Slightly Crooked Motor tube, now can't get casing in

Hey everyone,

I made an oopsie on my rocket and was wondering what I can do to get it working again.

Background information: A 30 inch long motor mount tube (bluetube) with 4 centering rings JB-welded to it which is then JB welded inside of a Bluetube/fiberglass airframe. Pushing the motor casing in, it smoothly slides in 2/3 of the way, but stops there as it gets stuck. It seems the blue tube is slightly bent 2/3s of the way in and this is preventing the motor casing from going completely in.

What I have done so far:

• I have tried sanding the motor mount tube, that has led me to the same spot that I am in.
• I have lightly sanded the casing, but don't think I should do that. It is a thick EX casing.

What I have considered...

• Dremeling half of the motor mount tube and then seeing if I can soak it with water to remove it?
• Putting motor casing on lathe and evenly sanding it. Really don't think I am going to do this. Not safe at all...
• Is there a solvent I can use to dissolve JB weld and remove rings?

What would you guys recommend? I am currently in a predicament :/

-TheHunterN

It seems unlikely that you could "bend" Blue Tube just by installing it in the airframe. Can you see inside the MMT? Maybe take a picture with a flash on your phone? In the past when I have had trouble inserting motor it is because of stray epoxy drippings.

Unfortunately I don't have a picture. Currently away from it. It is just something that has been bothering my mind since yesterday. Might have to put a pause until I get a picture. I locked everywhere for an epoxy drip or any weird raised bumps that could have caused it. But don't recall seeing anything.

How sure are you that it's bent? A blob of glue is more usual.

TheHunterN said:

I looked everywhere for an epoxy drip or any weird raised bumps that could have caused it. But don't recall seeing anything.

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It really doesn't take much, even a tiny smear. Often hard to find. It will take some surgical extraction though if it is 20" inside the MMT. Don't worry though, there are many methods and you have help here. Everything is fixable.

Dont get water near blue tube, but making a reamer using a dowel and some sandpaper will help sand deep in the tube and it can even be drill powered .

Heat will soften epoxy. EEEEven JB weld. Just go slow, heat it uppp and peel it off bit at a time. Damn sticky keys.

Thanks for the support guys, I will see if I can head out and grab it tomorrow. Going to make sure I bring a really strong flashlight to see if I can find any glue blobs.

That's why I keep a drawer full of 80 and 120 grit flapper wheels. Moisture and not exact tolerances of tubes is a constant fight. I've even found some PML couplers won't slide in their own size airframes.
Secondly, if you don't need it for airframe strength, motor tubes don't need to be the length of the motor case. If it's length is ok.

A tiny flashlight like a key ring or laser pointer style is the best for seeing down small tubes. Less in the way.

bill_s said:

A tiny flashlight like a key ring or laser pointer style is the best for seeing down small tubes. Less in the way.

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That is a good idea. A laser pointer would most likely make any undulations stand out.

Try dropping the casing in from the other end and see if it gets stuck at the same position.

I have the same issue with a MS Riley upscale with a long 75mm motor mount tube .

Like OP , did NOT accidentally splash a glob of glue midway through tube to cause excessive binding with motorcase 9 inches in .

Have tried sanding with dowel but blue tube does not sand like fg or paper so would like some suggestions also

Kenny

KenRico said:

I have the same issue with a MS Riley upscale with a long 75mm motor mount tube .

Like OP , did NOT accidentally splash a glob of glue midway through tube to cause excessive binding with motorcase 9 inches in .

Have tried sanding with dowel but blue tube does not sand like fg or paper so would like some suggestions also

Kenny

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Seems with 3" motor mount and 9" in, you could put an extension on a drill (I've seen 12" and 18") and then use a flap sander which is pretty aggressive at removing material.

Combined with a drill bit extension(s) you could reach a long way, good idea Tim.

Speaknoevil said:

Seems with 3" motor mount and 9" in, you could put an extension on a drill (I've seen 12" and 18") and then use a flap sander which is pretty aggressive at removing material.

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@TheHunterN .
Are you sure it is a problem with your MMT and not the motor casing? Maybe your case has a swell in it.

You say your MMT and CRs are already mounted in the airframe?
It could be a not-so-centering ring, the hole is offset and binding the MMT.
If it can't be fixed by sanding and it is definitely something wrong inside you may need to get to cutting. It will be in the extreme remedy realm but if you have to you have to.

Hey guys,

Sorry for the late response. It has been a fun time trying to get access to school since it got shut down and is now virtual. Here are some picture of the motor mount tube. I think I will have to do as you say and might have to cut the tube. I just got an M1340W and I will test fit that casing to see if it fits and if it is my casing or the motor mount tube.