Created: March 2000
Updated: November 22, 2009

Blower

Table of Contents

1. Caution
2. Foreword
3. Parts Discussion
4. Building Instructions
   1. Blower Template
   2. Blower Top & Bottom
   3. Blower Holes
   4. Metal Sizes
   5. Bolt Holes
   6. Mount Motor
   7. Completed Blower
5. Testing
6. Disclaimer
7. Frequently Asked Questions (FAQs)

Caution

Caution! This site shares what I learned about the fine dust hazards and what how I protect myself and my family. This particular page steps you through the process I used to build a blower. If you build a powerful high-speed blower incorrectly it could cause serious injury or damage. Please read the disclaimer below.

Challenge: Ok, so you made an exotic airfoil powered cyclone that leaves a chromed trailer hitch bald. An airfoil impeller provides too little pressure for my averaged sized shop. What affordable blower recommendation do you have for our average and larger sized shops?

Humm. Don't want much do you? Putting on my shop apron and envisioning a picture of what I want to build.







Foreword

Ideally, you need a good motor, good impeller, well designed blower, and a good cyclone that provides excellent separation and moves air efficiently. If you blow the collected air outside then just about any 3 hp dust collector with a trashcan separator lid or 5 hp small shop cyclone which provides little better separation than these trashcan separator lids works just fine. If you vent inside then you need a graduated filter bank or a very good cyclone fine dust separator with ample sized and rated filters. Although most small shop vendors provide poor dust collection advice, if you ignore that advice just a little help lets you pick and put together a very efficient fine dust collection system.

PartsDiscussion

You need to know a few things before you chase down your parts.

1. Motors - Barry owns Electric Motor Warehouse and he has decades of motor experience. He volunteered his time to help me learn more about electric motors to help me select the best motor to power my cyclone. I told Barry I like Baldor motors because my earlier projects used Baldor motors extensively. Barry warned me that Baldor imports most under 10 horsepower motors now. He said these imported Baldor motors provide poor quality and they fail often. Now he recommends the American made Leeson motors.
   
   Barry asked me to define my needs. I explained I needed a motor to power my cyclone blower. Because blower technology is mature most blowers of the same type and motor speed have near identical performance. This means we can size our blower and motor using any good fan table. A fan table will tell us the required impeller size, motor size, and ducting size if we know the static pressure and required airflow. We have the cubic feet per minute requirement tables from vendors who guarantee their customers a particular air quality. These tables show we need at least 1000 cubic feet per minute airflow at our larger stationary tools to get good fine dust collection. Also, my Static Pressure Calculator shows a typical two car garage sized shop generates 4" to 10" static pressure resistance meaning the friction and overhead from our ducting, fittings, hoods, and filters. We also know we want to use a backward curved (BC) type impeller to minimize noise. The Cincinnati Fan pressure blower table shows we need at least a 14" diameter BC impeller turning at 3450 RPM. At the minimum 4” resistance level this 14" impeller uses 3.27 horsepower to move a maximum 1377 CFM airflow. At the maximum 10" resistance level this 14" impeller only uses 2.34 horsepower but it then only moves only 846 CFM. Clearly the 1000 CFM minimum requires at least a 15" impeller, but 15" impellers proved near impossible to find, so early on I decided to just use a 14" diameter BC impeller and settle for less fine dust collection. I now have a few impllers custom made with the compression arbors, or you can buy a commercial blower and impeller. The 15" diameter works well, or you can upgrade to a 16" but that requires some minor changes to the cyclone to get full airflow.
   
   Barry explained that dust collection motors tend to be the heaviest we use in our shops so he recommends buying the best quality possible. Unlike a fan, dust collection equipment uses very large heavy impellers with lots of air resistance that cause very high starting loads. Normal fan motors burn up under these loads so we need heavy duty motors built to handle these high startup loads. Most compressor, pump, and farm duty motors will handle these high startup loads. He said these heavy duty motors come in 1, 2, 3 and 5 horsepower models. Additionally, these motors come with different service factors. A motor with a 1.0 service factor can run at 100% of its rated amperage without overheating and a 1.10 service factor motor can run at 110% of its maximum rated horsepower without overheating as long as it is not used in an already hot environment. The warmest place in a shop is at our ceilings or between rafters and it made little sense to buy a 1.10 service factor 3 hp motor when I knew that with the typical 14" diameter backward curved impeller that most other cyclone makers use we would regularly pull 3.47 hp. That would cause a 3 hp motor to eventually burn up. Buying a 3 hp motor made no sense when the cost to buy a real 5 hp motor was only $20 more. Since both motor sizes need the same power to turn the same sized impeller, the operating costs are near identical without having to worry about replacing motors from being overheated too often. I opted for the 5 hp motor which not only lets our motors stay cool by running well below its rated horsepower, but also lets us configure with a larger blower impeller to use some of that extra horsepower. Although most do not need the larger 15" or 16" impellers if they use the ducting sizes I recommend, I found using a 16" diameter impeller makes a big difference in my shop, as I have a number of tools that just could not be modified to accept bigger ports. This larger impeller allows use of all 6" diameter ducting and so increases the pressure that it will pull through some of my smaller 4" ports. Regardless, these Leeson motors are real 5 hp motors, not the inflated hp motors used on some vacuums and inexpensive air compressors.
   
   Barry also explained that when we make a blower, we need to use a face frame motor mount instead of a normal base mounted motor. The two pictured motors show the difference between a face frame mount and normal mount. The one on the left is a face frame mount meaning the front of the motor, that aluminum area, bolts directly to the blower housing. Note how the air holes wrap around to the side of that face so the needed cooling air can blow off to the side. The motor on the right is a standard mount and it has its cooling holes in front next to the motor shaft. These holes would be blocked if you mounted its face right to the blower housing as we need to do to keep the heavy impeller as close to the motor bearings as possible. Barry was willing to setup these motors with a face frame mount for no additional charge. I said go for it.
   
   That 5 hp Leeson heavy duty real 5 hp motor has been my motor of choice ever since (click here to see the custom Electric Motor Warehouse site for this motor setup up for fellow woodworkers!). Barry not only provided these motors to small shop woodworkers with the face frame mounts, he also agreed to provide them at a considerable discount and waived all commission to make that pricing even lower. They offer the Leeson Model # P145K34DB1B, 3450 rpm, 5 hp, 7/8” shaft, 20.8 rated amp motor with the added face frame mount: Leeson Motor Part #120554.00 part #175181. Electric Motor Warehouse as a favor to hobbyists prices this below what other dealers must pay in quantity 100. If you order this one, be sure to ask for having the face frame mounted for you and setup for CCW rotation. The next best and most affordable alternative is to buy a refurbished 3450 RPM pump motor locally. Most motors require careful installation to ensure ample airflow to keep from overheating.
   
