How to recover a retainer

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Simon

Simon

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OK, so it's happened again, rocket completely destroyed after parachute failed to deploy properly.
I am now recovering all the parts I can from the pieces, I have actually got everything except the motor retainer back. My problem is how to remove it from the motor tube as it's epoxied on with high temperature epoxy (JB-Weld). My oven isn't hot enough to free the bond, I was thinking of using a blowtorch, or putting it on a coal fire for a bit. Has anyone had any success with recovering parts that are attached using high temperature epoxy?
 
Xnay on the coal fire. A few passes with a pencil torch will soften the epoxy enuff to remove the MMT. You DON'T need to get it red-hot as this may destroy the temper and/or distort the threads. Note JB weld is heat resistant-not heat proof. Thread the motor retainer cap on with a little powdered graphite on the threads to use as a heat sink and screw it clockwise using leather gloves and pulling up as you heat it. Should come right off. The graphite prevents galling of the threads due to thermal expansion. I hate to admit it, but I've had to recover a few over the years myself.
 
Last edited:
Without an oven, I'd be concerned about the really high heat distorting the retainer parts.
Others will confirm or suggest a better way, but I think your best bet will be to mechanically clean the MMT and epoxy from the mounted retainer.
 
Take a quick visit to your local Harbor Freight or hardware store, pick up a heat gun. Spend two or three minutes with the heat directed against the joint. The heat will soften the epoxy enough to separate your parts. You will probably still need to do some manual cleaning of your threads.
We use this stuff by the gallons at my place of employment. (can't disclose)
Good luck!
 
I use a different technique. I cut the retainer off the end of motor tube and peel as much of the motor mount off as I can with needle nose pliers. I then use a dremel with a sanding drum to carefully remove the rest. I take it slow and stop when I get to the inside threads I then clean the threads with a dental pick.
 
terryg said:
I use a different technique. I cut the retainer off the end of motor tube and peel as much of the motor mount off as I can with needle nose pliers. I then use a dremel with a sanding drum to carefully remove the rest. I take it slow and stop when I get to the inside threads I then clean the threads with a dental pick.
Click to expand...

You saved me the trouble of typing. That is exactly what I did to recover a retainer from a re-kitted Lil Lunar Express.
 
I soak in vinegar ... removed a 38mm and 54 mm from cardboard most of the jb weld peels off
 
The best thing to do is contact Aeropack and ask them for advice on the issue, I'm sure their remedy will be better then ours. I haven't done this yet, but they would be the one I would contact first. :2:
 
I've removed them...
Fix the tube somewhere so it won't move around,,,
Heat with a propane torch gently and slowly all the way around...
You have to promise not to laugh....
The JB softens and lets go right about the same temp that the fiberglass bursts into flames........

Oh yeah....

Make certain that you do this outdoors..........lol...

Teddy
 
On a LOC MMT I didnt like the way it protruded from the V2.

After cutting the mmt I put the part with AP base in a cup of water and after a day or two peeled out the paper mmt . It did pull some of the jb weld with it.

After the tube was off I had access to the base itself..first I used moto tool drum sander until it would seat on new mmt fully. Sanded rough with 80 grit on the inside Then used the diamond wheel with the motor tube to random notch the inner base . It didnt really knorl it AP style but the hopscotch pattern was better than just 80 grit rough on the inside for new JB Weld to adhere to.

Kenny
 
Simon said:
I'm soaking it in vinegar overnight, seems like the easiest solution, I'll report back tomorrow

Many thanks for all the suggestions BTW
Click to expand...

Wow,, very cool..
I can't wait to hear..
But vinegar wouldn't do anything to the hardened JB Weld,,, would it ???

This sounds much more betterer then the whole "burst into flames" thingy.........lol...

Teddy
 
Well, I can report that vinegar didn't work for me in spite of soaking it overnight. I now have a retainer that's stuck to a motor tube that smells of vinegar.
I'll try my hot air gun next, I'm putting off Teddy's bursting into flames solution until last. :)
 
I recovered a retainer using the heat gun method. Make sure you have the retatainer screwed on before you start. Then run the heat gun directly against retainer, you'll want to do this for maybe 10min until everything gets really hot.

f431c210f4a2120c1f4106cc8a282efe.jpg


When you think it may be ready swap the heat gun over to the other end. Then try levering it off with a couple of screwdrivers. One thing to remember about heat guns, be careful to make sure they are getting enough cool air into them otherwise they may melt/catch fire/over heat.
 
michigander said:
I soak in vinegar ... removed a 38mm and 54 mm from cardboard most of the jb weld peels off
Click to expand...

First- I have no experience using aluminum retainers but I have been a rotary wing mechanic for 20 years, so take this however you wish.

Vinegar and aluminum can be a a less than ideal combination. If the finish is unbroken it is likely no big deal. I realize that in my job as a mechanic, I am looking at a much different time frame as far as fatigue is concerned but I believe that it would warrant a thorough cleaning if you use this method. Maybe there is an engineer or two out there that could shed some light?
 
terryg said:
I use a different technique. I cut the retainer off the end of motor tube and peel as much of the motor mount off as I can with needle nose pliers. I then use a dremel with a sanding drum to carefully remove the rest. I take it slow and stop when I get to the inside threads I then clean the threads with a dental pick.
Click to expand...

I use a similar technique. I just use the Dremel wire brush as opposed to the sanding drum to clean out the insides.
 
However you accomplish it,,
There is a temperature that the epoxy softens and lets go......
That # is different for different epoxies...
I think the # for JB Weld is 450 degrees...
This is not a question..
The problem for you to solve is how best to
Hold down the airframe so it can't move..
Put gentle pressure pulling on the retainer so it comes off as soon as the JB softens...
Heat gently and evenly all the way around....

Take 3 of 4 ft of #12 solid copper wire,, like from a piece of romex....
Skin the whole length and twist the copper around the retainer really tightly so it won't come off and you can pull on it....
Fix the airframe to something so it can't move...
Now you can hold the propane torch or heat gun in one hand and hold the copper wire
a couple of feet away from the heat with the other hand and gently pull.......

No kidding...
With the ignition source of the torch the glass flames up just as the retainer pops off.......

Teddy
 
onebadhawk said:
You have to promise not to laugh....
The JB softens and lets go right about the same temp that the fiberglass bursts into flames........
Click to expand...

Sorry...I lol'ed. I tried not to. I really did but this sounds like the kind of thing that would happen to me.
 
DAllen said:
Sorry...I lol'ed. I tried not to. I really did but this sounds like the kind of thing that would happen to me.
Click to expand...

Ohhhh mannn..
I forgot ...
I was supposed to put that Matt ( Black Brant ) acronym in there...

DAMHIKT............

Teddy
 
This is now turning into a mission, my heat gun hasn't been used for years and was in a damp basement, the damp has broken it it seems.
Not deterred, I have now ordered a new heat gun from Amazon which probably cost more than a replacement retainer.
It is arriving today, I will report back with either my success or failure
 
Simon said:
Well, I can report that vinegar didn't work for me in spite of soaking it overnight. I now have a retainer that's stuck to a motor tube that smells of vinegar.
I'll try my hot air gun next, I'm putting off Teddy's bursting into flames solution until last. :)
Click to expand...


sorry vinegar didn't work , my retainers stink of burnt AP
 
michigander said:
sorry vinegar didn't work , my retainers stink of burnt AP
Click to expand...

Someone here said he's an aircraft tech or mechanic of some sort
and he said that vinegar would attack or otherwise degrade aluminum....
I always soak my aft retainers and seal disks in white vinegar.....
I'm going to reduce the soak time to just what is necessary..
I won't leave them in the soak anymore...

Teddy
 
Hhhhheeeeyyyyyyyyyyy..
There ya go.........

Good for you...

Teddy
 
Wait.....what was wrong with the rocket? Fin can looks fine in the pics.
 
onebadhawk said:
Someone here said he's an aircraft tech or mechanic of some sort
and he said that vinegar would attack or otherwise degrade aluminum....
I always soak my aft retainers and seal disks in white vinegar.....
I'm going to reduce the soak time to just what is necessary..
I won't leave them in the soak anymore...
Teddy
Click to expand...

That was me. I'll have to play with some scrap and see what it does. We use a process where bare aluminum is chemically treated with a mild acid (controlled corrosion) and then and then washed to stop the reaction and leave a protective layer. It is much like anodizing but does not use an electrical current so the coating is much thinner and black is the only color choice.

I am no engineer and I do not use retainers but I would recommend that if you use vinegar to clean aluminum retainers, wash it with clean water afterwards and thoroughly wipe it dry.

I assume that carbon is the primary concern here. If that is the case, why not treat it as a fire arm. I have had the privilege of firing automatic weapons on a regular basis from time to time and I can attest to the value of proper lubrication when it comes time to clean. CLP was my friend with an M60. I left the components prone to carbon build up with a thin film of CLP and it took 20 minutes to clean after firing 1500 rounds.

Try the gun counter at your local sporting goods store, there are quite a few products that are designed to be used in high heat environments and clean carbon. You should be able to get small quantities to try for just a few dollars.

I'll play with some aluminum tomorrow and see if I see any short term effects from using vinegar as a cleaning agent.
 
Screaminhelo said:
That was me. I'll have to play with some scrap and see what it does. We use a process where bare aluminum is chemically treated with a mild acid (controlled corrosion) and then and then washed to stop the reaction and leave a protective layer. It is much like anodizing but does not use an electrical current so the coating is much thinner and black is the only color choice.

I am no engineer and I do not use retainers but I would recommend that if you use vinegar to clean aluminum retainers, wash it with clean water afterwards and thoroughly wipe it dry.

I assume that carbon is the primary concern here. If that is the case, why not treat it as a fire arm. I have had the privilege of firing automatic weapons on a regular basis from time to time and I can attest to the value of proper lubrication when it comes time to clean. CLP was my friend with an M60. I left the components prone to carbon build up with a thin film of CLP and it took 20 minutes to clean after firing 1500 rounds.

Try the gun counter at your local sporting goods store, there are quite a few products that are designed to be used in high heat environments and clean carbon. You should be able to get small quantities to try for just a few dollars.

I'll play with some aluminum tomorrow and see if I see any short term effects from using vinegar as a cleaning agent.
Click to expand...

Thank you very much Bill..
I am a bit finicky when it comes to cleaning my hardware...
Not nuts like some but I do like them pretty clean..
The residue from the AP burning can be a bear to remove..
Rather then fight with it white vinegar breaks it down..
A soak a bit of tooth brushing a bit more vinegar if necessary pretty much does it..
After I'm done it's the tooth brush again with soap and water...
I've never seen anything at all to make me concerned about the aluminum being chemically attacked...

Teddy
 

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