airfoil blower.docx

8/11/2019 Airfoil Blower.docx

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Airfoil Blower

Table of Contents

(click on topic to go there)

A.CautionB. ForewordC. IntroductionD.Building Instructions

1. Blower Template2. Blower Top & Bottom3. Blower Holes

4.

Metal Sizes5.

Bolt Holes6. Mount Motor7. Completed Blower

E. TestingF. Frequently Asked Questions (FAQs)G.

Disclaimer

A.

Caution

The purpose of this site is to share what I have learned with otherwoodworkers about the hazards of wood dust and what I did to help

protect myself and my family. This particular page steps you throughthe process I used to build a blower. A blower is a powerful high-speeddevice that if you build wrong could cause serious injury or damage.Please read the following disclaimer.

B.

ForewordAlthough I very much like the idea of an almost twice as efficientimpeller, most cannot use an airfoil impeller safely and they are notreadily available. There are two major problems with airfoilimpellers. Unlike a self cleaning material handling impeller, airfoilimpellers have tops making them caged impellers. This means they can

build up wood shavings and stringy material. When they do this theycan become badly out of balance. Worse, typical airfoil impellers have

bad stalling and buffeting problems when the pressure gets over about6. A one car garage sized shop will have a maximum pressure of

about 7 even with very carefully chosen large ducting. I worked withPaul Payton of Sheldons engineering and came up with a center vane
http://billpentz.com/woodworking/cyclone/AirfoilBlower.cfm#Cautionhttp://billpentz.com/woodworking/cyclone/AirfoilBlower.cfm#Cautionhttp://billpentz.com/woodworking/cyclone/AirfoilBlower.cfm#Forewordhttp://billpentz.com/woodworking/cyclone/AirfoilBlower.cfm#Forewordhttp://billpentz.com/woodworking/cyclone/AirfoilBlower.cfm#Introductionhttp://billpentz.com/woodworking/cyclone/AirfoilBlower.cfm#Introductionhttp://billpentz.com/woodworking/cyclone/AirfoilBlower.cfm#BuildingInstructionshttp://billpentz.com/woodworking/cyclone/AirfoilBlower.cfm#BuildingInstructionshttp://billpentz.com/woodworking/cyclone/AirfoilBlower.cfm#BlowerTemplatehttp://billpentz.com/woodworking/cyclone/AirfoilBlower.cfm#BlowerTemplatehttp://billpentz.com/woodworking/cyclone/AirfoilBlower.cfm#BlowerTopNBottomhttp://billpentz.com/woodworking/cyclone/AirfoilBlower.cfm#BlowerTopNBottomhttp://billpentz.com/woodworking/cyclone/AirfoilBlower.cfm#BlowerHoleshttp://billpentz.com/woodworking/cyclone/AirfoilBlower.cfm#BlowerHoleshttp://billpentz.com/woodworking/cyclone/AirfoilBlower.cfm#MetalSizeshttp://billpentz.com/woodworking/cyclone/AirfoilBlower.cfm#MetalSizeshttp://billpentz.com/woodworking/cyclone/AirfoilBlower.cfm#BoltHoleshttp://billpentz.com/woodworking/cyclone/AirfoilBlower.cfm#BoltHoleshttp://billpentz.com/woodworking/cyclone/AirfoilBlower.cfm#MountMotorhttp://billpentz.com/woodworking/cyclone/AirfoilBlower.cfm#MountMotorhttp://billpentz.com/woodworking/cyclone/AirfoilBlower.cfm#CompletedBlowerhttp://billpentz.com/woodworking/cyclone/AirfoilBlower.cfm#CompletedBlowerhttp://billpentz.com/woodworking/cyclone/AirfoilBlower.cfm#Testinghttp://billpentz.com/woodworking/cyclone/AirfoilBlower.cfm#Testinghttp://billpentz.com/woodworking/cyclone/AirfoilBlower.cfm#FAQshttp://billpentz.com/woodworking/cyclone/AirfoilBlower.cfm#FAQshttp://billpentz.com/woodworking/cyclone/AirfoilBlower.cfm#Disclaimerhttp://billpentz.com/woodworking/cyclone/AirfoilBlower.cfm#Disclaimerhttp://billpentz.com/woodworking/cyclone/AirfoilBlower.cfm#Disclaimerhttp://billpentz.com/woodworking/cyclone/AirfoilBlower.cfm#FAQshttp://billpentz.com/woodworking/cyclone/AirfoilBlower.cfm#Testinghttp://billpentz.com/woodworking/cyclone/AirfoilBlower.cfm#CompletedBlowerhttp://billpentz.com/woodworking/cyclone/AirfoilBlower.cfm#MountMotorhttp://billpentz.com/woodworking/cyclone/AirfoilBlower.cfm#BoltHoleshttp://billpentz.com/woodworking/cyclone/AirfoilBlower.cfm#MetalSizeshttp://billpentz.com/woodworking/cyclone/AirfoilBlower.cfm#BlowerHoleshttp://billpentz.com/woodworking/cyclone/AirfoilBlower.cfm#BlowerTopNBottomhttp://billpentz.com/woodworking/cyclone/AirfoilBlower.cfm#BlowerTemplatehttp://billpentz.com/woodworking/cyclone/AirfoilBlower.cfm#BuildingInstructionshttp://billpentz.com/woodworking/cyclone/AirfoilBlower.cfm#Introductionhttp://billpentz.com/woodworking/cyclone/AirfoilBlower.cfm#Forewordhttp://billpentz.com/woodworking/cyclone/AirfoilBlower.cfm#Caution


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in the airfoil that keeps this impeller from stalling up to about 8. With

an average two car garage sized shop running about 10 of static

pressure, we cannot use an airfoil impeller in shops larger than aone car garage. When the airfoil impeller gets out of balance or

begins buffeting it can quickly ruin motor bearings and even cause

these impellers to explosively fly apart. Even if you meet these needs,unfortunately Sheldons Engineering, the firm I had making the custom

extra heavy duty airfoil impellers was sold and the new owners havediscontinued selling these units.

