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Whisked away in a cyclone (dust separator style)

You could call it getting “horribly sidetracked”, “cascading project proliferation” or “autonomous task sprawl”.  But on the other hand one could just as easily describe it as being gripped by a fortuitously unplanned and fascinating problem.

The oak double doors have been on the go for a while now.  In their process we also seem to be slowly equipping the workshop with what we need to do a good job of it.  For me, each new tool is a whole world of excitement and learning – as I don’t seem capable of just buying something without doing a whole lot of research and understanding it.  And if I can think up some ways to make, improve, modify, or find a broken one to repair, all for the good.

So I just thought I would share some of the latest diversions, oh I mean extra projects.

Aside from the plethora of wooden jigs and the like for the router, one of the more recent and most exciting additions has been a second hand bandsaw.   I had been considering different bandsaws for over a year, so it’s fair to say I didn’t rush into it. Hover the mouse over to check it out.

It is a five year old Electra Beckum (is it just coincidence or are all my favourite things originating in Germany these days?), 30cm (12″) depth of cut.  Coming from the far reaches of e-bay, this was relatively cheap, costing us about ¼ of the RRP. It has multiple speeds for different materials, is of sheet steel construction with a cast iron table (as opposed to the all cast iron monsters), and came with one fairly naff looking blade and no guide fence.

Initial impressions:

  • Oh my word it is loud!  I thought decent bandsaws ran whisper quiet.
  • It can beast its way through the big thick oak posts I salvaged from the council workers.
  • It makes a lot of dust.
  • The cast iron table has quite a lot of surface rust – that shall be changed.
  • It is a nice size – not too big, not too small.
  • Noise and dust! Must reduce.

Ok I was well pleased, I have a nice bandsaw after all – thrown into the bargain I now get to learn lots about acoustics; insulation; dust particulate control; filtration theory; belts and pulley selection and balancing; variable frequency motor speed control systems, and probably a whole load more I can’t remember just now.

Lets talk about dust, and leave the rest for another day.  Dust is all too often an afterthought in tool design.  Cut a hole here at the bottom, where the dust seems to collect and leave it at that.  Never mind that to pull away all the dust being spewn all over the place from there will require a nuclear powered dust extractor…  There are a few simple principals to good dust control. 1. Dust is bad, don’t let it escape.  2. Don’t let it escape – this requires collecting it at source.

In this case at source is much further up than the stock connector, just under the table, the point at which the blade exits the wood being cut.  Collecting it from the bottom is not so good because it has plenty of time to sneak off, get into the pulleys, get clumsily trapped between the wheel and the blade, meet up with your lungs and have a picnic.  This means that inevitably some will be taking away your life force, and some will be maliciously wearing away the machine and causing more vibration (= more noise, that’s right dust and noise are in cahoots!).

OK so the bandsaw needs modding, I will go into the details of that some other time.  Onwards to dust extractor planning!  You see, I don’t have a dust extractor as such, and I don’t want to buy one (unless you spend a lot of money they are ineffectual, noisy, and blast the finest dust particulates, which are most dangerous to your health, all over the place). Instead my plan is to transform two household vacuums into an elite dust sniping force.  Problem: dust, especially fine wood dust like you get from a bandsaw, either flies straight through or blocks regular filters almost immediately, turning your house vac into an ineffectual wheezing gasbag.  In fact almost all vacuum cleaners come with the stipulation that thou shall not suck dust born of wood, brick, or cement.  Doing so will invalidate your warranty, and bring to your house the mockery and scorn of the hoover god.

One inadequate solution (and one I have been running for some time) is to run the inlet hose through a drop box. This catches a lot, even the majority, of the biggest particles, wood chips and so forth, but the finer dust (and sometimes even the not so fine dust) can sneak past. Thus when sanding wood, the vacuum performance drops off very quickly, because the fine dust has gone straight into the filters and blocked them up.  My unideal solution had been to vent the exhaust from the vacuum outside and do away with most of its filters.

