Removable Shock Cord Mount

Discussion in 'Techniques' started by McKailas Dad, Jul 12, 2010.

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  1. Jul 12, 2010 #1

    McKailas Dad

    McKailas Dad

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    I kinda copied this, but this is my version. I used .030 aluminum. I may have used thinner, but thats what I had laying around. I used a drill for the center hole, and tin snips for the rest. I hit it with some coarse sandpaper to get the OD just under the motor size. I hammered a screw into the tab for a hole, I didn't have a drill bit that small. It weighs in at barely a half a gram. The notch fits around the motor hook, with room to spare. I have not had any issues with motor fitment, its just *alittle* more snug. Those of you that friction-fit, would obviously have no issues, but I'm still a 'hooker' :roll:

    I have already needed to 'use' this, when my rocket was retrieved from a tree, I needed to replace the shock cord...works mint!

    Hope you like it! :D

    023.jpg

    024.jpg

    025.jpg
     
  2. Jul 15, 2010 #2

    McKailas Dad

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    I've flown it about five times so far, but should I be worried that the aluminum will fatigue from the heat? Would tin have been a better choice? I figured aluminum was lighter...I guess I'll keep testing and let you know.
     
  3. Jul 15, 2010 #3

    j.a.duke

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    I'm going to try stainless steel-get a small piece from onlinemetals.com and hopefully that will work as well as aluminum and be as easy to work with.

    Cheers,
    Jon
     
  4. Jul 15, 2010 #4

    McKailas Dad

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    Stainless, compared to aluminum, is very hard to cut, and considerably heavier. I used coarse sandpaper to get the final shape of the 'C'. Took about 5 minutes. Try hand sanding SS, and you'll be sanding till October. Might wanna try a Dremmel, or at least some type of power tool. <Tim Taylor grunt-grunt> ;)
     
  5. Jul 15, 2010 #5

    j.a.duke

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    I'll be wearing my Tool Time hat when working on this :D

    I might grab some scrap aluminum flashing squares that are in the garage to try this with first, but I think SS would be the way to go longer term.

    I assume that something like this could be laser cut from sheet stock pretty easily, and that's what I'd probably do long term (or see if some here steps up to create something like that).

    Cheers,
    Jon
     
  6. Jul 15, 2010 #6

    McKailas Dad

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    Oooh, a laser?! :y: Yea, mines on backorder, thats why I used snips :rolleyes:

    I think if you have access to laser cutting, the 'other' design may be better. I'm concerned about my design being folded over on itself. I figure if it does break, it will do so at the fold.

    I'm kind of surprized more people don't use this little widget. Yes, the tri-fold Estes works ok, and the Kevlar loop is a good idea, but neither are easily repaired/replaced. My future builds will definatly include this style removable mount...:confused2:

    Heck, if you laser out a batch, I'll take a handfull! Maybe slice out some 24mm while your at it? ;)
     
  7. Jul 16, 2010 #7

    bguffer

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    Looks like a good idea. If you could just tie a metal leader to a washer, i think it would be alot easier. Not sure if the motor would sit solid against it though.

    Bob
     
  8. Jul 16, 2010 #8

    dragon_rider10

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    The .pdf doesn't open for me. Corrupted file or something. I'm missing the basic concept here. How is the metal ring secured in the rocket- sandwiched between the motor and the engine block?
     
  9. Jul 16, 2010 #9

    McKailas Dad

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    Yes, exactly. That's what I really like about it, easily removable/replacable. Snag it with a small hooked pick, out it comes, easy-breezy.

    Here are some 'snips' of their design from Apogee Components 'Peak of Flight' site. (Issue 231, March 24, 2009)

    I made my design different, because I didn't have anything to cut inside the 'C', the way theirs is.

    On mine, I drilled the hole, then cut it out the 'C' shape and the leg. Leave it long, you can cut it off later... looks kinda like this ---C

    Gee, I do know somebody with a laser (former employer)...maybe I should have them zap out a hundred or so? Unless j.a.duke beats me too it :dark:

    Mhook1.JPG

    Mhook2.JPG

    Mhook3.JPG
     
  10. Jul 18, 2010 #10

    Handeman

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    I've been a BAR for seven years now and have been here on TRF for most of that. I still learn things here.

    I've never seen or heard of this type of anchor before, but it's a great idea! :D

    I might start using this instead of the tri-fold anchors I've been using in my LPRs.

    Thanks for the post!
     
  11. Jul 18, 2010 #11

    Kira_Majeric

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    This is a really neat concept. Thank you for the post.

    I am interested in this, I like it when things are easily fixed. I might have to talk my fiance into making me one. ^_^
     
  12. Jul 18, 2010 #12

    McKailas Dad

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    I think I'm gotta call my 'laser guy' on Monday. What do you think, 100 to start? I'll see about pricing...:D
     
  13. Jul 18, 2010 #13

    hcmbanjo

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    To McKaila's Dad,
    I didn't see any mention of James Jason Wentworth is this thread. Some of you might know him as "Blackshire" over on YORF. This is his concept and design.
    I noticed a link to the original article in the Apogee Peak of Flight, but I think Jason should get his thanks for such a great idea.
    He's also came up with a brilliant two-piece "T" motor adapter. I have two of those in my range box.

    To Jason,
    From me - Thanks for your innovation and input on the forums.
     
    Last edited: Jul 18, 2010
  14. Jul 18, 2010 #14

    McKailas Dad

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    I agree, I can not take any credit for originating this concept, although my design is just alittle different.

    So, Mr. Wentworth, I appologize for not giving you 'personal' credit. I thought my link to your design was enough to give you recognition.

    I think it's a great idea, and I give you kudos for coming up with it, and also sharing your idea with the rocket community. I sincerely hope you do not think I 'stold' your idea, I was simply trying to make an easier-to-fabricate design.

