Improved two stage dust collector mod

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Blog entry by Praedo posted 07-31-2014 02:25 AM 7325 reads 4 times favorited 0 comments Add to Favorites Watch

I wanted a dust collector for my garage workshop. A single-stage collector just wouldn’t do it: I had to have a dual-stage with a large bucket for chips. I have a two-car garage and two cars to park in it, so all of my equipment must be mobile and have a small enough footprint to fit around the perimeter at the end of the day. I didn’t have the budget for a true cyclone, so I decided to modify a regular single-stage dust collector.

I wanted the chip bucket to have a large capacity and be easy to remove. Finally, it needed to efficiently remove the chips, so that the filter wouldn’t get clogged too easily. I came up with this design which is a little different from what I see on the internet.

First, I found a used Grizzly 2hp dust collector on Craigslist. I talked the owner down to $150. It was a sweet deal because it also came with the Long Ranger remote. The blower seems to be like-new condition, so I’m pretty happy about that. It looked more or less like this at first:

I bought a cyclone filter from Wynn Environmental, and some hose, clamps, and fittings for the machines in the shop. Then I got to work.

My idea was to turn the blower on its side and place it on top of the collector body, so that the airflow would go through the collector, allowing the chips to fall through the Thien Baffle, then go through the blower and out to the filter. Please pardon the fact that I didn’t take pictures during construction, but I photographed the main parts as I was completing final assembly.

I built a router trammel and used it to cut neat circles and arcs. First, the bottom panel which sits atop the can:

I cut the 120 degree arc all the way through, and cut a groove to match the rim of the trash can. I partially filled the groove with silicone to help it seal. Here’s how it looks when it’s done:

I mig-welded together an angle steel frame to hold the bottom of the garbage can, and made it hang below the bottom of the collector, right above the wheels. I’m sure I could have used wood, but since I had a welder and some leftover steel, I figured I’d use it. I bolted it on so that it’s adjustable- if the air ever starts to leak in any place around the top of the can, I can tighten it up. You can see the square metal frame under the bottom of the can and the long bolts sticking up through the 2×4s.

The 2×4 frames are all joined together with half-lap joints. They are super easy to cut on the bandsaw, and give lots of glue surface.

The hole for the blower intake was too small to use the trammel, so I used a jigsaw. I got a little carried away, and had a bit of a gap. It’s a place that no one can see once it’s assembled, and nothing a little bondo couldn’t fix. We’ll just keep this slip of the saw our little secret.

Before sealing it all up, I made a neutral vane out of 6” steel A/C duct. They are designed to snap together. I cut the edge off so it would roll nicely, stuck it into the intake, and tack welded it to shape. Then I used some bondo to cement it into the intake. A neutral vane is important because it takes the incoming air to the place where the flow will be parallel with the flow going around the cyclone. If you leave it off, the air will be coming straight in, cutting across the circular airflow and causing turbulence, which will slow the circular motion dramatically. When it works properly, the fast-moving air laden with chips enters and goes around the circular path. Centrifugal force pushes the heavier-than-air chips against the side of the cyclone body, and friction slows them down. The chips drop through the slot in the Thien Baffle. The baffle prevents the cyclone motion from stirring up the can below, allowing the chips to settle gently. Otherwise, they’ll constantly get stirred up and get sucked into the filter. As the air slows, it moves to the center and gets sucked out the top of the chamber into the blower.

Now for the blower. I reinforced the top to hold its weight. Here it is from the side, with the blower output pointed right at you:

From the front. You can see the small gold latches which holds the top down onto the can. I’m planning to add a pair of gas springs to lift the top and hold it up when I’m emptying the bucket.

From the other side, with the intake hose. Also, you’ll see the maroon box is the Long Ranger, and a small metal junction box where I spliced the power cable to the Long Ranger.

Hinges on the back. I had to extend the frame about 6” so that when it opens the back of the can is freed up. I just used a pair of long gate hinges and bent them around the frame.

Now for the filter. I bought a Cyclone filter with flange from Wynn Environmental. I attached a piece of 1/2” plywood to the bottom with a few custom-made clips I cut from a nail plate. Then I glued a 4” plumbing cleanout into the bottom:

For the top I just bolted a piece of plywood to the gasket, cut a hole in the wood, and used the rest of my 5” metal HVAC pipe to connect the output hose to. I cut one end into little strips to make a flange on the inside, which I sealed with bondo and silicone. (sorry no inside pics).

I wanted the filter to be removable because I didn’t have enough room to leave it on and get my truck in the garage. The answer was very simple. Using some leftover 5/8 inch steel rod, I drilled two holes through the 2×4 frame and put them in. The filter just rests on top of the rods. When I store the collector, I pull the rods out.

Here’s the filter in storage. I mounted a rack to hold it by the top plate:

I painted all the wooden parts navy blue, because that’s the color I found at Lowes in the rack of what I call the OOPS paint- reduced to $12 for the gallon.

I tried it out and didn’t find any serious air leaks. The suction is great, and the separator works perfectly. I sucked up a bunch of stuff and couldn’t find anything in the filter at all, but plenty in the bucket:

This has been my first blog entry, so please feel free to make comments and suggestions. I hope I’ve added something constructive to this forum.

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