   If my pocketbook said otherwise, I could make do by going to my local Harbor Freight (HF) store with my discount coupon and grab on sale their 5 hp compressor motor. These used to be only 3 hp motors, but HF had so many returned they now sell a real 5 hp motor. You can pick one up at HF or order one from their catalog sales hoping it is on sale there. These come with a small 1/2” shaft which I think is a little small for a heavy impeller. I still think it is worth the money to buy a better quality motor for the most heavily used motor in your shop. Still, at under $100 on sale I can go through a number of these before reaching the cost of a better motor.

2. Impeller Material - I strongly recommend use of steel backward curved material handling impellers. Unfortunately a full dustbin, a plug in the cyclone cone, clumps of debris, a large surge of dust, or an air leak turns our cyclones into little more than a pipe that passes all right through the blower. This heavier junk we can suck up can severely damage any lightweight impeller and even cause them to explode. Between the potential for material hits, need to move a high volume of air, need for self-cleaning, and need to provide higher pressure, most available fans, aluminum impellers, plastic impellers, squirrel cage impellers, vacuum impellers, and airfoil impellers will not work to safely power a dust collector or cyclone.
   
   I wish I could drop it right here, but our small shop dust collection market continues to be bombarded with just plain bad information that ends up with my either having to answer innumerable email questions or respond on these pages. The same magazine top rated vendor who sold cyclones with plastic impellers and still produces expensive cyclones that provide little better separation than trashcan separator lids has overwhelmed small shop woodworkers with their advertizing the benefits of their aluminum alloy impellers. So many believe that nonsense that my choices are to either respond here or have to deal with far too many emails addressing the serious issues with aluminum impellers that leave me only recommending heavy steel impellers. This vendor correctly shares that because of their light weight aluminum alloy impellers come up to speed faster with a smaller starting load on our blower motors. What this vendor fails to share are the many important reasons why we should not use aluminum alloy impellers to power either a dust collector or cyclone.

   1. Although aluminum alloy impellers are cheaper to make, the major commercial blower makers strongly recommend against use of aluminum alloy impellers for dust collection. Their main concern is when the inevitable heavy block, knot, tool, nail, screw or other item gets sucked up and goes through the impeller these aluminum alloy impellers can explode.
      
      A number of small shop woodworkers complained on the major Internet based dust collection forums because their expensive cyclone blower aluminum alloy impellers exploded when hit with wood knots and other stuff sucked up by their cyclones. Sadly, all of those kinds of posts rapidly vanished from the major Internet woodworking forums whose livelihood depends upon vendor advertizing.

   2. This same cyclone vendor strongly puts down steel impellers on their web pages implying that steel impellers are so heavy they ruin motors from the high starting loads. As discussed before if you choose to use the gravely undersized motors this vendor sells, this startup load is a serious problem because it can quickly cause a motor to burn out from overheating. With a properly sized motor to handle the startup loads this concern is irrelevant.

   3. This same vendor also states on their web pages that steel impellers are a major fire risk and do not comply with the National Fire Protection Association (NFPA) guidelines. That is double nonsense.
      
      This same NFPA guideline also requires either putting our cyclones and blowers outside behind a suitable explosion barrier or using certified fire and explosion proof cyclone equipment. This vendor makes an indoor cyclone that is not certified as either fire or explosion proof. They would never pass that certification process because they use steel instead of aluminum blower housing and a plastic hose connected to a cardboard dust bin.
      
      Worse, if you look up the current warnings you will find that the experts on ventilation recommend against use of aluminum impellers. From the ACGIH's Industrial Ventilation: A Manual of Recommended Practice for Design, page 7-22, 26th Edition, 2007:
      
      "For many years aluminum alloy impellers have been specified to minimize sparking if the impeller were to contact other steel parts. This is still accepted, but tests by the U.S. Bureau of Mines and others have demonstrated that impact of aluminum with rusty steel creates a Thermite reaction and thus possible ignition hazards. Special care must be taken when aluminum alloys are used in the presence of steel."
      
      For those who don't recognize what a thermite reaction is, you already know because Fourth of July sparklers are made from powdered aluminum that when lit burn with a very bright, hot, high intensity flame. In other words, if you sucked up a rusty nail it could knock off a small piece of aluminum creating the equivalent of throwing part of a lit sparkler into either your dust bin or filter. Since I first wrote this page NFPA has acknowledged this thermite generated fire problem and now no longer recommends the use of aluminum and aluminum alloy impellers. So much for one vendor's touting their non-sparking impellers.

   4. Another frequent complaint with the aluminum impellers which also gets quickly deleted if shared on the Internet forums is the problem with these light aluminum alloy impellers slipping down the motor shafts then self destructing when they hit the blower housing. The major commercial blower makers use special star tipped set screws and a keyway to secure their aluminum impellers. They also warn that these impellers are not to be used on a vertical motor shaft because set screws cannot carry the weight of the impeller. When these impellers are mounted on a horizontal shaft the shaft carries the weight and there is almost no side to side pressure. When mounted on a vertical shaft the commercial blower makers strongly recommend using a tapered shafted motor with a bolt which screws into the motor shaft to lock in the impeller or use a compression arbor similar to what we use in our routers to hold bits securely when mounting impellers on a vertical shaft.

   In short, I strongly recommend against buying any cyclone with an aluminum alloy impeller and instead buying a good well balanced steel impeller.

3. Impeller Sizing - This is one of those areas where I provide far more information than many want or need to know, so the bottom line is if you use the Leeson 5 hp motor I recommend you use a 16” diameter impeller to get the maximum airflow and pressure from your motor. This added airflow and pressure are important. The increased airflow does a much better job collecting the fine dust and the increased pressure permits you to use all 6” diameter ducting and still move over 1200 CFM to any tool in your shop. How I got to this recommendation is a touch complicated.
   
   My engineering professor friends who helped me test every major brand and size of small shop dust collector and cyclone a few years ago were appalled at how poorly our small shop blowers were made. We actually had one small shop vendor who supplied exactly the same sized impeller with their 1.5 hp, 2 hp, and 3 hp dust collectors and cyclones. With our motors all turning at the same 3450 RPM for U.S. 60 cycle current, every one of those blowers moved exactly the same amount of air. What was very disappointing was finding only the Delta, Jet and Powermatic impellers were actually properly sized for their blowers. All others were either way too small or too large. An undersized impeller just spins leaving a good portion of your motor’s horsepower unused. An oversized impeller is required if you have a high resistance, but if it is tested without that resistance you get the incredibly high CFM numbers that so many of the less reputable vendors advertise. Worse, at these high CFM numbers from running in “free air” meaning with no resistance our motors are doing the most work. In our testing we found a number of cyclones 3 hp and smaller that frankly were running such oversized impellers which cased the motors to run so far above the motor horsepower we had two motors burn up. Talking with the testing groups that ran two more recent woodworker magazine cyclone tests they had the same problem and burned up three cyclone motors when testing. Vendors simply used way oversized impellers and then choked them down in real use with undersized ducting to save their motors. Unfortunately, they had to so choke down their impellers that not one moved a real 800 CFM let alone the 1000 CFM I recommend against typical shop higher resistance levels.
   
