Nord-Lock If you’ve ever driven an under-damped car down a rough road and felt vibrations that seemed powerful enough to dislodge organs, you know that things aren’t any easier for the car. The same forces acting on your body are acting on every nut and bolt, causing them to loosen and—if you’re driving fast enough—leading to a very bad day. Frog Racing, an amateur rally team based in Western Massachusetts, had one of those bad days when the nut holding a ball joint on one of its cars worked loose during a hill climb. To show how to prevent things like that from happening, it put together a thorough-but-concise YouTube video—roughly two minutes—on how vibrations affect hardware and what you can do about it. Nord-Lock The first step is to track which nuts and bolts are tightened to spec and which ones aren’t using specialized torque paint. If a nut or bolt starts to back out, it will break the stripe of paint like a wax seal, providing instant recognition without the need to break out a torque wrench and measure. As noted in the video, the most common types of nuts and washers are susceptible to loosening with enough vibration. The amount of time and the rate of loosening may vary, but it will happen if the conditions are severe enough. That’s why it’s important to thoroughly check everything when prepping a car for the track or a rally stage. According to the video, the best for keeping things in place are wedge-locking washers. These are actually pairs of washers that lock together via a cam-shaped edge on the inside, and have serrated exterior edges. Instead of relying on friction, they put geometry to work. The intonation of the cam surface (basically the indent made into the surface below the top edge) has a greater pitch than the bolt’s threads. This creates a wedge effect (hence the name “wedge-locking washers”) that’s much harder to overcome with vibration than the friction of threaded surfaces working against each other. All of this is explained in an easy-to-understand way in the video itself, so definitely give it a watch.
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