Tacho Disc

Tacho disc for cheap dc motor like this:
http://www.ebay.com/itm/smart-Car-Robot-Plastic-Tire-Wheel-with-DC-3-6v-Gear-Motor-for-arduino-/400985432465?hash=item5d5c982191:g:WVMAAOSwaNBUh7Xc

I have used it with a tacho counter like this:
http://www.ebay.com/itm/Slot-type-Optocoupler-Tacho-generator-Counter-Module-for-Arduino-Raspberry-pi-/281570892992?hash=item418eeedcc0:g:d8gAAOSwk5FUv1Kv

I did a few test prints before I had one that fitted perfect. I have uploaded the stl that in theory should fit perfect. I had to print with about 0.1mm oversize. And just in case any of you need something different, I have also uploaded the FreeCad file.

Update 160404: One of my friends had bought the same motors as I had... at least so we thought. It turned out that the shaft on the motors he got, was slightly closer to the edge of the gear box. Therefore I have made updated version (version small) that fits with the other type motor. The tacho for that is about 4 mm smaller.