DC Cooling Fan to identify direct or belt type

First we look at "DC Cooling Fan" is a direct or belt type, direct maintenance-free, because the blades mounted directly on the motor, there is no power loss generated by the power transfer, so the fan with the power of direct general wind than about 10% larger belt-type, from the "DC Cooling Fan" blades can be seen behind the shutters, when the suction fan opens directly to the bottom of the blade type is a 90-degree angle to the ground straight and parallel, (the bottom of the blower leaves where the wind speed minimum) and belt-type piece of fan just there gently flowing. noise while there is no direct friction generated, the most important thing is to maintain the belt type, generally "DC Cooling Fan" can be used on belt two years (imports) can only spend a small amount of a year, with a long time after the fan belt will loosen, after loosening fan flow will be significantly decreased.