This is a pretty simple DIY, but it lets you get the most circulation out of the least money. If you have some glue and tape laying around, you can have an adjustable blower that moves a stout amount of air for around $50.
Items List: (Name of vendor, price)
Lasko Blower model 4903 (Wal-Mart, $44.99)
Box cover, 6" (Ace, $2.39)
"Household Goop" glue (Either place)
Duct tape (Anywhere)
Tools needed:
Long Phillips head screwdriver
1 1/2" to 2" Hole saw (Size not critical)
Hacksaw, Drywall saw or Router
2. Opening the Shell
The object in question is the Stanley Blower, or squirrel cage blower or whatever. This one is actually made by Lasko but it's all the same. This is the little one they sell at Wal-Mart, model number 4903. They do make larger versions of this, but this DIY covers the smallest one, like this:
The process of adapting it to our use will apply to other similar blowers as well. This is not the same type of centrifugal fan as a Vortex, but these squirrel cage type fans can pull pretty well against static pressure (ducting.)
To begin with there are 3 screws that hold the two outer shell halves together. The first two are inside the feet that the blower sits on.
You can see where the assembler missed with the screw while driving it in.
To get to them, slide these rubber feet off to the sides. There is a bit of rubber cement holding them in, but a firm push with the thumbs will pop them off.
Like you see on the left, this reveals the two holes that we need to remove screws from.
Now remove the easily accessible third screw you can see holding the two outer shell halves together through the handle. (Not pictured.)
This is all you need to do to get the shell halves apart. At this point, you can skip to the 4- Hustling the Flow section, but if you want to see how to get the end cap off you can continue reading here.
In addition, you might find it useful to remove the blower wheel as detailed in the next section, to facilitate the modification we will make to it later.
3- Removing the end cap/outlets- For the Sake of Science!
There are 3 easily accessible screws holding the end cap with the outlets in it to the blower.
The final screw holding the end cap is actually under the blower wheel. Don't try to pry the end cap off yet.
The blower wheel needs to be removed to get that last screw- taking off the nut would be easy enough- but they put it on with red loctite.
The trick to red loctite is to back the nut off a little at a time, then tighten it again, over and over, each time blowing away the little red dust that chips off the threads. Take your time and keep backing it off little by little as you use the nut to clear the loctite out of the threads. Patience! The plastic blower wheel hole that mounts on the shaft has a flat that holds the shaft in place, but if you put gorilla torque on it you might damage it.
When you finally work it off, you can get to the last screw holding the end cap.
Why they couldn't move that 3/8" over where we could get to it, who knows.
Now you can look in there to your heart's content.
In here you can see the speed control and the outlets. No reason to mess with any of this really.
4- Hustling the Flow
This part is easy. We only need to block off the vents that once let air into the far side of the fan. This way the fan will spend all of its energy pulling air through the duct.
The first piece of tape easily covers the bottom of the slots.
The next piece closes off these slots completely. You can't say I never use duct tape- but I do try to avoid it.
Wouldn't be real DIY without a bit of duct tape anyway. The motor stays plenty cool, as we feed plenty of air into it.
5- Reinventing the Wheel. So easy a Cave Man could do it.
The only real internal modification needed is to open up a passage between the two halves of the blower wheel. Here it is removed from the motor.
http://forum.grasscity.com/photopost/data/2805/P50300371.JPG
The 2" hole saw was a perfect fit- I wouldn't go much bigger but you could use a bit smaller if it's what you have.
We needed to open a way for air to get into the far side of the turbine- these holes will do the trick. The wheel has three bolsters or gussets that neatly divide the wheel into three pie pieces. You can use this to place three holes evenly, effectively making it into a "Mag" wheel rather than a "Solid" type.
http://forum.grasscity.com/photopost/data/2805/P50300381.JPG
I positioned the holes by centering it left to right, while resting the hole saw against the blades of the wheel. Then I moved it 1/8" in toward the center and drilled the hole. Repeat twice more and the holes will be close enough to be balanced.
