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| are wire nuts vibration resistant? |
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| CatalinaWOW:
Not all wire nuts have a metal insert. I have come across many which are plastic only, and which are suitable only for low voltage, low power non-critical installations. So check and use good ones, which do have a helical coil inside, well attached to the body. In many cases a well installed wire nut is difficult to remove, and in some cases it is impossible without destroying the wires. Vibration loosens connections by a combination of unloading the joint and providing/allowing motion during that unloaded interval. The light weight of the wire nut and the contained wires means that truly incredible accelerations are required to remove the pre-load. Run some quick numbers with the torque you apply to a wire nut, the force multiplication that you get from the relatively shallow internal taper, the mass of the nut and wires and the vibration g's you expect to see. Even really severe vibration environments (satellite launchers and the like) tend to be only a few tens of g's. I would expect the circular saw vib levels to be a small fraction of a g except for the immediate period before the case is broken in a drop. |
| drussell:
--- Quote from: coppercone2 on November 02, 2018, 10:40:16 pm ---It just seems like since its twisted, the vibration can slowly loosen it --- End quote --- If a Marrette comes loose from the wires, it wasn't installed nearly tight enough. When installed properly the wires should be virtually fused together, not to mention that when you twist the Marrette all the way on tightly you should be doing it hard enough that it should twist the insulated part of the wires together for strain relief also. |
| drussell:
--- Quote from: CatalinaWOW on November 03, 2018, 01:55:21 am ---Not all wire nuts have a metal insert. I have come across many which are plastic only, and which are suitable only for low voltage, low power non-critical installations. So check and use good ones, which do have a helical coil inside, well attached to the body. --- End quote --- Yikes! That is downright awful! Toss straight in the trash if you ever see ones like that! Certainly always use good quality connectors! (...and properly rated and certified if they're for mains or any kind of high energy circuit.) At first I thought you were meaning the original MARR two piece style ones with the setscrew, which they DO still make. They're more expensive but might be better to use in some circumstances and can be re-terminated more easily, typically with damage to a shorter bit of the end of the wire than the twist-on spring "wire-nut" type. I like to use those when joining 8ga or 6ga instead of the big blue sized twist ones, though those do still make a good connection. This kind: Edit: Marrette Wire Connectors Product Guide Interestingly, it seems that they discontinued the giant "size 3" ones of those set-screw type, but they do still make the smaller sizes. |
| German_EE:
I don't know about vibration but here's a selection of connectors (including a wire nut) tested to destruction. I won't say which one wins as it will spoil the surprise. Here's another torture test |
| KL27x:
I have seen wire nuts inside of tools from the factory. I think they should be fine for a circular saw. I have soldered connectors inside of many power tools with a good amount of vibration, and I have only had one failure/repair, when I chucked an unbalanced mandrel in a die grinder. Some high frequency harmonic occurred and the case actually friction welded together. It took some good taps with a hammer to get it apart. While it was on, I touched a housing screw, and now I know why it nearly burned me. You could see the spot welds in the seams where the plastic fused. The grinder also had a crummy switch in it, and this pushed it over the edge.... So when it did this, the plug got about 200 years worth of starts and stops in about 20 seconds. The plug turned black. I replaced the cord and the outlet. Resoldered the broken wire and replaced the switch. Balanced the mandrel with a drill and a dremel, and all has been fine, ever since. |
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