My worst noob mistake yet... motor retainer in backwards. Help!

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ActingLikeAKid

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Last night I got headway on my Punisher Sport - the rear CR wouldn't seat all the way, so I spent an hour sanding epoxy (ugh). Got it stuck (UGH!) and retrieved it. Finally got everything slathered with JB Weld and put it in. Then I said "Hey, since I have the stuff out, let's put the retainer on"

So I did.

And this happened.
IMG_1477.jpg

I think it's salvageable if I just take a hacksaw to it and take off the bottom 1/8" or so.

Not how I wanted to start my morning :(

The JB Weld has been curing for 9 hours. It's not moving.
 

Danh

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Heat it up with a heat gun . the jb weld will soften up and you will be able to remove the retainer.
 

Steve Shannon

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You can remove it if you carefully heat the aluminum retainer with a torch. Keep the torch moving around the retainer and protect the BT with a couple layers of foil. Eventually the JB Weld will be soften. You may see smoke. Then you have to pull the retainer off quickly.
A friend of mine did this once. We only teased him a while.


[emoji1010] Steve Shannon [emoji1010]
 

dixontj93060

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Use a heat gun and try to direct only on the retainer (maybe wrap other aft areas with a couple rags). It won't take long, maybe two minutes and the JB Weld will soften enough to pull the retainer off (it will be hot so use leather gloves or other protection). Once you get it off you can clean up the tube with a sanding drum on a Dremel. It will be tougher to get the retainer cleaned up. A combination of heat followed by wiping with alcohol may work, otherwise you may have to get a new retainer, but at least the build can proceed.
 

ActingLikeAKid

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Don't have a heat gun or a torch (though this might be the day to get them) ... I'm guessing a hairdryer won't get hot enough....

Is this "minutes are critical" or will I be OK trying this this afternoon?

I may be able to swing by Lowe's on my lunch break and get a torch...
 

ActingLikeAKid

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Just had an idea: I have an electric cooktop that works by induction. I know it gets hot enough to toast marshmallows just by holding one over it. What if I turn on the stove and (for 20 seconds at a time until the retainer loosens or I burn the house down) I set the retainer on the stovetop? Theoretically, it should get the retainer hot pretty quick....
 

dixontj93060

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Just had an idea: I have an electric cooktop that works by induction. I know it gets hot enough to toast marshmallows just by holding one over it. What if I turn on the stove and (for 20 seconds at a time until the retainer loosens or I burn the house down) I set the retainer on the stovetop? Theoretically, it should get the retainer hot pretty quick....
Induction heating does not work with aluminum as it is not magnetic.
 

ActingLikeAKid

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Induction heating does not work with aluminum as it is not magnetic.
I'm an idiot. Conduction, not induction. See above about the marshmallows. I assure you, it gets plenty hot. 100% sure it's just a glass-top stove with real elements. Would that work?
I think I may need to finish my coffee before I do anything stupid(er).
 

dixontj93060

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I'm an idiot. Conduction, not induction. See above about the marshmallows. I assure you, it gets plenty hot. 100% sure it's just a glass-top stove with real elements. Would that work?
I think I may need to finish my coffee before I do anything stupid(er).
Ha! No problem. I'm still waking up too. In any case, the idea is just to take it slow/easy on the heat and direct it as much as possible just on the retainer otherwise you can end up with "charred", or at least a bit browned fiberglass which wouldn't look too great on that translucent body.
 

neil_w

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Would a soldering iron work as a way to apply heat directly to the retainer? Heat might be too localized at the point, but just a thought.
 

watermelonman

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I have never had any luck heating out JB Weld. If you can that is awesome, but it has yet to work for me. I see three other options.

1. Carefully Dremel the retainer body out and glue in a replacement. My TAPs guided me through this on a 75mm mount, though instead of a new glue in retainer I switched to a thrust plate. Still, there was definitely enough room left on the motor mount tube to glue a new retainer on. I used a relatively narrow metal bit with cutting ability on its sides as well as dead on. I cut the retainer in five spots then jammed a straight screwdriver head between the retainer and tube, and pliers to finish removing each section.

2. Replace the aft end of the motor tube and add a second centering ring. I imagine you could do this first by using that same Dremel bit to cut a circle at half the material diameter of the centering ring, then a small cutting wheel inside the motor mount tube further forward than the aft centering ring. Butt up your new centering ring, cut a section of new motor mount tube to length, and epoxy it all into place being careful about alignment. Glue a new retainer onto the new tube after that epoxy is dry enough to stay in place.

