Bicycle Crank Arm Magnet for Cadence Sensor - Wahoo, Bontrager, Cateye etc.

Cadence is how fast you're pedalling and some bike computers have the option to measure this for you. Some of those need a magnet on the crank arm. The problem is that the one that comes with the Wahoo BlueSC and Bontrager are part of a rubber band that splits when you try to put it on modern, wide, crank arms. And you might have also lost it because of this. The solution is to use a different type of magnet. This very simple design holds 2 of 10mm x 3mm magnets (they measure slightly thinner, but the model for FreeCAD is enclosed if you need to make adjustments). This size of magnet is easy to find, and the doubling up of the magnets gives a force slightly higher than the magnet included in the Wahoo kit. Two zip ties are also needs, again very easy to find. I've included two sized holes for this, one for 2.5mm wide ties, the other for 3.5mm wide ties. I had to use the 3.5mm wide ones to get a tie that was 140mm long, the 100mm weren't going to fit. Zip ties from Screw Fix, 2.5x100 code 65467, 3.5x140 code 62426. Magnets from Amazon, but there's so many similar ones from here and eBay.