What really happened? That means one blast gate must stay open at all times. We came up with a way to modify his firm's standard airfoil impeller with extra vanes to minimize the buffeting problems. What size would be best with this sized impeller? |
I made the motor holes by making a "rubbing" template of the face of the motor using graph paper with a carefully cut center. We agreed an airfoil impeller is NOT appropriate for dust collection systems that have a high static pressure, uses filters, uses ducting smaller than 6", or where at least one blast gate is not always open. With a little pressure on the gauge and pencil one time around left a nice perfect spiral. The motor and impeller are way too heavy for me to try to lift up and down, so I want them to get mounted and stay right there. I did roll them lightly over a large cylinder by hand to start setting their shape. I do know they had quite a few of these in progress, but with the change in ownership of this firm they stopped taking orders from individuals and will only do business with businesses. In fact, the cost of a full cyclone system using this approach should be about the same as buying a 2-hp dust collector that will pick up the chips, but not protect your health. Many reported back after using these solutions, they had problems. Although I provided a ducting resistance calculator, the bottom line here is you need to follow a few rules to ensure the safety and longevity of your impeller and motor: Use an efficient cyclone placed before the impeller. Calculate the size outlet wanted. |
You need the specially modified airfoil impellers which I have been told are no longer being made. Although far better than most that stall around 6" of pressure that is still way too little if your system needs 12" or more. For a blower that would go on a cyclone the inlet would neck from a 9" diameter smoothly down into the impeller. This is one of the tradeoffs we have to make in order to get much better performance than other impeller types that are stable across their whole range of static pressures. With that plus the roughly 3/8" more from using a router with collar to cut things out, I would have a plenty big enough outlet width. I used the larger impeller and very large ducts, so could filter. Ok now you have confused me but good. This store bought unit is a touch pricey at about $55 but well worth it with the airfoils. It worked well but stalled at too low of a pressure so was of no use in my dust collection system. I have made similar parts easily enough without too much trouble. That means this is a poor solution for larger shops and for shops where you are not willing to regularly inspect and clean the impeller to make sure it does not get out of balance. Personally after thinking about it I realized that my dust collection motor is the heaviest used motor in my shop, so it makes no sense to not buy a really good quality motor.
Most actually come with 10-micron filters which the vendors misrepresent as 1-micron filters. The metal height had to be tall enough for the blower plus the depth of the grooves and enough clearance to keep the motor bolts from hitting the impeller arbor bolts. I worked closely with their engineer and we came up with a special vane that lets the airfoil work with about one water column inch more pressure before it stalls, making it an excellent solution for a small one-car garage sized shop provided the cyclone is vented outside instead of into filters. We used a Dwyer Instruments 4015 model Magnehelic gauge with a Dwyer 166-6 pitot tube for measuring the pressure and computing the air flows. What kind of vibration dampeners are you using to support that weight? By using a static pressure calculator that computes the overall resistance my system built with 4" ducting computed out to have over 13" of resistance and that resistance dropped to 8.5" with 6" ducting. For my airfoil impeller, I used 1/2" clearance. My reason for wanting an airfoil impeller is of course that their performance is phenomenal. Instant rust! I might use my roller to create the flare. Why did you make the 3" hole? Hey! My Dust Collection Basics page covers much of what a hobbyist woodworker should know about collecting the dust in their workshop.
I'm going to try and make them do. Although I like the airfoil because it moves far more air with minimum power making it ideal in my shop, these are no longer available, so I would recommend you use a little larger motor like the Leeson 5 hp I recommend and buy a 15" or 16" diameter material handling impeller. If you have power problems similar to mine or just want the most efficient solution in terms of operating cost, the airfoil is the way to go. With this configuration, a wooden sheet or metal plate supports the motor and impeller weight. I bought a 12" DC-1200 impeller and it did not quite move the same as my larger and taller Cincinnati Fan 12" impeller. I did have to go with multiple pieces because I did not feel like paying for a 4' x 10' sheet. How did you test this blower? I will attach my supports to that plate and my ceiling beams. Using my Dwyer 2010 Magnehelic gauge it tested at 7.5" for its longest run. I also wanted quality without paying too much. Unfortunately, there is plenty of room for confusion on the direction of rotation. We also came up with a bigger airfoil with a similar modification that would work in a larger shop provided all was vented directly outside without filters. My testing shows that if you don't start by upgrading your hoods, you are not going to successfully collect the finest unhealthiest dust as it is made no matter how big the blower. My original measures on amperage were wrong because my amp meter had a tired battery and had been dropped. Unlike a self cleaning material handling impeller, airfoil impellers have tops making them caged impellers. Plus, if you told them you were using a 3 hp motor, they probably made you a full height impeller. Regardless, once I had the Delta motor I ordered the impeller to fit on a 7/8" motor shaft with a 3/16" keyway. These all poly filters need a minimum of 250 square feet but are recommended to be a full 500 square feet for my 1000 CFM airflow. Most 1.5 to 3 hp blowers use 5" circular outlets. Even a few of the vendor sites say to figure you are going to only get about half of the claimed airflow. How long to get your impeller? I had that same problem and was not able to figure that out by measuring as I had too many variables including a little dampness that had swelled portions of my Melamine backer. What we found was that wide open using all 6" diameter ducting the most we could draw with this impeller was 8.5 amps. A one car garage sized shop will have a maximum pressure of about 7" even with very carefully chosen large ducting. That amp reading says that I can safely open the blower inlet as long as the cyclone stays connected to the 6" ducting without concern about burning up the motor. Ideally this inlet should take on a hyperbolic shape for optimum airflow with least resistance. These are very good filters, but it takes a lot of them to give the real 500 minimum square feet we need for maximum filter life. Glen S. Miranker shared that he purchased his unit made by:
