Estes Leviathan/AT G71R-7 failure

[noffie79]

"Launched" my Leviathan for the first time today. It didn't go so well. I'm not sure when AT stopped producing this motor, or why, but I've flown three of them previous to this flight without issue. My luck changed today. I have no idea if it was a bad delay grain, simply a motor that was too old, or something I may have done wrong. If anyone has any input, I'd appreciate it! https://youtu.be/qKD2t6Jl3mQ

 

[joshismycaptain]

Sorry to hear that. Just watched the video. Unfortunately I have no knowledge on the subject. Is it badly damaged? We can't see the nose condition in the video. I gotta be honest,,, I was stoked for a catastrophic explosion video! I have a leviathan too. A pink one! Flown it a few times on G40 & G80. Cool model. Hope it's OK.

 

[pyrobob]

Wow, that's pretty wild. Total bummer though. If I recall AT had some persistent delay issues with this particular reload. Too short, too long, or just non functional; I'm not sure, but I am pretty certain the delay is why they stopped production. I haven't had a chance to wade through this, but here's some further intel for you: https://www.rocketryforum.com/showthread.php?15722-Aerotech-G71-4R

For what it's worth, they are working on a redesign and from what I gather should be available relatively soon.

 

[noffie79]

Here are pictures of the nozzel. No idea why it would've done that. Not sure if that was the cause of the problem, but still something I've never seen before.
And pics of the damage...

 

[noffie79]

 

[rstaff3]

Here are pictures of the nozzel. No idea why it would've done that. Not sure if that was the cause of the problem, but still something I've never seen before. View attachment 303939View attachment 303940
And pics of the damage...View attachment 303941

Probably the delay problem noted above. A nozzle off kilter or up in the motor is not uncommon when a reload lawndarts. The inside of the motor is partially burned and there isn't much holding the nozzle in place. Rocket stops, nozzle tried to keep going.

 

[noffie79]

Probably the delay problem noted above. A nozzle off kilter or up in the motor is not uncommon when a reload lawndarts. The inside of the motor is partially burned and there isn't much holding the nozzle in place. Rocket stops, nozzle tried to keep going.

That makes sense. Thanks. That's about the only thing I can come up with as well, bad delay grain. It comes with the territory. The rocket will be fixed and will fly again.

 

[Lowpuller]

Ouch!!!

I have a Leviathan that looked similar

 

[noffie79]

Ouch!!!

I have a Leviathan that looked similar

View attachment 303943

View attachment 303944

Wow! That thing experienced a whole new level of destruction. It's a bummer when it happens, but it makes for good videos and sharing of lawn dart photos.

 

[rcktnut]

Looks like the delay didn't even ignite until the rocket hit the ground, and after that took about 12 seconds, of course would take longer to burn without pressure. With the ignition problems you had, guess the delay did not ignite at lift off.

 

[Lowpuller]

It was so badly damaged I could not even reuse the "fin can".

 

[noffie79]

Looks like the delay didn't even ignite until the rocket hit the ground, and after that took about 12 seconds, of course would take longer to burn without pressure. With the ignition problems you had, guess the delay did not ignite at lift off.

That's exactly right. With the ignition problem, I was even wondering if maybe I hadn't inserted the igniter all the way. I used an AT First Fire Jr, and those tips can be on the large side and difficult to insert sometimes. I'll never knows the reason, whether it was delay grain failure or something that I did, but I'll make damn sure that igniters are inserted completely in the future.

 

[noffie79]

It was so badly damaged I could not even reuse the "fin can".

It doesn't look like it. At least the fin can on mine is salvageable. It'll fly again soon!

 

[dhbarr]

That's exactly right. With the ignition problem, I was even wondering if maybe I hadn't inserted the igniter all the way. I used an AT First Fire Jr, and those tips can be on the large side and difficult to insert sometimes. I'll never knows the reason, whether it was delay grain failure or something that I did, but I'll make damn sure that igniters are inserted completely in the future.

Four chuffs, nominal boost, extreme delay.

FWIW all of the other reports I've read on the g71r had the delay coming in way too short, immediately after burnout.

It seems significant the delay began to burn immediately after impact, but I can't think what could cause such behavior.

 

[tmacklin]

That's exactly right. With the ignition problem, I was even wondering if maybe I hadn't inserted the igniter all the way. I used an AT First Fire Jr, and those tips can be on the large side and difficult to insert sometimes. I'll never knows the reason, whether it was delay grain failure or something that I did, but I'll make damn sure that igniters are inserted completely in the future.

I think you are on to something here. For any composite engine to perform properly, the igniter must contact both the delay grain and upper portion of the propellant grain/s so that the entire propellant surface is burning under pressure. When the ignition occurs too low the flame front works its way upward and at a much slower rate and pressure. This could explain the "nominal boost" and "extreme delay" noted by dhbarr's post. The "four chuffs" could have been from an old engine that had picked up moisture in the grain.

 

[noffie79]

I think you are on to something here. For any composite engine to perform properly, the igniter must contact both the delay grain and upper portion of the propellant grain/s so that the entire propellant surface is burning under pressure. When the ignition occurs too low the flame front works its way upward and at a much slower rate and pressure. This could explain the "nominal boost" and "extreme delay" noted by dhbarr's post. The "four chuffs" could have been from an old engine that had picked up moisture in the grain.

That's a good possibility. I was disappointed, to say the least, considering that rocket had never been flown before. But it's something that happens, and I'm trying to learn from it. If it was my fault, so be it, but I don't think I'll know for certain if it was my error or a bad motor/delay grain.