   Because blower technology is mature, blowers of the same type and size provide near identical performance regardless of which commercial vendor we use. This means we can look at any good commercial fan table and use that table to size our impeller, our ducting main and our motor horsepower requirements. To use one of these fan tables we need to know three things, required minimum air volume, maximum resistance and minimum resistance.
   
   Air engineers long ago learned we must capture the fine airborne dust as it is made. A few of the newer tools such as the circular powered hand saw from Festool have proven that if tools are built from the ground up to totally contain all of the dust being made we can get excellent fine dust collection with a large shop vacuum. Unfortunately, almost all stationary tools come with little to no fine dust collection built in. As a result these tools make so much fine dust that spreads so rapidly normal exhaust fans and air cleaners cannot pull the airborne dust level down fast enough to ensure passing an air quality test. As a result, we have to collect the fine dust as it is made.
   
   Because almost every customer wants good fine dust collection without having to replace all their tools, air engineers long ago worked out how to ensure our typical stationary tool designs got good fine dust collection. To collect the fine dust at each source they found we have to start by making sure each tool is equipped with hoods that block all fast moving air streams. Additionally, we also must surround the working area of each tool with a “bubble” of air moving at least 50 FPM to overcome normal room air currents. The size of this bubble is defined by what level of fine dust collection we want. Air engineers did years of testing to determine how big of a “bubble” it takes to pull in the fine dust. Once we know the size of that “bubble” we can use the sphere surface area formula to compute the area of that sphere where A=4*Pi*r*r then put in our 50 FPM airspeed and that area with a little algebra into our air formula FPM=CFM/Area to calculate our needed CFM air volumes. A couple of decades of testing and experience have verified we need at our larger stationary tools that have upgraded hoods about 800 CFM to create a minimum “bubble” ample to meet OSHA air quality standards, roughly 900 CFM to meet ACGIH recommended air quality, and about 1000 CFM to meet medical and EPA recommendations.
   
   Sadly most small shop woodworkers and even most vendors wrongly assume that the roughly 350 CFM that provides excellent “chip collection” at our larger tools will also provide plenty of airflow to pull in the fine dust we know we can move with the lightest breath. The problem with this assumption is we are thinking in terms of blown instead of sucked air. Blowing a directed stream of air will hold together for quite a distance, but sucking has the airspeed fall off at roughly twelve times the distance squared because the air comes from all directions at once. You can easily test this. Wet a finger and see how far you can move it from your lips and still feel blown air. Try it again while sucking. Almost all can feel the blown air as far as they can reach. Conversely, we can only feel the sucked air out to a couple of inches. To cover a large area with sucked air we have to move a large volume.
   
   We can pick which air quality level we want and then use that required CFM value with our fan tables to pick our impeller size. Although many recommend the OSHA air quality levels that we can get with 800 CFM, I strongly recommend using medical and EPA recommended air quality levels that instead require at least 1000 CFM airflow to our larger tools.
   
   Before we can use our fan table we also need to know the highest and lowest resistance levels in our shop. The resistance is a measure of how much work our blower has to do to overcome the friction in our ducts, to turn the corners through wyes and elbows, to pull through a restrictive hood, and to push through a dirty filter. We measure this resistance in what are known as water column inches, meaning how high a blower would have to push or pull a column of water to overcome that resistance. We can add up the various resistance numbers by hand or do testing once we get our shop ducting built, but the most convenient way to calculate shop resistance is to use an already setup spreadsheet that lets us put in what we have then calculates the overall resistance levels. A good static calculator such as the one shared on these pages shows that a typical two car garage sized shop will have a minimum resistance of about 4” when connecting to an adjacent tool with a new clean filter.
   
   Calculating the maximum resistance is a little more difficult. As our filters build up a cake of dust trapped in the filter pores that does not come out with normal cleaning, they are said to season. This material trapped in the filter pores improves filtering by up to twenty fold, but also increases our resistance significantly. It typically takes nine to twelve deep cleaning cycles meaning as much as a couple of years before small shop woodworkers fully season our filters. Our having to breathe the finest invisible dust known to cause serious health problems for a few years while waiting for our filters to fully season is why I strongly dislike most small shop vendors advertizing “seasoned” filtering levels. The American Society of Heating, Refrigeration, and Air-conditioning Engineers (ASHRAE) is considered the world authority on filter measurement and performance. Our small shop vendors almost universally ignore the ASHRAE standard that requires all indoor filters, meaning those used in our shops, must be rated when clean and new rather than after becoming “fully seasoned”. Anyhow, in terms of resistance most small shop fine filters that start out brand new with only about 0.5” of resistance are far too small. This means that when seasoned their resistance will climb to at least 2.5” just after cleaning. While in use our filters will also build up a cake or layer of dust on the filter surfaces as we make dust. This cake also impedes airflow and the smaller the filter area the higher the resistance. Between seasoning and this cake of dust a brand new filter that only has 0.5” resistance can easily climb to 5” or more in use.
   
   In addition, to the filter resistance we also need to know the resistance of the longest ducting run in our shop to calculate the maximum resistance. We normally calculate a worst case situation in our shops to allow us to later move any tool to any location. Otherwise we would be forced to wheel our dust collector or cyclone right next to each tool. The maximum ducting resistance is for a distant tool that has two collection points like a table saw with both cabinet and over blade collection. Adding a fully seasoned filter to that ducting resistance gives a maximum resistance of about 9” in most shops. Unfortunately, that is not really the maximum as the maximum occurs when we have a dirty filter. A dirty filter can easily push the maximum resistance up to 12” before the airflow gets so blocked that we no longer get good fine dust collection.
   
   This 4” to 12” average pressure range coupled with the 800 to 1000 CFM is what requires us to use pressure blowers for dust collection. The other types of blowers either move too little air like vacuums or like most squirrel cage fans and airfoil impellers just cannot generate enough pressure to overcome our normal ducting, tool, and filter resistance. We also know we need heavy duty steel material handling impellers to ensure we do not break our impellers with inevitable material hits. We also need these material handling impellers to keep strings and shaving from getting caught on our impellers that would cause them to go out of balance and quickly ruin motor bearings. For our indoor dust collector and cyclones where noise is a serious consideration, we also want a backward curved (BC) impeller blade to minimize noise problems.
   
   Finally knowing our airflow and pressures we can look up our needed information from a good fan table. Also that table lets us pick the blower opening which matches our ducting size. Unlike again some of the nonsense advertizing, with small shops we should have a consistent size duct going right from our blower to each of our tools. Smaller duct sizes kill the airflows needed to keep larger mains from plugging or building up ducting dust piles that pose a serious fire risk. Going to the steel pressure blower fan table shared by Cincinnati Fan we see by looking down the 12” pressure column the first blower with a 6” inlet that will move at least our needed 1000 CFM is a 15.5” diameter impeller with 3.5” tall blades. The blower table shows this impeller will move a real 1022 CFM at 12” and draws a real 3.44 hp. To size our blower motor we simply look at this same impeller at our minimum resistance level. This 15.5” diameter impeller at 4” of resistance moves a real 1957 CFM and draws a real 4.88 hp which is why I have long recommended use of a 5 hp blower motor with at least a 15” diameter impeller and 5” diameter ducting.
   
