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Looking for some sort of 'cable quick release'

  1. Feb 19, 2012 #1
    I'm working on a design project and I need to find what I would call a 'cable quick release'. Basically, I need to be able to quickly release a cable that has ~3500 pounds of tension in it. Ideally, one would just use a pin you could pull out, but I'm fairly certain that would be difficult if not impossible. I've searched around google for such a device but have come up empty handed. Any ideas where I could find one or even what to call it?
     
  2. jcsd
  3. Feb 20, 2012 #2
    Hello,

    I am sorry to say I cannot direct you exactly to what you are looking for. However, I would suggest you locate your nearest Crane or Rigging company and inquire about this.

    Or, I recall seeing such a device used on the show "MythBusters" when they want to drop a heavy suspended object (such as a vehicle, or weights). I would try researching this route.

    Sorry I cannot be of more help. Good luck in your search.
     
  4. Feb 20, 2012 #3

    OldEngr63

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    Gold Member

    You could help to narrow the search if you would specify whether the connection needs to be reusable or not (can we simply cut the cable?), does it have to fully disconnect or does it simply need to release the load support while maintaining partial engagement (full separation is perhaps more difficult than simply dropping support for the load).

    In short, spell out more fully what you want to accomplish with this disconnect and it may become more evident how to accomplish it.
     
  5. Feb 20, 2012 #4
    VictoryMike: Thanks for the suggestion. Funny you bring up mythbusters since I was just thinking about that, what they have is exactly what I need.

    OldEngr: Ideally it would need to be reusable, we definitely wouldn't be able to just cut the cable. I would be ok if part of the release was destroyed and then that part was easily replaced i.e. something similar to an explosive bolt, but not explosive. If I understand the second part of your question right, it would need to fully disconnect. I want all of the load off the cable instantaneously.

    The application for this is for a catapult that's designed to launch a 3 kg projectile 50 meters. The energy must be stored in a spring. Turns out you need quite a bit of energy and some rather large springs, roughly 3,500 pounds worth. Anyway, we need to be able to compress the springs and then release them quickly. We plan on using a winch/ratchet with a cable/strap to compress the springs, but we haven't found a way to separate the springs from the tether yet. Thus why I'm posting this now. If you desire any more details, let me know.

    Also, I found this: quick release snap shackle
    Its made for some sailing application, and it looks like you just pull the string and the shackle releases. But can you tell if it would release under load?
     
  6. Feb 21, 2012 #5
    I am not confident that this will trigger a 3500 lb load, but here are plans I found for a trebuchet trigger, it could serve as a nice starting point.
    here
     
  7. Feb 21, 2012 #6
    I actually found that trebuchet trigger before. That is along the line of what I need, but I would prefer to be able to use a commercially available item. If I design something myself, I would need to do a complete stress analysis on every component of it which is more work than I need right now.
     
  8. Feb 22, 2012 #7
    You might have to, it's not generally advisable to drop loads (suspended or with otherwise stored energy) quickly and uncontrolled. For times when it is, the parts are usually application specific. I'm not saying you will not find something that works, but I can't imagine it will be easy.

    If it comes down to it, over-engineer it.
     
  9. Mar 18, 2012 #8
    If you're still looking for ideas, I know load wise you are still on your own but these exist.

    http://www.perfski.com/Waterskis/Trick-Skis/Masterline-Robbins-Trick-Release.html [Broken]
     
    Last edited by a moderator: May 5, 2017
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