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Some time ago I purchased one of those little Harbor Freight mini portable dust collectors. I got a helluva deal on it ($70 after stacking some discounts). It is this one:
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=94029
It sat unused for a while because I was pretty happy with my Ridgid vac-based cyclone.
HF claims 914-CFM and 9.4" of SP. We know that the CFM is nonsense, though. It has a single 4" inlet. According to BP a 4" pipe can carry about 400-CFM. My somewhat scientific testing (Loring will enlighten you on how far off these #'s can be, but at least I used two different anemometers) seems to indicate that this unit pulls about 370-CFM.
This unit is only twenty pounds but achieves some pretty impressive specs by using a universal motor spinning a small airfoil type impeller at 6400-RPM (typical DC's use radial impellers spinning at half that speed).
So I decided I'd build a larger cyclone separator and start using it. I started w/ a 30-gallon can and an MDF top. Added 4" fittings and my baffle and did some additional testing. I was happy to discover that adding the cyclone lid only causes an 18% hit to my CFM. That is fantastic by any cyclone standard.
I also had a chance to try connecting the entire assembly to my router table's downdraft box. I had to do this with a 2.25" reducer to a 2.25" hose, so NOT optimum. I was stunned to discover that airflow through the tiny (1.5"?) aperture in my router lift was sucking plenty of air. I had always imagined that real dust collectors would have difficulty moving air through such small holes, but this clearly isn't so, plenty of SP here.
I did limited testing with actual dust because I only have the stock (30-micron) bag filter for the DC at this time. It was able to separate 98.7% (by weight) of the dust I fed it (mostly fines left over from machining MDF and hardboard). It was perhaps a little better but I did have difficulty gathering all the dust from the garbage can when I was done with the test. Again, I only claim quack science in my methods.
I had previously posted that the DC is noisy. It still is. Part of that is the noise form the air movement, but certainly part of it is the universal motor, too. Still impressed with what a $70 machine can do, though. While this still doesn't provide the 600-800 CFM that some say is needed for fines collection, it is providing over twice the CFM of my current solution and is still compact enough to use, so it will become my new DC until I can make my giant separator lid with 6" outlet and twin 4" inlets, and run 6" PVC to my tools (yeah, right).
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=94029
It sat unused for a while because I was pretty happy with my Ridgid vac-based cyclone.
HF claims 914-CFM and 9.4" of SP. We know that the CFM is nonsense, though. It has a single 4" inlet. According to BP a 4" pipe can carry about 400-CFM. My somewhat scientific testing (Loring will enlighten you on how far off these #'s can be, but at least I used two different anemometers) seems to indicate that this unit pulls about 370-CFM.
This unit is only twenty pounds but achieves some pretty impressive specs by using a universal motor spinning a small airfoil type impeller at 6400-RPM (typical DC's use radial impellers spinning at half that speed).
So I decided I'd build a larger cyclone separator and start using it. I started w/ a 30-gallon can and an MDF top. Added 4" fittings and my baffle and did some additional testing. I was happy to discover that adding the cyclone lid only causes an 18% hit to my CFM. That is fantastic by any cyclone standard.
I also had a chance to try connecting the entire assembly to my router table's downdraft box. I had to do this with a 2.25" reducer to a 2.25" hose, so NOT optimum. I was stunned to discover that airflow through the tiny (1.5"?) aperture in my router lift was sucking plenty of air. I had always imagined that real dust collectors would have difficulty moving air through such small holes, but this clearly isn't so, plenty of SP here.
I did limited testing with actual dust because I only have the stock (30-micron) bag filter for the DC at this time. It was able to separate 98.7% (by weight) of the dust I fed it (mostly fines left over from machining MDF and hardboard). It was perhaps a little better but I did have difficulty gathering all the dust from the garbage can when I was done with the test. Again, I only claim quack science in my methods.
I had previously posted that the DC is noisy. It still is. Part of that is the noise form the air movement, but certainly part of it is the universal motor, too. Still impressed with what a $70 machine can do, though. While this still doesn't provide the 600-800 CFM that some say is needed for fines collection, it is providing over twice the CFM of my current solution and is still compact enough to use, so it will become my new DC until I can make my giant separator lid with 6" outlet and twin 4" inlets, and run 6" PVC to my tools (yeah, right).
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