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  1. #1
    Join Date
    16th February 2014
    Location
    Gilroy, CA
    Posts
    2,256

    Can someone measure the OD of a 38mm DMS motor for me?

    I need to cut a set of adapter rings to put a 38mm AT DMS motor in my 54mm mount. Does anyone have a 38mm DMS motor and a set of calipers? Can you give me the OD of the motor measured at the label?



    Thanks,


    Chris

    Chris Attebery
    TRA 6602 L3
    Personal best: 37,789' 1335mph

    www.ape-rc.com

  2. #2
    Join Date
    8th December 2009
    Location
    CA
    Posts
    1,982
    1.507"

    measured 3 different spent DMS J270W at the label....half label...half case..

    Tony


  3. #3
    Join Date
    16th February 2014
    Location
    Gilroy, CA
    Posts
    2,256
    Perfect. Thanks Tony.
    Chris Attebery
    TRA 6602 L3
    Personal best: 37,789' 1335mph

    www.ape-rc.com

  4. #4
    Join Date
    4th May 2010
    Location
    Silicon Valley
    Posts
    647
    Quote Originally Posted by tfish View Post
    1.507"

    measured 3 different spent DMS J270W at the label....half label...half case..

    Tony
    That is 3 thousandths of an inch shy of 38mm. It is basically 38mm.
    Karl Baumheckel
    TRA 11594 L3

  5. #5
    Join Date
    11th February 2018
    Location
    Guelph
    Posts
    55
    What is the spec for this metric case?

    ...answers in inches.

    This is how you crash landers into Mars folks....

  6. #6
    Join Date
    30th January 2013
    Location
    McKinney, TX
    Posts
    98
    All of the official DMS case dimension data is available from Aerotech here:

    http://www.aerotech-rocketry.com/resources.aspx?id=7

    According to their documents, 38mm case outer diameter is officially spec'ed at 1.500", with the diameter of the rear closure slightly larger at 1.630". Both diameters +/- .005 inches

    -Robert
    Last edited by rhildinger; 16th May 2018 at 05:52 PM. Reason: add in spec potential variance

  7. #7
    Join Date
    31st October 2016
    Location
    N/A
    Posts
    292
    Quote Originally Posted by karlbaum View Post
    That is 3 thousandths of an inch shy of 38mm. It is basically 38mm.
    I was wondering about that too. Since the question specified a measurement at the label, I figured the OP needed more precision than what it said on the box.

    Quote Originally Posted by jnobels View Post
    What is the spec for this metric case?

    ...answers in inches.

    This is how you crash landers into Mars folks....
    <smile>

    Looks like they stopped updating the Mars scorecard a while ago. I think the folks running the site were discouraged by the unlikely successes of the air-bag bounce landings of the rovers.

    There's more than one way to crash a lander -- the ESA managed it without the direct assistance of Americans and our weird fetish for imperial weights and measures.

    It is a little frustrating to work between unit systems. I tend to think in terms of SI, but I've gotten some comments and quizzical looks from LCOs when it's noticed that I've recorded the mass of the rocket in grams on the flight card. The acceleration due to gravity is near enough 10 m/s2 that the thrust-to-weight estimate is pretty effortless. The arithmetic of converting newtons to ounces or pounds is tedious and time consuming.
    NAR Level 1, Sheridan Oregon, 09/16/17 -- scratch built 7.6cm x 120cm rocket on an AT H182R.

  8. #8
    Join Date
    9th May 2009
    Posts
    1,658
    Quote Originally Posted by jnobels View Post
    This is how you crash landers into Mars folks....
    To be pedantic (I worked on both projects), that was an orbiter, not a lander: https://en.wikipedia.org/wiki/Mars_Climate_Orbiter

    The 1999 lander crash was due to a software bug, not a unit conversion. https://en.wikipedia.org/wiki/Mars_Polar_Lander


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