If you’ve ever driven a car filled with water on a bumpy road and felt vibrations that were powerful enough to dislodge limbs, you know things aren’t easy for cars. The same forces acting on your body are acting on every nut and bolt, causing them to loosen up and – if you’re driving fast enough – making your day much worse.
frog raceAn amateur rally team based in western Massachusetts was having one of those bad days when the nut holding the ball joint on one of its cars came loose while climbing a hill. To show how to prevent things like this from happening, it’s put together a thorough-but-brief YouTube video – about two minutes – on how vibrations affect hardware and what you can do about it.
The first step is to track which nuts and bolts are typically tightened and which are not using special torque paint. If a nut or bolt begins to back out, it will break the strip of paint like a wax seal, allowing immediate identification without the need to break out a torque wrench and measure.
As explained in the video, the most common types of nuts and washers are susceptible to loosening with sufficient vibration. The amount of time and rate of loosening can vary, but will occur only when conditions are severe enough. That’s why it’s important to check everything thoroughly when preparing a car for the track or rally stage.
Loose Nuts and Bolts on Race Cars – Torque Paint and Wedge Lock Washer Solution
According to the video, wedge-locking washers are best for keeping things in place. These are actually pairs of washers locked together by means of a cam-shaped edge on the inside, and serrated outside edges. Instead of relying on friction, he employed geometry. The intonation of the cam surface (essentially an indent made in the surface below the upper edge) has a higher pitch than the threads of the bolt. This creates a wedge effect (hence the name “wedge-locking washer”) that is much harder to overcome by vibration than the friction of threaded surfaces working against each other.
It’s all explained in an easily understandable way in the video itself, so be sure to watch it.
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