C.

Introduction

I did considerable homework on cyclones and dust collection that convincedme the key factors to effective dust collection were good tool hoods, efficientducting, a blower that moved ample air able to overcome the resistance of our

system static pressure, venting outside when the weather permits andotherwise venting inside into certified fine filters, and using a good cyclone. Istrongly recommend that you either build my cyclone design or buy a kit fromus because only the 5 hp small cyclone move ample air and none of the smallshop cyclone provide ample separation to work with good fine filters. Mostactually come with 10-micron filters which the vendors misrepresent as 1-micron filters. It is the 10-micron and finer dust which not only quickly clogsand ruins our filters, this same dust is well studied and the peer reviewedmedical studies are clear that this same sized dust is responsible for causingthe most long term damage to our respiratory systems. If this does not makegood sense, then please read myDust Collection Basicspages. My Dust

Collection Basics page covers much of what a hobbyist woodworker shouldknow about collecting the dust in their workshop. That Basics page explainsmuch of how airflow works and gives blower capabilities and tables for airrequirements thanks to some generous support by Chris O'Connor, APC SalesManager forAAF,a professional air engineering firm that designs industrialdust collection systems.

This page furthers my efforts with a very efficient blower design that you canbuild yourself quite inexpensively. In fact, the cost of a full cyclone systemusing this approach should be about the same as buying a 2-hp dust collectorthat will pick up the chips, but not protect your health.

D.

Requirements

You are welcome to go to my other pages for detailed explanations, but thebottom line is we need a blower that will not just move 1000 CFM, but willmove that 1000 CFM against the overhead resistance of our shops. We can get

by with just 450 CFM to our larger tools if we just want to do chipcollection meaning keep our floor clear of the sawdust and chips we would

otherwise sweep up with a broom. If we move 800 CFM to our larger tools

and we upgrade tool ports and hoods we will be able to meet the OSHA airquality standards. Unfortunately, even our own government says those OSHA
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standards are dated and the EPA says we should at least meet the five timestougher ACGIH standards. The medical community has long pushed for astandard that is fifty times tougher than the current OSHA standard and thismuch tougher standard is already the standard in Europe. I think it is foolish to

build a blower that moves less air than is needed to meet the higher standard.

My testing shows that if you don't start by upgrading your hoods, you arenot going to successfully collect the finest unhealthiest dust as it is made

no matter how big the blower.The issue is our blades, bits and cutters oftenlaunch the fine dust at over 100 miles an hour and even our biggest blowersrarely provide more than about 40 miles an hour air speed, so step one isfixing the hoods. Likewise, if you don't use at least 6" or larger ducting, pipes,and flex hose going right to each of our larger machines you will not move theneeded airflow. Smaller diameters will restrict the maximum cubic feet perminute (CFM) airflow that your system can support to around 450 CFM with4" duct and about 650 CFM with 5" duct. I can't believe so many

woodworkers get "tricked" as I was into buying a nice 2 or 3 hp dust collectorthen run it through an inefficient 4" flex hose that limits the CFM at theirmachines to around 450. Likewise, if you don't exhaust the air outside or usereally good low back pressure filters, you are not going to get rid of that finedust. By using a static pressure calculator that computes the overall resistancemy system built with 4 ducting computed out to have over 13 of resistance

and that resistance dropped to 8.5 with 6 ducting. Using my Dwyer 2010

Magnehelic gauge it tested at 7.5 for its longest run. This goes to show thatthe calculators only provide an estimate. Checking a material movement fantable said I could just get the 800 CFM I needed with a 2 HP 3450 RPM motorturning a 12 diameter impeller. Testing with my newBaldor 2 hp motor and12" Cincinnati Fan's straight bladed material movement impeller left me upset

because it tried to move too much air and over stressed the motor. My choiceswere 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.

I choked off the airflow just enough that my largest shortest run put the motorright at maximum amperage, then kept digging for other possible efficiencyimprovements. I slowly straightened out my ducting, replaced the rougherhoses, and got filters with more surface area, but my new cyclone with all thateffort still did not work as well at just basically collecting the dust as my prior

setup before all that expense and work. I then found a site that had efficiencyspreadsheets on the different types of blower impellers. That site showed thatthe 12" material movement impeller I purchased was only going to give me anefficiency rating of about 40% versus the high-end backward inclined (BI)

blowers and backward curved at closer to 60% and airfoil (AF) impellers atnear 80%. With either the backward inclined, backward curved, or airfoilimpeller, my 2-hp motor would do the job. Unfortunately, airfoil impellersneed a constant supply of air and can stall if the pressure goes over 7 creatingdestructive buffeting when they run out of air.

I then learned that there are some other good sources for impellers. Jet Tool's

Customer Service (800) 274-6848 sells replacement 11", 12", and 14" verygood quality, heavy duty backward curved impellers for very reasonable


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prices (each under $75 plus about $15 in shipping). You can go toJet Toolsand look up the DC-1100, DC-1200, or DC-1900 for part numbers. All ofthese need custom made arbors because the standard Jet bolt on motor arborsthat attach the impeller to the motor shaft are setup for the Jet tapered metricmotor shafts versus our standard motors with straight keyed shafts generally

with 7/8 diameter shafts. Please don't mess this up for the rest of us by failingto have your information already all figured out! I bought a 12" DC-1200impeller and it did not quite move the same as my larger and taller CincinnatiFan 12 impeller. With my cyclone adding extra resistance that 12 impeller

left me short of the 800 CFM I needed at my larger tools. I then bought a JetDC-1600 14 impeller and that worked like a champ, but needed a real 3 hp(or so called 5 hp compressor motor to turn it). That was a real problem for me

because my shop and home electrical service were already at maximum. Icould either power my larger tools or my dust collection motor, but not both.We need an impeller sized to overcome the extra resistance of a cyclone, plusis made from cast aluminum so it won't spark. Unfortunately they quit selling

these as separate items. Regardless of which of these ways you chose, you endup with serious bragging rights and a unit that you need to keep pets, smallchildren and wives away from! For this cyclone article/building plan I thoughtI'd try to find a good airfoil then use either the Cincinnati Fan or Jet impelleras a fallback if it was not successful.

