The simple Fan can be built using:
♦ a few of the parts supplied in the K'NEX 52-model tub, plus
♦ a K'NEX Battery Motor Blue
The instructions below may Downloaded if you prefer (.PDF 0.5Mb).
... and finally fix the fan blade onto the top of the shaft, so that the upwards-facing lug of the Tan interlocking clip fits into the white connector at the centre of the fan blade.
Your fan is now complete, and you can test it by switching on the motor.