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  1. #1
    Join Date
    8th December 2009
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    CA
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    Modified John Coker pads

    AeroPac has been using John's style of pads for as long as I've been a member... 15+ years. For the past few years rockets have gotten bigger and the motors have gotten more powerful. I've noticed that our pads had a tendency to wiggle under high thrust flights. (out at BR there seems to be quit a few of these) # years ago I made up some pretty simple guy line systems for the pads. Guys either did not know we had them or where in a hurry to fly. This winter I brought home one of the pads to see what else cold be done to strengthen them. Below is John's original design. The mast bracket is made from 1/4" stainless steel. and the flexing/wiggle comes from the point where the mast bracket ends and it's bolted to the legs. Too back up some these pads have been improved many times by a couple of people over the years to what they are now.
    My plane was to 'beef- up' the mast booms. This was accomplished by welding 3/8 x 3/4" SS flat bar turning the flat bar into more of "channel iron". This about maxed out my little welder her at home. Below is a photo of the 6 modified boom brackets. The first one was painted and the rest were left au naturel and adds some bling to our pretty beat up pads.
    Also, we have several booms each with either 1515 or 1010 rails. To make rail swaps easier I added 1010 rails to the backside of the 1515 booms. This makes them more useful and easier to swap...just flip it over! It may even add some strength to the booms.

    So now on to the reason for this thread. I volunteered to make 8 Modified Coker pads for a group I've been hanging out with lately. I don't plan on doing much writing from this point on. If my oldest son is up for it there might be a detailed set of plans of sorts at the end of this thread.

    Tony

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  2. #2
    Join Date
    8th December 2009
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    so what's a good start on materials for 8 Coker style pads?

    100' 3x3x 1/4 sq Al tube
    120' 1.5 x 1.5 x 1/8 sq Al tube
    12' 1 1/4 solid Al bar
    17' 3" structural Al Channel
    3 sq ft 1/4 Al plate
    A bunch of rail stops, 2 dozen Galv foundation bolts (boom adjustment bolts)
    and many more bolts not purchased yet.

    Blast deflectors: For years AeroPac has used blast bolted to the rail. For years we have been repairing rails and blast deflectors ripped off either by just the thrust or a cato or two. Having the blast deflector mounted to the rail or even the pad itself does not make sense. It just adds to forces on the pad that you really don't want or need...while trying to get your rocket to go where you point it. For this year we are using 2x2' x 3/16 steel plates laid right on the ground. This should be the least amount of influence on the pad itself.

    All the material (500#) is currently hanging from the rafters in my shop.

    I have a cut list and hope to get all this cut up in the next few days. Of course it's suppose to start raining again tomorrow!

    Tony

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    Last edited by tfish; 31st January 2017 at 01:24 AM.

  3. #3
    Join Date
    26th May 2011
    Location
    CA
    Posts
    753
    Looks like you're keeping plenty busy in retirement, Tony. I'll bring a couple rockets to XPRS that should be a good "wiggle" test for the new pads.

    Derek

  4. #4
    Join Date
    18th November 2016
    Location
    Fairfield, CA
    Posts
    6
    Real blast deflectors (4-6 inch steel ells) really should start to be incorporated somehow, IMHO.

  5. #5
    Join Date
    18th March 2009
    Location
    Wisconsin
    Posts
    3,467
    Quote Originally Posted by numbo View Post
    Real blast deflectors (4-6 inch steel ells) really should start to be incorporated somehow, IMHO.
    How would you keep them vertical? You really do not want them attached to the pad for reasons already discussed in this thread.

    I think your idea could be simplified using curved sheet steel on a steel frame. Basically sitting on the ground converting exhaust from vertical to horizontal. Likely need to be fixed to the ground.
    Mark Koelsch
    Tripoli 6155 L3
    Owner of http://www.rocketryfiles.com/
    Editor of http://www.thrustcurve.org/
    Keeper of the motor files

  6. #6
    Join Date
    30th January 2016
    Location
    US > OK > NE
    Posts
    3,222
    Yeah, spike-down plates isn't a terrible idea. A bit more setup, but a bit of added stability. I'm picturing a tuning fork on the back of a slide.

  7. #7
    Join Date
    8th December 2009
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    I'm about 2/3rds of the way done cutting out pieces. Below is 400# of aluminum and 350# of steel (blast deflectors) Cutting this produced about 7 gallons of "man glitter" -chips.