3. Use a small thrust plate equivalent. Remove the retainer and possibly part of the motor mount tube, but then use an airframe width centering ring or custom cut wood part to mount the retainer. This would be a simple matter of buying parts, if the rocket was larger, but I do not know of any this small. No 29mm flanged retainers either but a stub of motor mount could be enough.

I bet you could tape motors in against that retainer stub, too; far less elegant but no additional work needed.
 

ActingLikeAKid

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Y'all are awesome.

I tried an indirect method - putting an empty heavy-bottomed pot on the stove and putting the rocket on the bottom of the pot - but that wasn't getting anywhere.

Electric cooktop on high. Held it on for 10 seconds and tugged - nothing. Another 20 seconds - nothing. Another 30 seconds - "is that....." Another 30 seconds...pop!

IMG_1478.jpg

At this point, I think I need to bite the bullet & buy that Dremel I've been ogling; I think that's the only way.

Or I eat the $30 for the retainer and just put mirror clips in.
 

Cabernut

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Good job! I'll make note as I'm sure I'll do this at some point as well...

I suppose it wouldn't work if it were one of those plastic Estes retainers, but then again no big loss if one of those has to get dremelled off.
 

ActingLikeAKid

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Good job! I'll make note as I'm sure I'll do this at some point as well...

I suppose it wouldn't work if it were one of those plastic Estes retainers, but then again no big loss if one of those has to get dremelled off.
Yup.
 

noffie79

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I know I'm late to the part, and I'm really happy you got that retainer off. Just wanted to say that I picked up a heat gun at Harbor Freight for about $10 a few weeks ago.
 

davdue

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I know I'm late to the part, and I'm really happy you got that retainer off. Just wanted to say that I picked up a heat gun at Harbor Freight for about $10 a few weeks ago.
Definitely love Harbor Freight to tools you don't use very often. I did find out that if you plan to do a lot of grinding their Dremel won't take the heat and punishment. Crashed my L3 last AirFest and went to start cutting off the body tube from the fin can and by the time I was done cutting it off the bearings were shot. Oh well used if for several years for $20 rather than $70-80 for a Dremel brand.
 

Rex R

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the dremel is a worthwhile investment. be advised that, whenever you see one advertised as coming with however many pieces, that they count each sanding/cutting disk separately...:). a keyless chuck should be on your 'to get list'.
I have used an 80w iron to remove things from standard epoxy, the last time I wanted to reuse an aero pack retainer I used a mini-torch to apply heat.
Rex
 

Steve Shannon

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Good job using your cooktop! That's a great way to deliver heat specifically to the aluminum, which is what you needed.
I've removed several retainers from broken rockets using heat guns. I've never had it not work, but it does require more heat for JB Weld. The reason I suggested a torch instead was to concentrate the heat more on the aluminum to avoid damaging the motor mount tube. You found an even better way that I'm going to file for future use!
I usually remove any remaining JB Weld from the motor mount with a sharp chisel. That's fast and easy.
 

ActingLikeAKid

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Good job using your cooktop! That's a great way to deliver heat specifically to the aluminum, which is what you needed.
I've removed several retainers from broken rockets using heat guns. I've never had it not work, but it does require more heat for JB Weld. The reason I suggested a torch instead was to concentrate the heat more on the aluminum to avoid damaging the motor mount tube. You found an even better way that I'm going to file for future use!
I usually remove any remaining JB Weld from the motor mount with a sharp chisel. That's fast and easy.
I was picking at it with a boxcutter; there's not a ton of room in there. Hoping a dremel with a delicate tip will grind everything off that I need gone.
 

michigander

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I would try to soak that last bit in vinegar then it should scrape off with piece of Popsicle stick


been there
 

Rex R

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I would use this thingy, IIRC it is 5/16" in diameter with a slow to medium speed(and a lite touch). you only need to get enough removed to get the retainer onto the tube. a drum sander should work to remove the jb weld from the retainer.
Rex

wmspfin.jpg
 

Rex R

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grinding/sanding? certainly. heat will soften most epoxy, rather much doubt that vinegar will do anything to cured epoxy.
Rex
 

crossfire

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I have had good luck with a wire wheel for my dermal tool. No heat no soaking. It doesn't take long at all.
 

Steve Shannon

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I was picking at it with a boxcutter; there's not a ton of room in there. Hoping a dremel with a delicate tip will grind everything off that I need gone.
A box cutter has the edge on the side of a flexible blade. A chisel has the edge on a very stiff blade. There's no comparison. You can push straight down parallel to the axis of the MMT.
 
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