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question on AT G75J RMS

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tomsteve

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I have a couple of these( for the 29/180 case) and am planning a launch this weekend. went ahead today and packed the motor today. seems the motor "rattles" a little inside the case after assembly- when I shake it lightly- fore to aft direction- seems theres a bit of play in there. I went through the instructions very carefully a couple times to see if there was something I missed and even repacked the motor 3 times just to make sure. so now im wondering if im missing something here or if this is how the motor is when packed.
any insight would be greatly appreciated!
 

lawndartman

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I think you are good to go. Many AT motors 'rattle' a bit. If you packed it as per the instructions, I say 'Let 'er Eat!' BTW, I have flown many of them,nice motor! Tim Thomas L3
 

DavidMcCann

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grains rattling is normal. if a seal disc or liner is...that's not.
 

tomsteve

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I had the same question when I put my first AT motor together. I'm a CTI flyer, and they just don't rattle.

In the instructions, refer to step 2.9, figure 11 "It is normal if the grains rattle slightly inside the linerafter tightening."

http://www.aerotech-rocketry.com/cu...MS_Instructions/29mm/29_180-240j_in_20045.pdf

welp, I did miss something!! I didn't COMPLETELY read 2.9. I got through the resistance in threading thing, then moved on. DOH!!!

thanks all!!! hopin the weathers good for flying Saturday! I have a yank enterprises Hawk ive had for 16 years. its maiden flight was in the spring( of this year!) on a G76 and im thinking the G75 should make for a pretty awesome flight.
or
pack it in my estes nike????
dammit, I just gave myself a choice!!!!:y:
 

grouch

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I have one of these motors just waiting for the perfect day to fly it. Post pics!
 

watermelonman

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I think most motors that rattle are because of the manufacturer being too cheap to provide O rings, and hoping that the motor will come up to pressure in such a way that causes the grains to float in relation to each other.

Another solution is to curve one face of each grain. Cesaroni 54mm is like that, and I have had good luck with that on small EX motors.
 

tbonerocketeer

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I think most motors that rattle are because of the manufacturer being too cheap to provide O rings, and hoping that the motor will come up to pressure in such a way that causes the grains to float in relation to each other.

Another solution is to curve one face of each grain. Cesaroni 54mm is like that, and I have had good luck with that on small EX motors.
Grain facing like that takes more time, which would raise the labor costs, raising our cost. In 54mm motors, I don't think oring spacers would be wise. They have to pass through the nozzle if they don't get consumed, plus the performance gain is not worth the effort.
 

DavidMcCann

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They have to pass through the nozzle if they don't get consumed, plus the performance gain is not worth the effort.
You mean...when I fly a J510 that popping sound isn't breaking the sound barrier 5 times?
 

Rob702Martinez

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I had the same thing happen few weekends ago. Took it apart twice. 29/180 flew great.
 

markkoelsch

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You mean...when I fly a J510 that popping sound isn't breaking the sound barrier 5 times?
It is likely the grain liners being ejected as they burn up.

I have not flown the J510, but have flown a bunch of J570. The popping is very predictable. I should look at a Thrustcurve of it and see if the pops show up there.
 

DavidMcCann

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It is likely the grain liners being ejected as they burn up.

I have not flown the J510, but have flown a bunch of J570. The popping is very predictable. I should look at a Thrustcurve of it and see if the pops show up there.
yep. Was a sly joke about every time I fly one someone goes "did you just hear it break the sound barrier? Wow " when it was just puking casting tubes
 
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