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Ejection during boost

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sunderll

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Hi all....For many years, one of my favorite motors is the AT G-64. It has been super reliable with no failures until recently. After ignition everything looked good until the rocket was about 100 feet then the ejection charge lit off. I examined the motor and all the assembly of it and everything was in place with no obvious defects. I can't figure out what caused that. The casing and closures all look smooth and clean......has anyone else experienced this on this motor? Any ideas? THANKS!!
 

MikeyDSlagle

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Not with that motor but with that case. I had a F22 do the exact same thing last month. I just assumed I built it wrong, as I had not built a F for that case. The case has flown G loads before so I know it's good. Caused quite a bit of damage to my rocket.

Mikey D
 

loopy

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Typically something like that is either a misplaced o-ring (wrong size in the wrong place), or something wrong with the delay grain. If it sat on the pad smoking for awhile before it came up to pressure, it might have burnt through a portion of the delay grain before lifting off.
 

Steve Shannon

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An error (one of several over the years) that I have made, but just once, is to install the delay grain with the delay grain spacer on the wrong end. The o-ring must go around the end of the delay grain, not around the spacer. My results were just the same as yours.
Anything that might cause the delay grain o-ring to not seal could cause the same problem, a bit of dirt, too much grease, a deep scratch in the delay grain cavity wall, a nick or cut in the o-ring...


Steve Shannon
 

sunderll

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Thanks all for your suggestions. I did recheck the assembly and all was correct. The only thing odd was the delay grain white paper tube was ripped and burned lengthwise that I hadn't seen before. It was almost like the delay grain burned fast like the AP and not the slow burn as it should have. Unfortunately I didn't take any pictures of it. I'm going to inspect the hardware super carefully, load a new reload into it and fly it in an old cheap rocket. But I thank all for your advice!!
 

Buzzard

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Additionally, Aerotech has stated that the delay has to fit snuggly, otherwise the hot gases can bypass the delay and set off the ejection charge. They recommend using tape to ensure a good fit.
I flew a G64 a couple of months ago and the delay was loose. Taped it to fit tighter and the flight was successful. :2:

Chas:
 

Steve Shannon

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Thanks all for your suggestions. I did recheck the assembly and all was correct. The only thing odd was the delay grain white paper tube was ripped and burned lengthwise that I hadn't seen before. It was almost like the delay grain burned fast like the AP and not the slow burn as it should have. Unfortunately I didn't take any pictures of it. I'm going to inspect the hardware super carefully, load a new reload into it and fly it in an old cheap rocket. But I thank all for your advice!!
That burning and ripping of the delay grain insulator I think indicates that you had a leak past the delay grain o-ring which allowed hot combustion gases from the burning propellant to flow past the delay grain liner and out to the ejection charge, burning and cutting the delay grain liner as it flowed.
 

TangoJuliet

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That burning and ripping of the delay grain insulator I think indicates that you had a leak past the delay grain o-ring which allowed hot combustion gases from the burning propellant to flow past the delay grain liner and out to the ejection charge, burning and cutting the delay grain liner as it flowed.
A Post Accident Investigation Report written by a true Rocket Scientist! :wink:
 

Daddyisabar

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With AT GREASE IS THE WORD! I put a thin layer on the bottom 2/3's of the inside wall of the forward closure, then grease the O ring real good. I wipe my hands clean and carefully insert the delay grain in the right direction, making sure no grease is on top. No blow by or grease impeded ejection charges.

Lovingly sing the following song to all your AT reloads before flight:

I solve my problems and I see the light
We got a lovin' thing, we gotta feed it right
There ain't no danger we can go to far
We start believing now that we can be who we are

Grease is the word

They think our love is just a growing pain
Why don't they understand, It's just a crying shame
Their lips are lying only real is real
We stop the fight right now, we got to be what feel
Grease is the word
Is the word that you heard
It's got groove it's got meaning
Grease is the time, is the place, is the motion
Grease is the way we are feeling

We take the pressure and we throw away
Conventionalitly belongs to yesterday
There is a chance that we can make it so far
We start believing now but we can be who we are

Grease is the word
Is the word that you heard
It's got groove it's got meaning
Grease is the time, is the place is the motion
Grease is the way we are feeling

This is the life of illusion
Wrapped up in trouble (trouble), laced with confusion
What are we doing here?

We take the pressure and we throw away
Conventionality belongs to yesterday
There is a chance that we can make it so far
We start believing now that we can be who we are

Grease is the word
Is the word that you heard
It's got groove it's got meaning
Grease is the time, is the place is the motion
Grease is the way we are feeling

Grease is the word
Is the word that you heard
It's got groove it's got meaning
Grease is the time, is the place is the motion
Grease is the way we are feeling

Grease is the word
Is the word
Is the word
Is the word
 

Daddyisabar

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[video=youtube;8gqiyqu1GVE]https://www.youtube.com/watch?v=8gqiyqu1GVE[/video]

A nice flight on the G 64 is almost as purdy as Olivia!
 

Daddyisabar

Oddrocs Rule!
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Always build yer motors carefully the night before the launch with yer favorite grease. I'm a Dapper Dan Man.

[video=youtube;4hni4OIJXG4]https://www.youtube.com/watch?v=4hni4OIJXG4[/video]
 
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