These holes effectively feed the side of the blower wheel that would have pulled air from the vents we covered.
http://forum.grasscity.com/photopost/data/2805/P50300401.JPG
Take some time to clean up the edges of the holes the best you can. I used my plastic knife but you could use sandpaper or a dremel maybe. If you didn't take the wheel out of the housing to drill these holes, make sure to blow out the blower (heh heh) very well to keep any drill shavings out of the motor.
The plastic of the wheel is pretty thick there at the center.
http://forum.grasscity.com/photopost/data/2805/P50300391.JPG
The wheel won't lose much strength from this, but the blower will work much better if you don't omit this step.
At this point we're done with interior stuff so stick the blower wheel back in and replace the nut, nice and snug.
http://forum.grasscity.com/photopost/data/2805/P50300411.JPG
No need to loctite again if you get it tight.
Put the case back together and slip the rubber feet back on. Now the blower looks pretty much new, except how you can see right to the motor now.
http://forum.grasscity.com/photopost/data/2805/P50300421.JPG
In this pic the fan is actually running, but the camera was fast enough to catch the wheel turning. You can see that plenty of air will be going by the motor for cooling.
6- In-Duct-ion
I thought for a long time and went to many stores trying to find a quick and easy duct flange. Turns out 6" flanges aren't that common. You can order them, bu this is about instant gratification.
http://forum.grasscity.com/photopost/data/2805/P5050059.JPG
This "valve box lid" came from Ace and is meant to plug a 6" hole. It's got little cleats on the other side that hold the duct- the size is perfect for 6" flex duct.
The Ace part number is 4026597 if you want to ask for it.
http://forum.grasscity.com/photopost/data/2805/P5050058.JPG
You can see the upc too.
I chose to use a router with a top bearing bit to quickly and easily make it open inside. It conveniently had a hole for me to start my cut!
http://forum.grasscity.com/photopost/data/2805/P5050061.JPG
You could accomplish the cutout with any of several saws, a jigsaw, hacksaw, etc. or get a buddy with a router to help you. Just get rid of the flat part inside, leaving the ring with a lip.
I cut it out rough the first time. This lets the router make an easy, smooth second cut. You could probably achieve similar results with a hammer.
http://forum.grasscity.com/photopost/data/2805/P5050063.JPG
Whatever you use, just hack out the middle. You can see the cleats that actually hold the duct really well, just snap 2-3 turns of the metal wire over each side of the flange, and it holds it snug and leak free. I gave a pretty good tug and it held. It's working fine on mine right now with no clamp, but a clamp is never a bad idea, just in case.
The router bit with its guide makes this part easy. For me, and other router owners, that is. . .
http://forum.grasscity.com/photopost/data/2805/P5050064.JPG
The next part is easy to make up for this.
7- Stick'Em Up!
Take that nifty flange you made, and the blower. Test fitting them shows we can glue the thing on and still preserve the rotational capability of the blower.
http://forum.grasscity.com/photopost/data/2805/P5050065.JPG
As long as we do a careful and complete glue job, the thing should serve us well for years to come.
These preperation steps are optional, but try to at least do the cleaning with a solvent part. Plastic is tough to bond, especially two different types like we have here. Instead, we're going to use a contact cement, (Household Goop) to join the pieces with its sheer stickyness.
http://forum.grasscity.com/photopost/data/2805/P5050067.JPG
One such step is to sand the area where the flange will mate to the blower, with 180 grit or so. Whatever you have. These little scratches actually increase the surface area and irregularity, aiding the grip of the glue.
Here I am doing the same thing with the flange.
http://forum.grasscity.com/photopost/data/2805/P5050066.JPG
By rubbing the flange mating-surface down on a piece of 180 grit sandpaper, it helps flatten and roughen it at the same time. This is always good practice when you have to rely on the adhesive strength of a glue, rather than the bonding strength.