   Almost all small shop vendors now supply even their larger cyclones with only 14” diameter impellers. We can use the same blower table and see that at 9” of resistance a 14” diameter impeller with 6” ducting only moves 767 CFM and pulls 2.05 hp. That is close enough that a 2 hp motor would work just fine, but look at what kind of airflow we get at 12". At 12" resistance this 14" impeller moves so little air with such an unsteady flow that it does not even have a value in this table. In short, at normal maximum expected resistance a 14" diameter impeller does not even move enough air to provide the needed 350 CFM needed for good "chip collection". Next look at that same table and see what happens to the horsepower demand when the resistance is only 4” with that 14” diameter impeller. At 4” of resistance that impeller moves 1543 CFM while pulling 3.09 hp. Now look at that same table at what happens during the vendor supplied tests that instead use an 8” opening with 1” of total resistance. The airflow climbs to 1893 CFM while the horsepower climbs to 3.68 hp. Because the normal fixed speed 3450 RPM induction motors we use to power our dust collectors are made to pull starting loads six or more times their running loads, our vendors can get by with quick tests at these kind of horsepower loads. Unfortunately, if these loads go on for a few minutes the motors will quickly overheat and burn up.
   
   I know that many don’t want to spend more than they have to. When I first put up this web page in 2000 the only affordable sources for impellers were the 14” diameter impellers we could buy as replacement parts for the larger 3 hp dust collectors. The plans provided on these pages are optimized for this 14” sized impeller. Since then we now have a good source for the larger 15” and 16” impellers I recommend to get the larger airflows required for better fine dust collection. You can easily change these plans to work with the larger impellers. For the 15” make the spiral 1” larger and for the 16” make the spiral 2” larger for optimum performance.

4. Impeller Sourcing - A few have made their own impellers but you need to know that the forces involved with a 14", 15” or 16” impeller turning at 3450 RPM are measured in the tons. I have already had one welded impeller I was testing fly apart from those turning forces. I have not hit the ground so quickly since I served in the Vietnam War. There was little left of my blower and I was amazed that the heavy PETG plastic used in the previously made Clear Vue Cyclones actually held up far better than the 18-gauge steel. The plastic was only scratched while the steel was punched clean clear through. Unless you really know what you are doing, making your own impeller or grabbing just any old impeller can be potentially life threatening. I see no reason to take this risk trying to save a few dollars while making my dust collection system, so strongly recommend use of a good quality impeller designed for this type of use.
   
   With no other affordable sources available I used to recommend ordering the Jet DC-1900 14” diameter impeller part number 431006 from Jet Customer Service at 800-274-6848. My cost in 2001 was $57.76 plus $15.00 more for shipping. Costs now are about double that after a huge increase in the price of steel and much higher shipping costs. To attach this impeller to your motor shaft you need a custom arbor. With too many unable to build their own arbors, I had a machine shop make up arbors and sold them at cost. These arbors worked but even with their special star tipped set screws that dig into the motor shaft they could let the impellers slide plus these screws need replaced every time you remove the impeller. Otherwise the impeller can slip on the shaft, so I shifted to a good compression arbor. My machinist bought the compression arbors then welded a round plate with holes to match the Jet impeller. My machinist retired after being there for me for over thirty years, so the supply of these arbors stopped. One of my local friends Roy does a little machining and made his own Jet impeller arbor. He is a very busy fellow and making arbors is not his priority, but he also likes to help others out. You can contact him at RMcbra@aol.com to see if he can make one for you, but you need to work out your arrangements with him.

   

   After a few years of a steady supply, Jet ran out of impellers and those of us wanting to build our own cyclones and blowers waiting for months. After looking all over others found Cincinnati Fans sells a very heavy aluminum material handling impeller and a lighter air movement impeller. Both came with warnings not to use them for dust collection because material hits could cause the impellers to explode. Many ignored my advice and used the less expensive lighter Cincinnati Fan cast aluminum alloy impellers. When challenged with all going right through the blower which happens with a plugged cyclone, full dust bin, bad air leak, or big surge of dust, these impellers were damaged with a few even exploding. Even their heavier cast aluminum alloy material handling impeller should not ever be exposed to impacts, which means this impeller should be used after the cyclone and filter cartridges. Regardless, I worked out with their corporate headquarters an arrangement to let small shop woodworkers buy these heavier impellers from their local dealers for between $155 and $175 each. Because of the way their dealer arrangements work, most dealers still charged $237 plus shipping. And yes, I know two other import firms sell impellers for less, but their quality just did not pass my inspection and with over twenty tons of force involved with a spinning impeller going with low quality or a poorly balanced impeller just makes no sense. The main advantage of these impellers is the light aluminum alloy construction permits the impeller to come up to speed quicker with less wear and tear on the motor.
   
   These impellers cannot be used directly as delivered because they need a different way to mount to the motor shafts (see impeller mounting below). These impellers are designed for mounting on horizontal motor shafts. They use special Allen set screws with star points that dig into the motor shaft to hold the impeller from moving sideways. These screws must be replaced every time they are loosened. With our cyclones we mount our motor shafts vertically. These screws do a poor job of supporting the whole weight of the impeller. Many including me found the impellers slip down the motor shaft destroying the blower housings. In one of my test runs, I failed to replace those special star set screws as recommended and my impeller slipped down the shaft doing bad things to the impeller, motor, and blower housing. Anyhow, I quit recommending these aluminum alloy impellers after too many had problems.
   
   When Jet ran out of stock I paid to have a custom 14” material handling impeller built and certified by Sheldon’s Engineering with a far better compression arbor. After three years of sales I was about one third paid back when the engineer I worked with left Sheldon’s and that firm was sold. The new owners stopped honoring our agreement and stopped carefully packing the impellers they shipped so most arrived damaged and people complained to me. This never was intended to be a money making proposition, but I was not happy at covering that considerable loss and then having to do it all over again with another firm. Foolish or dedicated, I did so anyway for two more firms. I again subsidized the costs for test gear, testing, blower housing, and provided the engineering specifications. The first firm sent me an impeller that exploded due to poor workmanship in their welding and refused to make repair, so I moved on.
   
   I now have a machine shop make impellers for us and also have another firm CNC cut MDF top and bottom pieces to easily make a blower to work with that impeller. Electric Motor Warehouse provides discounted blowers with the right face frame mounting. In a cyclone this 5 hp motor actually was left with over 1 hp of unused capacity, so I engineered a 16" impeller. It uses that extra horsepower, but does require a few changes to the cyclone design to get full use of that extra flow. As shared above if you step up to a bigger impeller, you also need to use different dimensions for your blower opening and motor plate from those shared below. Remember that these firms I have helping do small shop owners a favor. Please don’t chase them away from helping us by burying them with questions and special orders.

