A different take on Cyclones

[PaulS]

In the october edition of Australian Woodworker (isn't it still September!!) There was an article about building your own cyclone. What liked about this was that it seemed quite an easy thing to make.

Here is a picture...

But a question for all you cyclone experts...

I was puzzled that the intake into the cyclone is at the bottom of the cyclone, rather than at the top, which makes me wonder how the dust would ever get into the bottom bag??

[barnsey]

I agree Paul - but the idea intrigues me. Don't see why I can't modify the extractor top half to achieve the cyclone effect then duct the "clean air" out side and I would think that I would suffer less losses compared to having two units to do the same job.

Worth a try I reckon!

Jamie

[Sturdee]

Paul,

I haven't seen the article but from the picture it does not look like a cyclone.

It looks like an ordinary 2 bag D/C except that the top bag has been replaced with a contraption that blows the unfiltered air to the outside. Would need to read the article to see if it is worthwile or effective.

Peter.

[PaulS]

Peter,

I agree it is isn't the normal looking cyclone. But the guy says it works - he only gets some dust going to the outlet during extremely heavy use (4-5 times per year). I guess the question is what is extremely heavy use?

Any way he says he has fitted a fine spray garden mister to the end of the outlet pipe so that any dust that does escape is turned into a slurry.

Paul

[Sturdee]

Paul,



I guess the question is what is extremely heavy use?


Yes. It depends on what use and what machines. I'll try to get hold of the article and have a look at it.

Ofcourse, it is better to put the whole lot outside the workshop in a attached lean to ( or in my case under the house which is vented to the ouside ) with an on/of switch in the workshop.

Peter.

[BigPop]

Just read the article myself and from what I can see it is not a 'true cylcone' as such. The unit operates like a normal bagged dust extractor but instead of using the the bags for filtering the dust and also restricting airflow both bags now trap the majority of the dust and the top tube is an exhaust tube and allows the finer particles of dust to be taken outside the workshop where it mixes with water before going into the atmosphere.

[troutface]

I have set up a cheapie using 40mm pvc as a main line, 40mm elbows, 20mm flex water pipe from the machines (couldn't get 25mm at Bunnings), some home made reducers (40mm -> 20mmm), an old vacuum cleaner and a 200ltr plastic drum. I needed to service a table saw, router table and sander, as well using a valet-type general vacuum head for quick clean up of shavings and the usual crud we collect in workshops.
I have a shelter outside for the unit and ran the main line inside by cutting a 50mm hole in the colour bond wall. Nice and quiet and less clutter. The flex plugs into the main line from any machine, and draws dust through the main into the lid of the drum. I set the 'draw in' line at the edge of the lid and angled it to shoot the dust along the side of the drum. This causes a vortex, with the dust spiralling down to the bottom along the walls of the drum. No funnels needed.
The outlet pipe from the drum to the vacuum cleaner is centered in the lid. When operating, the lid is sucked onto the drum by the vacuum. Only very fine dust goes into the vacuum bag as the rest is sent to the bottom. Since setting it up, I have collected 150 ltr of dust and shavings, but less than handful of fine dust is in the vaccuum cleaner bag! I empty the drum onto the garden to deter snails from the vegies. No CCA pine or other nasties are used in the shop.
I quickly learnt that anything that interrupts the flow will clog the line - particurly larger shavings or splintering from the router table - so 45 degree elbows are preferable to 90's for pick up points.
costs were $20 drum, $34 40mm pipe and fittings, $20 for 20mm flex and a discarded vac frm a mate!

[barnsey]

Just as a matter of interest this subject has been beaten to death on this forum on many occasions. I for one am a believer that I should be able to get an acceptable result by shortcutting SOME of the rules :rolleyes:

However to do that you need to go and read the rules according to BILL (Pentz). He had to get serious or his passion of woodworking was going to kill him :eek: :eek:

As he says, "It's not the dust you can see that's the problem" :eek:

IMHO a lot of what people try to do is an absolute waste of time. :p

In the end I suppose it is a case of different courses for different horses. If you are happy enough to win the Mt Isa Cup - great - but don't expect the money a Melbourne Cup Winner gets :D :D :D

[snow]

I guess like the rest who have contributed to this thread I had my doubts as to the effectivness of the cyclone built in the Nov AW mag. Anyway I wanted to make some changes to my system because I was sick and tired of the useless bag concept (too much fine dust for my liking). Previously I had put in 150mm mainlines with 100mm to each machine and wanted something better to complement the ducting.

I found some spare time over Christmas and came up with the variation that can be seen in the pics attached. The cone is easy to make as some nice individual in Holland has put the cone formulas into an easy to use spreadsheet (http://www.red-bag.nl/). Some pretty basic metal work and the job was done.

Ah, but I hear you ask, does the damn thing work though? Absolutely. There is just a very small amount of fine dust expelled. If this becomes an issue I will build an external filter box or may consider the water mist option.

Comments welcome

Snow

[DaveInOz]

Snow,

How do you generate the cyclone/vortex when you feed from the bottom of the funnel?
I'm happy that it works I was just wondering how.

[snow]

Dave,

I'm not really sure, but here is what I think is happening.

The cyclone is being fed from the bottom and most of the separation occurs as part of the existing housing arrangement. Because the exhaust outlet is about half way up the cone the air and dust is propelled (swirlilng) upward. The heavier dust is flung to the outside of the cone while the air escapes out the exhaust outlet. As the dust volume on the cone walls increases it slides down to be caught up in the central fan vortex. Some of the dust will head down to the main blue drum the rest will go for another trip around the cone. This continues until the unit is turned off, at which time the whole lot ends up in the blue drum.

As I said the above is my take on the process. If anyone who has more experience or skill (mine is limited) would like to offer an alternative I would like to hear it.

Snow

[Al Burdon]

The cyclone separator uses a very simple principle for separation GRAVITY
As you are already aware we use high volume blowers to move air from one part of the work shop to another and use this air flow to move dust as well.

If you change the direction of the air flow some dust follows but heavier particles resist the change (you will hear the heavier stuff rattle down the ducting.) The simple dust extracter with the bag relies on the heavier dust to drop into the lower bag and the upper bag to filter the dust from the air stream.

The function of the cyclone is to spin the air this centifugal force increases the gravitational effect and improving separation( extraction of dust from air stream) forcing the heavy particles outward as the air exit point is in the centre of the unit only the lightest of dust prticles can be carried over. As the air has to change direction significantly to exit there should be very little carry over.

The cyclone will work in both the push mode (like snow's unit) or in the suck mode as per the unit I have built. The only difference with these is the efficiency of the air stream.

This separation method is used quite extensively for liquids as well.

So in summary the cyclone is for increasing the separation effect and the fan is for creating the air stream to move the dust.

[Taffy]

We don't need to BUILD cyclones in Queensland,

We just wait for January then they are free. ;)

Taffy

[Al Burdon]

Yes and they separate the dust from the workshop and the house and the street and the flora and fauna. A little too efficiently maybe

:D