Help! Motor case stuck in layup

Discussion in 'Techniques' started by Scrapmaster87, Dec 3, 2019.

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  1. Dec 3, 2019 #1

    Scrapmaster87

    Scrapmaster87

    Scrapmaster87

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    So right now I have my case and tube in the freezer right now to buy time to find the best solution...

    Ok, so last night I rolled a a motor mount tube with 4 layers of 0.010" thick 7781 e-glass over 1 wrap of parchment paper with slow cure laminating epoxy (leap-tech). I left the layup to cure 8n my basement for about 20 hours before removing the case (low 60's/high 50's)

    Here's where I got stupid/impatient, I figured the very slight tackiness was from the texture left by the peel-ply. I grabbed a piece of sandpaper and a pair of gloves to smooth up the tube in hot soapy water. When I got the tube hot it became soft, like I could crush it by hand if I wanted to.

    Since I now had a slightly deformed tube in hand, I figured the best course of action was to cool the tube off and get the motor case back in so it cures to the correct shape. I got the case back in as shown then temperature cycled it to erase any sort of plastic memory.

    I started getting a bad feeling about this, I tried to press the tube off by hand and only succeeded in buckling it slightly. All of this happened in the course of about 45 minutes. Normally I've been curing my layups at around 125-135 degrees, do I do this (or go hotter) and try to press the case out? The case was never treated with a wax or anything to help release any type of bond. Right now it should be easy to cut the tube off to play it safe IMG_20191202_223617.jpeg
     
  2. Dec 3, 2019 #2

    tfish

    tfish

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    I would try freezing it...Then try to 'shock' it into moving. I'd try slamming it (the forward end) onto a floor mat and see if it wants to move. This may take a few freeze and slams to get things freed up..once it starts to move...try twisting it in your hands...you may be able to find a sweet (easy) spot. I've has some CTI case were the forward ends were slightly bigger...so I'd try taking it off the other end...

    PS...don't destroy the motor case trying to get a few $ of glass and epoxy off the case. Cheaper to 'cut' the tube off and start over.

    Tony
     
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  3. Dec 3, 2019 #3

    rokit

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    If you have the tools and materials, make a centering ring (or just a hole in a piece of wood or preferably something harder like G10) that just fits the motor case. It'll help give leverage when you're doing the slamming. If you don't have forearms like Popeye, you can use a vice (or something like that) to rest the CR on, and a rubber mallet (or hammer and a piece of wood) to persuade the casing to start moving.

    Mike
     
  4. Dec 4, 2019 #4

    Scrapmaster87

    Scrapmaster87

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    This did the trick! Shame I lost a good bit of the screen printing of my 2003/2004 5g case.

    My printed tailcone-motor retainer did the trick along with another case.

    Tony, watching your layup videos inspired me to go straight back into diy composite for my first build for getting back into HPR.

    IMG_20191203_221013.jpeg
     
  5. Dec 6, 2019 at 8:29 PM #5

    SDramstad

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    What kind of epoxy were you using?

    Nevermind. I should pay more attention when I read....

    Dang bifocals.............
     
  6. Dec 6, 2019 at 8:41 PM #6

    SDramstad

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    Found this on their website.

    Description of Epoxy Hardeners
    All working times(pot life) are based upon an optimum working temperature of about 80 degrees F. Temperatures variations will greatly affect curing times, and when below 65F can sometimes double curing times. Other factors that affect epoxy curing can be moisture and humidity, as well as the thickness of lamination.


    Normally I've been curing my layups at around 125-135 degrees

    Why? I didnt see anywhere on the website that showed this had to be heated.
     
  7. Dec 6, 2019 at 8:49 PM #7

    Scrapmaster87

    Scrapmaster87

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    125-135 is how hot the hairdryer I use gets. This'll get the layup cured in a few hours vs. days in this case.
     
  8. Dec 6, 2019 at 9:08 PM #8

    tfish

    tfish

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    Sorry for getting you addicted again!
    I hear there is some sort of 12 step method to quiting.
    I can't admit that I have a problem yet..so I see no end yet.

    Tony
     
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  9. Dec 6, 2019 at 9:42 PM #9

    richP

    richP

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    OK, I'll bite.
    Why do you want the MMT to be so tight against the case? How difficult will it be to remove a motor after flight, when the tubes are hot,dirty,etc..
     
  10. Dec 7, 2019 at 4:59 AM #10

    Scrapmaster87

    Scrapmaster87

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    This is a screw up that I'm paying for by having to sand the ID my new tube. If I had heated the layup right after I finished it, I'd have a nice slip fit on the case. What actually happened is that the glass was curing over a non-thermally expanded motor case. I then proceed to remove the glass before it was done curing to wet sand it in some hot water. The handling in hot water deformed it.

    In reality this build could benefit from a tighter motor fit as I'm using a 3d printed screw-on tailcone for motor retention. A 1.5" ID x 2.25" OD steel washer in the picture above will be what's touching the aft closure. Turns out a 2"-4.5 class 1A/B thread prints real nicely in PETG.
     

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