Are spring lock washers an acceptable alternative to Nord-Lock washers on FRC battery lugs?
I realize Nord-Lock is the gold standard, but would these be good enough for this application? Maybe nylocks are just as good?
We’'ll see how long it takes for James to respond…
Although I don’t have much personal experience with this style of washer, my understanding is that they are better than split washers, but not great. I’d say the goal with your battery lug is to never have any movement. Nord-Loks and grasshopper nuts are certainly the state of the art in FRC to my knowledge, but if your battery cables are strain relieved so that they never pull on the lugs it doesn’t matter nearly as much what fasteners you use and a regular nylock and properly torquing your screws will probably be sufficient.
From the NASA fastener manual:
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Thanks for that document. I did see one of James’s posts about spring washers. I thought maybe lugs might be different application. Never heard of grasshopper washers, will go looking.
(Hopefully I’m not needlessly triggering people!)
I’ve always used button head #10-32 1/2" Machine Screws and Nylon Lock Nuts. Never have loosened up.
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They’re pretty cheap, and seem to posses the inherent qualities you want in a lock washer for electrical systems. These may actually work out better than nord-locks (but not grasshopper nuts) for this specific joint, and will resist a bit of creep from the soft battery terminals and lugs.
Just Nylocks are completely fine for any team that is very careful about not straining the battery terminal joints or has some kind of solid cable securing mechanism. Gotta torque to spec though.
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Gr5 full size Nylocks on grade 5 or better socket cap screws is fine for 90% of teams. Get it all at Ace Hardware if you don’t wanna buy a box of 100 on McMaster.
Those spring locks look decent, they’d be an upgrade from flat washers. Anywhere below Alliance Captain / Pick 1 goals, I wouldn’t bother McMastering the single part, but I’d throw it in if I was already getting some other things.
The Chief Approved State of the Art is nordlock on grasshopper nut with grade 8 socket cap screw.
( I don’t think the McMaster locking patch screws have the patch in the right place, it’d be interesting to look at the price to get a set ran with the patch located to hit the grasshopper nut )
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FRC is in trouble if that’s us this year! 
These are “Grade F” when referring to the nut and actually kinda difficult to source - either mcmaster delisted them or I’ve been using standard low-strength nylocks with fine results and I’m pretty sure it’s the second.
Springs and spring lock washers have to have a preload comparable to that of the bolt tension to be useful, especially for electrical contacts where high contact force is required. A torqued battery fastener is on the order of 1000lbf of tension and I would bet $1 that the spring washer is completely flat well before then.
I would not recommend springs as locking elements for anything but highly specialized cases, and FRC batteries are not highly specialized.
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