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AT M 1350 DMS motor with an issue

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Jim Hinton

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Hi Folks;

I'm planning on making my L3 cert launch on Sat. June 1 at Northern Colorado Rocketry's Mile Hi Mayhem launch. I have the rocket ready and was preparing to prep the motor. The large DMS motors attach the forward bulkhead/closure by epoxying it into place in the front of the casing. That's why I was starting a little early as the epoxy needs to be fully cured before flight. I ran into an issue however, the epoxy that was included with the motor is not so good. A significany amount of the resin has hardened in the bottle. This may be a real time saver, but I don't have much faith in the bond that one will achieve with partially pre cured epoxy. I have reached out to AT and the motor vendor, but I have not been contacted. Due to the tight time constraints, I am a little doubtful that AT could get me replacement adhesive in time for the planned launch. I have lots of epoxy on hand including West Systems. Does anyone know what would be a suitable substitute adhesive? I think most epoxies would work, and I think my slo-cure West Systems could certainly do the job. I would like a confirmation before heading down that road. Thanks for the help folks!

Jim
 

rharshberger

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Hi Folks;

I'm planning on making my L3 cert launch on Sat. June 1 at Northern Colorado Rocketry's Mile Hi Mayhem launch. I have the rocket ready and was preparing to prep the motor. The large DMS motors attach the forward bulkhead/closure by epoxying it into place in the front of the casing. That's why I was starting a little early as the epoxy needs to be fully cured before flight. I ran into an issue however, the epoxy that was included with the motor is not so good. A significany amount of the resin has hardened in the bottle. This may be a real time saver, but I don't have much faith in the bond that one will achieve with partially pre cured epoxy. I have reached out to AT and the motor vendor, but I have not been contacted. Due to the tight time constraints, I am a little doubtful that AT could get me replacement adhesive in time for the planned launch. I have lots of epoxy on hand including West Systems. Does anyone know what would be a suitable substitute adhesive? I think most epoxies would work, and I think my slo-cure West Systems could certainly do the job. I would like a confirmation before heading down that road. Thanks for the help folks!

Jim
Sometimes gentle heat will restore the epoxy components. I generally use HOT tap water as a water bath to bring the temp of the epoxy component up and it helps the crystallization to dissolve.
 

Jim Hinton

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Sometimes gentle heat will restore the epoxy components. I generally use HOT tap water as a water bath to bring the temp of the epoxy component up and it helps the crystallization to dissolve.
Hi Rich
That certainly seemed to be a reasonable solution so I gave it a go. I had limited success getting the resin to reliquify. I treated it with hot tap water after taping the bottle up to avoid water infiltration. Several attempts, about 15 minutes total, about 1/3 of the solid reliquified. That doesn't seem promising. I'm tempted to try short bursts in the microwave. If anyone can aim me at a suitable substitute epoxy, I'd appreciate it.

Jim
 

Steve Shannon

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Hi Rich
That certainly seemed to be a reasonable solution so I gave it a go. I had limited success getting the resin to reliquify. I treated it with hot tap water after taping the bottle up to avoid water infiltration. Several attempts, about 15 minutes total, about 1/3 of the solid reliquified. That doesn't seem promising. I'm tempted to try short bursts in the microwave. If anyone can aim me at a suitable substitute epoxy, I'd appreciate it.

Jim
I would not microwave it. I would put it in a car in the sun until the entire amount liquified. It could easily take an hour or more.

Otherwise any epoxy should be fine. If buying epoxy just for this, I would just get a set of Bob Smith Industries or other hobby epoxy of a cure time that you’re comfortable with. I’d probably get 30 minute epoxy.
Otherwise, I always have a gallon or so of West Systems or Aeropoxy. Aeropoxy cures slowly, which I like, but means you would want to use the epoxy a few days before you intend to fly.
 

Jim Hinton

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I would not microwave it. I would put it in a car in the sun until the entire amount liquified. It could easily take an hour or more.

