assembly problem

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Well-Known Member
Apr 24, 2004
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im assembling my AT e18-7w reload and theres a tube that goes into the tube that holds the propellant grain. it wont move at all. i cant get in in or out. i think this looks like it is just an optional piece and im thinking about just taking my hobby knife and cutting it off at the end of the tube and continuing on. is that ok?
It is a spacer, it is needed to keep teh grain from really sliding in the liner.
well i got it most of the way into the tube but the very end that sticks up (about 1/2 inch up) is really crumpled and wont go down. can i cut that off?
No...the nozzle should not be loose.

It sounds like the grain liner was too tight and got messed up when you put it in the case. It's fairly common for the grain liner to be too tight on the 24mm RMS loads. If the liner is too tight, I just carefully peel off the top layer of paper so it will fit into the case. As a matter of fact, I flew both an E18 and a F12 24mm load today and had to peel paper off both loads.

If the liner is ruined....and it sounds like it is....DO NOT use this load. Take it all out of the case and start over. If you give Aerotech a call, I bet that they'll send you the parts you need to re-do this load for free.

I hope this helps. You want to make sure you put it together correctly or you run the chance of a CATO that will ruin your 24/40 case.
ok i shoved it in as far as possible then cut off the crumpled part. to make up for the bit that was cut off i used to chopped up 24mm tubing to complete the spacer. i dot think it was enough thaough. so im going to put some more on there to make the grain flush with the liner, that should stop the nozzle from wiggling
I wouldn't try making your own motor parts. I'd call AT, they should be pretty good about replacing a spacer/liner. About teh loose nozzle- did you use all the o-rings? if it is loose even then, definitely call Aerotech. A loose nozzle could swivel during flight and expel gasses somewhere else than straight down the roll axis of your rocket, and you could end up with a giant spinner. Or, exhaust could escape around the nozzle and cause a depressurization, which with AP would extinguish the motor. Also if it were to depressurize in that manner, I imagine parts of the nozzle could be eroded.
its not like i modified any major part of the motor. i just replaced one tube with another tube. and yes i fixed to nozzel wiggle.
Yeah... About the time you are cutting your own cardboard to make the nozzle fit right, it's about time to pull every ting out, and throw it in the trash, and start over. This time though, follow the directions a little more carefully, and get a parent to help...:)

No offense meant at all, if you took any...:)
It may just be a cardboard tube, but it's a fairly important part of the motor. The grain liner not only protects the casing from heat when the propellant is burning. It also provides the o-rings something to seal against and hold the pressure. The length dimension is important.

Here is a pdf assembly drawing of the E18-7 load straight from Aerotech's website.

Notice that the o-rings are loaded when you screw on the closures and they press up against the grain liner.

It would be better to take it apart and start over.
START OVER!! I loaded a motor wrong ( I inverted the delay with spacer) and my motor ended up in the back of someones car, without the rocket. Please follow eveyones advice and try it again and folow the directions exactly, even if it means reading them over 10 times. It will be better in the long run.
ok i dont think i explainde this well enough. the propellent grain fits the tube perfectly, the problem was the spacer that i assume works like an engine block to keep the propellant grain from sliding up the motor casing when it lights. the spacer i got was slightly warped and would not fit all the way down the tube since it was about 1/4 inch short. so when the nozzle was inserted and the ring on the end was screwed into place the nozzle would be pushed the extra 1/4 inch up and that would cause the nozzle to wiggle. i tried pushing the spacer down and got it partally down with some success but it was just to warped to fit and need an extra bit of space to fit the propellent snugly against the nozzle. with the extra space added to complete the motor the nozzle no longer wiggles so am i ok to fly it?
You should just call Aerotech and ask for a replacement liner and spacer. That money you spend on the call it may even be toll free) could be the insurance for your rocket and possibly someone else's property. The part that you made yourself may not be up to the pressure specifications of the motor, so when it ignites the spacer could be pushed forward and the nozzle COULD wiggle. Also, making your own motor parts may void your NAR/TRA insurance.

i launched it today with no problems due to motor malfunction. but i was dumb enough to put a 7 second delay on it with my onyx. the rocket didnt go as high as i thought it would and it core sampled with a crowd pleasing pop of the parachute deploying at almost exactly the same time as it hit the ground. but it had no damage so i dug it out, bought a new reload(with 4 second delay),and flew it again fine. thanks for your help i appreciate it.
Ahh I love those, bring a chuckle to my poor miserable life......but most importantly you learned something. And people don't learn if they're always told NO. or YOU CAN'T, or I WON'T ALLOW IT! it was all worth it regardless of the loss of the rocket.

I despise those who say you CAN' keep flyin' and keep learnin'!


The grain spacer is there to keep the grain from wiggling around. Since the igniter needs to be at the forward end of the propellant grain (and not at the forward end of the whole motor), the grain cannot shift, or else the igniter will loose it's place at the forward end of the grain. That is a bad thing. As long as you don't care about the warranty/possible legal issues and you have a pretty tight fit between the casting tube and liner, you would be alright.
Originally posted by Chuck Rudy
Ahh I love those, bring a chuckle to my poor miserable life......but most importantly you learned something. And people don't learn if they're always told NO. or YOU CAN'T, or I WON'T ALLOW IT! it was all worth it regardless of the loss of the rocket.

I despise those who say you CAN' keep flyin' and keep learnin'!



i didnt loose the rocket. in fact the only damage from that core sample was an intresting looking mud pattern on the nose cone