Frankly, my airfoil experiment was a dismal failure. I purchased a total of fivedifferent airfoil impellers all sized just right to move the 800 to 1000 CFM Iwanted through my cyclone. All moved a ton of air until I hooked them up tomy cyclone and ducting. Then I had serious problems. All had severe stallingand chattering problems beginning at just over 5 of backpressure and by thetime I reached the 7.5 of pressure for my longest run, I was seriously in fear

my blower would self destruct from the terrible noise and vibration. I thoughtthere should be some way to get an airfoil that did not stall quite so early.

Paul Paton, P.Eng., with Sheldon's Engineering spent quite a bit of his timelistening to my concerns then helping me come up with a solution. We agreed

an airfoil impeller is NOT appropriate for dust collection systems that

have a high static pressure, ducting smaller than 6", or where at least one

blast gate is not always open, but felt a system could be built that wouldwork well with one. An airfoil needs a steady supply of air without too much

resistance or it stalls. It also requires regular cleaning or can get out ofbalance. Either stalling or an out of balance condition can cause destructivebuffeting. That can ruin motor bearings and cause an impeller to explode.Based on the numbers of hits on my web sites, over eighty five thousand in thesix months before I contacted him, Mr. Paton felt this was a viable market forhis firm and agreed to work with me. He came up with a way to modify hisfirm's standard airfoil impeller with extra vanes to minimize the buffeting

problems. By making it a 25-pound monster with special center vanes, hethought it would be less inclined to stall and the mass from this all steel unitwith thick base and huge steel arbor would minimize the buffeting. For myshop with its new larger ducting, dual minimal resistance filters, and efficient

cyclone this looked right for me. It promised to be an excellent solution forother hobbyists as well. I agreed to buy one for testing. He said his firm would
http://woodworking.jettools.com/Products.aspx?ByCat&cat=333122http://woodworking.jettools.com/Products.aspx?ByCat&cat=333122http://woodworking.jettools.com/Products.aspx?ByCat&cat=333122http://woodworking.jettools.com/Products.aspx?ByCat&cat=333122


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offer that specially modified impeller to those who built my cyclone design ata very attractive price. He agreed to sell at their quantity 100 price which isabout half of what other airfoil impellers of the same size cost withoutmodifications. I bought one, tested it with my 7.5 of resistance and it workedwell without the stalling and buffeting problems until the resistance went over

8. That means this is a poor solution for larger shops and for shopswhere you are not willing to regularly inspect and clean the impeller to

make sure it does not get out of balance.

My reason for wanting an airfoil impeller is of course that their performance isphenomenal. A 12" airfoil driven by only a 2 hp motor is rated at 1200 CFM at7"sp. It produces 1700 CFM at 4", 2000 CFM at 2", and 2250 CFM at 0". TheDC vendors would wrongly advertise these units as 2 hp and 2250 CFM at 7"static pressure. The problem with an airfoil is when they hit their peak

pressure that is all you get. It will not go higher if you restrict the flow like anormal fan will. This means that keeping the total system resistance as low as

possible is vital. Once you exceed that static pressure maximum the airfoilbegins to stall because the air begins to bounce from center to outside of thewheel causing potentially damaging buffeting. That means one blast gate muststay open at all times. This is one of the tradeoffs we have to make in order toget much better performance than other impeller types that are stable acrosstheir whole range of static pressures. Another trade off is these impellers willnot tolerate large material hits, only very fine dust so they MUST be used onthe clean side of a cyclone. And the final tradeoff is you have to periodicallyclean your impeller so it does not build up a cake of dust and get out of

balance. With my cyclone only generating a few ounces of dust out of thefilters for each full trashcan of sawdust and my doing limited hobbyistwoodworking, I put a note on my calendar to check it once a quarter. Afterusing it for a while I'll share what seems to be a more reasonable frequency.

The solution to ensuring that there is always enough airflow so theairfoil will not stall is to either built a trap that will open if the static

pressure gets too high or use what is known as a barometric dampeneras pictured here. This store bought unit is a touch pricey at about $55

but well worth it with the airfoils. I'm using a hinged trap door that liftsand then settles onto foam weather stripping. I added weight until italso barely lifted with one gate open, but opened wide with all gatesclosed. Glen S. Miranker shared that he purchased his unit made by:

Residential Control Systems Inc.

11460 Sunrise Gold Circle Suite ARancho Cordova, CA 95742
http://billpentz.com/woodworking/cyclone/images/BarometricDampener.jpg


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(916) 635-6784

While looking for my impeller I made up my mind to buy theinexpensive Harbor Freight motor that was on sale. To check their

sales click onHarbor Freightthen select the on sale link followed bymotors. Their heavy duty 1.15 service factor 3450 RPM compressormotor is the best choice available from them, but unless it is on sale itis better to buy fromElectric Motor Warehouse.My motor choicechanged when I stumbled across a huge closeout of new 2 hp Deltamotors and bought one off eBay. Unlike the big material handlingimpellers the airfoil is nearly twice as efficient so I could use a 2 hpinstead of needing at least a 3.5 hp motor to turn a 14" diametermaterial handling impeller. Just make sure whatever motor you get,that you accurately match the direction of rotation, shaft size, andkeyway size to your impeller order. Regardless, once I had the Delta

motor I ordered the impeller to fit on a 7/8" motor shaft with a 3/16"keyway. My Delta motor turns counter clockwise when looking at theend of the shaft with the motor behind and cannotbe reversed as theneeded leads are buried under the coils, so I had to make sure I orderedan impeller from Sheldon's Engineering in Canada that turned in thecorrect direction. Both arrived in great shape and I went to work

building a blower housing (shroud) to test this new impeller and newmotor combination.

