Homemade Motor Retainers

Discussion in 'High Power Rocketry (HPR)' started by qquake2k, May 20, 2010.

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  1. May 24, 2010 #31

    Handeman

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    I use the threaded inserts and various shaped clips for motor retension in most of my rockets. I did build one that had a minimum diameter and required positive retention. I used two metal loops (parts of paper clips) and some wire to hold the motor in.

    IMG_0065.jpg
     
  2. May 24, 2010 #32

    MarkII

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    Although it is slightly more complicated to construct, it is far better from a safety standpoint to attach retainers with screws that thread into the rocket, rather that having them bolt onto a fixed metal stud that projects out of the rocket. Designing a hobby rocket with a spear-like metal projection, even if it is at the aft end, is not the safest of practices.

    MK
     
  3. Jun 9, 2019 #33

    Ted Curtis

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    Old thread but, Quest 4runner has a four engine cluster held in by a washer, nut screwed into threaded rod tailing from aft. Always thought it was genius, never really pondered safety, doh!
     
  4. Jun 9, 2019 #34

    kuririn

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    The retainers that screw INTO threaded inserts still will have the screw project OUT the rear. I don't see it as a bigger issue than engine hooks that project out the end of the rocket. I'd be much more concerned about metal tipped nose cones at the FRONT of the rocket if it should come down ballistically.
     
  5. Jun 9, 2019 #35

    Ted Curtis

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    Very astute observation!
     
  6. Jun 9, 2019 #36

    Andrew_ASC

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    My favorite one was Nytrunner’s Big SAM using a hose clamp he found in a garage.
     
  7. Jun 9, 2019 #37

    kuririn

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    BTW here's a picture of my homemade engine retention system:
    0609190840.jpg
     
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  8. Jun 9, 2019 #38

    Wallace

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    Can be as simple,complex,easy,cheap,heavy, light or expensive as you want it to be. Foil tape is about as cheap as it gets if you want reliability. Although foil tape itself is rather expensive. Think I paid $15 for my last roll?
     
  9. Jun 9, 2019 #39

    Wallace

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    The true value in using foil tape is that it WILL come off (without leaving sticky messes behind) when you desire..
     
  10. Jun 10, 2019 #40

    Ez2cDave

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    I hope you don't use masking tape on reloadable HPR motors . . .
     
  11. Jun 10, 2019 #41

    timbucktoo

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  12. Jun 10, 2019 #42

    rharshberger

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    Yep! Masking tape for friction fit and aluminum HVAC foil tape for a secure wrap around motor tube and rear closure/thrust ring of motor.
     
  13. Jun 10, 2019 #43

    Ez2cDave

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  14. Jun 12, 2019 #44

    Duster45

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    I've always used all thread bonded to the motor mount tube. One piece with 3 to 4 inchs of bonded area works on most applications. Sometimes a thin spacer is needed between threads and motor mount tube to allow for aft closure clearance. 100_2354.JPG 100_2355.JPG
     
  15. Jun 12, 2019 #45

    prfesser

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    Some years ago I lost a 38mm Dr. Rocket casing via friction fitting. Lucky that both the casing and the chute were ejected, so I didn't lose the rocket. I will always opt for positive retention except (maybe) when using 18mm BP motors.

    Positive retention can cost less than a single roll of tape. It doesn't have to be elaborate; one tee-nut installed in the aft centering ring, one bolt to fit the nut, and a clip cut from a scrap of sheet metal, drilled and bent to a Z-shape. For redundancy, two teenuts, two bolts, two clips on opposite sides of the motor.

    Best -- Terry
     
  16. Jun 12, 2019 #46

    CoachSteve

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    Water bottle caps and threaded neck
    [​IMG]
    [​IMG]
     
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  17. Jun 13, 2019 #47

    JohnCoker

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    If you're using electronics, you can also retain many reloads from the front-end using a threaded forward closure. I do this in preference to aft retention for larger motors, arranging it so that the bridle attaches to a threaded rod that goes into the forward closure.
     
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  18. Jun 14, 2019 #48

    beeblebrox

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    One of the best methods since the '70s!!! Lucerne Test Range Approved!
     
  19. Jun 15, 2019 #49

    Ez2cDave

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    Don't MESS with "Old School" . . . !
     
  20. Jun 30, 2019 #50

    Handeman

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    I've used McMaster-Carr brass threaded inserts for Hardwood in 6-32 to screw into the rear centering ring. You can put those into any existing plywood CR.
     
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  21. Jul 1, 2019 #51

    Binder Design

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    I pioneered that method for minimum diameter flights. Rock solid to mach 3+ in a rocket called Mr. Scary. 300g launch on a 38mm L motor.
     
  22. Jul 3, 2019 #52

    _kestrel_

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    Here are a few I made for 38mm motors out of 6061-T6 aluminium. IMG_20190703_114221 - Copy.jpg
     
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