Thread: Cyclone separator into open bag, no filters on external exhaust.

Thanks fellas. Will have to do more reading, learning, looking around. Hopefully will find a bargain on the suckyMota, because I don't think the whole system is going to be cheap by the time the dust settles into the trash can.

My apologies to anyone here who already knew about this one and was hoping to keep it on the down low. For everyone else looking, especially those in Victoria, here's one of those holytek models up for auction online: http://www.graysonline.com/lot/0002-...brand?spr=true Good luck.

Good find, BUT it looks like it's 3 phase. Make sure it will suit your installation before you bid on it.

It says 3 phase in the description, durr Dave!

3 phase is good, you'd probably want to run it from a vfd anyway to maximise airflow if used with a cyclone.

3ph could be considered a bonus, if you put a VFD on it, it can be run on 240V, and you can get some more speed out of it.

There is that, thanks.

On a different note, given this will be going outside the shed, why don't I save myself a bunch of time and possibly some money, and just buy a 3hp or more double-bagger with a 6" inlet and park it out the back of the shed?

And on an even more different note, isn't it quite incredible how absolutely hopeless much of the new machinery is, when it comes to capturing dust? I just ran my new table saw and the dust collection is utterly disgraceful. It 'leaks' vacuum from almost more places than it holds vacuum. There are gaps I could almost drive a bus through. Insane. I'll have to make time to build a better collection/enclosure area for it. Now I'm slightly more aware of dust issues, I'm seeing things differently and can scarcely believe how hopeless some of my machines are.

Low pressure, high volume collectors like dust extractors rely on airflow in to a cabinet/collection point to create the necessary air flow to take the dust away. So be careful about covering all those air inlet points into your saw or you'll extract next to nothing.

At the rate things are going, I'll have to buy at least an ammeter and make incremental changes one at a time and read what the motor is telling me. i think this dust collection part of this forum ought to come with some sort of "rabbit hole" warning that flashes and users have to click a "I've been warned" button to keep reading.

Originally Posted by dropstix

There is that, thanks.

On a different note, given this will be going outside the shed, why don't I save myself a bunch of time and possibly some money, and just buy a 3hp or more double-bagger with a 6" inlet and park it out the back of the shed?

yes, that makes sense. A cyclone will cost you airflow, if you don't need it then don't have it.

H'mm, filters cost you airflow as well. Damned if you do damned if you don't!

Originally Posted by dropstix

At the rate things are going, I'll have to buy at least an ammeter and make incremental changes one at a time and read what the motor is telling me. i think this dust collection part of this forum ought to come with some sort of "rabbit hole" warning that flashes and users have to click a "I've been warned" button to keep reading.

The typical range of currents a SP 3 HP motor/impeller will show between a fully open load and cavitation is < 3A, On mine I see 6.9 to 9.2 or 2.4A.
If you use an ammeter with a 0.1 A resolution (which is equivalent to 1 in 30 or 3%) means you may not see any small changes you make.
To see small changes you will need an ammeter that can read in the 0.01 range and this will give you a resolution of 1:300
However, rather than buying an ammeter you should consider using a simple U -tube manometer. - the typical pressure changes you will see between fully open load and cavitation should be around the 4-5" or 100-125 mm and you should be able to read that to 1mm which is better than 1%.

Originally Posted by aldav

Low pressure, high volume collectors like dust extractors rely on airflow in to a cabinet/collection point to create the necessary air flow to take the dust away. So be careful about covering all those air inlet points into your saw or you'll extract next to nothing.

Absolutely - most TS do not have enough large holes to allow enough air into the cabinet to enable the air to be extracted. This smaller holes or slots can be almost completely discounted in contributing to air flow. To maximise the flow from a cabinet you want minimum pressure loss, i.e. minimal vacuum inside the cabinet.

Originally Posted by aldav

H'mm, filters cost you airflow as well. Damned if you do damned if you don't!

Assuming we're comparing filters on a dust collector to an unfiltered cyclone, in my experience the pressure losses are similar.

The real difference comes comes from the work required to continually keep the filters clean in order to maintain a reasonable airflow compared to having a constant level of cyclonic performance.

On doing a cyclone group build, this is best done regionally, IME. The components are large, as is the the assembled cyclone, which creates transport challenges. Also, the complement of skills available varies from place to place. For example, the local skills may favour plywood or fibreglass over sheet metal.

When I did mine to the Pentz cyclone design (with cone ratio of 3) about ten years ago I teamed up with the local Men's Shed. They got one and I got some help to speed up my job, and the Shed got a favourable price on commercially rolling and seam bending the two 1.5m long cones.

Unless the drop bins are let overflow, these ratio 3 cyclones are close to 100% effective in separating out the fine dust from the air stream (if matched to an appropriately speced fan unit). The Men's Shed periodically lets their drop bin overflow, but I rarely let that happen on mine. I have removed about one cup of very fine dust in total from below my pleated filter over the last decade. On average I run mine about 400hrs/yr.

At the Men's Shed they insert a polypropylene bag inside their dropbox with just four cuphooks on which to hang it open. Nothing is added inside the bag to prevent it 'sucking' up into the cyclone.

Theoretically that should not happen if the drop box connection to the cyclone is airtight. If correctly constructed, the stall point (the point where the airstream stalls and drops its particle load, then reverses direction to flow back up the centre) of the cyclone is at the very bottom of the cone. Without any air leaks there should be no suck up out of the drop box. Perhaps a thin empty garbage bag tests the limits of that.

Originally Posted by Muchacho

Assuming we're comparing filters on a dust collector to an unfiltered cyclone, in my experience the pressure losses are similar.
The real difference comes comes from the work required to continually keep the filters clean in order to maintain a reasonable airflow compared to having a constant level of cyclonic performance.

The smallest pressure drops on cyclones are the BP design which is 2.25"W and that is there at all times.

According to BP, a "Std" bag has a pressure loss of 2" WC, Large 5 micron bags (e.g. needlefelt) have

Apart from standard bags most filters will initially have better air flow performance than cyclones (especially ad hoc cyclones). The extent to which filters degrade or choke up depends on what dust making activity is involved. For sanding hardwood it will choke quicker than say for Table Sawing softwoods.

The real difference comes comes from the work required to continually keep the filters clean in order to maintain a reasonable airflow compared to having a constant level of cyclonic performance.

Yep - the number of DCs I have seen with collection bags near full continuing to be used and users wondering why they have no suck does not surprise me.

For conventional DCs using collection bags and filters, as a rough guide you should ALWAYS at least empty your collection bags and clean the filters when the bag is no more than half full. If you are doing a lot of sanding then you might want to think about maintenance even more often. There is also a time element involved as the constant swirling of the dust in the collection bag generates fine dust from the existing sawdust inside the collection bag. This means emptying and cleaning even more often.