I made this blower so the entire blower housing can slip off leaving theimpeller and motor still attached and hanging from vibration dampersfrom my ceiling. The motor and impeller are way too heavy for me totry to lift up and down, so I want them to get mounted and stay rightthere. With this configuration, a wooden sheet or metal plate supportsthe motor and impeller weight. I will attach my supports to that plateand my ceiling beams. The plate will actually hold the cyclone as well.MDF should be plenty strong for the blower top and bottom. The MDFcan also serve for the top of the cyclone, as it only has to carry theweight of the cyclone. I actually used some thick Melamine left overfrom another project instead of MDF.

E.

Building Instructions1. Blower Template

Start by making a blower template to route the grooves in

the blower top (motor) and bottom (cyclone) for the sheet

metal.a.

Calculate the size outlet wanted. Most 1.5 to 3 hpblowers use 5" circular outlets. If the outlet was a 5"pipe the outlet area would be 2.5*2.5*pi = 19.63 sq. in.and the square root of that is 4.43" to make a squareoutlet with the same area. Knowing my impeller with
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clearances makes the blower shroud 6" tall, any outletwidth bigger than 4.5" would do for me. Yours might bedifferent. Dividing 4.5" by pi sent me off looking for acylinder that was 1.43" in diameter. I had a new

pressure regulator sitting on my workbench that

measured out at 1.5". With that plus the roughly 3/8"more from using a router with collar to cut things out, Iwould have a plenty big enough outlet width.

b. I laid out the impeller width on my pattern on a piece of6mm Baltic birch plywood. It was left over frommaking one of myportable massage tables,but I like touse this material for templates because it is flat, strong,smooth, and does not have any voids.

c.

I then used double sided tape to stick down that gaugeto provide a cylinder to wind around and get thechanging radius needed to make a spiral. For that radiusI used glass reinforced strapping tape sticky side awayfrom the gauge. On the other end I taped a pencil thatwas held flat and upright by on an old tape roll. Thattape roll provided a nice flat base that kept the pencilvertical, so all I had to do was keep tension on as I wentaround to draw the spiral. I pre-wound the tape after

finding I got a much smoother circle when unwinding.With a little pressure on the gauge and pencil one time
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around left a nice perfect spiral.

d. A little work with my scroll saw got it cut out slightlyoversized except for the sharp angle that I took pains to

get right on. Some sanding and I ended up with a nearperfect spiral template to use for cutting my grooves!

2. Blower Top & Bottom

Now route the grooves in the top and bottom for the sheet

metal.

a.

Start by centering the template on the top and bottomwith all oriented just as they will be when assembled. If


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you look real close you will see that under the router Iextended the template right to the edge of my board.Remember to double check that the template outlet is

pointed in the right direction for your impeller.Backward inclined (BI) and airfoil (AF) impellers don't

work so well unless turning in the right direction. Idrilled a hole through the center and one at 6" inchesaway using a 1/4" bit through the template and both thetop and bottom. Those holes ensure the template sits inthe right place on both pieces to make perfect mirrorimages and will hold things stable for the carriage boltsthat whole the whole thing together later. I slipped acouple of threaded knobs through these holes and drewthem tight to hold the template firmly in place forrouting.

b.

With the template firmly bolted in place, carefully startrouting beginning with the blower outlet edge off theside of the board. I used a 1/8" bit set to a depth ofabout 3/16". With a small bit you have to go real slowand let the bit do the work. Trust me, my first one letthe smoke out and put me a day behind on this project

waiting for a store to open to go buy a replacement. (Forwhat it is worth, letting the smoke out is an electrical


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term that was used by early digital engineers. We allknew that all that fine wiring and stuff was really a ruse.Those chips worked on highly compressed smoke.When you let the smoke out they never worked again!)

c. Before taking it all apart I marked the ends of the pieces

and labeled each so they will not get turned aroundduring the machining. I also wrote bottom and top on

both faces of the template and matching top and bottomon my Melamine. Now route the other side making surethe template is correctly placed to make a perfect mirrorimage.

3. Blower Holes

Now make some holes for your blower impeller and your

blower inlet.1. Now center the impeller on where it will go double

checking its orientation.. I used a 1/8" clearance off theside of my impeller to the sheet metal groove, but

because the impeller has a raised base the picture makesit looks more like a 1/2" spacing!


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2. Getting the air inlet hole exactly over the impeller poseda little challenge, even with a centering hole goingthrough the top and bottom. The problem is the inletinto the impeller needs to sit at exactly 1/8" inside theimpeller with only 1/8" clearance. With my impeller

and motor mounted separately and not built onto theblower shroud. My solution was to first cut a shaft holein the top board that would let me lower the impellerdown flush. That allowed tracing around the impelleritself to make the cutout. Once the top cutout was done,

bolting the top and bottom boards together let me laythe impeller down well centered then trace the inletexactly.

3.

The inlet hole for an airfoil impeller needs to hold aflaring that puts the air 1/8" deep into the impeller foroptimum performance. It also needs to stay within 1/8"of the sides of the impeller inlet so almost all theincoming air goes right to the airfoils. Had I notcarefully drawn the blower inlet and positioning on my

piece in advance, it would have been near impossible tocenter this just right.


