AeroTech Open Thread

[3stoogesrocketry]

I have to peel tha labels off all my H-13 motors even if they go in, they are too tight after firing to remove them, even after cooling...

Does the glue from the lable get to hot and glue itself into the tube , or are they literally expanding ?

 

[burkefj]

Does the glue from the lable get to hot and glue itself into the tube , or are they literally expanding ?

It's a combination, they are expanding a bit and the heat is causing some of my cardboard loc-aerotech type tubes to shrink slightly, maybe the glue used, I've had to switch to pml phenolic motor tubes to stop the issue completely.

 

[Antares JS]

Suggestion when you're peeling labels off - wipe down the motor with goo gone to remove any errant adhesive that could cause problems post-firing.

 

[burkefj]

Suggestion when you're peeling labels off - wipe down the motor with goo gone to remove any errant adhesive that could cause problems post-firing.

Attention Hall in my case I use a razor blade to remove the label and using adhesive remover and lightly sand it so that's not an issue in my case

 

[AeroTech]

I feel like this discussion should be brought in here:
https://www.rocketryforum.com/threads/do-you-have-to-peel-labels-off-24mm-qjets.172806/

The 24mm Q-Jets were designed to fit standard 24mm motor mount tubes. They can be a little snug near the nozzle end due to expansion from nozzle pressing at that end but they will fit.

From Bob Sanford:

"I have been flying 24mm Q-Jet motors (D22 & E26) for almost a year now and I have never had to peel off the outer layer.

I have flown the 24mm Q-Jets in an 1985 vintage Estes Renegade kit, a clone of the Estes Maxi-Icarus I built in 2007 and an Estes Maxi-Alpha 3 among others.

One thing I have noticed is that if a lot of glue was used to attach the centering rings to the motor mount tube the tube will shrink slightly where the glue is located. This can make it hard to push in the rocket motor."

If you have a fitment problem, why not sand the inside of your motor mount tube slightly instead of having to peel the label off each motor?

 

[AdAstraPerAspera]

Don't worry about weakening the motor mount by sanding it out a bit. Grab your Dremel with a fine grit drum, and have at it.

The motor mount, other than where the thrust ring of the motor presses on it, really isn't a necessary structural component. I know of guys who fly O motors without them. Just centering rings sized for the motor instead of a mount. The thrust ring contacts the aft centering ring directly, and the fin tabs are on the other side.

My next (modest sized high power) scratch build may end up getting built this way. The only reason I use motor mounts on most rockets is because kits and standard parts are made that way. It does make construction easier in some ways with fin mounting and such. If you do use them, you can make other mods, like leaving out all but one centering ring (to stop ejection gases, usually the forward one). Think outside the box, and have fun!

 

[StreuB1]

One thing I have noticed is that if a lot of glue was used to attach the centering rings to the motor mount tube the tube will shrink slightly where the glue is located. This can make it hard to push in the rocket motor."

+1

 

[Jay Dub 4009]

Aerotech,

I don’t know if it’s real or perceived only, but it seems like alot of vendors are pretty thin on motors currently. Is there anything you can elaborate on production/supply constraints or is it all in my head?

 

[AeroTech]

Aerotech,

I don’t know if it’s real or perceived only, but it seems like alot of vendors are pretty thin on motors currently. Is there anything you can elaborate on production/supply constraints or is it all in my head?

Lead times for most dealer orders are currently running 8-12 weeks. We have experienced high demand since roughly last September. Raw material lead times have in some cases unexpectedly increased from 1 month to 3 months. We are hiring as necessary and currently have 22 employees.

 

[Jay Dub 4009]

Thank you !

 

[tbonerocketeer]

Aerotech,

I don’t know if it’s real or perceived only, but it seems like alot of vendors are pretty thin on motors currently. Is there anything you can elaborate on production/supply constraints or is it all in my head?

Define thin?

 

[Jay Dub 4009]

Define thin?

When shopping around for some 75/54mm reloads a few weeks ago, wild man, Chris and a few other vendors were sold out of what seemed like 75% or more of their reloads for those sizes. I didn’t take the time to gather have empirical data to support this, but Goto their web stores and it still seems to be the case.

 

[Hobie1dog]

A friend gave me a J350 motor 10-12 years ago. Today I got it out and he had put one grain in the liner. It is stuck/frozen in place and bulging out in a dome shape.

today I'm going to try using a big dowel that may be close to the liner ID and tap the grain out. I'm hoping I can also sand the grain flat again and use 500 grit sandpaper on this grain and the others to get them to fit. I was going to use this for my Level 2

 

[AeroTech]

A friend gave me a J350 motor 10-12 years ago. Today I got it out and he had put one grain in the liner. It is stuck/frozen in place and bulging out in a dome shape.

today I'm going to try using a big dowel that may be close to the liner ID and tap the grain out. I'm hoping I can also sand the grain flat again and use 500 grit sandpaper on this grain and the others to get them to fit. I was going to use this for my Level 2

I would cut the dome off with a hobby knife and peel the outer paper layer if necessary to help the grain fit properly.

