6" or 5" drops?

[Navin R. Johnson]

I bought a used 2hp Onieda Dust Gorilla with a Baldor motor and some duct work. I've read all of Bill Pentz site, as well as the 75 pages of duct collection posts on this site, but would like some real world confirmation on my idea.

I'm thinking of running 6" everywhere and using 5" for the drops to blastgates, and 5" flex pipe with a reducer at the machines in order to keep the velocity in the vertical sections high enough (some of my smaller tools have a cast 4" port that cannot be modified). I feel with a if I ran 6" drops and 6" flex pipe to the machines that the 4" ports could not support the flowrate required to move dust in a vertical 6" drop. Also, running 6" all the way to each machine could also push the motor off its curve by not suppling having enough resistance and burn the motor out. (my manual actually stated to use 2ft of 7", 10 ft of 6" and the rest 5" for a 2 hp machine...this seemed restricted to me).

It seems the whole system is a fine balance between capturing fines, moving chips, and staying on your cyclones curve.

I notice someone here had a similar setup with a 2.5 dust gorilla using a 6" main and 5" drops. Has anyone else used 6" mains and 5" drops and flex to machines with 4" ports?
Thanks for any help!
N

[Paul Wunder]

Navin,

We can all take educated guesses as to whether a 6" or 5" drop is best, but unless you have already done so, find Bill Pentz's "Static Calculator (XLS)" spreadsheet on his website. Using your fan curve and your layout of your equipment and the port sizes, you can quickly model various drop sizes and distances to see if the resulting cfms are adequate. Using this spreadsheet before I purchased my ClearVue, I was able to size what I needed.