AT Initiator

[Elapid]

Pros:
Kit went together in about 45 minutes, quite an easy build. the through-the-wall fin attatchment is rock-solid! Nice diameter rocket and went up nicely on an F20-4 Econojet motor.
sturdy construction, body fell a good 200' and was unhurt.

Cons:
unfortunately, the motor hooks don't seem to be very good at retaining motors.
both the Cheetah and the Initiator came down smoldering. the initiator started a fire when the shock cord burned through!
parachute was burned by the ejection charge gases and the model came down fast. the baffle caught on fire and when the chute dropped it to the ground a brush fire was instantaneous.

i like the idea of not having to use ejection wadding, but i think i've had quite ENOUGH of AT's baffled system that ensures the motor will eject and burns through the model from the inside out, weakening the structure with each flight.


Summary:

While the construction is solid, i don't like my rockets catching fire, so i won't be buying any more Aerotech rocket kits, and the ones i do have will have the baffles removed and i'll use wadding like normal people.

 

[Ryan S.]

I have never had a problem with ATs baffle, did you remember to put the wire mesh in there?

I did lose a motor casing once though due to the motor hook not holding the motor in

 

[Elapid]

but still the plastic baffle caught fire and melted through the shock cord, the parachute either got singed in the fire, or by the ejection gases. i believe the former, since the rocket was coming down so fast...

maybe something flame-retardant would make more sense than flammable plastic pieces.

i'm really disappointed.
i don't want to fly them for fear of hurting someone if there's another failure.

 

[Larry]

I don't doubt your word, but I find it very unusual. I have an Initiator that has more than a dozen great flights on with no problems at all. I have heard of a few engine hook problems, but I've never had a problem there either. Sorry to hear of your problem. The Aerotech Kits are some of my favorite midpowered kits...Larry

 

[Elapid]

seems to be a joke, really.
0 retentions for two flights...
two separate models...

i'm thinking of using a more positive retention device in the future. i'm going to put a section of 1/4" allthread on the new, improved centering ring. it will go through the rear ring and i can use any of a number of strategies to retain the casing, from a simple tab, to a full ring...


here's a pic of the burned section of the motor mount

 

[Elapid]

it appears that the baffle caught fire, melting the epoxy (from now on i'll use JB Weld for any joints that contact the motor side of the MMT) and releasing the main body from the recovery system. the nose/recovery system landed in some dry grass igniting a small brush fire which could have easily spread out of control. the shock cord burned through before it hit the ground, so the parachute landed outside the fire. the burning plastic baffle actually started the fire. i'll go recover that today.

 

[Elapid]

i wonder...
these are old style F20-4 afaik, i think the new ones have a full length casing?

 

[astrowolf67]

A quick question, and I only ask because I've caught someone making this mistake on the way out to the launch pad. Are you using the motor adapter spacer that came with the kit? And the cardboard one that comes with the motors?

 

[Elapid]

yes, i used both the phenolic spacer that came with the kit as well as the cardboard one that came with the motor.

the spacers were both still inside the MMT, i just removed them.
the motor clip and the thrust ring are intact.

the forward phenolic CR, the plastic baffle, and the heat absorber are gone.

i have fashioned a new CR from Birch Plywood, some 10-32 allthread will be used for motor retention.

 

[Darian Rachal]

I've shot quite afew AT rockets over the years & never had a problem like what you describe. I did have an Estes D or E cato in my Cheetah & blew the baffle system out.

For you to have a problem with 2 AT rockets is quite unusual. I've flown the old AT econojets as well, with no problem. If you ever solve the problem, let us know.

 

[Stones]

I've got to add to the previous posts. Umteen flights with Econos with the Mustang, Warthog, and a baffle system I put in an Estes Executioner. Never had a problem with any of these. Most I can see is a little sooty residue inside the BT and I've never burned a chute. That pic of the melted plastic looks like it would be more from a flareup of powder, rather than an ejection "explosion". Alot of heat there to do that damage. Just a theory, mind you.
At any rate, give Aerotech a call and the motors AND rockets should be replaced without a problem.

