Locking bullet connectors

3689499307?profile=originalI prefer to use bullet connectors between motor and ESC. Lot's of folks use solder on these joints for a very good reason. One loose connection on a multirotor motor circuit can spell disaster. In addition to the possibility of a loose connection, it is often the case that the heat shrink insulation can leave a small gap between the two parts of the bullet. I want all my electrons to stay where they belong : / 

So here is a solution to both issues:

Break out the manual 3D printer(hot glue gun)

Cut out a piece of silicone sheet to use as an ad-hoc mold

Apply a small bead of the glue and use the silicon to shape a thin film evenly around the joint

Peels off cleanly when you need to break the connection.

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Comments

  • Yes Tammo, hot glue and fingers-the burn that keeps on giving.
    : /
  • I am also a hotglue fan. Sometimes i use it to isolate cable connections if I forgot to put shrinkwrap on them before soldering :)
    Thanks for the tip about silicone sheets for "sculpting" the glue.
    Using fingers for that is not recommended.
  • John, Thanks for that NASA technical standards link, I love looking through those kinds of papers!

  • This is a useful thread. Thanks!  Somewhere out there is a great summary of stress-relief and vibration-mitigation techniques for wiring/cabling and other electronic/electrical assemblies. Something a bit more oriented to UAV hobbyists than this. (Decades ago, I did conformal coating (aka potting) of circuit boards with Solithane. Not a good idea if disassembly for repair or maintenance is expected.)

  • ikrase,

    I could see how that might prevent jiggle and micro arcing in a slightly loose connector.

    This is also a good idea for high humidity/corrosive environments --  So long as it was a very clean application, don't want to let those electrons out!

    Dialectic grease on the outside might be a fool-proof way to at least get some moisture protection.

    I use a plastic-safe spray lube (for electrical connectors) on my battery plugs, it makes life easier -- especially with cold hands.

  • One idea that occurs to me is to fill the bullet connectors with conductive grease or something like that. 

  • Nice Daryl, I like that solution a lot!
  • I like this, good and simple.  I opted to use silicone fuel tubing instead as that's what I had lying around at the time.

    3692601589?profile=original

  • First let me say that I am in no way disparaging heat shrink tubing. I love that stuff and use it everywhere. I simply wanted to illustrate a method for molding hot glue into something more useful than an amorphous stringy blob.

    As to my preference for using connectors versus solder, this stems from two primary design factors in my craft:

    *At this point everything I build is a prototype and therefore I want nothing locked in. I'm constantly trying new components and configurations.

    *The end use I'm building towards requires field repair-ability be close to the top of the design hierarchy.

    My interests are single operator camera piloting for sports and adventure documentation, and scientific field work. Camera piloting is simply FPV with the goal of cinematic composition- often low, fast, and in close proximity to various hazards. It's very easy to get distracted with shot composition and loose track of the ground! This means a high probability of crashing coupled with remote and difficult to access locations. I won't have a grip truck full of ready to fly backups. Cordless hot glue is a vital tool in field repair.

    Here are a couple of other examples of hot glue use and componentized design-

    3692601437?profile=original

    Hot glue encapsulation for Attosensor (this can be heat polished if aesthetics are a concern)

    3692601454?profile=original

    Bus bolts allow easy component replacement and excellent star topology power distribution. Hot glue encapsulation is used to lock the nuts and prevent accidental shorts, omitted here for clarity. In future designs this will be addressed with a plastic housing around the terminals.

    3692601228?profile=original

    Simple and lightweight.

  • Mine have cleared heat-shrink. Hot melt gets flaky and fails far too quickly for me to try using that for bullet connectors.

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