The first drawback of sleeve bearing fans is that the gap between the shaft and the inside of the bearing bore needs to be as small as possible to minimize rotor wobble and tilt as it turns. However, this increases the contact area between the shaft and the sleeve, creating friction that limits how quickly and easily the fan can be started, while also requiring more energy to keep it turning. Secondly, in a straightforward sleeve bearing, there are no additional methods of holding the rotor in position. This means the rotor weight is borne entirely by the shaft sitting in the sleeve. As the shaft rotates, it gradually wears away the inside of the bearing bore distorting the cross-section of the sleeve over time. In fans that always operate in the same orientation, this results in an oval-shaped bearing sleeve that can make the bearing noisier, while affecting the rotation of the fan, causing it to wobble. This issue of bearing wear becomes a particular problem for fans in portable equipment, where operation at multiple orientations and angles causes the inside of the bearing to get worn in different directions and become uneven. In either case, this wear process shortens the life of the bearing and/or the whole fan unit. Lastly, sleeve bearings traditionally include an oil ring and Mylar washer at either end of the bore that retain the lubricant that is required to keep the shaft turning smoothly and quietly. However, these components add friction and hinder the escape of gases generated by rotational friction. If these gases cannot escape, they solidify into nitride particles, which gradually build up, impeding the shaft’s rotation and shortening the life of the bearing.