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  1. #1
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    Question about motor mount tube length

    I am planning a Estes Nike Smoke build. Kit 7247; the BT-60 body tube one. I want to put a 24mm motor mount in. what length should the MMT be?
    For future builds is there a general rule of thumb for how long a MMT should be in relation to the longest motor I plan to use?

    NAR# 104365

  2. #2
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    Are you building for blackpowder or composites?

    Other than Cesaroni composite reloads (which not too many people fly due to expense and HAZMAT) there aren't 24mm motors longer than 3.75 inches. That gets you up to a midrange F in composites.

    In larger diameters you typically have larger motors stick out the top of the mount. However in 24mm many motors do not have thrust rings at the nozzle so you typically use a motor block positioned for 3.75 inch motors and add a 1" spacer to fly shorter ones (e.g. C11 & D12 in Estes and E15, E30 and 24/40 loads in composites.) Such spacers are included in Estes E kits or can be made from 1" off a spent motor.

    In answer to your second question I've never really learned a good rule. With BP you almost always want approx. the length of the motor but composites you can make it much shorter.

    NAR #104043

    crmrc.org

  3. #3
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    I would make the mount the length of an Estes D motor and use an Estes twist on connector. You can use longer motors if you leave out any hooks or blocks. Masking tape thrust rings work great. I have had two problems with longer mounts when using Estes tubes. First, composite delays tend to have an afterburn that can play havoc on the tube. Also if you use the a few Ds and then move up to Es you find the fit can be bad with built up residue. This is a down side of not using a block/spring retainer with a spacer. Just my 2.

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  4. #4
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    Thanks for the replies. I plan to mainly fly Aerotech composite 24mm reloads with a screw on retainer. no forward motor block needed.
    I will make it about the same length as the motor case.
    NAR# 104365

  5. #5
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    Estes twist on connector
    what is this?
    NAR# 104365

  6. #6
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    Estes brand plastic motor retainer.

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    Jim V

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    NAR #101467
    L1 - 5/21/16 Estes Mega Der Red Max H128W to 1,021'


  7. #7
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    18th January 2009
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    It's a two part PVC retainer...look on the Estes site. They make 24mm and 29mm versions. The latter come in their PSII kits.

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    Dick Stafford
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  8. #8
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    Oh wait...screw on is the proper description. Twisting works if you keep at it.

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    Dick Stafford
    The member formerly known as the Pointy-Haired Moderator.
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  9. #9
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    Quote Originally Posted by solid_fuel View Post
    Thanks for the replies. I plan to mainly fly Aerotech composite 24mm reloads with a screw on retainer. no forward motor block needed.
    I will make it about the same length as the motor case.
    Per my earlier suggestions, said reloads come in two lengths. Don't limit yourself.

    Sent from my SAMSUNG-SGH-I337 using Rocketry Forum mobile app
    Dick Stafford
    The member formerly known as the Pointy-Haired Moderator.
    The Original Rocket Dungeon
    Volunteer compiler of product news for ROCKETS Magazine

  10. #10
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    Quote Originally Posted by solid_fuel View Post
    Thanks for the replies. I plan to mainly fly Aerotech composite 24mm reloads with a screw on retainer. no forward motor block needed.
    I will make it about the same length as the motor case.
    With no forward motor block you'll be fine with whatever length. It doesn't make much difference if your motor sticks out the top.

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    NAR #104043

    crmrc.org

  11. #11
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    Per my earlier suggestions, said reloads come in two lengths. Don't limit yourself.
    I would like to get this rocket back after flight
    NAR# 104365

  12. #12
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    Quote Originally Posted by LithosphereRocketry View Post
    Are you building for blackpowder or composites?

    Other than Cesaroni composite reloads (which not too many people fly due to expense and HAZMAT) . . .
    ???
    NAR Level 3 #96210

  13. #13
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    Quote Originally Posted by Nathan View Post
    ???
    In 24mm I mean. In larger diameters I agree that CTI is pretty common.

    NAR #104043

    crmrc.org

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