    Next time I find something to share, that is not my idea, I will give personal recognition to the one that originated it.

    Again, I appoligize for any confusion...:eek:
     
  15. Jul 19, 2010 #15

    j.a.duke

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    I think Jeff was just trying to pass along his modification of Jason's idea-I tried to cut one out when I first saw it in the Apogee newsletter-just didn't have the right tool(s) or material (like who has litho tin just lying around?).

    Jeff's modification makes perfect sense for those of us who don't have a full machine shop at our disposal, just the basic tools.

    He did link to the source in the very first paragraph (fourth word), so that credits both Tim and Jason.

    Now, back to our regularly scheduled programming...

    Cheers,
    Jon
     
  16. Jul 19, 2010 #16

    j.a.duke

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    Let's see:

    13mm

    18mm

    20mm (Quest "D")

    24mm


    I'd be game for at least 5 of each myself out of stainless or similar.

    I'm thinking if the lithographic tin referenced in the article is strong enough, then light gauge stainless will be fine.

    This would let me fly my "historical" models from 30+ years ago.

    And I'd love to figure out a way to mount these into new builds but have them removable (like those 3M things that you pull a tab and they unmount from the wall with minimal damage).

    Cheers,
    Jon
     
  17. Jul 19, 2010 #17

    McKailas Dad

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    Jon, thanks for that. I didn't really think I was stepping on anyones toes.

    There was *alittle* carbon buildup, but not like it was welded in. I made the OD around 16-17mm, a fuzz smaller than the motor. I figured better to small than too big in this case. I didn't want it wedged, or forced in...Easy in, easy out!

    I didn't want to say Easy Off, cause that may have a copywrite....:p (sorry, had to :D)
     
  18. Jul 24, 2010 #18

    Rex R

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    let me know if you 'need' a test subject for a 24mm (D) mount, I've got a vintage rocket* that will need a new shock cord :).
    *maxi-streak
    rex
     
  19. Jan 11, 2012 #19

    McKailas Dad

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    Just a progress report, these things are holding up great! I have made handfulls of them, and not 1 single failure from breakage, burn through, anything.

    I've now made 13, 18 and 24mm.....

    Try em!

    It's the last shock cord mount you will need.


    Ever.


    .
     
  20. Jan 11, 2012 #20

    qquake2k

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    What a great idea! Expanding on Jeff's two-piece idea, what about using a thin metal washer? You could notch it for the motor hook, and bend a strip of metal to attach to the washer for the recovery attachment point.
     
  21. Jan 11, 2012 #21

    McKailas Dad

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    Qquake2k, it's actually only 1 piece.

    I drill a hole (~1/2" or same ID as motor), then, outline the motor but leave a tang, about 1/4" wide by 1 1/2" long. You can shorten it later if needed.

    Cut and shape with tin snips, file or sand to shape (to match OD of motor).

    Using pliers, bend the tang over the hole, then bend up, making sure you clear the motor block. The tang ends up right about in the middle of the motor, looking down.

    The bent area may need to be sanded more to fit. I leave the tang a bit wide just for that reason. Cutting the small slice for the motor stop hook is not always needed, but I prefer to.

    Drill, punch (or laser :rolleyes: ) a small hole for shock cord/steel leader/Kevlar. Done.

    Would it be easier with....pics?

    You could probably do something similar with a thin washer, but short of welding on a tang, I'm not sure how you would attach it.


    (oh, and thanks again, Blackshire....great idea!)
     
  22. Jan 11, 2012 #22

    qquake2k

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    Okay, I see how you did it. Makes total sense now.
     
  23. Jan 12, 2012 #23

    Stymye

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    simple and very effective idea..now you have to give it a name.

    first I've seen this as well:handshake:
     
  24. Jan 12, 2012 #24

    [POW]Eagle159

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    First time I saw this thread.....And
    I LOVE the idea, works for all the peoples needs...Small, Strong, Replaceable too!
    Neat little thing:wink:
     
  25. Jun 18, 2012 #25

    McKailas Dad

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    Bump again!

    Yup, 2 years old and still holding.

    I actually did talk to somebody about manufacturing these, but they seemed a bit pricey. (laser cut stainless steel)

    The first piece is the most expensive.

    I may have to talk to them again, it's been awhile, and maybe the price has dropped...?
     
  26. Jun 18, 2012 #26

    chadrog

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    Unlikely, the price of steel has gone up the last couple years. Did you get out to JC today? Looks like I missed a nice day.
     
  27. Jun 18, 2012 #27

    j.a.duke

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    Jeff,

    What were you quoted per piece? At what quantity?

    I'd probably buy a bunch to use both in new builds as well as retrofits. Since BARing back in '07, I've already had a couple of kevlar cords fail-not sure if it was my bad building technique or an issue with the kevlar (too small for the number of flights)

    I've been overbuilding, but this would solve multiple issues at once.

    Thanks.

    Cheers,
    Jon
     
  28. Jun 18, 2012 #28

    BLT50568

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    Sorry for a newbie question.

    How do you attach this to the rocket? Do you glue the spent engine inside the rocket? I'm just not quite understanding it.

    edit..... Ok, now I think I get it. It's just the metal ring that is slid in above the engine?
     
    Last edited: Jun 18, 2012
  29. Jun 18, 2012 #29

    Rocketbuilder

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    McKaila's Dad,
    I'm also interested in what they would cost. If they're not too expensive, I'd probably buy several. I love the idea! :)
     
  30. Jun 18, 2012 #30

    BLT50568

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    I got to thinking...... Could you take a washer and cut a notch out of it, then bend a piece of SS and use something like JB weld to adhere the tab to the washer?
     

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