 

[Elapid]

i've only flown it once and the heat sink material seems to be deteriorating, black bits of shavings fall out the end when i shake the rocket.

i don't think aerotech owes me anything.
the rocket survived, only the chute was destroyed in the mishap.

the liftoff seemed a little slow, maybe 3 - 5 seconds from when the igniter smoked and the rocket lifted off. the tower of black smoke was sweeeeet! the white smoke of the delay charge followed normally, marking apogee quite well. the ejection charge went off on time, maybe a little late, but the whole model was descending on the chute (a bit fast, possibly the chute was melted at this point) until the burning baffle melted, releasing the main body tube. the centering ring, burning baffle, and nosecone floated down on the chute.

i have replaced the forward centering ring with a hand-carved aircraft plywood piece. i used an estes-type shock cord mount and 6 feet of 1/2" wide 100% cotton elastic shock cord.

I just need to install a foolproof motor retention device.

next time i'll take some video!

 

[loopy]

Yeah, some of the shavings will come out after every flight, and they recommend replacing them every dozen flights or so.

Sorry to hear about your bad luck with the kits - I've personally never had any problems, but I've only launched one Econojet. I mostly use reloads, and I've launched my Initiator on four reloads with no incident. I've also successfully launched my Mustang and Strong Arm with no problems at all.

I think your repair on the mmt looks great, and you should have no problems.

For those who have experienced the AT hook kicking the motor (once again, hasn't happened to me), I've seen people wrap floral wire or tie wraps around the motor tube/hook to hold the hook in place for the flight. Just a thought.

Loopy

 

[Stymye]

I second the tie wrap idea.especially when using the smaller reload casings in hook type motormounts

 

[firemanup]

Doesn't sound like a rocket problem at all..

How closely did you inspect the motor afterward..????

I had a very similar flight with my AT Warthog a couple months ago.. the problem was the top end of the motor let go and it was thrusting from both ends.. the rocket was still able to get airborne but burnt everything up inside...

I can think of nothing short of a top end leak/failure that would cause what you're describing and that again is back at the motor.. not the rocket...

Looking at your pictures they look exactly the same as mine..

We really need to investigate things when we have problems like this... especially fire issues..

Here's the specific page on my site that shows some of the pics I have.. and the top end of the motor...

https://www.firemanrocketry.com/launch41104.htm

 

[Elapid]

that's a big reason why i haven't treid any of the relaods yet. i can't afford to lose hardware. zip ties looked like the hot ticket when i was browsing the hardware aisles. i almost got one of those variety packs.

i tried to remove the 'thumbs down' icon from the post, seems a little harsh. the model is STOUT, unbroken from its fall, and flew arrow-straight and high.

my *only* complaint is with the ejection system and motor retention method.

 

[Elapid]

but every event happened in orderly, expected fashion.
ignition, boost, delay, ejection.
it was a perfect flight!

the chute opened up at around 1000' and the model was dropping fast!, the chute must have been damaged at that point.

i used epoxy on the motor mount construction, put the little slits in the tube and forced glue into them to retain the baffle/heatsink assembly. the whole end of the motor mount tube is burned away.
OH MAN!
i think i figured it out.
looks like i forgot to epoxy the forward ring to the body tube though, so when the motor tube burned through, the whole baffle assembly separated from the rocket and floated down on the chute. before that part hit the ground, the shock cord burned through and dropped the burning plastic into the grass. the parachute was on the outside of the grass fire and not damaged subsequent to the landing.

if i had secured the ring to the body wall, it might have held the burning pieces inside the body tube. if the motor hadn't kicked out there wouldn't be enough airflow through the body tube to support combustion for long, but since there was ample airflow, the embers were fanned into flame...

that's my current theory.
i need to go back to the crash site and recover any pieces. i expect to find the forward centering ring, baffle, and heat sink material.

 

[firemanup]

Elapid..