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For a blower that would go on a cyclone the inlet would

neck from a 9" diameter smoothly down into theimpeller. For testing this blower, I wanted to limit theairflow with the same 6" diameter ducting that will beused in my system and with quite a few people waitingfor some results, I made a simple inlet by flaring a pieceof 6" S&D PVC pipe that I worked over with my heatgun to open it up to be 1/4" less than the diameter of myinlet. Ideally this inlet should take on a hyperbolic shapefor optimum airflow with least resistance. For a normal

backward inclined or backward curved dust collectorimpeller, 1/2" clearance is ample by itself without

having to build a special inlet.


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Initially I recommended that this would be a piece that Iwould buy with the impeller, but have since found thatthese special inlets are very costly. I have made similar

parts easily enough without too much trouble.Truthfully, making a wooden mandrel with the right

shape on my lathe, then inserting about three inches of aPVC pipe segment into hot oil would soften it enoughto slip that mandrel in and squeeze all down to make a

perfect form. Alternatively, making that mandrel withmy router would be more difficult as I would have to

build it up from layers, but in my bit collection are acouple of nice curves that would work just fine. I alsohave access to a PVC plastic vacuum forming servicethat could make these up once I had a mandrel to use asa mold. The professional PVC formers use hotantifreeze to warm the larger sections of pipe, but I

would use hot oil because my heat gun is just notenough unless you do a very little at a time. I was in ahurry to get those results posted so did not spend thekind of time on mine I should have. The advantage ofthe PVC is by cutting just the right hole in the blower itfits nicely and locked in place with a little hot melt glue.


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Metal Sides

Next form the metal and put into the grooves. . To size the thickness of my metal I used a micrometer

on my two existing industrial blowers and found they

both were made from stamped 18 gauge steel so Idecided to use the same. The metal height had to be tallenough for the blower plus the depth of the grooves andenough clearance to keep the motor bolts from hittingthe impeller arbor bolts. For my airfoil impeller, I used1/2" clearance. I did have to go with multiple pieces

because I did not feel like paying for a 4' x 10' sheet. Icheated and had them cut right on at my metal shop ontheir big plate cutter. In hindsight, having three piecesactually worked in my favor as they were far easier towork with and bend. I did roll them lightly over a large

cylinder by hand to start setting their shape. To makethe sharp outlet bend I skipped the one-hour round tripto the campus shop and instead used just a little appliedforce (read hammer).

a. It took me a while to realize that I needed to carefullyroll the metal over a cylinder to get it to have just the

right curve. With lots of fooling and adjustment, Ifinally got it so that it would lay in the groove without


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much tension. I then flipped it over and double-checkedto make sure that was also true on the other side. When

both fit just right without having to force anything, Iinstalled the pieces.

Bolt Holes

Now make holes for the carriage bolts that hold the blower

halves together.

I used my compass and with some messing around laid out 6equally spaced holes around the outside of the groove. I then

bolted the pieces together and drilled matching holes for the


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carriage bolts.

Mount Motor

Now mount the motor..

I made the motor holes by making a "rubbing" templateof the face of the motor using graph paper with acarefully cut center. The center slipped over the motorshaft and made it easy to align that paper template to thetop piece. The template was taped to the top piece then


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holes were drilled.

a.

Because I am going to use this blower for some testingand will be taking it apart repeatedly until I get the holesizes just right, I made the motor and impeller to be ableto mount independent of the cyclone. Note you can see

the inlet sticking up in this picture so it will fit right


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into the impeller.

b.

I needed an oversized hole in the blower housing thatwill let me easily slip the housing on and off. This holeis big enough to let the motor and impeller hang fromtheir support while removing the cyclone withouthaving to lift the blower up and down. Allowing themotor and blower to hang independently also makes itmuch easier to install and to take off the cyclone for


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repairs or cleaning.

c.

The motor mounting board screws tightly to the motorface so there will be no air leak. It also bolts tightly tothe top of the blower. In my final configuration I'll putsome insulation between it and the top of the blower toensure no leak there as well.

Completed Blower


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Here is the completed blower with motor.

Testing. There were two concerns that I was testing with this

setup. The first was that we had appropriately sized theimpeller so it would not over stress the 2 hp Deltamotors. The second was to make sure that themodifications minimized any potential of stalling athigher static pressure loads that could damage theimpeller or motor.


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a. I've secured it in place and added a test pipe.

b. By slowly blocking the inlet I was finally able togenerate a little bit of stalling at about a 2" circularopening. As I restricted the airflow the motor currentdid decrease like the standard impellers do, but I limitedthe inlet tube to 6" to make sure my 2 hp did not try tomove so much air it burned itself up. Regardless, the

buffeting was minimal and did not seem appreciableeven with the inlet totally blocked. I do not think it will

be a problem provided those who use this unit minimizetheir static pressure and do not block the airflow totally.They should go with 6" ducting and none less than 4",

plus open large cartridge filters and always keeping one

blast gate open to avoid the buffeting.


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c. I did call for help as my cousin Phillip who is also anengineer joined us for Thanksgiving and we put him towork. My original measures on amperage were wrong

because my amp meter had a tired battery and had beendropped. What we found was that wide open using all

6" diameter ducting the most we could draw with thisimpeller was 8.5 amps. That amp reading says that I cansafely open the blower inlet as long as the cyclone staysconnected to the 6" ducting without concern about

burning up the motor.


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d.

Hooking up the Dwyer Magnehelic gauge showed 3.2"of water which translates to 7160.34 feet per minute(FPM) air velocity. Dividing 28.313 square inches (thesurface area of my 6" duct) by 144 square inches (thearea in one square foot of a duct in inches) times that


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7160 gave a 1407 CFM!

e.

The bottom line is this impeller is nothing short ofincredible. It provided more airflow by quite a bit overmy similar sized radial vaned impeller driven by anidentical motor. And it does so with less amperage!

