Advice on building a separator for a 4.5HP blower

[tomservo]

I'm building my DC system from scratch, and I want to implement a Thien separator in my system. For the blower I will be building a housing around a 14" TEK355 DC airfoil powered by a 4.5HP motor. The intake on the airfoil is 9", so I am guessing that I will need a larger than usual separator.

Are there any sizing guidelines or rules for building an effective unit?

Here's what I am thinking so far:

Blower sits right on top of a 16-17" tall separator with a 9" bell mouth sticking in 4.5".

8" ducting, material enters the cyclone with a rectangular injector at the top of the chamber.

Baffle with a 1 1/4" slot, made of thin material and tapered around the slot area.

....

Would I be better off going with like 7" ports? I'm wondering if I build it too big, I'll probably need more flow for the separation than I will have running one tool at a time. I suppose I could just always leave a floor sweep open or something for the CFM.

Should the cyclone spin the same direction as the impeller?

[tomservo]

I built the scroll for the blower yesterday, took longer than I thought it would but the fit is pretty good. I put BLO on it to finish it, which is part of why it took so long. It takes forever but I really like the way BLO (properly applied) holds up to weather, and this thing is going to live in a sort of lean-to shed next to my garage. In other words I want it to survive the potential occasional wetting.

I will put up some pictures later but with an unrestricted inlet (but with no bell mouth) and outlet (which is 5 1/2" x 8") the motor draws ~36A at startup and once run up it settles to 10.9A, which is under the 11.7A rating. On low speed (1725) it draws 3.7A which is more than the rated 3.4A (1/2HP at that speed) but I expect it will be fine as low speed is really just for startup. On low speed startup it only draws ~16A, so you spin it up to low then flip it to high for less stress on the motor.

When the system is more complete I plan on characterizing the blower, measuring SP levels and determining flow.