---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Mon 04/25/16: 6 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 03:53 AM - Screw Terminals (racerjerry) 2. 06:42 AM - Re: Screw Terminals (user9253) 3. 09:05 AM - Re: Re: Screw Terminals (Eric Page) 4. 09:05 AM - Re: Screw Terminals (Robert L. Nuckolls, III) 5. 11:54 AM - Re: Check My Work (David Lloyd) 6. 11:59 AM - Re: Check My Work (David Lloyd) ________________________________ Message 1 _____________________________________ Time: 03:53:53 AM PST US Subject: AeroElectric-List: Screw Terminals From: "racerjerry" Screw type terminations scare the hell out of me - except when they are done correctly. I have seen way too many products & screw type terminal strips installed in OBAM aircraft that were designed for static operation that do not have any type of locking mechanism to counter normal vibration. Most quality switches come with terminal screws that have a captive lock-washer as well as a plain thin washer under it so as to provide a locking mechanism for the screw head, but not scar the device being attached. I am very partial to aircraft quality internal star lock-washers. They are inexpensive, corrosion resistant and do not side load the screw/stud as common split lock-washers are prone to do. They are also thinner than a split washer. If I am installing against a ring terminal; unless it's captive, I normally omit the plain washer and let the stars bite into everything for a solid, secure and vibration resistant connection. The internal star lock-washers should be replaced each time they are removed, but at least check that ears are not completely flattened out. $2 worth will last you a lifetime. Current prices from Aircraft Spruce: MS35333-37 (#6) $0.02 MS35333-38 (#8) $0.02 AN960-6L (#6) $0.02 or $1.60 /100 AN960-8L (#8) $0.02 or $1.60 /100 -------- Jerry King Read this topic online here: http://forums.matronics.com/viewtopic.php?p=455423#455423 ________________________________ Message 2 _____________________________________ Time: 06:42:39 AM PST US Subject: AeroElectric-List: Re: Screw Terminals From: "user9253" It turns out that the split ring lock washers that we have been using for years are not actually lock washers at all. In fact, their spring characteristic can actually cause fasteners to loosen sooner. I have not seen split ring lock wasters used on newer cars. Internal star lock washers are good. Even better are wedge-lock washers. They are used in pairs with the wedges facing each other. When a bolt or nut starts to loosen, the wedges move apart slightly. That causes the fastener to stretch, which makes it difficult for the fastener to loosen anymore. It requires much more force to loosen than to tighten fasteners installed with wedge-lock washers. Matco brakes and Sensenich props use wedge-lock washers without any other locking devices or safety wire. Youtube movie about wedge-lock washers: https://www.youtube.com/watch?v=IKwWu2w1gGk I am not recommending wedge-lock washers for small screws. But I am recommending that split ring lock washers NOT be used anyplace on an aircraft, or for any application with the intent of preventing a fastener from loosening. -------- Joe Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=455430#455430 ________________________________ Message 3 _____________________________________ Time: 09:05:11 AM PST US Subject: Re: AeroElectric-List: Re: Screw Terminals From: Eric Page Very interesting product. It appears to work well, but I wonder if the radial impression marks that they create can serve as stress risers in softer materials like aluminum. Also, it looks like it wouldn't take very much over-torque to gall an aluminum surface or scrape off the cladding. Perhaps this is why aviation still predominantly uses castle nuts on flat washers. Not advocating against Nord-Lock, just thinking out loud... Eric > On Apr 25, 2016, at 6:41 AM, user9253 wrote: > [...] Even better are wedge-lock washers. They are used in pairs with the wedges facing each other. When a bolt or nut starts to loosen, the wedges move apart slightly. That causes the fastener to stretch, which makes it difficult for the fastener to loosen anymore. It requires much more force to loosen than to tighten fasteners installed with wedge-lock washers. Matco brakes and Sensenich props use wedge-lock washers without any other locking devices or safety wire. > Youtube movie about wedge-lock washers: > https://www.youtube.com/watch?v=IKwWu2w1gGk ________________________________ Message 4 _____________________________________ Time: 09:05:27 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Screw Terminals At 05:52 AM 4/25/2016, you wrote: > >Screw type terminations scare the hell out of me - except when they >are done correctly. I have seen way too many products & screw >type terminal strips installed in OBAM aircraft that were designed >for static operation that do not have any type of locking mechanism >to counter normal vibration. Most quality switches come with >terminal