Bill Pentz
07-12-2003, 3:43 AM
I'm sharing a serious caution from a fellow engineer who is building a cyclone using my Cyclone Plan (http://cnets.net/~eclectic/woodworking/cyclone/CyclonePlan.html) and Budget Blower (http://cnets.net/~eclectic/woodworking/cyclone/BudBlower.html) plans. In looking at historical posts on this forum made from my design directly or from the Dust Eliminator cyclone kits from my design, he sees quite a few that appear to be turning their impellers backward.
Running an impeller backward in my "budget blower" plan will actually make for a little more airflow and better static pressure, but sets up nasty vibrations. These vibrations can ruin a motor and make the light weight aluminum impellers fail, meaning fly apart. All impellers should be regularly inspected and cleaned when needed to ensure they do not get out of balance. Having had one of my test impellers fly apart during testing, I can assure you that this is not something to mess with!
Coupled to this caution is a further concern about the use of the large aluminum Cincinnati Fan backward curved impellers. This particular impeller was designed for clean air, and needs to be further protected from material hits. When a cyclone plugs or the bin gets full, the impeller takes material hits (about once or twice a month for most of us). Finally, any time you remove one of these Cincinnati impellers, you must replace the special star type Allen screws and dress the motor shaft or your impeller can slip off during operation (learned that one the hard way myself). I much prefer the far stronger compression arbors.
I personally started two years ago with one of the Cincinnati Fan aluminum impellers and still have it, but upgraded my own system to use a heavy steel impeller. I recommend the less costly Jet impeller or safer Sheldon's Engineering steel impellers that use compression arbors.
My plans are correct. They carefully specify the direction of rotation for the blower and recommend use of good heavy steel impellers. Please note the proper orientation of the blower outlet compared to the way the curved parts of the blades face.
bill
http://cnets.net/~eclectic/woodworking/cyclone/construction/ImpellerRotation.GIF
Running an impeller backward in my "budget blower" plan will actually make for a little more airflow and better static pressure, but sets up nasty vibrations. These vibrations can ruin a motor and make the light weight aluminum impellers fail, meaning fly apart. All impellers should be regularly inspected and cleaned when needed to ensure they do not get out of balance. Having had one of my test impellers fly apart during testing, I can assure you that this is not something to mess with!
Coupled to this caution is a further concern about the use of the large aluminum Cincinnati Fan backward curved impellers. This particular impeller was designed for clean air, and needs to be further protected from material hits. When a cyclone plugs or the bin gets full, the impeller takes material hits (about once or twice a month for most of us). Finally, any time you remove one of these Cincinnati impellers, you must replace the special star type Allen screws and dress the motor shaft or your impeller can slip off during operation (learned that one the hard way myself). I much prefer the far stronger compression arbors.
I personally started two years ago with one of the Cincinnati Fan aluminum impellers and still have it, but upgraded my own system to use a heavy steel impeller. I recommend the less costly Jet impeller or safer Sheldon's Engineering steel impellers that use compression arbors.
My plans are correct. They carefully specify the direction of rotation for the blower and recommend use of good heavy steel impellers. Please note the proper orientation of the blower outlet compared to the way the curved parts of the blades face.
bill
http://cnets.net/~eclectic/woodworking/cyclone/construction/ImpellerRotation.GIF