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  1. #1
    Join Date
    11th October 2016
    Location
    Twin Cities, MN
    Posts
    298

    Shock cord mounting in 38mm MD...

    Need some advice on this...
    Since there is no motor mount or centering ring to mount it to how do I do this?
    I'm flying CTI casings... Is there any way to plug it and put an anchor point on it?
    I found the forward closures made by aerotech... Can I use it in my CTI motors and casings?
    I can't seem to find a CTI threaded forward closure.
    Any help is appreciated!

    Chris
    TRA 16662
    L1: 30 October 16, 3" Formula 75, 29mm H123, 871 Ft.
    L2: 13 May 17: 4" Tomach, 54mm K650, 6756 Ft.

  2. #2
    Join Date
    22nd July 2011
    Location
    Where ever the the boss sends me...
    Posts
    2,807
    If you have room, you could glue in a ring just to mount the cord.
    Someone makes an anchor that gets epoxied into the tube. It is threaded for an eye.... Here we go, https://wildmanrocketry.com/collecti...nimum-diameter

    Terry

    NAR L1
    L2 is on hold, maybe never

  3. #3
    Join Date
    21st December 2013
    Location
    Australia
    Posts
    480
    You need one of these adapters.
    https://www.apogeerockets.com/Building_Supplies/Motor_Retainers_Hooks/Minimum_Diameter_Retainers/Pro-38_Delay_Ejection_Closure_Adapter


    I believe you can unofficially get away with just attaching an eye bolt to it, although it is recommended you use a minimum diameter retainer.
    QRS: 124
    AMRS: 32 L2
    Highest Altitude: 10,849 feet
    Largest Motor: CTI 1115J530 IM
    Current Projects:
    Purple Parrot, X Wing


  4. #4
    Join Date
    10th July 2007
    Location
    Melbourne, Australia
    Posts
    1,468
    I have used one of the 54mm versions of the same sort of thing every time I use my 54mm CTI casing. Works really well.
    TRA 13430, Level 3

    "Everybody's simulation model is guilty until proven innocent" (Thomas H. Lawrence 1994)

  5. #5
    Join Date
    11th October 2016
    Location
    Twin Cities, MN
    Posts
    298
    Awesome. Thanks guys!
    Chris
    TRA 16662
    L1: 30 October 16, 3" Formula 75, 29mm H123, 871 Ft.
    L2: 13 May 17: 4" Tomach, 54mm K650, 6756 Ft.

  6. #6
    Join Date
    11th October 2016
    Location
    Twin Cities, MN
    Posts
    298
    Side question... how am I supposed to fit different casing sizes in?
    Chris
    TRA 16662
    L1: 30 October 16, 3" Formula 75, 29mm H123, 871 Ft.
    L2: 13 May 17: 4" Tomach, 54mm K650, 6756 Ft.

  7. #7
    Join Date
    11th October 2016
    Location
    Twin Cities, MN
    Posts
    298
    I'm going to be friction fitting the motor, so could I just mount the MD retainer as high up as a 6g XL casing and fly the friction fit motor as planned?
    Seems like a sound idea...
    Chris
    TRA 16662
    L1: 30 October 16, 3" Formula 75, 29mm H123, 871 Ft.
    L2: 13 May 17: 4" Tomach, 54mm K650, 6756 Ft.

  8. #8
    Join Date
    6th September 2009
    Posts
    1,761

  9. #9
    Join Date
    10th July 2007
    Location
    Melbourne, Australia
    Posts
    1,468
    Side question... how am I supposed to fit different casing sizes in?
    I usually mount the MD mount at the location that lets me put the longest motor available in the rocket. Shorter motors are dealt with by using short threaded spacers.

    There are other ways of dealing with this too. As someone suggested, just use regular motor retention (aft) or something (I won't mention friction fitting) and use the adaptor at the top for only the shock cord attachment.
    TRA 13430, Level 3

    "Everybody's simulation model is guilty until proven innocent" (Thomas H. Lawrence 1994)

  10. #10
    Join Date
    11th October 2016
    Location
    Twin Cities, MN
    Posts
    298
    The second and third would be the ones I would do...
    So the third one just uses an empty BP charge well? Super easy!
    Why bother cracking it open? You could just use it again right? SUPER CHEAP!! lol
    That removable one that is held in by rivets or set screws is awesome!
    Chris
    TRA 16662
    L1: 30 October 16, 3" Formula 75, 29mm H123, 871 Ft.
    L2: 13 May 17: 4" Tomach, 54mm K650, 6756 Ft.

  11. #11
    Join Date
    18th January 2009
    Location
    Savannnah, Ga
    Posts
    7,917
    Quote Originally Posted by Ccolvin968 View Post
    So the third one just uses an empty BP charge well? Super easy!
    Why bother cracking it open? You could just use it again right? SUPER CHEAP!! lol
    That removable one that is held in by rivets or set screws is awesome!
    No...not an old empty charge well.
    Rather the new one on every reload.
    I crack it with a hammer after flight...to easily remove the eye-b ...use on next new reload.

    I would be apprehensive about re-using the forward closure after flight, the smoke has been burnt and possible damage to it. Only plastic. You could clean it up a bit fill cavity with epoxy & try to re-use.
    Let us know how that goes.

    I for one find it so simple/easy to do, sticking an E/B into new closure every use, only takes literally "5" minutes.
    Jim Hendricksen
    L-3 Tripoli 9693
    [ICBM, Orangeburg,SC R.I.P.] - QCRS ,Princeton ILL - MDRA , Price Maryland - Woosh, Bong Wisconsin- ROCC, Charlotte NC , ICBM Camden SC
    "Made" member of Chicago & Carolina Rocket Mafia
    Rocketry...........an exact science.......but not exactly !!!

  12. #12
    Join Date
    18th January 2009
    Location
    Savannnah, Ga
    Posts
    7,917
    Good job Buckeye...keep those links for future use. You can be the "official" poster of minimum recovery hook-up, how to.

    I have reposted those threads so many times over the years....seems like that Q, comes up every few months, after the cycle of new..... newbies arrive.
    Jim Hendricksen
    L-3 Tripoli 9693
    [ICBM, Orangeburg,SC R.I.P.] - QCRS ,Princeton ILL - MDRA , Price Maryland - Woosh, Bong Wisconsin- ROCC, Charlotte NC , ICBM Camden SC
    "Made" member of Chicago & Carolina Rocket Mafia
    Rocketry...........an exact science.......but not exactly !!!

  13. #13
    Join Date
    6th September 2009
    Posts
    1,761
    Quote Originally Posted by blackjack2564 View Post
    Good job Buckeye...keep those links for future use. You can be the "official" poster of minimum recovery hook-up, how to.

    I have reposted those threads so many times over the years....seems like that Q, comes up every few months, after the cycle of new..... newbies arrive.
    I learned from the best! Crazy Jim always has the simple, yet elegant, solution.

    With all the MD madness going on now, the BH38 build should be a sticky. Maybe I will write up my own build thread - retroactively!


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