Static pressure is derived from the difference between the air flow during a measured obstruction, and unobstructed air flow. It takes all three numbers to figure Static pressure.
Estimating isn't very scientific or accurate, but perfection is often not worth the effort.
Using touch to feel flow though the cooler, and seeing good cooling performance, is good enough for most of us.
That being said, "4 times the static pressure" is a very bold clame to make with no solid ground to stand on.
For credibility. If it is so easy, what is the problem with just showing us this basic math proving that fan has 4 times the static pressure.
If you have accurate flow measurements, a known measured flow obstruction, and the math is sound, it is not an estimate, you're dead on.
Each type of bearing has its good points and bad points.
For a fan facing upward, avoid sleeve bearings. Sleeve bearings wear a lot faster when mounted in any orientation other than vertical.
Ball Bearings are very free flowing, efficient, quiet (if maintained well), endure hot temps better, and are the preferred bearing for high performance and high out-putt fans.
Rifle bearings are sleeves that have a spiral groove in the contact surface that pumps lubricating fluid from a reservoir. Fluid Dynamic Bearings, and Hydro Dynamic Bearings are similar, and all share a high degree of the ball bearings good points, including life span.
A Magnetic bearing fan's shaft floats in a magnetic field. This seems like it would be the perfect bearing, but this fan's Achilles Hill is the low CFM out-putt that its design limitations confine it to.
Edited by Luke Cool - 10/18/14 at 8:54pm