Another important step is to clean the surfaces to be mated with a solvent, such as isopropyl alcohol.
http://forum.grasscity.com/photopost/data/2805/P5050068.JPG
This is also important when gluing. The combination of these techniques can greatly improve the strength of the adhesion. It would be a disaster to have this flange come off at the wrong time!
The next part is pretty obvious- glue it and stick it. Take care not to get too much on the inside, but be sure not to have any voids in the glue between mating surfaces.
http://forum.grasscity.com/photopost/data/2805/P5050069.JPG
Surface area is our friend here, so we need a continuous, unbroken layer of sealant between mating surfaces. That will also preclude any leaks.
This stuff dries clear and dries pretty fast, just hold it in place for a few seconds after you put it on and then let it sit for 30 minutes.
http://forum.grasscity.com/photopost/data/2805/P5050075.JPG
You can even run a fillet around the outer rim.
I was frankly quite surprised at how well this glue worked. The duct is well attached, with a good few square inches of surface area glued to the blower.
http://forum.grasscity.com/photopost/data/2805/P5050073.JPG
I gave it some pretty good tugs, and I trust it. Glue like this will also withstand any temperature this setup will normally see.
Now you have an adjustable speed, strong blower with handy duct flange.
http://forum.grasscity.com/photopost/data/2805/P5050076.JPG
The blower can still rotate to accommodate whatever direction you'd like it to exhaust in.
The duct fits right on. The valve box cover really is just the right size.
http://forum.grasscity.com/photopost/data/2805/P5050077.JPG
The cleats that originally held the cover in do a great job of holding the duct. I feel as long as you snap two or three turns of the wire over each cleat, the duct pretty much is secure. A zip tie would seal the deal though.
Speaking of the exhaust, it would be really simple to adapt the output back to 6" duct or to a carbon filter by using a register box like this.
http://forum.grasscity.com/photopost/data/2805/P5040009.JPG
Just stick it over the nozzle and tape it, you got instant 6" adapter.
Here is the blower in action in the attic. I simply set it on top of my original blower, a Panasonic Whisperline FV-20. I switched the duct connected to my light to this blower.
http://forum.grasscity.com/photopost/data/2805/P5050079.JPG
There was an immediate increase in airflow- I could tell right away it was a stronger blower.
8- Conclusion. Of High Blower Prices!
So I switched this out for my regular fan, a Panasonic Whisperline FV-20 whole-house air circulator. These two fans are essentially the same thing motor and blower wise, the difference lies mostly in the case. They are both essentially a squirrel cage fan, but the Panasonic is permanently set to low speed, and has a lot of insulation, both to make it quiet.
This blower can run flat out thanks to its on-board speed control and less restrictive design.
The original blower was rated at 240 CFM. I figure if it does 80% of that against 6 feet of duct, that's 200 CFM actual, probably. Just a guess, I have no way to measure.
With the new blower, I feel that I get about 15-25% more flow, (as measured with my calibrated hand, on the high setting) which means probably 240-250 actual cfm out of the new blower in the same situation.
The cost was about 2/5ths of the $127 Panasonic. It is a little louder, but the dull rushing sound doesn't penetrate and since mine runs in the attic I can not hear it downstairs except for at the intake.
When I close the closet door, I can hear and audibly larger inrush of air under the door. This blower pulls like a champ.
Basically, if absolute stealth is not required, this blower will do a fine job of cooling your HID light or small grow room. It can be adapted to a wide variety of situations and will do a great job for you, the carpet cleaning lady for our business uses this exact item to dry carpets, runing them for days on end and she says hers (she has 10) never break. Most modern fans will run for years, and these have a continuous duty motor suited to this use.
I'm getting ready to upgrade to 1000w soon and I have no worries that this little blower will keep me nice and cool. . . Freeing up my other blower to independently control room circulation, and the whole setup was less than one Vortex fan of equivalent CFM!
Thanks for looking everyone and please feel free to mention any improvements I can make to this DIY.
I hope it was clear and complete so folks can make their own low cost blowers!
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