Why are launch rods in the middle of the pad

Discussion in 'Ground Support' started by Knuckledragger, Sep 2, 2019.

Help Support The Rocketry Forum by donating:

  1. Sep 2, 2019 #1

    Knuckledragger

    Knuckledragger

    Knuckledragger

    TLAR Engineering hack

    Joined:
    May 23, 2017
    Messages:
    116
    Likes Received:
    13
    and the weight of the rocket left to hang out over the outer two thirds? Inquiring minds want to know...
     
  2. Sep 2, 2019 #2

    gldknght

    gldknght

    gldknght

    Well-Known Member

    Joined:
    Jan 26, 2011
    Messages:
    738
    Likes Received:
    69
    No matter where your rod is positioned on your pad, if your rocket is threatening to tip your pad over, you need a bigger pad.
     
    tomsteve and Steve Shannon like this.
  3. Sep 2, 2019 #3

    James Harechmak

    James Harechmak

    James Harechmak

    Well-Known Member

    Joined:
    Dec 29, 2018
    Messages:
    133
    Likes Received:
    42
    Gender:
    Male
    Location:
    Appalachia
    Not all rods are in the middle. The Centuri Servo Launcher had it out at one end. Don't know if it counts but all the old 12v lantern battery launchers were centered in the cap but weight wise off to one side when installed on a battery.
     
  4. Sep 2, 2019 #4

    Knuckledragger

    Knuckledragger

    Knuckledragger

    TLAR Engineering hack

    Joined:
    May 23, 2017
    Messages:
    116
    Likes Received:
    13
    Gldkngt and James
    I was looking at building a launch pad to be able to carry most of my equipment in it and was wondering what drove manufacturers to locate the rod in the center. Jaw stands - center, pads - center, Rails - center, towers - booyah not offset. Saw Centuri and a couple other older launch pads with off-center launch rods but still wondered if having a rocket weight loading the rod to one side contributed to whip. Getting ready to launch my Big Daddy X and thought about the outer two fins not resting on anything and how that affects speed and forces on the mid to upper part of the launch rod until there is enough airflow over the fins to direct travel.
     
  5. Sep 2, 2019 #5

    jlabrasca

    jlabrasca

    jlabrasca

    Well-Known Member

    Joined:
    Oct 31, 2016
    Messages:
    1,167
    Likes Received:
    317
    https://www.siriusrocketry.biz/ishop/oddl-rockets-raise-spring-10-pack-1047.html

    Unless the launch lugs run up through the center of the rocket, the weight of the rocket is going to be one side or the other of the rod no matter where the blast deflector is.

    And the blast deflector is just what the name says -- something to keep the hot exhaust from reaching stuff that might burn or melt. It is not, necessarily, there to support the weight of the rocket before launch.

    As for why so many blast deflector designs have the rod going up the middle; maybe because it's easier to manufacture them this way, or maybe because it offers greater flexibility in how the rocket is racked?

    https://jonrocket.com/store/products/blast-model-rocket-blast-deflector
     
  6. Sep 3, 2019 #6

    FredA

    FredA

    FredA

    Well-Known Member

    Joined:
    Jan 19, 2009
    Messages:
    1,803
    Likes Received:
    97
    "As for why so many blast deflector designs have the rod going up the middle"
    EASY and symmetrical loading so the pad doesn't tip over - the "blast plate" does take a blast.
     
  7. Sep 3, 2019 #7

    Matt_The_RocketMan

    Matt_The_RocketMan

    Matt_The_RocketMan

    Well-Known Member

    Joined:
    Feb 7, 2019
    Messages:
    660
    Likes Received:
    79
    Gender:
    Male
    Location:
    Houston TX
    If you are worrying about the launch rod being in the middle, this may be cause it provides the most use of the deflection shield. If you are worried about the rod being tipped over, buy a longer single piece rod from Lowes, or HDP, you can buy in either iron or aluminum length and diameters are differentiated. Instead of having a base that stops the rod mid above ground... stick the rod into the ground this should help with the flex... also if you want to just make the rod shorter by taking half of the rod piece off... if you need more question on this PM me, ill get back with you tommorow asap.

    First Rocket Meeting in 3 months coming up wish me luck new peeps to teach and new trophies to win!!
     

Share This Page