5. Blower Housing - I was stunned when my professor friends and I tested every major brand and size of small shop dust collector and cyclone a few years ago. Most of these housings were incredibly poorly designed and even more poorly made. A blower requires a smooth spiral shape to provide a good steady airflow without causing pulsing which kills blower efficiency and raises sound levels dramatically. Most small shop dust collector and cyclone blowers, in fact all the major brands except for Delta, Jet and Powermatic had blowers with very poorly made housings. Many did not even use spiral shaped housings but instead round housings with the impeller offset to one side. Most blower housings forced round into square ducting and had very rough ridges, loose metal, and other junk pushed right into the air stream. The engineering professors I did this testing with were amazed. They said blower technology is mature and just about any engineering graduate can look up what it takes to make a far better material handling blower. What we found with our testing is only those three vendors had performance that matched industry norms and all others were below, some very badly. The worst was that aluminum impeller cyclone that used a circle shaped blower with an impeller that had the support castings for the blades in the middle of the airflow.

BuildingInstructions

1. Head hurts a little but carefully putting the impeller on that motor shaft using the Lock-Tite as ordered.

2. Making a mad run to the orange box to get a 220V plug and cord. Ouch! $14, grumbling like crazy because I forgot to get two bayonet connectors, one eye connector, and one strain relief fitting, then going back again, $1.89. Carefully soldering my connectors, and firing up the motor. Yes! It goes counter clockwise when looking at the impeller with the motor behind just like my Jet impellers;

3. Layout: This whole section was redone thanks to some tips from a couple of net friends who are blower experts. Unfortunately the information provided was not well interpreted and I translated it wrong. Trying again with more changes!! The result is much smaller than the technique used to make the big airfoil impeller blower housing without any big sacrifice in efficiency!
   
   Start by looking over the Build Your Own Airfoil Blower instructions;

   
   
   Blower Layout
   

   Click drawing to open a larger drawing of the 14" blower design! Although this will work with a 15" impeller you would get better performance and less noise by scaling this drawing to work with a 15" impeller if you are going to use a 15" impeller. If your printer will let you rescale the printing, simply print out the 14" full size at 107% and the resulting drawing will be right on for a 15" impeller. Many browsers automatically rescale the picture to fit on a single screen. To make it readable it needs to be larger. With Microsoft IE click to open the drawing then move your mouse to the lower right corner. When an orange box appears, click on it for a larger image.

   

   Edward Thomas was kind enough to make a full sized drawings of both the 14” and `16” blower plans as downloadable and printable PDF files. Although the 14” is a workable plan, it is not the latest and I strongly recommend using my 18" cyclone with a 5x10 inch inlet and 8" diamter outlet, plus 16” Blower and 16” diameter impeller with 5 hp Leeson motor. You can use the corner registration marks on my blower plans to print a full sized layout for either a 15" or a 16" blower including the spiral that many find difficult to draw on 8.5” x 11” paper. I suggest you print on clear sheets to make it easier to match the registration marks. Here are 14” blower plans for standard 8.5 x 11" paper, legal sized paper and 14” version for 13" wide carriage printer.
   
   For people who use this method you should check that your printer prints to "size" and square. If the printer is set to "reduce to fit" there may be a problem. I recommend checking the 18" circle at right angles and both 45's.

4. Rotation: I get too many questions about impeller rotation. What you need for ideal performance is your impeller turning with the blades rounded portion leading and the cyclone built so the inlet causes the incoming air to turn in exactly this same direction.
   
   If you turn your impeller backward it will make a ton of noise. If your airflow in the cyclone does not match the direction the impeller turns then your motor must do more work to reverse that spin and you lose considerable performance. Remember that the airflow inside the cyclone spins in the same direction going down as it does when it comes back up and exits the cyclone into the blower.
   
   For dust collection we use material handling impellers. A material handling impeller uses a flat bottom disk with vanes and no top cap as you would have in either a caged or airfoil impeller. The steel blades taper to the impeller center so strings and shavings just slip off without causing clogging. Although this works well and makes for a tough impeller, the result is only one step removed from an air raid siren in terms of noise.
   
   Fan designers found they could trade a little efficiency for about half the noise by angling the blades away from the direction of rotation. They then discovered that if they made those backward inclined blades curved (creating what they call a backward curved blade) they got back some of the efficiency and reduced noise even more so.
   
   Now why all this is important is you can run an impeller in either direction. Going with it the right way with the curve pointing into the direction of rotation will save you about half the power and cost you about 1" of overall pressure. Running a backward curved impeller the wrong way works getting better high-end performance of about 100 CFM and one more inch of pressure in trade for using more power and making lots more noise. The working performance is also less. The other problem is of course that doing so can setup vibrations that could destroy the motor early and with plastic and aluminum impellers, could result in impeller failure. I strongly recommend against running them backward! I've actually tested impellers both ways and find it is much easier on my motor and ears to turn it in the right direction. In any case please use an amp meter to make sure it all works and does not over-stress your motor. This picture shows the correct way to turn a backward curved impeller. The red impeller is a Jet and turns CCW when looking at the vanes. The silver impeller is a Cincinnati Fan aluminum impeller that turns clockwise. I do not recommend use of aluminum or plastic impellers in either dust collectors or cyclones because they can self destruct! Note the ends of the blade tips point away from the direction of rotation.

   
   

   Take a few minutes, study your impeller and figure out which way it should rotate. Make sure your motor turns it the right way and then use my plan for either clockwise or counter clockwise construction. The pictures here are for either the Jet or our counter clockwise rotating impellers when viewed from the vane side of the impeller with the motor positioned behind the impeller.

5. Inlet: The inlet goes centered right over the impeller. The ideal inlet for that 14" impeller is 10" from my fan table on the Dust Collection Basics page. But that same table tells me at that big of an opening, my horsepower will go way over for my budget motor that only has a real 3 hp. I tested and found that with the Leeson motor, 14” diameter impeller, and cyclone that I can use up to a 7” cyclone opening and 7” diameter mains and still keep enough airspeed to prevent the mains from plugging or building up piles of dust. Moreover, the 7” ducting amply restricts the airflow that the 14” material handling impellers do not have a problem drawing too many amps with the Leeson motors. For the smaller motors, 6” ducting and a restrictor blast gate is required to keep the impeller from pushing so much air it draws too many amps. Because the ducting sets the maximum airflow, I can size the blower inlet to the cyclone outlet. That lets me use a 9” diameter opening for my 18” diameter cyclones and a 10” diameter inlet for my 20” diameter cyclones.

6. Impeller Clearance: Unlike my airfoil that requires a 1/8" clearance to the closest point of the blower shroud, material movement impellers become sirens if you don't have enough clearance. Some of the blower theory I read said to use a 10% clearance as a minimum to keep the noise manageable. For a 14” diameter impeller this comes out as a 1.4” clearance between the impeller and the bend in the blower housing known as the “gore point”. This distance works fine without excessive noise.
   
   Fortunately, unlike the airfoil, material movement impellers can have up to 1/2 of their blade width sticking into the outlet air stream. The more the impeller overlaps the outlet, the smaller the blower. Using no overlap creates a huge blower. After lots of fooling around I came up with a 3” overlap and end up with a blower sized near the size of my cyclone. That also leaves plenty of room to pass larger pieces of wood without jamming the blower. With the impeller there, we can start our spirals with a much shorter cord ending up with a far smaller blower and still plenty of airflow.

