AeroElectric-List Digest Archive

Thu 09/29/16


Total Messages Posted: 2



Today's Message Index:
----------------------
 
     1. 09:57 AM - Re: Solder splices/connections (Robert L. Nuckolls, III)
     2. 08:51 PM - Strobe Grounding (mike@vision499.com)
 
 
 


Message 1


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    Time: 09:57:43 AM PST US
    From: "Robert L. Nuckolls, III" <nuckolls.bob@aeroelectric.com>
    Subject: Re: Solder splices/connections
    At 04:29 PM 9/28/2016, you wrote: >The stress riser that occurs at the interface between wire strands >and solder filled wire strands if not mechanically supported is a >candidate for fatigue failure due to vibration induced flexing of the wire > >This is true of field splices and soldiered pin/wire connection. > >Good mechanical support/strain relief is imperative to prevent >fatigue failure of the connection/soldier joint. Yes, stresses due to flexing of any material is a function of thickness/diameter of object and the magnitude of the bending . . . which under vibration gives rise to cyclical tension/compression forces on the material. A second of 1" copper rod flexed through x-degrees will fail in a tiny fraction of the same cycles impressed on a 0.020" strand of copper. This is why welding cable is made from a bizillion strands of copper 'cat hair' as are braided copper bonding straps . . . http://tinyurl.com/jxsf55j . . . are unlikely to fail under flexure stresses over lifetime of the installation. Whether or not a solder-solidification of strands presents a more/less severe stress riser point than a crimp- solidification is kinda splitting hairs. When used in a situation that imposes cyclical forces on the joint, there is significant risk of failure at the transition from solid to strands in BOTH technologies. This fact of physics gave rise to the double crimped, 'pre insulated' terminals of all stripe but most famously, PIDG style terminals offered by many suppliers for the last 70 or so years. http://tinyurl.com/zkmh7kj When the joining is effected with solder, folks in-the-know strive to achieve two goals. Join the wires and support the insulation just outside the junction. http://tinyurl.com/ju4gvvg Arguments favoring one process over the other have no solid foundation in risk reduction. It's not difficult to apply either process in a manner that will exceed the service life of the airplane. You can mess up a potentially good crimped installation too. http://tinyurl.com/hekmvyz This terminal was observed on an accident aircraft where, amongst many other shorfalls, some terminals were not properly installed. Understand the physics, acquire the tools and PRACTICE. Bob . . .


    Message 2


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    Time: 08:51:33 PM PST US
    Subject: Strobe Grounding
    From: mike@vision499.com
    I have installed a Whelen HDACF Power Supply in my composite aircraft and the instructions make no mention of grounding the shield in the cables to the strobes. Should I ground the shield and if yes should it be one or both ends. Thanks Mike




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