Originally Posted by Erick Silver
OK I have to replace my Cooler Master Fans. My front Megaflow 200mm fan is at 660~ rpm maxxed out and my top Megaflow 200mm is at 720~rpm maxxed out. Cooler Master R4 Red LED 120mm fans I have at P/P on my H60 are at 1810~rpm pull and 1750~push. I would like to see a little more of the same numbers on my fans. Any suggestions? Would like to try to keep all fans the same manufacturer.
My suggestion, don't use the CM fans for the top fans. They use sleeve bearings for their Megaflow fans. Sleeve bearing only remain lubricated in vertical position. The rotation of the fan in the bearing spreads oil across both halves of the bearing when in a vertical position. But if a Sleeve bearing is mounted horizontally, like they are in top-mounted fans, then all the oil collects at the bottom of the bearing, the top begins to wear, rattle, become unbalanced and leads to failure (and annoyance of the highest degree).
I personally am still looking for a 200mm fan that uses at least rifle bearings. Rifle bearings are nearly identical to sleeve bearings, but instead of being smooth, either the internal or the external bearing has a spiral groove carved in along it's length and around 2pi of it's circumference (4pi radians can be done, but there is some debate if it helps - or even if it hinders). What this does is create an Archimedes screw along the length of the bearing, helping to distribute oil more evenly when mounted horizontally. The downside is, when mounted vertically, you can get oil being "piled up" on one side of the bearing - like what happens with sleeve bearing fans that are mounted horizontally. You also need to make sure the rifling moves oil upwards, against the force of gravity. Frequently, these fan put the oil reservoir on the same side as the fan itself. So you need to note the angle of the blades, and the direction of rotation. The rifling can only operate in the direction of rotation, and the cap of the fan has to be down. So with the fan cap down, it functions as an exhaust, that's all it can ever be (without damaging the bearing). If it functions as an intake with the cap down, then same deal - it can only ever be used as an intake.
This is why fluid and "maglev" bearings (magnets perfectly balance and suspend the impeller; it never touches anything unless forced to) are starting to become to popular. There are no orientations to consider, like with Ball bearings, and they are quiet, like Sleeve bearings (when brand new)
**NOTE** That is not to say Sleeve Bearings are the Anti-Christ of fans. They're not. They are very good at what they do, quiet and last about as long as you would want a fan for - as long as they are in a vertical position.