 

[FlyBy01]

We were actually in the process of certifying an M-class 75mm DM reload about four years ago, the M1955DM. But one CATOed during certification and a redesigned version CATOed on our test stand, so the project was "back burnered".
View attachment 519331

Any chance it will be moved onto the front burner soon?

 

[rharshberger]

We were actually in the process of certifying an M-class 75mm DM reload about four years ago, the M1955DM. But one CATOed during certification and a redesigned version CATOed on our test stand, so the project was "back burnered".
View attachment 519331

The M1955DM was the only reason I bought a 75/7680 case, maybe someday I wull get to fly the Nuclear Sledgehammer on a M sparky (my NS was built as the sustainer of a two stage so it only has a 75mm mmt).

 

[AeroTech]

Any chance it will be moved onto the front burner soon?

It's still an enigma as to why we had trouble with it. We need to give it some more time and thought, resolution to these types of issues eventually come to light from the subconscious.

 

[0011001100]

It's still an enigma as to why we had trouble with it. We need to give it some more time and thought, resolution to these types of issues eventually come to light from the subconscious.

Could it have been slag building up faster than the phenolic was eroding?

 

[Hobie1dog]

I got the swollen up grain knocked out of the liner. The date code was June, 1997 (25 years old) Sanded off the excess propellant sticking up above the paper liner on all 6 grains, which was likely about 5%

Looked at the assembly instructions but couldn't figure out why the nozzle is plugged.

 

[Hybrid33]

The nozzle is plugged because the mold it was made in has a core pin stack up issue . Could be damage, wear or possibly it was never correct . It should not be plugged .

 

[Hobie1dog]

The nozzle is plugged because the mold it was made in has a core pin stack up issue . Could be damage, wear or possibly it was never correct . It should not be plugged .

It came out of the original package that way.

 

[rharshberger]

It came out of the original package that way.

The nozzle is plugged because the mold it was made in has a core pin stack up issue . Could be damage, wear or possibly it was never correct . It should not be plugged .

Or its just flash and easily removed with hobby knife.

 

[AeroTech]

It came out of the original package that way.

Just use a hobby knife and remove the flashing.

 

[FlyBy01]

It's still an enigma as to why we had trouble with it. We need to give it some more time and thought, resolution to these types of issues eventually come to light from the subconscious.

Guess I'm going to have to do with the 98mm for my Level 3

 

[Tom Flint]

This is a great explanation! I have a follow-up question. Back in 2002 or so Apogee sold 13 mm composite contest motors. I used the C motors myself and they were very cool. I believe they were made by AeroTech. If so, how did they get around these issues?

I don't speak in any official capacity here, but I flew the B7 13mm motors back then. They were blue thunder propellant with a C-slot grain geometry, so the delay issue cited here wouldn't be a problem with those. The C-slot geometry made them longer burning than similar motors which have a core down the center like the Q-jets. I think it would be difficult or impossible to get the igniter properly positioned in a Q-jet if it had an offset core due to most of them being only partially filled with propellant grain. Also, with the B7's being motors geared toward competition flyers, production cost was not nearly as much of a factor as it is in Q-jets which need to meet a price point not too far off black powder motors, hence the Q-jets' clay nozzles and associated design challenges they present.

 

[Hobie1dog]

Sandy H thinks I shouldn't use this 25 year old J350 in any rocket I care about. Problem is, I'm living on SS Income. I have almost no spendable income. The only way I can buy things is to sell something I currently own.

 

[jimzcatz]

It will be fine

 

[Steve Shannon]

Sandy H thinks I shouldn't use this 25 year old J350 in any rocket I care about. Problem is, I'm living on SS Income. I have almost no spendable income. The only way I can buy things is to sell something I currently own.

So it sounds like if you don’t use it you won’t be flying the rocket. What’s the use of having a rocket that you can’t fly? If you use the motor and it works, it could be awhile before you can fly again. If you use the motor and it doesn’t work, are you any worse off?
Although I’ve seen issues with grains swelling or developing a white crust, I don’t recall seeing a Cato that was directly related to an old composite motor. Just inspect the grains well before assembling the motor, clean them up with sandpaper if needed and use a good igniter. Have fun flying it.

 

[Hobie1dog]

So it sounds like if you don’t use it you won’t be flying the rocket. What’s the use of having a rocket that you can’t fly? If you use the motor and it works, it could be awhile before you can fly again. If you use the motor and it doesn’t work, are you any worse off?
Although I’ve seen issues with grains swelling or developing a white crust, I don’t recall seeing a Cato that was directly related to an old composite motor. Just inspect the grains well before assembling the motor, clean them up with sandpaper if needed and use a good igniter. Have fun flying it.

Will take your advice, thanks.

 

[AeroTech]

Could it have been slag building up faster than the phenolic was eroding?

I suppose that is a possibility but the CATOs happened at ignition I believe. My current theory is propellant slumping (critical modulus failure) due to the lower solids loading and relative softness of DM propellant. May have to harden it up somehow.