Hello all together, nice to find an expert on wiring procedures, all your comments are fully correct Bruce!
For the Boeing B747/ B727/ B737 etc. we had of course all kind of tools for all the different MIL a nd aerospace connectors and wire-types available. Unfortunately these are quite expensive and they have to be requalified from time to time for professional use. For stripping off the wire insulation we did prefer the mechanical way. For each qualified (MIL/Space/ Aerospace) there are different special cutting blades with different 'holes' in for each gauge. Thermal stripping was not allowed because outgassing. When working with Teflon, Tefzell etc. (but as well for others as PVC!) the gases are very toxic and agressive for humans and corrosive, specially on the contact surfaces to be contacted! (Kapton was an exception because it is nearly impossible to cut properly without any damage to the wire surface (mech.), but special precautions (venting and cleaning) must be strictly followed when therm. stripping!) Good stripping tools and cutter inserts were manufactured by 'Ideal', some cutting blades we got from the wire manufacturer eg. from Raychem. Such cutting blades do not touch the wire core surface! The critical points are cold flow and hardening of copper under high pressure. As result the wires tends to break, with too low pressure the wire strains do not 'cold weld' (in fact gas tight!) and not provide correct contacts. For the SpaceLab D2 mission (Spaceshuttle) and for the later Satellite-projects etc. we made very frequent pull out tests and from time to time microscopic inspections on the crimped section. After all, yes the persons working with these procedures were special trained and examined. But no, it is not that complicated as it appears, and the well crimped contacts are the most reliable connections, but strain reliefs behind the contacts are essential. I do as well, when possible, apply my crimping tools. regards, Arnold On Fri, 27 Jul 2007 06:22:05 -0700, Bruce Lane wrote: >Good day, >... >> >On 27-Jul-07 at 08:29 Peter Vince wrote: >... >>I was surprised to read that crimping is considered most reliable... >... >> There is some truth in your tale about the crimps in the broadcast >> world, but you are also correct to point out that "adequate" (I like to say >> "proper") crimping is critical to making the connection reliable. > In the avionics world, it is rare that you will find a soldered > connection in the wiring harnesses. 99.9% of everything in there is crimped. > The difference is that the various contacts and plugs, both conventional and coaxial, are attached by well-trained folk using the best available tools. > When properly done, with the right cable prep (ideally, thermal > strippers) and the right crimping tools (mil-spec hex crimps for the > coaxials, mil-spec eight-way indent for the conventionals), a crimp > connection has the same strength and gas tightness of a cold weld. I've been fortunate, over the years, to have gotten hold of the right tools and dies for everything I do through Boeing's surplus store. The contents of one of my tool chest drawers would have run into five figures worth of spending had it not been for them. > Keep the peace(es). >-=-=-=-=-=-=-=-=-=-=-=- >Bruce Lane, Owner & Head Hardware Heavy, >Blue Feather Technologies -- http://www.bluefeathertech.com >kyrrin (at) bluefeathertech do/t c=o=m >"If Salvador Dali had owned a computer, would it have been equipped with >surreal ports?" _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
