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Thread: Oddroc pyramid

  1. #1
    Join Date
    19th June 2017
    Location
    Vacaville, CA
    Posts
    411

    Oddroc pyramid

    Found this at work sitting on a pallet of boxes. I thought it was ment to fly. And it shall....

    I brushed some thinned epoxy on the inside. I used some dense 1/8" fiber board for the forward and aft bulkhead. Put it all together with 5 minute epoxy.

    I used a 3" tube and a 29mm motor mount. Two centering rings to make the motor/recovery piston.

    The mid bay will hold the parachute, and the top bay will hold some small kevlar cord.

    Its weighing in at 12.5oz without motor. Stands 12" tall and is 9.5" wide at the base.
    Click image for larger version. 

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    Sent from my VS988 using Tapatalk

    Eric Hamilton, NAR, TRA
    SARG, LUNAR
    Level 1, Estes Argent, H115DM
    Level 2, Scratchbuilt 2.6", J270G

  2. #2
    Join Date
    27th July 2014
    Location
    south beloit, IL
    Posts
    2,474
    Make sure you put some weight in the top, or it'll fly wonky!

    Looks cool- bright yellow should be easy to spot.

    NAR# 99285
    Tripoli# 16283
    L1- 4/26/2015 Madcow Cowabunga- H123SK
    L2- 11/1/2015 Wildman Darkstar 2.6- J355RL
    L3- 11/3/2017 Wildman V2 6" - M1780NT
    Woosh
    QCRS

  3. #3
    Join Date
    3rd October 2016
    Posts
    236
    Great find. You just saved yourself at least $30 compared to buying a kit, if you can find them. I have the smaller of Sunward's two pyramids, the "Khufu's Pyramid". Pop pod with streamer recovery and parachute for the pyramid. Great, stable flyer with 60 grams of nose weight. High drag, low flyer, always gets comments from the spectators.

  4. #4
    Join Date
    9th October 2013
    Location
    San Jose, CA
    Posts
    690
    Did you fly this yet? I picked up one of those no-stack 'cones' from the registration table at LUNAR yesterday, assuming you provided those, thanks! So is your MMT w/centering rings designed to eject from the 3" tube to release the parachute? If so, what keeps it in place until ejection? Thoughts on good motors? I'm guessing OR won't give a good sim for something like this.
    Will Ferry (Launches & Videos) NAR #96512 (L2) / TRA #15328 (L2) / LUNAR #2759
    L1: 9/2013 @ XPRS, GLR T-Bolt "Thunderbolt" (R.I.P.), H148R
    L2: 4/2016 @ TCC Helm, Binder Design Excel w/DD "dd2.xls", J315R
    Impulse flown (flights): 2013: 767Ns (2), 2014: 4298Ns (8), 2015: 7486Ns (16), 2016: 11693Ns (18), 2017: 11138Ns (16), 2018: 3879Ns (5)

  5. #5
    Join Date
    15th June 2011
    Location
    Macon GA
    Posts
    2,450
    Quote Originally Posted by kuririn View Post
    You just saved yourself at least $30 compared to buying a kit, if you can find them. <snip> High drag, low flyer, always gets comments from the spectators.
    Money was the primary reason I created the pyramid in the first place. I was your typical broke kid, looking for a way to make rockets as cheaply as possible. I didn't use ANY commercial parts in the original, even the motor tube was rolled from notebook paper.

    And even with the 18mm motor version, people always made comments about the flights.
    LW Bercini
    TRA #00134 / NAR #18121
    Seeing "the box" from the rear view mirror since 1970


    I don't measure my enjoyment of the hobby in Newton-Seconds

    It never ceases to amaze me how so many otherwise intelligent people have such poor reading comprehension.

  6. #6
    Join Date
    27th August 2011
    Location
    West Tennessee
    Posts
    2,780
    Quote Originally Posted by djs View Post

    Looks cool- bright yellow should be easy to spot.
    Not that it is likely to go TOO far!
    It is amazing what you can do when you don't have a choice.

    Smart people learn from their mistakes.
    REALLY SMART PEOPLE learn from OTHERS' mistakes.

  7. #7
    Join Date
    19th June 2017
    Location
    Vacaville, CA
    Posts
    411
    Yes, I did fly it last month at the SARG launch on an F32. I bet the stack of "No Stack" signs was put out by Toby V. He mentioned doing that.

    Mine flew great to ~225' while under boost, after boost it did a few flips in the air and the ejected the engine pod right on time.

    So the 3" tube is glued into the square pyramid rings. The 29mm motor tube has two 3"-29mm centering rings glued on, dividing the motor can into three sections. The top section is 2" and holds the folded Kevlar shock cord. The middle section is 3" and holds the parachute. The bottom section is about 1" long for taping the motor. The centering rings are friction fit into the 3in tube and hold tight until ejection.

    The 15' of 1/8" kevlar is epoxied to the forward end of the 3" tube. It then goes under the top CR about 1 foot and has a loop for parachute attatchment. It is epoxied to the top section. The shock cord was also folded into a 4" bundle and bent around top motor section. Wrapping it around the tube multiple time might have fouled deployment. The 24" parachute was Z-folded into a 3"x4" rectangle and bent around the center section just prior to piston insertion into the rocket. I filled the space above the motor in the 29mm tube with dog barf. Between that, the kevlar shock cord bunch and the forward CR, no ejection charge got to the parachute section.

    I have a video of the flight. But I'm not sure how to upload videos.
    Eric Hamilton, NAR, TRA
    SARG, LUNAR
    Level 1, Estes Argent, H115DM
    Level 2, Scratchbuilt 2.6", J270G

  8. #8
    Join Date
    19th June 2017
    Location
    Vacaville, CA
    Posts
    411
    https://youtu.be/WRn1MeGYGIsClick image for larger version. 

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    Sent from my VS988 using Tapatalk

    Eric Hamilton, NAR, TRA
    SARG, LUNAR
    Level 1, Estes Argent, H115DM
    Level 2, Scratchbuilt 2.6", J270G

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