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    Tony

  8. #8
    Join Date
    10th April 2009
    Location
    Auckland, NZ
    Posts
    1,486
    That's a lot of cutting you've had going on Tony, hope you have a bandsaw? I like the idea of putting 1010 and 1515 rails back to back, I think I will do that with the new pad we are going to build.

  9. #9
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    8th December 2009
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    Chrisn, I think a band saw would take much more time. I cut all then tubing with a cheap garage sale Delta chop saw. Each cut took about 10 seconds. Switching back and forth between 90 and 45 degree cuts is very quick.

    Tony

  10. #10
    Join Date
    13th April 2013
    Location
    San Francisco
    Posts
    1,282
    Wow, that is a lot of pads, Tony!
    AERO-PAC, ROC, LUNAR (TRA & NAR)
    jcrocket.com thrustcurve.org

  11. #11
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    The 1515 rails arrived yesterday.

    Tony

  12. #12
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    8th December 2009
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    Must be spring time here in California! These 1515 Booms just sprouted up this week!

    Tony
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  13. #13
    Join Date
    16th February 2014
    Location
    Gilroy, CA
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    2,139
    Wow Tony! Those look great. Are they 16' or 20' rails?
    Chris Attebery
    TRA 6602 L3
    Personal best: 37,789' 1335mph

    www.ape-rc.com

  14. #14
    Join Date
    13th April 2013
    Location
    San Francisco
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    1,282
    Wow, impressive!
    AERO-PAC, ROC, LUNAR (TRA & NAR)
    jcrocket.com thrustcurve.org

  15. #15
    Join Date
    28th June 2016
    Location
    PA
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    662
    Quote Originally Posted by tfish View Post
    Must be spring time here in California! These 1515 Booms just sprouted up this week!

    Tony
    What are the color bands for?
    TRA #10518 ---- MDRA #106

    L1, 6/25/2016: Modified MadCow Super Batray, CTI I236 BS
    L2, 9/17/2016: Modified RW Patriot, CTI J280 SS
    L3, 4/8/2017: RW Formula 200, CTI M1810 RL

    Max Altitude: 4,978', L3 Cert flight
    Max Speed: Mach ???, L3 Cert flight

  16. #16
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    8th December 2009
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    CA
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    Chris, 15 foot..
    John, Thanks..
    Nate, Each Boom has about 12 - 5/16" holes that need to line up perfectly for each piece of 8 Booms to be inter changeable. I'm old school and mark holes with a tape measure and center punch. Meaning each boom is made to match itself. Color coding helps figure out which 2 pieces are a matched pair.

    Tony

  17. #17
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    I just finished up the pads. I still need to add "safety ribbons" to the guy lines. And drill a hole in each of the blast deflector plates. I will be delivering them this week.

    8 pads
    15 foot 1515 rails
    2 guy line systems
    4 rail camera mounts
    Misc extra parts and supplies...
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    Last edited by tfish; 15th June 2017 at 09:29 PM.

  18. #18
    Join Date
    16th February 2014
    Location
    Gilroy, CA
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    2,139
    You forgot the pontoons.
    Chris Attebery
    TRA 6602 L3
    Personal best: 37,789' 1335mph

    www.ape-rc.com

  19. #19
    Join Date
    23rd July 2011
    Location
    Butte, MT
    Posts
    1,999
    Nice work Tony!


    Steve Shannon
    Steve Shannon
    L3CC, TAP, Director, Tripoli Rocketry Association

  20. #20
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    The pads worked out great.

    Tony
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    Last edited by tfish; 27th June 2017 at 06:41 AM.

  21. #21
    Join Date
    18th January 2009
    Posts
    1,804
    Nice pads! I believe the Longhorn Rocketry Association guys flew off a similar one in New Mexico last week. Hmm..., didn't I just see one of those? Or are they one in the same?

    Jim

  22. #22
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    And I thought I could sneak into New Mexico without being seen. Spaceport America https://spaceportamericacup.com/ is a really cool place to launch from! The pads worked great! I'll post a launch report soon.

    The 'reps' from GoPro really liked the "bird house" camera mounts..

    Tony

    Last edited by tfish; 27th June 2017 at 06:40 AM.

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