Designing A Pen Clip That Never Bends Out Of Shape
If you’ve ever used a ballpoint pen with a clip on the top, you’ve probably noticed they bend pretty easily. The clip relies on you only bending it a small amount to clip it on to things; bend it too far, and it ends up permanently deformed. [Craighill] decided to develop a pen clip that didn’t suffer this ugly malady. The wire clip design easily opens wide because the spring wire is not actually deforming much at all. Credit: YouTube video, via screenshot The problem with regular pen clips comes down to simple materials science. Bend the steel clip a little bit, and the stress in the material remains below the elastic limit—so it springs back to its original shape. Push it too far, though, and you’ll end up getting into the plastic deformation region, where you’ve applied so much stress that the material is permanently deformed. [Craighill] noted this problem, and contemplated whether a better type of clip was possible. An exploration of carabiner clips served to highlight ...