This special mount does not have classical axles or expensive roller bearings - neither in declination nor in right ascension!
Instead, optical tube and fork rotate in special bearings where a hard-chrome plated ball rests in a spherical PTFE-seat. This assures an absolute freeness of backlash and breakaway torque.
In RA the friction wheel is not only a drive element but an integral component of the bearing!
Having a diameter of 500 mm, the friction wheels fullfill the rule of thumb saying that the wheel-diameter should not be less than mirror diameter.
As the drives do not have any worm wheels, the system is largely free of periodic errors.