Did it kick the motor.. ? I'm tellin ya your pictures are exactly the same as mine.. that motor burnt through at the top..it's the only way that the top end and chute could get burnt like that...

If you don't have the motor to confirm otherwise i really, really think that motor let go up top and burnt everything up..there's just no other explanation for it to torch it like that...

My rocket too launched and went up, and it had a huge hole in the top end.. so it basically went up under about half thrust or less..and still flew up...

A smaller hole would be enough to burn everything up but still allow enough thrust to really get the rocket up there..

Just my guess.. 2 cents worth.. but looking at your pics, especially the one down into the motor tube.. that's not caused by an ejection charge...

 

[firemanup]

Here's looking down inside the body tube at the top of the motor tube where the top end of the baffle system was..before the flight..

<img src="https://members.aol.com/firemanup/insidebodytube.jpg">

 

[firemanup]

Here's the top end of the baffle system ....it was glued in as per directions but the heat/flame was too much and it burnt away and let go.. you can see the eye bolt in the picture and what's left of the top centering ring and platic baffle system..

<img src="https://members.aol.com/firemanup/baffletopend.jpg">

 

[firemanup]

All the parts after we gathered them up....

<img src="https://members.aol.com/firemanup/meltedparts.jpg">

 

[firemanup]

The faulty motor..

<img src="https://www.firemanrocketry.com/images/g40b.jpg">

 

[Elapid]

have a look inside the body tube, doesn't really look like yours.

 

[Elapid]

hehehhe!

 

[firemanup]

No it doesn't look the same in the body tube but i still feel the motor tubes look the same..

Mine had a grand canyon hole/failure in the top end.. i'm still thinking a smaller hole would do exactly what you described, also would explain why you still got such a good boost...

Anyway... just my best guess.. either way it doesn't sound like a rocket or kit failure to me... more along the lines that something went awry with the motor...

Hope ya can find the motor itself.. will be interesting to get a peak at the top end of it..

 

[Elapid]

b4 i replaced the forward centering ring
the only real damage is to the front section of MMT tube. it appears that several inches are missing from the powder burn pattern.

 

[firemanup]

Yeh that looks like what i'd suspect for the same failure i had, only under a smaller scale...

As you can see in my pic of all the parts we gathered up mine was so bad you the chute melted alltogether rolled up and never deployed..

Yours, to me anyway, seems like the same failure just much smaller scale, explaining why you have a very good thrust, and a slower failure, so to speak before everything burnt through, and a partial chute opening...

 

[Elapid]

how could the ejection charge go off *on time*?

everyone counts....dont they?

one potato, two potato, three potato, four potato...

ok...any time now...

*pop*
deployment!


on a similar vein, when i got my cheetah back after the first flight, it was still smoldering inside. enough so that when i blew into the tube, it sounded like blowing on hot coals and the smoke got denser coming out the end of the tube...it took several minutes for me to recover the model and the whole thing is on video. that was on an estes E9-6.

JB Weld

 

[firemanup]

Have no clue how the ejection charge fires correctly, like on mine it also fired.. and that's a grand canyon hole in the top....

However there's also a split in the side.. i dunno if the fire/flame leaked out the side then when the ejection charge fired it busted the large hole in the top..??

If it's not a top end motor failure, and with what you describe with the cheetah.. it almost sounds as if something flamable has gotten onto the inside of the motor tubes....i dunno what you're using for adhesives but it seems strange..

Especially when you look at the vast numbers of others here on the forum, as well as off that have launched AT birds, and do launch AT birds all the time and have no problems with the motor tubes catching on fire, not to mention all the other brands that use basically the same motor tubes..wound paper... and they don't catch or light..??

Dunno.. hope you get it figured out though....

 

[firemanup]

On the other hand though you're the only one that actually saw the flights and you're the one with the recovered parts actually in hand, able to look them over.....so you'll probably have the best perspective on everything...

I'm real curious to see the top end of the motor if you're ever able to recover it...

Good luck with the repairs....