Cato

[David Schwantz]

Had a cato yesterday. Blew the rear closure out at about 50'. Bulged the threads at rear of case, now garbage. Could not find the rear closure. Aeropack retainer ring bent up, found that. About 1/8" of 2 of the grains are still in the case, almost like the grains separated. Delay not burnt. Liner intact, no burns or breaks. Seal disk o ring good and still in groove. Forward o ring in place and ok. Any ideas??

 

[Banzai88]

What motor?

 

[David Schwantz]

OOPs. K2050ST Aerotech

 

[SDramstad]

Did the forward grains burn?

 

[David Schwantz]

Not completely. If you look at the pic you can see the grain at the rear is about 1/8th" thick now, and hollow. Looks like it blew out a partial core of the grain. Same at forward end.

 

[rfjustin]

When motor was assembled, aft o-ring sat in nozzle groove and tightened in place without issue? How much rear closure gap after aft closure fully tightened? Just askin, you don't wrench the piss out of the aft closure do you?

Sorry to see of the issue, that's frustrating. I've flown 6-7 of these without issue. Grain bonded, or not so much?

 

[David Schwantz]

Hand tighten only. 1/16 gap.I also have flown several of these. great motor.

 

[David Schwantz]

Nozzle end

 

[TheTank]

Did you grain bond it? Aerotech has this motor on their list of motors that needs to be grain bonded. With such a violent motor, all it takes is it to try to chuck a casting tube through the nozzle and plug it for a millisecond before it goes boom city. Ive flown several, love the motor. But I have grain bonded them all because they are pretty much a controlled explosion.

 

[David Schwantz]

Looked at my list. This one was # 9 that I have flown. Never bonded any of them. In fact no bonding instructions were included.

 

[David Schwantz]

Also if you can see in the pic, that is a hollow chunk of propellant in the liner. It's like it blew out the core of a grain

 

[TheTank]

Looked at my list. This one was # 9 that I have flown. Never bonded any of them. In fact no bonding instructions were included.

I dont know when the added it to the list but it was on the list they released recently. I just always bonded mine based on the aggressive burn and a previous experience on my first one that took half the nozzle with it which was better than a full blown grenade. Could also have been a void or crack in the grain if you are seeing pieces or the violence of the disassembly shattered the grain on its way out with the casting tube when trying to get rammed through the nozzle.

 

[David Schwantz]

First time I had one go boom. Not wanting it again

 

[David Schwantz]

So hoping someone might have some insight.

 

[David Schwantz]

This one took the back end of the rocket with it.

 

[TheTank]

Side note too.... if you emailed Karl and sent him the pics and advised that you weren't aware of the recent updates to bond it, I'm sure Aerotech will work with you on a warranty. They always been helpful to me.

 

[TheTank]

So hoping someone might have some insight.

It kicking the rear closure screams nozzle clog me to unless the threads in rear were compromised which I doubt. Im thinking grain bonding down the road should prevent that if it was the cause.

Maybe @AeroTech can advise?

 

[David Schwantz]

Pics were sent to aerotech through my dealer.

 

[rfjustin]

It kicking the rear closure screams nozzle clog me to unless the threads in rear were compromised which I doubt. Im thinking grain bonding down the road should prevent that if it was the cause.

Maybe @AeroTech can advise?

You might be onto something there... if a grain collapsed and clogged the nozzle, bada boom. I agree, best for AT to opine here.

 

[David Schwantz]

I have another, New in tube. I will have to look to see if it has bonding instructions with it

 

[TheTank]

Pics were sent to aerotech through my dealer.

Ok. If your dealer is handling the warranty process for you, that should be fine too. When I had a void in a grain that I couldnt see and it caused a mid-case burn through, aerotech made good on my reload and my hardware that was taken out.

 

[TheTank]

I have another, New in tube. I will have to look to see if it has bonding instructions with it

Even without instructions, bond that one. It wont do any harm to do it and I know its on the list now. All depends on the production date and when the advisement was added.

 

[ksaves2]

No matter what one does a CATO is always sitting in the wings.

 

[ksaves2]

CATO's will happen no matter what one does. I had more CATO's with commercial motors than I've had with some I've mixed. It was mainly with the long-necked 24 and 38mm commercial motors I had an issue with. Still have the burned out casings in the garage for souvenirs. Some burned out in front, some in the back. AT will sell anyone motor parts for a price. I have a kick-ass 2 grain 38mm motor I've mixed that runs in AT hardware and I have to use a nozzle from a J350 to fly it. Even then I had to drill it out just a "little" bit. The program Burnsim can only tell so much as there is not an "erosive" nozzle setting.
It really flew nicely in the rockets I put it in and never had a CATO with it. Put'em up really high mind you!

It would be nearly impossible to have an erosive nozzle setting in Burnsim. Only works with non-erosive graphite nozzles. Still, it gave me an idea of what the initial case pressure was so I could plan accordingly. Erosive nozzles can save a mixer if they spend the money on AT "consumables".

Kurt

 

[pugachu]

Just curious if it was a light rocket with high acceleration. The super thunder kicks hard, and it's possible one of the grains collapsed under high gees. It looks like most of the fuel burnt up before the 'event', and if it was only 50' up when it popped, thats burning very very fast.

I'm sorry about the loss of your rocket.

 

[AeroTech]

It kicking the rear closure screams nozzle clog me to unless the threads in rear were compromised which I doubt. Im thinking grain bonding down the road should prevent that if it was the cause.

Maybe @AeroTech can advise?

This reload requires grain bonding.

 

[Syclone]

I have another, New in tube. I will have to look to see if it has bonding instructions with it

I bought a K2050 recently and it didn't mention grain bonding anywhere in the instructions. Date code on the tube was 02212303.

 

[cerving]

I literally got one yesterday... 02212302, no mention of bonding either. I'll mark the package, for sure.

 

[3stoogesrocketry]

Nozzle end

This motor was almost done burning , that's why there is almost no propelent left. The core is concentric to the grain. The only issue I see is the almost dime size hole at the 3 o'clock position in the grain....