Frequently Asked Questions

I'm a hobbyist with an insane job. I enjoy making things in wood asa form of stress relief. I just want a system that I can turn on when Ineed it, empty the collection barrel when it gets full and enjoy usingthe system while knowing I am protecting my family's and my lungs.Is this the right blower for me? Although I like the airfoil because itmoves far more air with minimum power making it ideal in my shop,these are no longer available, so I would recommend you use a littlelarger motor like the Leeson I recommend and buying a materialhandling impeller.

When I first built my cyclone I was out of circuit capacity. I either hadto use an airfoil or go with an impeller and motor too small to movethe air we know is needed for good fine dust collection. It was not

practical for me to make a huge investment in upgrading the power tomy home. If you have power problems similar to mine or just want the


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most efficient solution in terms of operating cost, the airfoil is the wayto go. It comes with a price. You not only have to find one of theseexpensive impellers, but also have to make an air trap that opens so theimpeller will not stall, must do regular inspections, and must do regularcleaning. If those do not suit your style of woodworking, then I

seriously recommend that you instead build my budget blower and usea larger motor.

What is the impeller part number and how do I order? I was not thesupplier, just another customer of Sheldons Engineering and they nolonger carry these special units. When they did the original impellerwas their model 1225 ULF. That is the impeller to go with a 2 hpmotor. They had a larger size to go with a 3 hp motor. You also need toensure that either your motor is reversible or you get an impellerdesigned to match the rotation of your motor. Additionally, you needto make sure they include a compression arbor that matches yourmotor shaft size.

I'm confused because from your picture I can see that this is aclockwise turning impeller, but the motor you chose says it is clearly acounter clockwise motor that the vendor says cannot be reversed indirection? You are correct. You cannot reverse that motor's directioneasily. Unfortunately, there is plenty of room for confusion on thedirection of rotation. Impeller makers determine rotation direction thesame way that machinists do. They consider drill bits as right handedor clockwise turning. Conversely, some motor makers use two

opposite standards for determining the direction of rotation. Some lookat the shaft from the motor side and some from the end of the shaftwith the motor behind. The Delta 2 hp motor when looking at the shaftwith the motor behind turns counter clockwise. Because many newermotors, including that Delta, CANNOTbe reversed, you need to becareful in letting Sheldon's Engineering know which way your motorturns. Telling them that it is for one of my setups with the Delta isimportant.

How long to get your impeller? It took about three weeks to get the

impeller made, balanced, and delivered. I do know they have quite afew of these now in progress, so you need to ask what the schedule iswhen you order.

Any other impeller ordering concerns? Other than they are nolonger available?

Hey! I called about buying one of those specially shaped inlets andthey charge a fortune for them! How did you make yours? I used a heatgun, some thick gloves and built mine outside with a fan blowing thedangerous vapors away. It took a lot of fussing and was a pain, but itdid come out pretty well. I had no idea they were all that expensive.Sorry! If I was to go into production on these, I would turn a mandrel


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on my lathe just the right size and use a couple of heat guns at once tomake it a lot easier.

What did the motor cost, from which firm, why did you pick thatmotor? I wanted a good heavy duty motor that could run all day

without a problem. In motor terms this meant I wanted one that had a1.0 or better service factor (meaning can run 100% of the time at rated

power). I also wanted quality without paying too much. I've had manyyears of good service from Delta motors made by Marathon. When Isaw a vendor had purchased many new surplus 2 hp Delta motors andwas selling them on EBAY with shipping prepaid, I did a little morehomework, then bought one. I bought from eBay from Eric(TheGoodMember). When he sold out of these motors, I did not lookfor a new supplier because by then I had upgraded my electricalservice and wanted a real 5 hp turning a 15 or larger material handling

impeller. This is in my opinion represents the minimum to moveenough air to meet the medical air quality recommendations which arenow the European Union standard. them.

How did you test this blower? When? My cousin and I finished ourtesting of the airfoil on Friday, November 29th, 2002. We followed theDwyer Magnehelic gauge recommendations to setup our test bench,mount the pitot in the right place, and set the proper length ofrestrictive ducting. We double checked our gauges and work. We useda Dwyer Instruments 4015 model Magnehelic gauge with a Dwyer166-6 pitot tube for measuring the pressure and computing the air

flows.

What were your test results? With an extended 6" pipe in place tolimit airflow sized in length to meet the test parameters, thisimpeller/blower measured at 3.2" of water static pressure. After goingthrough the Dwyer formulas and cross checking this comes out to awhopping 7160.34 feet per minute (FPM) airflow. Multiplying by theduct size in square inches divided by 144 square inches gave a real1407 cubic feet per minute (CFM) at whatever we connect this to.Because I used a centerline single point of measure, the result needs

stepped down by 10%.

What amperage did the motor draw? My original amperagemeasurement was just over 10 amps, but my cousin found a problemwith my meter from being dropped that we fixed and checked with asecond meter. The actual amperage came in at 8.4 amps.

Why did you check the motor amperage? Pressure blowers do themost work when moving the most air. When a blower gets too muchair, you can easily over-stress the motor and cause it to overheat anddie. Frankly, in helping to review some recent magazine testing Idiscovered that a well known cyclone vendor had their units testedwith a gravely oversized cyclone and blower inlet. This will move lots


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more air, but caused at least three of their motors to burn up during thatmagazine testing. That is what we tested with the amp meter and usingstandard 6 test duct. We wanted to ensure the actual current it drew

did not exceed the motor's designed runtime rating located on themotor plate. We also wanted a real number that others could expect to

get rather than some pie in the sky advertising hype that only leads todisappointment. The results of that test showed we can run this motorall day long moving lots of air while driving this big impeller without a

problem of drawing too much current or overheating. Because theimpeller is so heavy and starts fully loaded, it does draw a lot ofamperage on startup, but now that I've run this for almost a year, it hasnot been a problem.

