An "R"-powered rocket build

Discussion in 'High Power Rocketry (HPR)' started by Rail Dawg, Nov 30, 2018.

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  1. Jul 12, 2019 #2071

    Rail Dawg

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    Am curious what other projects are potentially slated for LDRS 38?

    Anyone here have some info on what's in the pipeline?

    Thanks.

    Chuck C.
     
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  2. Jul 12, 2019 #2072

    Ez2cDave

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  3. Jul 14, 2019 at 8:02 AM #2073

    Rail Dawg

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    Rocket is set for a 10’ motor.

    Got the back-up recovery system in place. (2) 1/2” Kevlar straps that are bulletproof-secured into the upper part of the booster. They will attach via quick links to the 3/4” eyebolt on top of the motor.

    Still working on drogue section but now that the 10’ motor placement is locked in this section will be easy to finish.

    AvBay will slide into upper part of drogue section and be secured with (8) 1/4” bolts. AvBay needs to be removable to access charge cannons for drogue.

    Need to do these AvBay bolts for both ends but that should be pretty straightforward.

    Still need to beef up fiberglass nosecone and install Delrin rail guides. After that get electronics installed onto AvBay sled.

    Still some work to do but with LDRS 7 weeks away there’s plenty of time to finish with time to spare.

    Got one Q motor to test and one to build.

    Need to get some pics posted and will do so in the next few days.

    Chuck C.
     
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  4. Jul 14, 2019 at 1:13 PM #2074

    Ez2cDave

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    Chuck,

    Don't fall into the "I have plenty of time" trap . . . Those 7 weeks will fly by, before you know it !

    "From my chair" :

    (1) Charge Cannons need to be tested.

    (2) Nose cone must be reinforced.

    (3) Install Rail Guides.

    (4) Test Electronics.

    (5) Make or purchase Recovery Harnesses. ( Take a look at "OneBadHawk" ) http://onebadhawk.com/index.html

    (6) Attach Fin Can to Airframe securely.

    (7) Priming, Painting, & Graphics.

    (8) Motor Static Testing & Igniter Development /Testing.

    (9) Verify CG with R Motor, Recovery Devices, and Electronics installed.

    (10) Etc, Etc, Etc . . .

    Something WILL come up, unexpectedly !

    Dave F.

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  5. Jul 14, 2019 at 5:35 PM #2075

    Rail Dawg

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    Well put Dave.

    Thanks.

    Chuck C.
     
  6. Jul 14, 2019 at 6:00 PM #2076

    neil_w

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    Just balance it on your finger, right?
     
  7. Jul 14, 2019 at 6:03 PM #2077

    mperegrinefalcon

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    Real question time, how even do you check the CG on something this big?
     
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  8. Jul 14, 2019 at 8:33 PM #2078

    fyrechaser

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    It will take several folks to lift and place for balance....
     
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  9. Jul 15, 2019 at 2:00 AM #2079

    Ez2cDave

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    Chuck,

    Got your back, at all times, sir !

    Dave F.

    STEELY-EYED MISSILE MEN - AVATAR.jpg
     
  10. Jul 15, 2019 at 1:13 PM #2080

    Rail Dawg

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    Just to verify Vern since I’m getting to the nosecone soon.

    Will install a 54mm tube probably more than 18” long that will butt up against the non-metal tip of the nosecone.

    There will be a bulkplate of course that will have the 54mm tube capped at the bottom. I’ll bring some 54mm coupler that we can cut to length as needed.

    Looks like that will cover our bases correct?

    I appreciate your offer to run Miss Kate as I think this will be a real crowd-pleaser.

    Although there is full confidence that the motor will perform beautifully perhaps we should design an escape rocket for the nosecone so Miss Kate can be safely carried away should something happen on the pad.

    Ok that’s a poor attempt at humor lol.

    Chuck C.
     
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  11. Jul 15, 2019 at 1:34 PM #2081

    Charles_McG

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    Couldn’t you rest it on 2 scales - one on either side of the Cg? Wouldn’t the position of the Cg between the scales be the ratio of the weights?
     
  12. Jul 15, 2019 at 2:16 PM #2082

    Flyfalcons

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    Weight x Arm = Moment is a proven method to determine CG when using scales.
     
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  13. Jul 15, 2019 at 3:15 PM #2083

    Bat-mite

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    With a few people and a sawhorse, it can be done by balancing.
     
  14. Jul 15, 2019 at 3:32 PM #2084

    VernK

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    Yes, that is exactly what we need. Perfect!
     