The impeller engineer for the Canadian firm I bought an airfoil from spent quite a bit of his time listening to my concerns then helping me come up with a solution. Amazon Best Sellers
I did considerable homework on cyclones and dust collection that convinced me the key factors to effective dust collection were good tool hoods, efficient ducting, a blower that moved ample air able to overcome the resistance of our system static pressure, venting outside when the weather permits and otherwise venting inside into certified fine filters, and using a good cyclone. After too many complaints and ruined motors I finally asked the new owner to stop sales and pull my name and endorsement off their pages. Unlike the big material handling impellers the airfoil is nearly twice as efficient so I could use a 2 hp instead of needing at least a 3.5 hp motor to turn a 14" diameter material handling impeller. To use my Dwyer magnehelic gauge I needed a piece that was at least 60" long with a hole 9" from the face of the blower. I did this to get the sizing/spacing right and to let me make the blower-housing mount separately from the motor and impeller. The medical community has long pushed for a standard that is fifty times tougher than the current OSHA standard and this much tougher standard is already the standard in Europe. When the airfoil impeller gets out of balance or begins buffeting it can quickly ruin motor bearings, catch your motor on fire and even cause these impellers to explosively fly apart. Plus that would be much easier to install. Either stalling or an out of balance condition can cause destructive buffeting. My choices were to buy a bigger motor or choke off the air inlet further killing CFM performance to make sure I did not burn up my motor. Hooking up the Dwyer Magnehelic gauge showed 3.2" of water which translates to 7160.34 feet per minute (FPM) air velocity. We need an impeller sized to overcome the extra resistance of a cyclone, plus is made from cast aluminum so it won't spark. In motor terms this meant I wanted one that had a 1.0 or better service factor (meaning can run 100% of the time at rated power). In terms of the bottom of my blower, meaning the part opposite the motor that mounts on the cyclone, you need to remember that my goal was to quickly get something ready for testing. Those chips worked on highly compressed smoke. When they do this they can become badly out of balance. We all knew that all that fine wiring and stuff was really a ruse. That can ruin motor bearings, cause the motor to catch on fire and cause an impeller to explode. I agreed to buy one for testing. Although I very much like the idea of an almost twice as efficient impeller, most cannot use an airfoil impeller safely and they are not readily available. Amazon Prime. The template was taped to the top piece then holes were drilled. For this blower to work, it needs a very efficient cyclone, minimal resistance air filters, good hoods, and a sound ducting design. I found some nice rubber dampeners at a surplus store, four for $3. Too much of that can ruin the impeller and the motor bearings. The actual amperage came in at 8.4 amps. A little work with my scroll saw got it cut out slightly oversized except for the sharp angle that I took pains to get right on. That allowed tracing around the impeller itself to make the cutout. I did call for help as my cousin Phillip who is also an engineer joined us for Thanksgiving and we put him to work. You can order Farr compatible filters from Wynn Environmental for less cost. With a small bit you have to go real slow and let the bit do the work. You are welcome to go to my other pages for detailed explanations, but the bottom line is we need a blower that will not just move 1000 CFM, but will move that 1000 CFM against the overhead resistance of our shops. Truthfully, making a wooden mandrel with the right shape on my lathe, then inserting about three inches of a PVC pipe segment into hot oil would soften it enough to slip that mandrel in and squeeze all down to make a perfect form. Shipping them safely required careful expensive crating and lots of very dense foam padding. Because the impeller is so heavy and starts fully loaded, it does draw a lot of amperage on startup, but now that I've run this for almost a year, it has not been a problem. This goes to show that the calculators only provide an estimate. The plate will actually hold the cyclone as well. Do you have any other suggestions? On the other end I taped a pencil that was held flat and upright by on an old tape roll. I personally use the Wynn "nano" filters because they provide much better protection for not much more cost. He started blaming the small shop owners and refused to make repair. What were your test results? I strongly recommend that you either build my cyclone design or buy a kit from us because only the 5 hp small cyclone move ample air and none of the small shop cyclone provide ample separation to work with good fine filters. Hobbyist suppliers can claim anything they want as long as they can devise a test that will "prove" their ability to perform at their claimed rate for a few microseconds. I drilled a hole through the center and one at 6" inches away using a 1/4" bit through the template and both the top and bottom. I used a 1/8" clearance off the side of my impeller to the sheet metal groove, but because the impeller has a raised base the picture makes it looks more like a 1/2" spacing! How did you ever come up with the calculation to get your inlet to sit exactly 1/8" inside your airfoil impeller? Those lucky enough to find the all spun bond polyester truck air filters report these can be washed up to four times and they work fairly well but because they are not coated with release agents our heavy wood dust volumes rapidly cause them to plug and need far more cleaning that those who get filters made for the heavy wood dust loads. I thought there should be some way to get an airfoil that did not stall quite so early. I did that so the impeller would sit down flush instead of being held up on its tall arbor. Amazon Daily Deals
I made this blower so the entire blower housing can slip off leaving the impeller and motor still attached and hanging from vibration dampers from my ceiling. I think the easiest and best thing to do would be to make the blower inlet a nicely flared entry that reduces down from the 9" (or 10" if you build a 20" diameter cyclone). Although you could use an 18" diameter cyclone, you would be better off to use either a 20" or 22" diameter unit and end up with just a tiny bit worse separation but with even less resistance. Then I had serious problems. Which filters did you use in your setup? All airfoil impellers have a very narrow range of static pressure that they work well within before they begin to stall.
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