Originally published March 1998
On 28 February 1998, 10 or so hearty EAAers gathered at Rosamond Skypark to sit at the font of airborne electronic wisdom as being spouted forth by our own Charlie Wagner. This was the continuation and completion of Charlie's programs presented last November and December. Topics covered included cutting and stripping, crimping, Molex connectors, soldering, shrink tubing, splicing, wire bundling, and wire supports. Each subject came with plenty of example tools, demonstrations, and chances for hands-on buffoonery as we tried to emulate the skills of the master.
By far, the most popular topic was crimping. We've all read where the homebuilder's guru (Tony Bingelis) implored us to only crimp connectors on wires, not to solder them on. Soldering stiffens the joint, and coupled with vibration tend to "lead" to fatigue failures (and I don't mean you getting tired of fixing broken wires). If you were like me, anytime you tried to crimp a connector onto a wire with the $10 crimping pliers you bought at Radio Shack, you ended up with a connector that fell off the end of the wire when you were done. In desperation, you ended up soldering it on just to keep it in place. Well, it turns out, you were probably using the wrong terminals and using the wrong (or at least sub-optimal) tool! Charlie showed us the good type of connectors and pointed out that virtually every connector requires its own specific crimping tool! All of the good crimping tools are of a ratcheting type. Once crimping is started, a ratchet holds the tool in its last position, and does not release until you have squeezed hard enough to properly crimp the terminal.
Charlie shows Miles Bowen and George Gennuso the proper technique for stripping a battery cable
Crimping is like a swaging process. The metal of the connector is not just pressed against the wire, holding it by friction like a spring clamp. In a good crimp, the pressure is sufficient to plastically deform the metal, causing the connector metal to "flow" around the wire, thus forming the bond. Additionally, a second crimp (formed at the same time with the proper tool) clamps the insulation, giving additional support to the wire.
Charlie welcomed the skeptical Project Police with a demonstration. He picked up a random connector (of the proper size for the wire in hand), crimped it on the end of said wire, then invited Miles to hold the connector in a Vise-Grip. He then connected the wire to the hook of an uncalibrated spring fish scale (only for use on fish caught in the months of March, April, and May) and proceeded to try to separate the wire from the connector. Russ Erb was the official data observer, and confirmed that the scale bottomed out at 28 pounds with no failure. Charlie then removed the scale and pulled the wire to failure. It finally slipped out at an estimated 40 to 50 pounds.
Even if soldering is not appropriate for terminals, there are areas where it is still required and appropriate. Did you know that there are thermostatically controlled soldering guns available? Of course, they cost more, and Charlie has at least one. So we talked about soldering techniques too.
Charlie also warned us of the evils of using wire strippers with guillotine blades. The best strippers have blades with shoulders that rest on the insulation so that the underlying wire is not nicked. Charlie admits that even he nicks a wire occasionally, but if more than 2 strands fall out, he cuts it off and re-strips.
If Radio Shack is the hardware store of the electrical world, Charlie showed us catalogs for the Aircraft Spruces and Wicks. One of Charlie's favorites is Mouser (http://www.mouser.com), who has a very nice catalog and will sell items in any quantity you want. Their web site will show you any page of their catalog in a PDF file. Other familiar electrical suppliers are Digi-Key (http://www.digi-key.com) and Newark (http://www.newark.com). An excellent source for those hard-to-find tools is Jensen Tools (http://www.jensentools.com).
Contents of The Leading Edge and these web pages are the viewpoints of the authors. No claim is made and no liability is assumed, expressed or implied as to the technical accuracy or safety of the material presented. The viewpoints expressed are not necessarily those of Chapter 1000 or the Experimental Aircraft Association.
Revised -- 24 September 1998