7. Impeller Mounting: One of the main reasons I recommend our impellers besides their being professionally balanced, is they use a compression hub to hold them tightly on the motor shaft. My early designs that used the Cincinnati Fan and Jet impellers held on to the motor shaft with setscrews tend to be a problem. You need to use the special toothed setscrews and replace them every time you loosen them, otherwise your impeller can slip down the shaft. I had one that I was testing slip and what it did to my wooden blower housing was almost as ugly as how much that noise scared me. You can safely mount these kinds of impellers, but need to do quite a bit of work to get them right. Here is a solution from Gary French that works for me.
   
   I decided to build my own blower, based on the information on your site, using the Leeson motor and a Cincinnati Fan impeller. I've finished the blower, and am just waiting to get the cyclone kit I ordered. In precise engineering terms, the blower blows like crazy! In a previous e-mail, you warned about the attachment method used by CF, which is, to say the least, problematic. As an engineer, I can't see how this kind of attachment could make it onto something as potentially dangerous as this application. Anyway, end of rant. I decided to see if I could come up with a better way of holding the impeller on the shaft, without going through too much hassle or expense. I came up with a fairly simple solution that I decided to share with you. The original setscrews are still needed, since they keep the impeller from shifting back and forth rotationally on the shaft at startup and shutdown, especially the one located over the key. To those set screws I added a collar mounted on the motor shaft and a beefy fender washer that clamps the impeller against the collar. Under the impeller I needed to add a shim and bushing to put the impeller at the right height on the shaft. The only machine work that is required is to drill and tap a 3/8-16UNC hole in the end of the motor shaft, which I was able to do (carefully!) with a hand drill, a regular tap, and a bottom tap. The parts required are available from McMaster Carr and Orchard Supply:
   
   Orchard Supply
   0.875 Shim 18 gauge
   Star Washer
   
   McMaster Carr
   Flanged Bronze Bushing #7815K52
   3/8" UNC 3/4" long bolt and Fender Washer #91117A222
   
   The total cost was about $15. I hope this is useful to you. I can certainly sleep much better, confident that the impeller will not slip off the motor shaft.
   
   Note that Lock-Tite is a must for this application to keep that bolt from coming loose.
   
   Regards, Gary French
   
   Further discussion with Gary indicated the impeller casting is not perfectly flat on the front and back, so there is uneven contact. Unless both the top and bottom of the impeller are made flat, tightening the hold down bolt could force the impeller to "wobble" causing a dynamic imbalance. That can be corrected as follows:
   
   You need to have both the top and bottom of the impeller surfaced flat with reference to the hole. Although a machine shop would be best, a good small machinist square and patience would work. You could make up a simple hone that would work fairly quickly. Buy a 7/8" shaft (I'd use plastic and Gary found a socket the right size). Square, drill and then tap both ends. Make up an emery cloth on a fender washer to serve as a hone, perhaps with a little lapping paste. Then carefully spin that shaft with a hand drill to quickly take down the aluminum impeller alloy to have nice flat faces both top and bottom. One effect of the sanding on the impeller is that a thicker shim is required between the bushing and impeller. I had an extra 18-gauge shim that I used, but a single 14-gauge shim would work just as well.

8. Spiral Configuration: Picking the right spiral takes some work to get it all right. We need a nice smooth curve that gets keeps right distance from the impeller. To draw that curve we have to decide on the blower outlet width. We have some flexibility with blower width because the compressed exiting air can go through up to a 25% smaller outlet. Larger does not hurt a thing.

9. Outlet height: Figuring out the outlet height is easy because it is the same height as the blower height. The blower inside needs to have clearance above the blower blades ample to pass chunks, 1/2" for clearance below the impeller, plus the height of the impeller. For the Jet DC-1900 14" impeller that is 3 5/8" tall we can use 1.5" above and a 1/2" below for clearance giving an inside height of 5 5/8".

10. Blower side width: That outlet height also tells us the height of our metal or polycarbonate for the sides. Add the 3/16" top and bottom grooves to trap the blower sides, and we get an even 6" to have our metal or plastic dealer cut our blower sides.

11. Outlet width: The outlet width needs to be equal or bigger than whatever limits the blower input and must also be big enough to provide the clearance we need on our spiral. With a 6" duct and smaller inlet, we can calculate the minimum outlet area. A 6" round duct and 6" round cyclone inlet each have an area of about 28 1/4" square inches (Pi*(D/2)^2). Divide that by the blower height of 5 5/8 gives a calculated minimum width of just over 5". Rather than go through the hours of work to build a custom transition, my plan fits one of the ready made HVAC pieces. This size is not optimum, but good enough and makes a nice small manageable blower that will fit a standard fitting without having to build a custom transition.
    
    HVAC transitions always come in even inch increments. I found an 8" round transition fits near perfectly. It has a perimeter of Pi * D = 3.14159 * 8 = 25.133" Perimeter = Width + Width + Height + Height or Width = (Perimeter - Height - Height) / 2 = 6 15/16". To make the round fit on the rectangle, we need to hammer the corners square to make the height match the 5 5/8” blower height making the width 7". Cutting into each corner and bending the top and bottom at ninety degrees provides plenty of attachment area for a good tight seal. That seal is critical in terms of controlling the really fine dust.

12. Spiral layout: With that sized outlet the next question is how to make the spirals for the blower top and bottom. Both have a spiral outer shape plus a spiral groove that holds the blower sides. Anything except a smooth spiral will make pressure waves that will pulse badly, make lots of extra noise, and hurt efficiency. We need to make the curve as a true rather than approximated spiral. Although in drafting class they teach an easy way to make a spiral using a compass with four different radius settings, this is a bad technique because it changes the airflow four times creating pressure waves that hurt performance and add more noise. To make a true spiral the easiest way is to pick a center, then attach a marker to that center with a string. As the string winds around the center, the radius consistently deceases. In fact, if we know the amount we want that to decrease in one turn, we know that the circumference of the center. Since circumference = Pi x diameter, we can calculate a diameter for our center. I found an old gauge that was right on and used it for my center.
    
    Drawing the template is not hard, but does take a little patience. Mark out the center, north, south, east and west intersections where the spiral should hit. At the center I used double-sided tape to lock my cylinder to wind around. Instead of string, I used fiberglass reinforced packing tape as my band plus the roll to make it easier to make a better line when unwinding the tape. Use a constant tension and swing the arc on the template making sure it stays right on. My first took a handful of tries, but eventually came out right on. This template ends up being sized perfectly to make the groove in the top. When flipped over it also is used to make the groove in the bottom. Bolt the top and bottom together with the grooves together and lined up. Now draw around the template using a 1” spacer to get the outside cutting line. Cut out both pieces at the same time to make a perfect match.

