Micro water pump

This is a small side project for my combat boat 90. The project can be seen here:
http://depronized.com/2018/01/16/the-combat-boat-90-project/

Ironically, a cooling water pump for the motors proved to be the hardest part of the whole project! There are basically 3 problems with a micro pump design.

1. Water surface tension. At this scale, the water surface tension prevents the water from coming into the inlet unless some suction force is applied, and the impeller isn't capable of generating enough suction. However, I've increased the inlet hole diameter and intend to place the pump below water line so hopefully those two factors will make it work. Printing of a second prototype is in the works.

2. Centrifugal wheel friction. If the wheel spins free and touches surrounding parts it can "weld". This can be prevented by a very carful alignment of the impeller so that it doesn't touch the surrounding. A way is to place a piece of paper between the pump house and the impeller.