This is a DIY spring clutch which you can use in many different projects. I designed it so it is compatible with LEGO now, but you can connect it to any other motors as well. The working principle is, that the centrifugal force pushes the sliding parts to the side of the housing so it drives it.
To make this, you have to print out the housing parts and the middle part and 3 pieces of the sliding part. You also need a simple rubber, which you will place around the three sliding parts.
This video may help you to understand: