Regarding the unlabeled parts below the friction rotor assembly:
The device directly below the rotor's bottom plate is a shaft collar, which is fastened to the plate and also has setscrews that grip the shaft. The light colored object beneath the shaft collar, and the two other light colored objects below that one, are solid teflon seals which fit closely to the shaft, but allow free rotation. A flexible type of seal is shown below the third teflon seal, and is enclosed by an endcap at the bottom of the upper bearing and seal assembly.

Note that the radiator should be moved to a location further away from the rotor shaft, and is only shown this way for illustrative purposes. If left in a similar position, though, note that the drive belt could be extended to operate a radiator blower fan to speed up heat extraction and move the heat away from the underside of the unit. Another option would be to build the radiator into the water hopper so that the heat is dissipated efficiently. This also has the advantage of helping to preheat the water in the hopper.