 

[Nick@JET]

Longest burning G71 I've ever seen, too bad it was just that, burning. That stinks Ryan I too have a ..."stumpy to stretched" Leviathan. Still motor deploy, good time to convert it.

I've had a few of the G7# LMS chuff several times before coming up to pressure but have never seen the delay start burn after touch down, almost like it slid and lit or quite a coincidence that it started smoking at the time of impact.

 

[Nytrunner]

Ouch, I hate to see a scrapped Leviathan, much less two in the same thread. Easily my favorite PSII kit.
I'll be sure to check my igniter insertion to keep my Scion->Leviathan refit safe.

 

[noffie79]

Longest burning G71 I've ever seen, too bad it was just that, burning. That stinks Ryan I too have a ..."stumpy to stretched" Leviathan. Still motor deploy, good time to convert it.

I've had a few of the G7# LMS chuff several times before coming up to pressure but have never seen the delay start burn after touch down, almost like it slid and lit or quite a coincidence that it started smoking at the time of impact.

I remember seeing your stretched Leviathan! Sure does fly well. I'm going to order some parts in a bit, both to fix this one and to build another one. A Scion and a slotted body tube is all that's needed. I have a Scion in the build pile already, but another one won't hurt. Besides, this Leviathan has turned into an elusive creature for me. This was my third one. Hopefully I won't have to scrape parts together to build very many more. Lol

 

[tmacklin]

That's a good possibility. I was disappointed, to say the least, considering that rocket had never been flown before. But it's something that happens, and I'm trying to learn from it. If it was my fault, so be it, but I don't think I'll know for certain if it was my error or a bad motor/delay grain.

It might be that when the engine went through the "chuffing mode" but didn't fully ignite, the igniter was dislodged and pushed downward to the lower grains, resulting in the unfortunate chain of events. I had something similar happen to me on an old AT G40-10. That engine was maybe 10 years old and the package had been opened but was not flown immediately (several months IIRC). It chuffed several times but finally came up to pressure and functioned as designed.

If you are looking for a replacement Leviathan kit, I have two for sale on my website. :smile:

 

[K'Tesh]

Sorry to hear that the rocket was damaged. :sad:

Just a FYI, you can post videos in your post by clicking the "Insert Video" icon (looks like a filmstrip or a ladder) that resides between the "Insert Image" and "Wrap [Quote.] Tags around selected text".

[video=youtube;qKD2t6Jl3mQ]https://www.youtube.com/watch?v=qKD2t6Jl3mQ&feature=youtu.be[/video]

Looks like it was a nice looking rocket before the lawndart... any pics?

 

[noffie79]

It might be that when the engine went through the "chuffing mode" but didn't fully ignite, the igniter was dislodged and pushed downward to the lower grains, resulting in the unfortunate chain of events. I had something similar happen to me on an old AT G40-10. That engine was maybe 10 years old and the package had been opened but was not flown immediately (several months IIRC). It chuffed several times but finally came up to pressure and functioned as designed.

If you are looking for a replacement Leviathan kit, I have two for sale on my website. :smile:

I agree. It was an unfortunate chain of events and there's nothing I can do about it now. I just hope it doesn't happen again! What's your website?

 

[tmacklin]

I agree. It was an unfortunate chain of events and there's nothing I can do about it now. I just hope it doesn't happen again! What's your website?

Just click on the blue text at the bottom of this reply. It should take you straight to my home page. :smile:

 

[noffie79]

Just click on the blue text at the bottom of this reply. It should take you straight to my home page. :smile:

I'm using the iPhone app, so there is no link. I'll have to wait until morning once I'm home from work and can get on the computer.

 

[noffie79]

Sorry to hear that the rocket was damaged. :sad:

Just a FYI, you can post videos in your post by clicking the "Insert Video" icon (looks like a filmstrip or a ladder) that resides between the "Insert Image" and "Wrap [Quote.] Tags around selected text".

[video=youtube;qKD2t6Jl3mQ]https://www.youtube.com/watch?v=qKD2t6Jl3mQ&feature=youtu.be[/video]

Looks like it was a nice looking rocket before the lawndart... any pics?

I use the iPhone app, so the only way for me to share videos is posting the YouTube link. The only picture I had of it was from about three minutes before tragedy struck, while it was sitting in the pad...

 

[K'Tesh]

I use the iPhone app, so the only way for me to share videos is posting the YouTube link. The only picture I had of it was from about three minutes before tragedy struck, while it was sitting in the pad...View attachment 303951

Thanks for sharing the picture.

I didn't know that the iPhone can't insert videos... Now I do.

Again, sorry about the damage, looks like it was a pretty clean rocket.

 

[noffie79]

Thanks for sharing the picture.

I didn't know that the iPhone can't insert videos... Now I do.

Again, sorry about the damage, looks like it was a pretty clean rocket.

Thanks, it was. First flight too! Oh well, it'll get rebuilt and fly again soon.

 

[K'Tesh]

Thanks, it was. First flight too! Oh well, it'll get rebuilt and fly again soon.

Hint...Take more pics :wink:

 

[Fred Garvin]

Bummer......too bad.....the Levi is such a great bird, capable and strong. Hate to see one encounter extreme drag conditions....

 

[Rex R]

I've been testing a theory I have about 'bonus' delays...with only 5 'tests' I can't say conclusively that it works. theory: bonus delays are caused by the delay element not igniting at engine start due to oxidation of the delay surface. so I have been giving my delays a few swipes with 60 grit sandpaper. so far no bonus delay. I note that the starters do not touch the delays in 24mm 1grain Ds & Es and 29mm Es & Fs(AT) as one is supposed to tape the top of the propellant (the tape gets burned through Very quickly with even just a chuff).
Rex