screws that have a captive lock-washer as well as a plain >thin washer under it so as to provide a locking mechanism for the >screw head, but not scar the device being attached. True . . . All mil-qualified switches will come with internal tooth lock washers and I've never encountered a condition precipitated by a loose screw. Switch and breaker panels are never assembled in a production airframe. They are put together on sub-assemblies in good lighting, air conditioned spaces by people standing upright or sitting on a chair. The sub assembly, with a medusa of pendant cables and wires is assembled to the airframe with a few screws and 'plugged in' with perhaps a few fat wires dropping onto studs. Most breakers and switches with threaded fasteners have steel screws into brass 'nuts'. Recommended torque values for fastening are in the 8 in-lb range . . . and this number is generally 60% of ultimate. Assembly benches at Beech used torque limiting screwdrivers to do final tightening of threaded fasteners. You can often pick up adjustable, torque limiting screwdrivers off eBay. Few OBAM/SE-TC aircraft are assembled like leggos . . . and none will be easy/convenient/comfortable to troubleshoot. Further, the assembler is comparatively Wwaaaayyy down on the learning curve for achieving consistent tightening torque. At the same time, we have an opportunity to do FMEA studies which guarantee that NO single disconnection for loose screw or any other reason causes a bad day in the cockpit. Many variations in desirable switch styles/features will drive the decision toward threaded fasteners which are not evil, only different. It's like the difference between crimped and soldered. Both are entirely satisfactory when applied with confidence . . . it's just another skill to learn. Bob . . . ________________________________ Message 5 _____________________________________ Time: 11:54:05 AM PST US From: "David Lloyd" Subject: Re: AeroElectric-List: Check My Work At first glance, that pic shows a poor solder joint. The wire is captured correctly but, the joint to the terminal is poor. The solder should pool out in a graceful way and appear very attached. Someti mes best to lightly sand the terminal metal first so solder can attach to b ase metal. D --------------------------------------------------------------------------- ----- ----- Original Message ----- From: Art Zemon To: aeroelectric-list@matronics.com Sent: Sunday, April 24, 2016 12:53 PM Subject: AeroElectric-List: Check My Work I found some old dogbone connectors in the basement and have been doing s ome practicing. Googling didn't turn up any examples of a well soldered joi nt so please give me some feedback. (I did find a YouTube video of someone teaching soldering... he had a roll of electrical tape!) The wire is 20 AWG in this sample: Is that how it should look? BTW, it is a pure delight to use the WES51. I have never bought anything better than a $25 soldering pencil for myself. I wish I could have afforded something like this back when I was in junior high and in high school and was building lots o' stuff. Thanks, -- Art Z. -- http://CheerfulCurmudgeon.com/ "If I am not for myself, who is for me? And if I am only for myself, what am I? And if not now, when?" Hillel --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus ________________________________ Message 6 _____________________________________ Time: 11:59:28 AM PST US From: "David Lloyd" Subject: Re: AeroElectric-List: Check My Work Oops. . . I probably spoke out of turn. I did not see the 2nd image where the wire passes thru and is soldered on b oth sides. That joint maybe Ok. . The only flaw is that I cannot see the smooth fan-out of the solder edges. It looks like the solder is fighting against some sort of plating on the terminal. On a joint like that, I woul d probably try to flow some solder on the terminal first. Just enough to ge t a wet look but, not enough to block the wire hole. If that flows normall y, then attach the wire and flow additional material to bind it all in one unit. ----- Original Message ----- From: Art Zemon To: aeroelectric-list@matronics.com Sent: Sunday, April 24, 2016 12:53 PM Subject: AeroElectric-List: Check My Work I found some old dogbone connectors in the basement and have been doing s ome practicing. Googling didn't turn up any examples of a well soldered joi nt so please give me some feedback. (I did find a YouTube video of someone teaching soldering... he had a roll of electrical tape!) The wire is 20 AWG in this sample: Is that how it should look? BTW, it is a pure delight to use the WES51. I have never bought anything better than a $25 soldering pencil for myself. I wish I could have afforded something like this back when I was in junior high and in high school and was building lots o' stuff. Thanks, -- Art Z. -- http://CheerfulCurmudgeon.com/ "If I am not for myself, who is for me? And if I am only for myself, what am I? And if not now, when?" 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