Homemade Cyclone Dust Collection System

Part 2: Blower

by Steve Silca

The blower is powered by a Harbor Freight 5 HP compressor duty motor propelling a 14” impeller from Jet Tools (now called WMH Tools). Please look at the Cost Analysis for the prices of these items. Although it’s a 5 HP motor, it draws 15 amps, so it is really much closer to a 3 HP motor. I had my friend who’s a machinist make a custom bushing to make the hole in the impeller (which is some metric figure around 7/8”) adapt to the 5/8” arbor coming out of the motor. He machined the bushing, and drilled and tapped four holes in it which accept set screws that affix the bushing to the motor arbor. Then, he took the flange that came with the impeller and drilled and tapped two holes 90 degrees apart in it. These holes accept set screws that affix the impeller to the bushing. The bushing was milled with two flats 90 degrees apart against which these two set screws are tightened. These flats make the assembly extra secure. All the set screws were installed with lock-tite for security as well.

WARNING: After about a month of use, I was turning on the dust collector one night to show it to a friend. Right when I turned it on, there was a screeching sound and a clatter in the blower housing. I knew what had happened, but just to be sure, I disconnected the blower outlet from the hose that goes to the filter housing. Sure enough, the impeller had slipped off the bushing, and was resting on the bottom of the blower housing. Luckily, no damage had been done to any of the components, since the impeller didn’t fall off when it was spinning at 3450 RPM, rather when the motor was just being turned on. I was actually somewhat glad this happened, because I had been looking for a reason to take the whole cyclone down and re-mount it to the cement wall. The first installation in the rafters of the floor above was causing major vibration trouble (see the Installation page for further discussion on this). Taking the cyclone down was a little depressing, but I was thrilled that I had taken Bill’s advice and designed the blower so that the housing could be easily removed from the motor/impeller assembly (see discussion in the last paragraph of this page). Otherwise, I would have had to completely rip apart the entire blower housing to re-affix the impeller to the motor.

New impeller mounting with roll pin and hardened steel set screws.

Upon closer inspection of the impeller, my machinist friend who had made the bushing discovered what he thought was the problem. He said that the two set screws which hold the impeller against the bushing had worn away because they were stainless, which apparently makes them softer. So, we replaced those with two hardened steel set screws. This was fine, but I did not want to go through the process of taking this dust collector apart again, so we elected to take one more step. We put the impeller on the bushing exactly where it should be when it’s installed, and drilled a hole through the flange on the impeller and through the bushing – all the way through both. The bushing is longer than the motor arbor, so we did this at a point beyond the arbor so we wouldn’t be drilling through that. This hole accepted a roll pin that goes through the impeller flange and the bushing. Now, with the better set screws set in with lock-tite and the roll pin, I am 100% confident that the impeller will not fall off again.

The picture at the side shows the blower components: the motor with the bushing attached to the arbor, the impeller with the two threaded holes in the flange to accept set screws to tighten against the bushing, the motor mounting board with the rabbeted hole that accepts the motor arbor (this rabbet received a bead of caulk when the motor was attached to seal that connection), and the piece of ½” angle iron and bolts that I used to attach the motor to the board.



This picture shows a side view of what it all looks like when it’s assembled.












The bolts that hold the 1/2" angle iron to the motor mounting board had to be recessed because the blower housing gets pulled up tight against this board (the picture at the side is of the bottom of the motor mounting board and shows how these four bolts are recessed as well as the four bolts and fender washers that hold the motor mounting board to its hangers).






Blower outlet sealed with epoxy. Note 14 1/2" access hole
on top fits over impeller, and is caulked where the
sheet metal spiral meets the MDF

The blower was constructed a la Bill Pentz airfoil blower plan. The materials are ¾” MDF and 20 gauge galvanized sheet metal (I was fortunate to find a 7” wide scrap at the sheet metal supplier which I cut down to about 5 ¾” to make this blower). I cut an 8” diameter hole on the bottom of the housing for the inlet to the blower, because the center pipe in the middle of my cyclone was going to be a piece of 8” snap-lock. On the other side of the blower housing is a hole with approximately a 14 ½” diameter. This is the case because the blower housing is designed to first be attached to the top of the cyclone, and then slip over the impeller, which is already affixed to the motor. The outlet of the blower is 5”x7” and designed to have an area slightly larger than that of a 6” circle, since that is the size hose that would convey the air and fine dust to the filter. I used a basic 6” HVAC take-off to adapt the rectangular output of the blower to the 6” flex hose. The take-off was sealed with epoxy, and the groove where the MDF receives the sheet metal spiral was sealed along the outside with a caulk gun.


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© 2003 by Steve Silca . All rights reserved.
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