Why did you make a big deal out of the airflow you got which isnot much better than the 2 horsepower inexpensive dust collector I just

bought? This is not a hill to die on! Hobbyist suppliers can claimanything 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.My testing found most cyclone and blower vendors sell systems thatget about half their advertised maximum airflows. Even a few of thevendor sites say to figure you are going to only get about half of theclaimed airflow. The advantage of this unit is it produces a real flowunder real working conditions, and does so through increasedefficiency.

What were the limits again and why can't I use an airfoil with my

existing all 4" ducting setup? Using 4" ducting limits the airflow at thepressures we get from airfoil or dust collector blowers to around 450CFM and makes for a much higher resistance. Typically, a shop

plumbed with 4" ducting needs 12" or more of static pressure to moveenough air to pull in the fine dust at the source before it gets launchedinto your shop. All airfoil impellers have a very narrow range of static

pressure that they work well within before they begin to stall. Thisparticular airfoil impeller with its special design can handle up to about8". Although far better than most that stall around 6 of pressure that isstill way too little if your system needs 12" or more. As soon as theresistance of your ducting, cyclone, filters, etc. goes too high, the

airfoil stalls and begins to chatter as the air bounces around the center.Too much of that can ruin the impeller and the motor bearings. Toavoid this problem we need to only use the airfoils with shops thatgenerated 7" or less total static pressure measured in water columninches.

What are the rules to maintain this kind of impeller? Although Iprovided a ducting resistance calculator, the bottom line here is youneed to follow a few rules to ensure the safety and longevity of yourimpeller and motor:


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. Use an efficient cyclone placed before the impeller. Placing theimpeller before will let the sawdust go through the impeller andthese were never designed to handle hits nor are they selfcleaning;

a.

Use all large 6 ducting and ducting runs with minimalresistance;

b. Use at least one five foot long run before the cyclone. This willadd enough resistance so the blower does not try to move toomuch air;

c. Keep the equivalent of at least one 6" duct open at all times;

d. Use large minimal resistance filters;

e. Keep your filters clean enough that they don't create too muchback pressure;

f.

Keep an eye on the overall pressure/amperage of your systemto make sure it is working efficiently.

Will this blower support multiple blast gates open at once? I onlybuilt it for one, but depending upon the size of your ducting, what you

want to do, on and on, you might be able to get enough airflow to runtwo blast gates at once. In fact, if you only have a small one open, youreally should open a larger one at the same time to make sure you keepup ample airflow.

From my perspective, your blower looks good, but will it workwith a real system in my larger three-car garage sized shop?No. Eventhe larger airfoil will not be able to overcome the static pressure insuch a large shop. Also, there is a lot more to a system than just the

blower. For this blower to work, it needs a very efficient cyclone,minimal resistance air filters, good hoods, and a sound ducting design.

I think my system using my cyclone, all large 6" ducts, only 6" flexhoses, and a set of Torit filters keeps my personal system well underthe 7" to 8" of static pressure that will cause problems with this blower.This gives me the ability to take care of the dust collection at themachine sources in a pretty good sized shop (large 3 car garage). Itgives me the 800+ CFM at each of my large machines and 4000+ FPMairspeed needed to get rid of that dust.

Which filters did you use in your setup? The filters I purchasedwere from directly from the Donaldson-Torit retail outlet on line. My

set of four 0.2 Donaldson-Torit filters have the advantage of being allpolyester, but cost me double what the poly paper blended filters cost.


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Two came with metal caps and two with plastic caps. The plastic waseasier to work with. All had both ends open. The cost on these filterswas high and because I did was not a commercial firm buying multiplefilters, there were some shipping damage and high shipping costs.Donaldson-Torit has since worked through those issues.

Meanwhile, when it came time to replace my filters I shifted over toanother supplier. I've had great service and support with excellent

prices on both filters and flex hose fromWynn Environmental thatJack Diemer found and referred me to. Also, make sure you check outyour local suppliers. Many are now using a single 300 square Farrcompatible filter from Wynn Environmental instead of the two Toritcompatible units. I think that if you can afford it, you should do likeme and buy a pair of the Farr compatibles filters would give far morelife, better filtering, and be an overall better value.

I've also recently heard of good service and pricing from Filter Mart onthe all poly Torit compatible filters like I first used. You name yourown price.

Money is tight and I would like to use just one Farr filter as someof the guys have been doing instead of the two Torit units you used.Would that work equally well, and do you know which Farr filter to

buy? Do you have any other suggestions?

. My friend Alan used a single pleated Farr cartridgefilter and it works well for him. He bought the Farrmodel 125154-005 from MPW Filtration (picturedabove) which has since been sold to CLARCOR Inc.

Similar filters are available from a variety of sources.The dimensions are: 12.75 in. O.D.; 8.375 in. I.D.; 34
http://www.wynnenv.com/http://www.wynnenv.com/http://www.wynnenv.com/http://www.wynnenv.com/


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in. long; 284 sq. ft. area; 80/20 blend filter, and 0.5micron filtering. You can order Farr compatible filtersfrom Wynn Environmental for less cost.

a.

Another option is MSC Direct carries the DonalsonTorit dust collector cartridge filters for similar pricing

and reasonable shipping.

The filters MSC sells are made by Filtration Group ofJoliet, Illinois, model number is 80002.

b. Finally, a few have written me that they have gottennice sub 1 micron filters for free or almost no cost fromlarge truck depots and professional woodworking shops.By getting the all spun bond polyester filters, they canwash them up and end up with a pretty nice unit atminimal or no cost.

Do you have a simple drawing giving a cross section through thecenter of the assembled blower? Maybe, this picture might help. Itshows how I mounted the blower on a separate board that then mountson top of the top of the blower shroud. I did this to get thesizing/spacing right and to let me make the blower-housing mountseparately from the motor and impeller.