  15. Jul 15, 2019 at 10:47 PM #2085

    Ez2cDave

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    The rocket has a liftoff weight of 700-800 lbs . . . Trying to balance it on a horizontal 2x4 of a sawhorse would be the "Kiss of Death" !

    There would either be too much force concentrated in one small area of the airframe and the rocket would "snap in two" or the 2x4 of the sawhorse would break and drop the rocket to the ground.

    Dave F.

    STEELY-EYED MISSILE MEN - AVATAR.jpg
     
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  16. Jul 15, 2019 at 11:42 PM #2086

    mperegrinefalcon

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    Yeah, that would be bad. I didn't realize this was a 700-800 pound rocket, I thought maybe 200-300.

    I think just placing it on two scales and calculating it would be the best.
     
  17. Jul 15, 2019 at 11:49 PM #2087

    Rob702Martinez

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    Balance it on your shoulder? :rolleyes:
     
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  18. Jul 16, 2019 at 12:05 AM #2088

    davdue

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    Sounds like a perfect test for the steely eyed missile men. Lol
     
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  19. Jul 16, 2019 at 12:21 AM #2089

    Ez2cDave

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    Fortunately, for Chuck, the Steely-Eyed Missile Men are taking a serious look at the "logistics" of doing an "all-up" CG check.

    Safety for those involved and the rocket itself are of primary concern.

    At present, I'm looking at the possibility of using a "sling" to establish the CG.

    Dave F.

    STEELY-EYED MISSILE MEN - AVATAR.jpg
     
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  20. Jul 16, 2019 at 1:12 AM #2090

    rcktnut

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    I'd find a nice tree with a sturdy low branch, hook up a come-along to the branch and either assemble the rocket on the ground or appropriate amount of bucks put sling at approximate CG and crank it up a few inches. Adjust until CG is found.

    I'll add or a joist or an engine puller, anything overhead that is capable of handling the weight.
     
    Last edited: Jul 16, 2019 at 2:24 AM
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  21. Jul 16, 2019 at 1:19 AM #2091

    Nytrunner

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    Component CG analysis.

    Determine the CG of the pieces, and determine the composite CG location.
     
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  22. Jul 16, 2019 at 2:01 AM #2092

    Ez2cDave

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    That's an intriguing idea . . . Can you please provide more details, as I have never used that method ?

    Thanks,

    Dave F.

    STEELY-EYED MISSILE MEN - AVATAR.jpg
     
  23. Jul 16, 2019 at 2:15 AM #2093

    Nytrunner

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    The engineering team, whoever they are, should be abke to handle it.

    Each piece of the rocket has its own weight (w) and its own CG at a location within that piece. Carefully record those weights and CGs.

    When stacked together (on paper or real life), record the distance (x) of each piece's CG from the base of the rocket . Multiply each section's weight by its corresponding distance and Add them together (w1x1 + w2x2 + w3x3 + etc...)

    Divide that sum by the total mass of the rocket, and the result is the CG of the whole thing (aka, the composite object)

    Link below

    http://hyperphysics.phy-astr.gsu.edu/hbase/cm.html
     
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  24. Jul 16, 2019 at 2:37 AM #2094

    neil_w

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    Or heck, just chuck the data into OR (real measurements and overrides)
     
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  25. Jul 16, 2019 at 3:07 AM #2095

    Ez2cDave

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    Thanks for the link !

    Dave F.

    STEELY-EYED MISSILE MEN - AVATAR.jpg
     
  26. Jul 16, 2019 at 3:13 AM #2096

    blackjack2564

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    +1
    how we did with a 675lb one. Used the hitch on truck to pull rocket a few inches above ground.
    used 1inch TN.[4500lb rated] loop tied with bowline so it could slide into position. Simple and you KNOW exactly where CG is..no guessing with calculations.

    Block & tackle would be even better.
     
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  27. Jul 16, 2019 at 3:05 PM #2097

    fyrechaser

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    +2 Jim

    In my humble opinion this method is the absolute best way to get an accurate CG location for a project this size. It can be done safely and quickly with a little preparation.
     
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  28. Jul 16, 2019 at 9:41 PM #2098

    Ez2cDave

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    To All,

    Just so long as we don't try to "Swing Test" it . . . LOL !

    Dave F.




    STEELY-EYED MISSILE MEN - AVATAR.jpg
     
  29. Jul 17, 2019 at 1:29 AM #2099

    Theory

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    X3 No replacement for real world numbers
     
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  30. Jul 17, 2019 at 1:42 AM #2100

    Ez2cDave

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    Accuracy Uber Alles !

    Dave F.

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