Hi. I wanted to build a small dust extractor
that was smaller than one of the big dust extractors
but not as powerful or loud as a shop vac.
Something where I just need to collect a little bit of dust.
Not so hard and you don't want something super loud
or consuming as much power as a shop vac does.
So, I built this thing. My small dust extractor.
Now building this thing has been a lot of experimentation.
So, in this video, I'm just gonna talk about
how I built the blower for this thing.
I bought this motor/blower unit from a surplus sale a long time ago.
And this has only got a 1/3 horsepower motor.
And it blows almost as hard as a shop vac.
So, I figured 1/3 horsepower should be enough.
But, I didn't want to use this unit here because
I have no idea where you could get another one of them.
So, really nobody else could reproduce this.
So, instead I used a 1/3 horsepower motor
that came out of a tile saw that I got out of the garbage.
New tile saw's can be had for as low as fifty dollars.
So, these motors are not that expensive.
So, this is running way too slow and drawing way too much current so
that motor's overloaded.
So, the reason this fan is overloaded is it's drawing too much air
and it has to accelerate a lot of air.
So, if I just block air flow into it
it'll speed up quite a lot.
If I put the fan in a round enclosure
it can spin up much faster.
And that's, pretty much full speed.
So, I have a primitive sort of rounding core here with a gap right there.
And the hole in the middle.
So, let's test this again.
So, this is not running full speed.
So, I'm still overloading that motor.
I have to shorten those fan blades a little bit more.
Because it just doesn't have enough power to turn that thing
when there's all the air flow in it.
For any sort of radial centrifugal type blower
the more air we have flowing in it, the harder it has to work.
So, let's plug this guy in.
And it's considerably above 360 watts.
Then stop the air
And now we're down to about 185 watts.
Less than half of what I had before.
The reason the blower needs more power when there's more air flow
is whenever new air flows in here
that has to be accelerated round and round and shot out here.
Whereas if I plug it up
the same air can just circulate around and around
and around. So there's much less work the blower has to do.
In the meantime, I have to sharpen these blades a little bit.
I kept experimenting with this blower and I kept shortening and shortening the blades.
Because I just didn't have enough power.
But then I didn't have enough pressure anymore so
with a sufficiently round enclosure and restricting the air flow
I could make the blades a little bit longer again.
So, I had to glue some pieces of wood on there.
I've been having a lot of difficulty because my motor is just not powerful.
And, I'm thinking this impeller may not be the most efficient.
For most fans of this type you have
an impeller of a bunch of curved blades
that is sandwiched between two smooth discs.
So, I've made this new impeller.
Which
fits into here, like so.
And, the blades curve away from the direction of rotation.
Which is how they always go for greater efficiency.
So, that way as the air moves out
some of the Coriolis forces actually cause it to be pushed out further.
And, we're putting a little bit less torque on the motor.
So, hopefully that will work.
Now, I've tried this out before.
But, just the centrifugal force caused it to warp a little bit
and rub against the sides here.
So, next I need to glue this disc on here.
And, hopefully that will prevent warpage. But then you can't see the blades anymore.
So, I've been getting some vibrations from this impeller.
So, I know it's not perfectly balanced.
And I figure the best way to balance this impeller
is I've got a marble that just barely doesn't fit through the hole in here.
And then to try to put this whole thing down on a block of wood.
And I can see that it tilts this way. This side's always lower.
So, I want to cut away a bit of wood from here.
Try to bring it so it sits level.
Well, I think that's as best as I'm gonna get it.
We're running at 450 watts.
Looks like this is working well. And it's blowing really hard.
Let me show you. See the sawdust pile?
This blows it away.
So, with the new impeller and the blower. The blower worked well enough.
And, then I focus on building the rest of the dust extractor.
The blower, on it's own blows quite hard.
Hard enough to suspend one of these marbles above the outlet.
I used a pitot tube to measure the air speed.
I got it 132 millimeters of water
which works out to about 46 meters per second
on the outlet. Or about 167 kilometers per hour.
That works out to about 55 liters per second
or 120 CFM of air.
If I completely block intake static suction is about 230 millimeters of water.
But the power consumption drops by about half.
The other main component of this dust extractor
is the centrifugal separator. Which is sort of a cross between
a thien baffle and a cyclone separator.
And that thing is interesting enough
that I'll make another video just about that.