13. Going back to the orange box and buying a $22 piece of thick plywood or MDF;

14. Pricing some sheet metal and the hardware:

    1. 13- 3/8 X 8 carriage bolts to connect blower halves

    2. 13-3/8 nylock nuts for carriage bolts

    3. 13-3/8X2 fender washers for top of carriage bolts

    4. 13-1/2X2 fender washers for head of carriage bolts

    5. 6-1/4X1 bolts to mount motor plate to blower

    6. 12-1/4X2 fender washers for motor plate bolts

    7. 6-1/4 nylock nuts for motor plate bolts

    8. 4-3/8X3/4 bolts to mount motor to motor plate

    9. 4-3/8 lock washers for motor mount bolts

    10. 1-16X1/8 galvanized motor mounting plate

    11. 2-18ga. Galvanized metal for spiral

    12. 1-pattern for router template to rout spiral

    13. 1- 4’ of foam seal for motor plate

    14. 5-1/8X1/8 pop rivets to connect spiral metal pieces

    
    

15. Dazzling the world by making a spiral template unwrapping around my appropriately sized cylinder then following it twice on MDF or plywood to make a sandwich with mirrored matching grooves;

    
    

16. With the blower top and bottom stuck together with double-sided tape drilled all the matching hardware holes at once so the holes all align just right. Used my band saw with the pieces still together rough cut the blower top and bottom pieces, followed by a sander for exact shaping. Separated the pieces and bolted the template centered on the top. Used my 5/16" router collar and a 1/8" bit to cut the top spiral going slow to keep the bit from overheating. Bolt the template upside down to do the same on the bottom.

    
    
    
    
    

17. Used my circle-cutting router jig to route a ½” ledge on the blower top with a diameter and depth for a tight fit for the motor plate. The motor plate needs to be recessed because the motor shafts on both the Harbor Freight and the Leeson motors are otherwise just too short to get a good grip on the impeller. The recess also holds the gasket seal (just a piece of stick on foam insulating tape). Next again use the circle-cutting jig to route a bottom blower piece hole to match the outlet from the cyclone. Then rout the holes blower top hole big enough so the impeller will side through. This lets the blower housing and cyclone get removed without having to take down the heavy motor and impeller assembly. That will save your back, makes inspection and service much easier. It is a good idea to use a 3/8" round over on the inside edge of this inlet hole to smooth the airflow coming into the blower;

    
    
    
    

18. Putting in place the metal blower sides and securing them together where they meet;

    
    
    
    

19. Mounting the motor making sure enough room is left for airflow into the front of the motor, and yet ensuring a nice seal on the rim around the shaft. This approach lets the motor stay mounted if you want to take the cyclone down for cleaning or clearing;

    
    

20. Bragging like crazy because tested it out and got a real 1498 CFM, 7600 FPM, 3.8" static pressure, and all at 12.9 amps. I got the same test results with either the Jet or our impellers. At first I was not sure on my wiring, so started with the impeller turning the wrong way. Although that can generate higher end CFM and pressure, it is not a good thing to do. Not only does it flatten the blower curve in the useful area, running the impeller backward can also can burn up motors and cause impellers to fail. Regardless, with all turning the right way, I now have a real blower that can instantly turn into a Dust Collector with a couple of bags and it totally blows away anything else available under 3 horsepower at four times the expense;

    
    
    

21. Struggling because I know it only needs a nice pair of 300 square foot Wynn cartridge filters make a huge difference in my shop air, but thinking about that Make Your Own Cyclone.

22. Buying a single 4'x10' sheet of 24 gauge galvanized steel and spending another $12 on solder, playing with my new Cleco fasteners from the Air Tool Store instead of screws or pop-rivets, lots of careful layout, my hand sore from all the cutting, and then gently soldering all using my propane torch;
    
    Mounting my blower on the cyclone;

    
    

23. There are two major options on filters. If you use industrial numbers, you really need a lot of filter area to minimize the backpressure on your blower, and to reduce how often you need to clean the filters. Fortunately, certified dust collector cartridge filters come with huge amounts of filtering area. One of the largest is the 300 square foot Farr compatible 0.5-micron cartridge air filter. That is just about the minimum practical size. Although one of these will work, I recommend using two because the result greatly reduces filter resistance, cuts the cleaning frequency by more than half, and will just about double overall filter life. Still, if money is a problem, because my cyclone design has proven so efficient you don't need to clean the filters very often. This makes use of one Farr filter ample and saves the cost of having to buy two or more filters.
    
    Alternatively, the Donaldson Torit brand filters are the industry standard and far more available. These run typically about 226 square feet and also come in either 0.5 or finer cartridges. I personally started with a pair of the Torit 0.2-micron compatible cartridges with cleanout for my own system, but I pretty much had no other choice because my lung problems required me to use the best cartridges I could find. The advantage of two is of course less cleaning and less backpressure, but more cost. Using two also lets me flow the air through "backward" without worrying about the filters clogging quite as quickly.
    
    In either case, strangely the major filter suppliers really don't care for hobbyist business. My local Farr outlet totally declines to do any business at all. Likewise, my outlet for Donaldson Torit is www.buy-filter.com and they also no longer seem to have any interest at all in doing business with hobbyists. Tired of bent, damaged filters and poor service, I went looking for a supplier that could provide me either a Farr compatible or a Torit compatible, and found one (thanks Jack Diemer), Wynn Environmental. Dick and Rick who run that firm appreciate our business with good advice, support, service, and prices. Buying either a pair of their Farr 300 square foot 0.5 micron compatible filters (9E300BL) or their custom Donaldson Torit compatible 0.5-micron top quality filters with two open ends and making a filter stack then moving on.
    
    Alternatively, Farr in Ottawa, Canada appears to sell to the public. Farr Part# 211736-1 HemiPleat filters, for $215.00 EACH (Specs:~ 300ft², ~13" diameter by 34" long, ~ 99.4% efficiency at 0.5 microns, and ~1000 CFM at 0.5" SP). Camfill Farr, Old Innes Rd., Ottawa, Ont., Tel: 613-521-5555.

    

Frequently Asked Questions - Budget Blower

1. I live at 5800 feet altitude and am concerned about the air pressure requiring me to use a different impeller. Can I use the same 14” impeller that others use and get ample performance? No, you need a bigger impeller when at higher altitudes.
   
   Picking the right impeller is not that hard, but does take a little thought and work. You pick the impeller that will move the needed air when all your resistances are added up. A typical 2-car garage sized shop will have about 7” of resistance in its ducting. To that add 2.5” if you use my cyclone design or add 4.5” if you use one of the other hobbyist cyclones or a trash can separator lid. Now add 0.5” if you use a pair of the Torit style cartridge filters, 1” if you use just one Torit style filter, 0.75” if you use one Farr style filter, or 0.25” if you use a pair of the Farr style filters. So with my cyclone, pair of Farr compatible filters, and typical shop you would be at a static pressure requirement of 10”. From the Cincinnati Fan steel pressure blower altitude table we get a 1.25 adjustment factor at 6000 feet. We always round up to ensure ample capacity. Multiplying that 10” * 1.25 gives us a need for 12.5” of static pressure. Then looking at that same vendor’s following 3450 RPM fan table we see that the first impeller that will do the job with a 6” inlet is a 15 ½” x 5” tall backward curved impeller being run by a 3.37 horsepower motor. That becomes the impeller and motor size that you need to use at your altitude to provide 800 CFM at your larger machines. Although that is the actual draw on the motor during operation, getting a big heavy impeller like this up to speed requires at least a real 3.5 hp and preferably a 5 hp motor.

