Full time tool collector, part time woodworker
- 25 Sep 2011
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I've attached a spreadsheet that performs the basic design calculations for sizing a blower. I'm not sure that I have recommended a particular motor power in this thread (correct me if I'm wrong). Generally though, you can see the flow rates required for different diameter ducting to keep dust in suspension with a flow velocity of 20m/s given in one of the posts above. Working with fairly standard 4" ducting for medium-sized machines that the hobbyist will typically use, you need a flow rate of at least 565m³/hr, which is right on the limit of a 1hp motor if you want to provide a half-decent 2-2.5kPa stall pressure (and especially if using an inertial separator, which if properly sized with have a pressure drop of around 1.5kPa before you account for flow losses elsewhere in the system).