Building a Bill Pentz's Designed Cyclone

I bought a Dust Collector (DC) a while back, it is a big unit, and while not new,
it sure works well at collecting the dust.

The problem is the filter bags do not work very well, there is a lot of very fine dust that gets by the bags,
I end up with a very fine talc like coating of dust EVERYWHERE.
This dust is the WORST kind of dust to be breathing in all the time.

The solution, after a lot of research on the net, is a cyclone.
If the cyclone is built correctly, then it should remove all the fine dust and provide a lot of suction at each tool
Partly to accomplish this I've run 6" pipe and flex hose to each machine, no reductions down to 4" as is usually done.

Cyclone Basics

In spite of what some would like us to believe, dust collection cyclones are simple tanks with no moving parts and have been used for dust separation for over seventy years. They are made up of just a few parts, an air inlet, an outer cylinder, an air outlet, and cone with dust chute that connects to a collection bin with flex hose. Dirty air comes in through an inlet and spins quickly around. This spinning throws the heavier particles outward to the cyclone walls. Airflow on the cyclone walls is slowed by friction. Particles get trapped in the slower moving air then gravity pulls them down. As the air continues to spin it slows and drops downward. The cone on the bottom of the cyclone forces that slowing air to keep the particles pressed tightly to the walls. Those particles continue to slide downward and eventually exit out a dust chute into the collection bin. The dust chute is sealed tightly to the bottom of the cyclone with no air leaks to stir up the collected dust. At a certain place inside the cyclone called a neutral point, the spinning clean air reverses direction and comes up through the center of the cyclone then exits through the cyclone outlet.

Although just about any cyclone design will separate the heavier particles, it takes quite a bit of work to build a design that will efficiently separate off most of the finest particles so they don't clog our filters. Any air turbulence from these parts will dramatically increase resistance and significantly reduce fine particle separation efficiency. A smooth inlet is needed to carefully start the air stream right on the side of the cyclone. The smaller the diameter of a cyclone, the faster the air must move and the better the separation. Likewise, the smaller the cyclone diameter the larger the blower needed to overcome the resistance. It takes more work to push air in smaller circles. Cyclones with longer cones provide better the fine material separation. Likewise, longer cones create more resistance because the air has to run more revolutions. You can compute a near ideal cone length for maximum separation efficiency based upon air speed, inlet, and cyclone diameter. Finally, the larger the cyclone outlet, the less resistance and slower the airflow making for much finer the separation.

(The above text was shamelessly copied from Mr. Pentz's website, if you are looking at learning about cyclones, or building one like I'm doing, there is no better resource I know of)

There is a company making Mr. Pentz's cyclone out of clear plastic, they are really cool
The company is called Clear Vue Cyclones, you can see a really cool video of the cyclone working by right clicking and selecting "Save As" from "THIS" link (the file is about 1.3 Mb)

Know that you know how a Cyclone works, I'll get into showing you what I've done to build one, as buying one from the US and having it shipped here would cost WAY too much money.

The first major hurdle I have it finding the galvanized sheet metal, I did find it at my favorite DIY center,
Joyful Honda, but the size is kind of small, about 3' x 6'.
This means that I'll have to make the cone part of the cyclone from two pieces of sheet metal, what a pain!

Here I have the sheet metal on the bench, with my tin snips and some rulers etc.

Something that I did that helped is to clamp a blocking board to the bench, this way the sheet metal could be pushed into the board and made sliding the snips forward much easier.

I need to make some templates to hold everything round while building the cyclone.
Here are the first circles I cut, they are 18", don't ask me why I did this, my cyclone is NOT an 18" unit!!

Using Mr. Pentz's advice, I roll the sheet metal over a 6" piece of PVC pipe, this is a very good way of making the sheet metal conform to the shape needed.

Here is the steel wrapped around the 18" templates.........Whoops, wrong sized templates!!!

Through careful forming I was able to get almost no gap at the joint,
this makes putting the main cylinder together much easier.

To stitch up the cylinder I've opted for using my MIG welder,
I'll drill holes and then button hole weld it.

The cone part of the cyclone has turned out to be the most difficult.
I had to use two pieces of sheet metal to get the size I needed, the lay out was a chore.

Here I am drawing the large arcs for the cone, I used a piece of plywood and some nails, worked well.

Lots of very precise measurements here, some serious head scratching but I got it done.

Here is the cyclone all welded up sitting on the upper cylinder, just to test the fit
(I know the upper unit is upside down!)

Next I made the outlet tube, on the right, and the dust chute, which goes at the very bottom of the cone

The next part I had to make is the inlet, it is not round, but rectangular in shape.

To make things easier, and as I know I will use it again and again, I made a sheet metal brake

Give Me A Brake <- if you click this link you can see the creation of this unit.

I'm now cutting and bending the tabs on the cone and the main cylinder, this took a lot of time and effort!

Here is the cone with all the tabs cut and bent, ready to join the main cylinder

Here you can see the tabs bent out. I used my Kline linesmen pliers, the worked very well

Now I have to join the two units. I put the template rings back into the main unit and the cone, I left the template ring in the cone about 1/4" proud, and the then put the template ring in the main unit about 1/4" into the cylinder, this way the template rings will line the cone and the main cylinder up (I hope!)

The tabs on the cone are slightly longer than the ones on the main cylinder, so when everything is lined up, I bent the longer tabs over the shorter ones, again I used the Kline pliers.

Looking up at the bent tabs, the ones on the left have been "tapped" over ,
while the ones on the right have not yet been tapped over.
I found that tapping with a medium sized hammer to be a very quick and easy way to do the second bend.

Here you can see on the left, the tabs have been tapped over, and on the right, they have been crimped.

The next thing to do is move this now LARGE unit to the work bench and take out the template rings, then I have to cut out and install the air ramp.

Now I have to install this air ramp and then do some more tin work, as I have to make a transition from the round &2 pipe to the rectangular inlet.

Because the motor and blower unit is so tall (50cm) I thought I would put the blower on the side,
but the two 45s together end up being taller than the motor blower unit!

I'm going to try to cut down the two 45s so that I can get the extra height I need.

The air ramp is important in the whole scheme of things, so I wanted to get it right,
but I tell you, so far I'm just about pulling my hair out!

I'm starting to think that I may have made a big boo boo here, maybe the "Inlet Tube" is not supposed to be all nice and square, but more of a squished rectangle?
Mr. Pentz's plans are not clear on this point (well to me they are not, but I could be missing something, would not be the first time!!).

I'm also thinking that the bent "tabs" on the air ramp may not be the best idea,
as they make the ramp hard to manipulate, bend and stretch.

In spots, there is as much as a 1/4" gap!
The cylinder is nice and round, the cone on the bottom is keeping it round,
and the outside ring is keeping the top nice and round too.

From inside the cone, looking from the top to the bottom,
from here it looks OK, but it is not....

Even with the slight gap at the top, there is still a lot of extra material......?

I really don't want to bug Bill Pentz about this, the guy seems stacked up with things to do, but I might just have to e-mail him about this.....

This pic is from the top down without the center air outlet cylinder in place.

The gray line is the caulking, I also spent an hour or so caulking the whole cyclone.

This is looking up through the cone, the center outlet cylinder is in place in this shot.

Here is the view from the top with the top inside and outside rings in place,
and the center outlet cylinder.

I cut down the flange area of these two 45s make the whole unit shorter, shorter by 20 Cm!!