2. Bill, please help. I found the motor you recommended surplus for a great price, but have no clue how to wire it up. This is one of those that got me into trouble before. I used to just send people to the Leeson, Baldor or other appropriate motor wiring page, but most had trouble finding and applying the specific information. I then put on my web pages not only my motor wiring diagrams, but shared the circuit, building instructions, and parts list for the nice remote controlled switch that Jim Halbert designed and was kind enough to build for me. Without mincing any words one fellow electrified his cyclone, another melted the end off a screwdriver and a third tried to burn his house down. My attorney said I could be held liable and it was not a good idea for me to recommend anything except suggesting you follow the vendor instructions, adhere to your local codes, and work safely. If you look at the installation page it give specific instructions for properly wiring your Leeson motor directly from the vendor. This same page also give details on how to mount your cyclone inexpensively. Likewise you can go to Mark Goodall's excellent Motor Wiring Page to learn more about motor wiring.
   
   Please recognize we are working with dangerous power here so you need to ensure your work is safe and the results meet local code.

3. I got lucky and a friend found a surplus 11" steel impeller at work with tall 5" vanes. Can I use this impeller with that 2 hp Delta Motor, and what kind of performance should I expect? The short answer is maybe leaning toward yes, but you need to make a custom blower housing and carefully ensure with an amp meter that the unit does not over stress the motor on start up or when running.
   
   Anyhow, the blade height does make a difference but not nearly as much as in the case with a fluid. Air tends to be pretty limited in terms of how big of a vacuum you can generate. By that I mean waving a bigger paddle with the bottom closed quickly reaches a point of no return if air cannot get to that extra surface area. The result is you get some additional pressure and a little more volume but not a huge amount. There are some fan charts on the Cincinnati Fan site that might help you compute the performance, plus I have seen some with my searches through Google. Still, if you were to ask how well this will work I would make an educated guess:

   1. I would bet the performance would be similar to that of a 12" impeller, probably a little too small for a 2-car or larger sized shop, or a shop with any larger professional grade tools (see the CFM requirements table on the DC Basics page).

   2. I've only worked with one impeller like that and found that it worked well, but was so heavy that it pulled far too much motor amperage when being brought up to speed by a 2 hp Delta motor. I shifted over to my 3 hp and it worked fine.

4. I am going blind looking at your blower design. Does the groove for the metal motor mounting plate go on top or the bottom of the upper piece of plywood? I hope you realized that clicking on that picture gives you a full sized picture. On some browsers you will get a larger picture but not full sized until you also click on the orange square.
   
   The motor mount plate goes on top of the blower housing, not under the plywood. I squeezed that plate onto a piece of the same foam weather stripping I used on mine, then measured that depth and used it to set the depth of the groove. The result is my motor plate fits flush on top and is held in place with the big fender washers. For those with short motor shafts, you may want to inset that plate as far as you can. If you do so, then you need to also inset your fender washers so they hold the blower on tight.
   
   The reason for putting that groove on top, is you can take down the blower shroud and cyclone without having to remove the motor and blower.

5. You used the Delta 2 hp motor to power your airfoil. Can I use this same good quality motor that has exactly the same mounting face as the Leeson you recommend to power a 14" jet impeller? If so, why don’t you recommend this far less expensive motor? Yes, you can power the Jet 14" impeller with that Delta 2 hp motor, but you are pushing that motor right to its very limit. It takes a lot of current that is really hard on motors to bring a big heavy impeller up to speed. In my opinion doing this to the most heavily used motor in your shop does not make good sense and will wear out motors. That is why I instead recommend a compressor motor designed to start a heavy load and recommend a larger horsepower motor that will not struggle so hard.
   
   Still, with this motor costing a quarter as much, many choose to use them to power their cyclones. You need to use an amp meter to ensure this motor does not try to push so much air it burns up. In testing in my shop with ducting and all gates open, it drew too much amperage and would have quickly burned up if left to run that way for too long. You can regulate that airflow by closing down the inlet to the cyclone or the blower inlet. I put a blast gate about 6’ from the cyclone inlet in my main to regulate the airflow. Putting that gate at least 5’ from the cyclone inlet helps keep the airflow settled before it gets to the cyclone and kills fine dust separation with too much turbulence. With my most open run of all 6” ducting, this 10 amp rated motor drew 10.4 amps. That is too much and will eventually hurt the motor. I closed down that blast gate until the most open run was right at 10 amps. It looked like about a 5.25” opening. Overall airflow dropped to about 1200 CFM, but that is still ample to provide excellent dust collection. Running this with more than one gate open drew way too many amps, so using this motor requires care.
   
   Remember that the Jet impeller comes with an arbor that uses a metric sized shaft and relies on a bolt through the motor shaft plus setscrews to ensure it stays in place. You need to have a custom arbor made. Most motors do not have a threaded motor shaft, so your custom arbor becomes dependent upon a couple of setscrews to hold the impeller onto the shaft. They will do the job only if you use the special setscrews with the barbed tips that dig into the motor shaft. These screws must be replaced every time you loosen those screws.
   
   I've had one test impeller come loose on the shaft. The keyway let it slide straight down. What it did to my blower-housing bottom was about the same as dropping that housing on a moving table saw blade. The noise cost my dog a few years of life as well.

6. I have a 2 hp dust collector motor and was wondering if I can just add a 14” impeller? Most likely you need to make a blower housing because yours will either be too small or make terrible noises with the larger impeller. I think you should use a bigger motor (see above discussion on the Delta 2 hp motor). Generally when asked this question, unless you have a 3 hp dust collector I recommend selling your existing dust collector and using the money to help pay for a good motor and impeller then making my budget blower.

7. Should I use the Sheldon's material movement impeller or the Ed Morgano impeller instead of the Jet 14" impeller?
   
   Sheldon's no longer makes these impellers or sells to small shop woodworkers, so I recommend you use our impeller with the Leeson 5 hp motor unless you have the 20" diameter cyclone then I would recommend using our 16" diameter impeller. Both of these material movement impellers have a built in compression fit arbor that holds far better than having to make or modify the Jet arbor. The 7/8" standard arbor on our impeller is compatible with both the Delta and Leeson motors I recommend, but too large for the 5/8" shaft on the Harbor Freight motors or on many commercial motors 5 hp and larger that use a 1 1/8 or 1 1/4" motor shaft. Most get their impellers with a 7/8" arbor, but the gripping portion can be ordered with a 5/8", 7/8" or other sized arbor at an additional charge and delay in getting that part. The cost when considering the arbor for these impellers is actually less than the Jet impeller, and unlike the Jet these are professionally balanced top quality impellers, instead of just stamped units.


Now having major bragging rights, but has anyone seen my cat?

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