Recently Cobra Brushless Motors released a v2 version of the 2100kv, 2300kv, 2400kv and 2850kv CM motors. Some of our customers were inquiring about the new upgrades in these motors, so hopefully this covers these improvements!
The locking system for the magnets is created by having a machined lip on the inside surface of the flux ring the overlaps the back end of the magnets slightly. This captures the magnet and prevents it from sliding back and out of the motor. They have also started additional high-temperature industrial epoxy in between the magnets to prevent them from shifting side to side.
The following photos illustrate the difference. The first one is a side by side comparison of the rotor assemblies from a Cobra CM-2206-2400-V1 motor (on the left), and the new CM-2206-2400-V2 motor (on the right). As always, the blue material is epoxy putty that is used as balancing weight to dynamically balance the rotor assemblies to eliminate vibration when the motor is rotating at high speed.
Here is a close-up shot of the original V1 rotor housing. In this photo you can see the back edge of the magnets and the back edge of the rotor can. The magnets are securely attached to the inside surface of the rotor with epoxy glue:
Here is a close-up of the new V2 rotor housing. The back edge of the rotor can is about 50% thicker. This is because a lip has been machined onto the back edge of the rotor can that comes up and covers about 1/3 of the thickness of the magnet. This prevents the magnets from sliding back and coming out of the motor. You can also see the additional black epoxy that has been added in between and up the sides of the magnets to further lock them into place and prevent any shifting from side to side.
With these changes that have been made to the rotor assemblies, the only way to get the magnets to come loose would be to fly the quad straight into a brick wall.