Otherwise any epoxy should be fine. If buying epoxy just for this, I would just get a set of Bob Smith Industries or other hobby epoxy of a cure time that you’re comfortable with. I’d probably get 30 minute epoxy.
Otherwise, I always have a gallon or so of West Systems or Aeropoxy. Aeropoxy cures slowly, which I like, but means you would want to use the epoxy a few days before you intend to fly.
Thanks for the response Steve. I have a problem with using the supplied epoxy as it should not have hardened prior to mixing. It has been stored in my basement for a month or so, no temp extremes. I am suspicious that the bottle for the resin was contaminated, producing the undesired reaction. I have West Systems on hand and I am intending to use that. My only concern is heat compatibility. The aluminum bulkhead that gets epoxied in contains the tracking charge and will produce heat of course. The bulkhead has a large o-ring installed before the epoxy is poured in. The o-ring goes around the outside of the bulkhead and will seal the epoxy off from the propellant. It seems to me that pressure in the motor should go to zero before the delay gets the bulkhead hot enough to be an issue. It would really suck if I am wrong on that however. Always an intrinsic risk with flying a rocket. No response from AT or the vendor, so I sure appreciate the folks from the forum jumping in on this. I think I'm about to find out how West Systems works in this application.

Jim
 

rharshberger

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Thanks for the response Steve. I have a problem with using the supplied epoxy as it should not have hardened prior to mixing. It has been stored in my basement for a month or so, no temp extremes. I am suspicious that the bottle for the resin was contaminated, producing the undesired reaction. I have West Systems on hand and I am intending to use that. My only concern is heat compatibility. The aluminum bulkhead that gets epoxied in contains the tracking charge and will produce heat of course. The bulkhead has a large o-ring installed before the epoxy is poured in. The o-ring goes around the outside of the bulkhead and will seal the epoxy off from the propellant. It seems to me that pressure in the motor should go to zero before the delay gets the bulkhead hot enough to be an issue. It would really suck if I am wrong on that however. Always an intrinsic risk with flying a rocket. No response from AT or the vendor, so I sure appreciate the folks from the forum jumping in on this. I think I'm about to find out how West Systems works in this application.

Jim
Contact Karl at Aerotech, he can answer your question. Use the customer service email on the AT website, they will make sure Karl gets the message.
 

Ez2cDave

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Does Aerotech use a High-Temp epoxy, similar to Cotronics products ?

Would JB Weld be and acceptable substitute ?

Dave F.
 

Steve Shannon

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Contact Karl at Aerotech, he can answer your question. Use the customer service email on the AT website, they will make sure Karl gets the message.
I agree; Karl can answer definitively. The dealer you bought the motor from should be able to get you an answer quickly also.
It takes a lot of heat to cause epoxy to fail and heat transfer is not instantaneous. I don’t think you need high temperature epoxy for this application, but I don’t know for sure.
 

Jim Hinton

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Hi Folks Thanks for all of the advice and help. I was able to speak to Karl at Aerotech (Thank you for the info Rich) and he stated that West Systems with the slow hardener would work fine. He said that he would not use a 'quick cure' epoxy in this application. Karl also said that the epoxy that Aerotech includes with these engines is a marine epoxy, a slow cure laminating epoxy. Hopefully this thread will pop up for the next intrepid rocketeer that finds themselves in this situation. That pretty well clears the decks for my L3 launch, I'm certainly looking forward to Saturday. Thanks again for taking the time to help me out, Rocketeers are definitely special people.

Jim
 

Ez2cDave

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Hi Folks Thanks for all of the advice and help. I was able to speak to Karl at Aerotech (Thank you for the info Rich) and he stated that West Systems with the slow hardener would work fine. He said that he would not use a 'quick cure' epoxy in this application. Karl also said that the epoxy that Aerotech includes with these engines is a marine epoxy, a slow cure laminating epoxy. Hopefully this thread will pop up for the next intrepid rocketeer that finds themselves in this situation. That pretty well clears the decks for my L3 launch, I'm certainly looking forward to Saturday. Thanks again for taking the time to help me out, Rocketeers are definitely special people.

Jim
Jim,

"Adapt & overcome" . . . "Failure is not an option" !

Success on you L3 Cert flight !

Dave F.
 

Jim Hinton

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did it work
Hi James;

As always, there is more to the story. Rather than belabor the Forum with yet another rendition, you can check out the whole saga in the thread; My L3 Rocket is Complete. To cut to the chase, West Systems slow cure is a suitable replacement for the Epoxy that AT includes with the large DMS motors. Unfortunately, on closer examination, I discovered that the nozzle was installed with a cant of approx. 5 to 10 degrees. Fortunately, I discovered that prior to launch. The story has a happy ending though. You can check out the mentioned thread for more details.

Jim
 
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