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Ok now you have confused me good. First, you said the bottom ofyour blower is going to mount on the cyclone outlet. The cycloneoutlet from your plan is D/2 or 9" for an 18" cyclone. Why did youmake it only 6" large? In terms of the bottom of my blower, meaningthe part opposite the motor that mounts on the cyclone, you need to

remember that my goal was to quickly get something ready for testing.I wanted to be able to mate to a 6" ID piece of S&D PVC. To use myDwyer magnehelic gauge I needed a piece that was at least 60" longwith a hole 9" from the face of the blower. From my measurements, Iconcluded that as long as you have at least a 60" long piece of pipeholding the airflow from getting out of control, you can make thatopening as large or small as you would like. Mine ended up being thesize of 6" ID S&D PVC that I let hang out about 4" to mate with mytest pipe. I will change that sizing if I decide to actually mount that

blower on a cyclone. I may make a little smaller metal based case,simply because I have a room problem where that big blower will be in

the way of my garage door.

Assuming there is some good reason for your having only a 6"blower inlet, what size blower inlet should I make for my blower? My6" inlet was to fit on a test pipe to check out the blower to make sure itworked before recommending it for others to try. I think the easiest and

best thing to do would be to make the blower inlet a nicely flared entrythat reduces down from the 9" (or 10" if you build a 20" diametercyclone). Working over a $5 tapered HVAC reducer that goes from10" to 8" to make it a 9" to 8" would work and not be too difficult to

do. I might use my roller to create the flare.

You say you made the steel for the blower sides from metal thatwas 6" tall. I bought an airfoil impeller from that same firm for my 3hp motor and 6" is too short. Why? My impeller is not a full height andwith each of these units being custom made, there are bound to besome small differences in sizing. Plus, if you told them you were usinga 3 hp motor, they probably made you a full height impeller. Since Ican't tell the exact sizes for your impeller, you need to take the time tofigure out what will work best for yourself. Wish I could help more,

but that is just not possible from here.

I am confused by one of your photos. You clearly show one of thesandwich pieces with a 3" hole yet later I see one with a big hole andthe other with about a 6" hole for PVC. Why did you make the 3"hole? I did that so the impeller would sit down flush instead of beingheld up on its tall arbor. I wanted to use the actual impeller to draw thesized hole I needed to make the blower shroud removable. That savedhaving to measure and guess and let me set my 1/8" clearance right on.Also, I wanted my actual result to be dead on for both the top and

bottom so I could hold the 1/8" clearance on the inlet.


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I like the idea of mounting the motor and impeller, then being ableto remove the blower housing and cyclone without having to lift upthat heavy motor. What kind of vibration dampeners are you using tosupport that weight? I found some nice rubber dampeners at a surplusstore, four for $3. I'm going to try and make them do. If not, on my

previous cyclone I used four I got from Granger's sized to hold about1/3 of the weight of the motor, blower, and cyclone combined.

I've been banging my head into the wall for an hour. How did youever come up with the calculation to get your inlet to sit exactly 1/8"inside your airfoil impeller? *Laughing* I had that same problem andwas not able to figure that out by measuring as I had too manyvariables including a little dampness that had swelled portions of myMelamine. So what I did was cheat by making the inlet hole a verytight fit on the PVC and putting the flared piece of PVC through beforeI bolted the sandwich together. Once it was bolted together I gentlyworked the PVC down and by feeling through the hole was able to getit positioned just right, then locked it in place with hot melt glue tohold it still and seal the joint. Had I not made that sacrifice 3" hole youasked about earlier, I would never had gotten the inlet centered towithin 1/8".

I see your Cyclone Plan page lets you use an Excel spreadsheet tobuild the size cyclone you want. What size would be best with thissized impeller? Although you could use an 18" diameter cyclone, youwould 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. Ibuilt an 18" because that is all the room I have with enough clearancefor my garage door.

I have planed on using 8" diameter pipe connected to the cartridgefilters and the blower outlet. Is there any problem with this?Nope, butyou would have less noise if you followed Larry Adcock's(WoodSucker designer) suggestion and used insulated HVAC ductinginstead. Plus that would be much easier to install.

I see that you used regular steel for your blower instead of thegalvanized stuff you recommend on the cyclone. Does it matter? Yes. Ialso have to watch my pennies, so buy my metal from Blue CollarSupply, a great surplus shop in Sacramento. They did not haveanything galvanized in the size and thickness I wanted, so I got metalthat was not plated and plan on doing some serious painting withepoxy appliance finish because the wood coming in hits hard enoughthat it releases water and generates heat. Instant rust!

Hope this covers your questions.

bill


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Disclaimer

The drawings, procedures and words shared on these pages are for informationonly. Your actions are your responsibility - VERIFY and CHECKinformation out before proceeding, and don't attempt anything without therequired skills. Although I've taken every care to ensure what I have done and

presented is safe, dust collection equipment uses electrical components andblowers that when improperly built, used, or maintained may cause seriousinjury or even death, so USE THIS INFORMATION AT YOUR OWNRISK!At the same time, unless you as a woodworker provide appropriate

protections for the fine wood dust you make, you put your health, the health ofthose close to you, and even the health of your pets at risk. Long termexposure to fine wood dust eventually harms most woodworkers. Please takethe time to protect yourself and those close to you. HIRE APROFESSIONAL ENGINEERto design, specify, test, and certify

performance of any dust collection system if you have a commercial or anindustrial application, allergies, other medical problems, people working foryou, a large shop, work with hazardous materials, or are subject to regulatoryoversight. Neither I (Bill Pentz) nor any other references or links on these

pages will accept any liability for any damages or injury caused to people orproperty from the using of this information or from any associated links. Noclaims are expressed or implied as to the safety, usefulness, or accuracy of thisinformation.

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