davidshewitt
Active Member
I assembled a L1500T and there's a 5mm gap between the end of the case and aft closure. I cannot get it to go on any farther. Anyone else experienced this. I am not going to fly the motor.
98mm Aft Closure Tolerance
- Thread starter davidshewitt
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Loosen the forward closer by about 2.5mm, screw down the aft closer by 2.5mm. You have now split the difference on both ends. Are the threads completely engaging on the forward and aft closers, if so you are good to go. If you are not completely satisfied call Aerotech customer service.
Definitely don't do that. Forward closure needs to be completely screwed down.
Some gap on the aft closure is fine; not sure whether amount you have is within that margin.
davidshewitt
Active Member
I've had this problem on multiple motors (usually 54mm ones). I did fly one successfully with a gap, but all the threads were engaged. Another I had the liner replaced by the on-site AT vendor.
With at least one thread not engaged I doubt it's safe to fly this motor. :-(
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5mm is a bit bigger than 1/8in which is a little over 3mm. I would contact aero tech warranty, for what it's with the forward closure should ALWAYS be fully seated. If you're going to have a failure, it's much better the aft closure fails than the fore closure.
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Aerotech has in their instructions to tighten the forward all the way down. There is a acceptable tolerance of +1/8" inch in the instructions. Are the grains still sliding free internally?
davidshewitt
Active Member
I bonded the grains into the liner as per the instructions.
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Ok , was not aware the L1500 was a bonded motor. The motor should be absolutely fine as long as the nozzle is tight and has no wiggle.
rfjustin
Well-Known Member
Send it. I flew an M-2225 SW with that much gap without issue. I made damn sure I felt o-ring compression on the aft closure (which I did), and that motor also required grain bonding. IIRC there was a post or two about AT cutting liners a little bit longer, but not finding those posts right now...
davidshewitt
Active Member
I spent several grand and over a year on this rocket... I don't want to be lamenting that if the rocket blows up.
I emailed AT warranty. I'll see what they say.
rfjustin
Well-Known Member
davidshewitt
Active Member
He did! To sum it up:Karl will get back to you im sure.
I'm hoping to see great pics of the flight!
* The FWD closure *must* be tightened all the way.
* The liners are a tiny bit longer now, and about 1/8" or slightly wider gap is normal.
* A strap wrench can be used to tighten it further. I did this and got one more mm (vertical) of engagement.
rfjustin
Well-Known Member
Awesome, love it!
Nice !
Gotta love the customer service at AT !
And thanks for sharing that info @davidshewitt !!
-- kjh
davidshewitt
Active Member
Another question: is this motor still certified with this much a gap?
I had the same issue with an L2500 I flew back in December even after tightening the aft closure with a strap wrench.
rfjustin
Well-Known Member
Why wouldn't it be? The design of the motor didn't change simply because the liner is just a hair longer.
Don't overthink this, you are good to go...
Send it!
davidshewitt
Active Member
I flew the rocket today, however I flew it on an M1600R instead of the L1500T. Even the M1600R had a gap at the back, but it was 2mm, well within tolerance.
For me, it was the tolerance as specified by AeroTech (1/8") that was the deciding factor in not flying the L1500T.
For me, it was the tolerance as specified by AeroTech (1/8") that was the deciding factor in not flying the L1500T.
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NEVER use a tool to tighten an Aerotech closure .
you will never gain anything good .
bobbyg23
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Please don't do this!!!!!!!!!!!! The forward closure NEEEDS to be tight.
Remember that when you have to take it off after the flight.
We were taught many years ago there is no need or reason to use a tool and nothing good could come from it .
With that said we are all getting older and not able to crank on things like we used to.
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Had a similar 'issue' on the new AT N4000 and it flew just fine.
davidshewitt
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How big was the gap? Was it over 1/8"?
The gap on my L1500T is over 1/8" with one full thread exposed. This is outside of AT specs. I do not think it's safe to fly, and several people at my club agreed when I showed them.
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Aerotech/RCS should publish a master list of liner lengths (and tolerances) per reload. And make a public announcement to allow end users to shorten the liner if it's too long. This would keep the modification within the rules for certified motors. If it's too short, send it back for warranty replacement.
I think I found the root cause. I saved the spent L2500 reload parts so I measured it. The liner is 12.813", but the assembly drawing shows 12.688". For a comparison my M4500 liner is 18.75", which exactly matches the assemble drawing and is left with ~1/16 gap when the closure is tightened.
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Only a suggestion. Take your motor apart, I know the grains are glued in, those can stay as is for now. Did you glue the nozzle in as well? Pull the forward seal disk and with a cheap set of accurate digital calipers measure from the face edge of the liner to the face edge of the forward grain. Then measure the amount of the forward seal disk is engaged into the liner. There should be a measurable distace between them. If there is no distance, then proceed. If you can, do the same with the aft end. If your nozzle is glued in as well, contach aerotech for a new liner and remove the grains. If there is a gap , take some good double sided tape and tape a sheet of 120 grit sand paper to a sturdy thick table top. lightly sand id a circular eliptical motion. Measure often as it will sand fast.
Same here. I flew several AT 75 reloads this year with the longer liner and larger gap at the aft closure. I had the same concerns as OP when I first saw it but after AT said good to go, I flew the first one without issues and never looked back after that.
Even after Karl said it was good to go, you still didn't feel comfortable flying it?