This works OK, but there are a few drawbacks.  1. You cant remove all the filters – you need something to stop the dust and other bits getting sucked in, before they go through the vacuum’s impeller – so that you don’t get grinding destruction.  2. Ever felt the heat coming out of a vacuum cleaners exhaust? It is nice and warm, all that waste heat, along with any other residual heat in the room, is getting wasted by being pumped outside :(

It has served me well but it is time to retire the drop box, and begin pursuing a cyclonic dust separator.  Yes, its a bit like the Dyson.  Except better, because we are less limited by space (we need a fairly big collection point for the dust after all), and not so worried about mass producing and cost per unit.  The basic design I am using is adapted from Bill Pentz’s design which has been shown to work very well.

I wanted to make the cyclone clear, so you could see what was going on inside. This was important to me, because despite the amount of reading I have done around the subject, cyclonic filtration still seems a bit like magic to me and I wanted to watch it actually happening in detail.  Having it transparent also means I can observe the performance differences when I tweak the design, change the airflow, or vary the waste matter being separated.  In short having it clear is just a lot cooler.

I am writing this entry right after my first cyclone test, with a lot more still to do on this dust sniper project.  For now, I am well pleased – in general results are good, and wood dust is zipping down and into the collection barrel where it rests undisturbed.  So yeah, updates and probably a step-by-step to follow, but for now here’s a few pics and a little footage of the first test of the cyclone.

Below you can see the upper body of the cyclone, with downwards angled inlet and air ramp.

dust cyclone upper

Temporarily assembled, ready to be built into the quiet efficient ‘dust sniper’ system.

Dust cyclone

“Take joy in your digressions. Because that is where the unexpected arises. That is the experimental aspect. If you know where you will end up when you begin, nothing has happened in the meantime. You have to be willing to surprise yourself writing things you didn’t think you thought.” (Massumi 2002: 20,21).  (That’s right, I did actually read this stuff for my PhD).

Responses to Whisked away in a cyclone (dust separator style)

  1. Steve

    The safety on/off switch will (if not broken) work as an off if you just hit the cover, it should transfer your push to the switch.

  2. Bongo

    That’s what I thought to begin with, confused me for some time. Must be broken some how then, but I can’t see how – no bent, snapped or warped looking bits??

  3. thomas

    That is a very beautiful cyclone. What type of plastic did you use and how did you put it together ? Would love to build one myself. thanks

  4. Bongo

    Hi Thomas,
    thanks. I have built two of them now, using slightly different methods. Both use polycarbonate and the supporting bands are scrap acrylic from a skip raid. I am in the process of writing a full build guide, and will put that up ASAP.
    Cheers, B.

  5. thomas

    Hi B.

    Sounds awesome. I cant wait. This is a project I have been wanting to do a long time, but have been missing the hands on how to guide and where and what to buy.

    thanks so much

  6. Bongo

    Hi Thomas, Ok most of it is up on the project pages now.. Any questions, just ask.

  7. thomas

    Oh my. What a treasure trove of information. I have addictively been reading it for days now. Even at work on my Iphone.

    I cant wait to get started on this myself. please keep up the good work and info sharing. it is truly something awesome.

    thanks so much


  8. Gord Goebel

    Hi Bongo,
    A few questions.
    1. Is it possible the stop button has been replaced with a shorter one? I have seen these kind of switches and they work as Steve described on June 11th, 2010. You have to lift the cover to turn them on but pressing the cover turns the off button.
    2. Is the ‘air ramp’ really helpful / necessary? It seems the air would move down by itself as there is air coming in at the top and it has nowhere else to go.
    3. Did you have to make the cone yourself?


  9. Bongo

    Hi Gordie,
    1. I think I found that the plastic cover must have been cast wrongly or something. I have snapped the bottom catch off, and now it functions as Steve suggested – which is nice.

    2. Yes! The air ramp prevents any air crashing into the back of the inlet. While you are right, the air would circulate down, because it is going that way anyway, some would branch out and hit into the flat edges of the inlet, and cause turbulence and disrupt the smooth airflow. Would it make a massive difference to exclude it? Probably not – but you may as well make the cyclone as efficient as possible.

    3. Yes. Check out for full instructions.

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