI motors. I think Jim Jarvis was the one who first figured it out. I've used it for several years now and have not had any failures, but I do know at least one flyer that had a burn through even after trying it.
I suspect I tried the epoxy method first, and I was discussing it with Jerone at the time of the accident. However, I am starting to believe that greasing the liner may be at least as important. I have flown at least a half dozen of the K300's and have not had problems with them. None of these were glued, but all were greased. I have also flown many of the K160's (shorter but similar design) and they have all worked.

This problem by the OP seems to be something else though, with the nozzle failing. Close-up photos of that would be helpful. I'm also curious why the most recent picture seems to show flame out of both ends?

Jim
 

rfjustin

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I suspect I tried the epoxy method first, and I was discussing it with Jerone at the time of the accident. However, I am starting to believe that greasing the liner may be at least as important. I have flown at least a half dozen of the K300's and have not had problems with them. None of these were glued, but all were greased. I have also flown many of the K160's (shorter but similar design) and they have all worked.

This problem by the OP seems to be something else though, with the nozzle failing. Close-up photos of that would be helpful. I'm also curious why the most recent picture seems to show flame out of both ends?

Jim
More info/pics from OP here as well: https://www.rocketryforum.com/threads/cti-discussion-thread.162183/page-19#post-2210562
 

manixFan

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That solution is for blow-bys, case bubbles, etc. It won't, AFAIK, fix a CATO. The CATO seems to be something unique to the K300 (so far anyway.)
Yeah, I mixed up two threads I was reading, one about the forward closure issue and this one, where the nozzle blew out. The epoxy seal trick doesn't seem like it would have any effect here.

But most in my club would not really be that granular with the word CATO - we generally use it to refer to any kind of motor failure. To me, the long case blow-by is certainly a form of a CATO, at least based on the damage I've seen them create. If the motor case is has a big hole in it after the event, to me that meets the definition.


Tony
 

mikec

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However, I am starting to believe that greasing the liner may be at least as important. I have flown at least a half dozen of the K300's and have not had problems with them.
I agree. Several years ago, I had a K300 with severe forward blow-by that ended up incinerating the rocket. Discussing it with Jeroen, it was possible that the forward O-ring had rolled out of its slot because of crud in the case and inadequate lube. Hence CTI's recommendation of silicone spray for long motors.

The blow-by/case bubbling is clearly not due to the O-ring, but at the interface of the forward closure and the liner, and that's where the gluing helps.

This most recent CATOing at/near ignition sounds more like propellant voids or some other excessive burn rate problem. I haven't experienced that yet, but have radically cut back on flying CTI of late.
 

JimJarvis50

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I agree. Several years ago, I had a K300 with severe forward blow-by that ended up incinerating the rocket. Discussing it with Jeroen, it was possible that the forward O-ring had rolled out of its slot because of crud in the case and inadequate lube. Hence CTI's recommendation of silicone spray for long motors.

The blow-by/case bubbling is clearly not due to the O-ring, but at the interface of the forward closure and the liner, and that's where the gluing helps.
Just so it's clear, my belief that greasing the liner is important is not due to the forward O-ring. Rather, it is to prevent gases leaving the interface at the liner/closure from having a pathway into the void area between the liner and the case. If the pathway is blocked by grease, the gases won't come out and burn through the case. I think CTI suspects the same thing. In the CTI thread, Bob said "And also I think that filling in the gap between the liner and case with grease allows less gas to seep through the closure/liner". So, I glue and grease these motors.

I must be slow, but I'm still not following the two K300 failures here. From the pics in the CTI thread, one appears to be a failure of the case itself above the rear closure and the other appears to be a failure of the nozzle. Pics aren't always easy to interpret, but these don't look the same? I'm still curious about why there is flame coming from both ends of the rocket in the most recent flight? I'm just trying to understand what happened.

Jim



image0.jpg
K300 remains.jpg
 

T34zac

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Did you try the epoxy seal method on either motor? Basically you run a bead of JB weld around the liner and the top of the top grain and then seat the forward closure with a twist to try and prevent blow by. It's been discussed in a number of posts about the long CTI motors. I think Jim Jarvis was the one who first figured it out. I've used it for several years now and have not had any failures, but I do know at least one flyer that had a burn through even after trying it.

I have been flying the 54mm 6XLs for years - primarily the L265 and L935, and the L640 when it was available. I have one each for the L265 and L935 on hand. I've also flown a fair number of the long 38mm motors - the J150 and J530 and also have one of each on hand. (I sense a pattern.) I've not had a failure but I've seen many of them personally, and of course have read the reports here as well. I know motors have been decertified in the past for safety issues if they failed enough, but then others, like the Estes E engines that I read a lot about, remain in service. I'm not sure what the right call here is but I feel like I'm sitting on a ticking time bomb, and it's only a matter of when, not if, I'll lose a rocket to a long CTI motor.

