ok so a little bit of Background, myself and MJB were having a discussion about what type of drywasher fan works better flat or beveled edge i thought beveled would work better he thought not. these were the test results and we thought it would be best to share with you lot who might be making your own dry washers at some stage. MJB won by a margin in the argument but kicked my ass when it comes to making fans.
Let me first say i think the only restriction on these fans is the actual weight that they have to turn these fans are so well made.
Notably the fans both get more air space than mine as my fans are about 30% larger and protrude past the 3" opening quite a bit which this test has proven to be wasted space and non essential weight.
As such i didn't even test mine i knew right away that these fans performed smoother and better both in dial up and once air was removed continued to spin for some time. Notably the actual fan kick back i.e. fan feel on my face when testing was notably higher on the flat profile (subject 2).
so is this good or bad? i don't know I'll test in the field with dry dirt and see, maybe I'll have to incorporate a screen to deaden the impact of the direct pressure on the material or maybe the flat edge blade solves a problem here with minimal rpm impact.
The flat edges seemed to spread the wind force outward instead of upward.
So there was not a significant difference and these results would vary massively if the box was on more or less of an angle removing or adding to gravitational pull.
this is rpm taken on the outer counterweight, if taken from the fan center these fans were getting between 5-9000rpm because all surfaces are reflective its very hard to get a good test or accurate result.
now for results
test 1 subject bent edge
test 2 subject straight edge