Once I use up what I have on hand, that's it until CTI figures something out. What kills me is the one Aerotech motor I flew as a substitute cato'd due to a cracked liner. I lost an Orangeburg 2000 LDRS case due to that.

I get rocket motors can have issues, but when an issue is as persistent as the failure mode of the longer CTI motors, it needs to be fixed, and sooner than later.


Tony
The first one came with the nozzle glued into the liner from the factory. I also epoxied in the forward closure after hearing about all the problems CTI 54mm motors have had in the past. Liner was also greased prior to putting into the case. The threaded section on the closure bulged and blew off as soon as the motor came up to pressure.

Second one didn't come with the nozzle glued to the liner and I also did not glue the forward closure in either, per instruction of Robert DeHate of AMW. I did grease the liner as I did last time, and as I do with all reloads. The burn lasted a bit longer this time around, however it blew the entire rear end of the casing off instead.
 

T34zac

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I suspect I tried the epoxy method first, and I was discussing it with Jerone at the time of the accident. However, I am starting to believe that greasing the liner may be at least as important. I have flown at least a half dozen of the K300's and have not had problems with them. None of these were glued, but all were greased. I have also flown many of the K160's (shorter but similar design) and they have all worked.

This problem by the OP seems to be something else though, with the nozzle failing. Close-up photos of that would be helpful. I'm also curious why the most recent picture seems to show flame out of both ends?

Jim
There's nothing I'm doing with this reload that is out of the ordinary. I've also flown plenty of CTI 54mm reloads (K160 and K261 included) and never had issue apart from the K300. I honestly suspect it's an issue related to newer K300s, as the manufacture dates of mine were dated 2019 and 2020. Possibly a nozzle throat that's too small.

I'll get photos of both my cases as they are now when I get a chance.
 

T34zac

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Just so it's clear, my belief that greasing the liner is important is not due to the forward O-ring. Rather, it is to prevent gases leaving the interface at the liner/closure from having a pathway into the void area between the liner and the case. If the pathway is blocked by grease, the gases won't come out and burn through the case. I think CTI suspects the same thing. In the CTI thread, Bob said "And also I think that filling in the gap between the liner and case with grease allows less gas to seep through the closure/liner". So, I glue and grease these motors.

I must be slow, but I'm still not following the two K300 failures here. From the pics in the CTI thread, one appears to be a failure of the case itself above the rear closure and the other appears to be a failure of the nozzle. Pics aren't always easy to interpret, but these don't look the same? I'm still curious about why there is flame coming from both ends of the rocket in the most recent flight? I'm just trying to understand what happened.

Jim



View attachment 492909View attachment 492908
The pictures here are of both cases post cato. First picture is the second failure I had.

In the photo of it burning from both ends, that's the grain of the second motor after it got ejected form the motor case
 

JimJarvis50

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The first one came with the nozzle glued into the liner from the factory. I also epoxied in the forward closure after hearing about all the problems CTI 54mm motors have had in the past. Liner was also greased prior to putting into the case. The threaded section on the closure bulged and blew off as soon as the motor came up to pressure.

Second one didn't come with the nozzle glued to the liner and I also did not glue the forward closure in either, per instruction of Robert DeHate of AMW. I did grease the liner as I did last time, and as I do with all reloads. The burn lasted a bit longer this time around, however it blew the entire rear end of the casing off instead.
So, for the first failure, all of the threads are still on the case, but the closure got blown off?

For the second, where did the case shear off? Is it just above the rear closure? Just wondering if it is the same type of problem that "normally" happens on the forward closure.

Jim
 

T34zac

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So, for the first failure, all of the threads are still on the case, but the closure got blown off?

For the second, where did the case shear off? Is it just above the rear closure? Just wondering if it is the same type of problem that "normally" happens on the forward closure.

Jim
First case the threads are still there, the closure bulged at the threads and came off that way.

Second seemed to shear off right above the threads as evidenced by the damage to the fin can. I have yet to put both cases side by side to confirm, and the closure was not found for it.
 

JimJarvis50

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First case the threads are still there, the closure bulged at the threads and came off that way.

Second seemed to shear off right above the threads as evidenced by the damage to the fin can. I have yet to put both cases side by side to confirm, and the closure was not found for it.
Be interesting to see the two cases side by side. The two indentations on the second case look similar to what happens with the forward closure issue. Bulges followed by the top of the case shearing off. Looks a lot like the K300 from XPRS (you know the one I'm talking about).

Jim
 
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