Thread: How High can it suck?

Regardless of which DC unit you go for you need at least 6 inch ducting to move enough air to capture the very fine dust at the source. There is no escaping this fundamental truth. 6 inch ductwork and machine ports are a requirement if you are going to capture the fine dust, not an option.

If you get a Clear Vue with a Variable Frequency Drive you do not need 3 phase power ... a 240 V, 15 Amp circuit to the cyclone is ample. I was quoted about $2,500 for 3 phase power, and under $350 for the VFD. The choice was easy because I did not need 3 phase power anywhere else.

Then you need to modify the ports on your machines so you do not restrict the air flow at the machine. All mine except for my combination jointer/thicknesser have been modified to 6 inch ... it was easier than I thought and everything works very well. Just this morning SWMBO commented on how not only my shed, but also her house, is free of dust. The jointer/thicknesser is a problem because I haven't yet figured out how to get a lot more air INTO the machine where it counts ... but am working on a few ideas.

So, if you want to catch the fine dust the three figures you must remember are, 4,000 ... 1,000 ... and 6:

1. minimum of 4,000 FPM of air to ensure the dust stays in suspension and does not settle out in your ducts.
2. 1,000 CFM through a 6 inch duct, to move enough air to capture the fine dust at source.
3. 6 inch minimum duct size. Any smaller and you will not get the 4,000 and 1,000 regardless of the size and power of your DC unit.

You could always go for a 2 HP Dusty ... but if you choose this path you must have a short 6 inch flexy between the DC and the machine to get enough air flowing, so no ducted system.

If you go for smaller ductwork, you will have a chip collector, not a dust collector, and it is the fine dust that damages our lungs. That is why I located my shop vac outside ... they produce a lot of very fine dust that is invisible at first, but which gradually builds up so it can be seen.

What do you want? If you want fine dust collection there is no avoiding the magic numbers of 4,000 ... 1,000 ... 6.

Originally Posted by John SamuelSo, if you want to catch the fine dust the three figures you must remember are, 4,000 ... 1,000 ... and 6:
[LIST=1

[*]minimum of 4,000 FPM of air to ensure the dust stays in suspension and does not settle out in your ducts.[*]1,000 CFM through a 6 inch duct, to move enough air to capture the fine dust at source.[*]6 inch minimum duct size. Any smaller and you will not get the 4,000 and 1,000 regardless of the size and power of your DC unit.[/LIST]

Good summary John

Just a little more specificity on point #2, the 1000 cfm is technically at the machine dust making point. This will in practice require more than 1000 cfm in the duct because it is very difficult for 1000 cfm to take place right at the source.

The above criteria may not necessarily pick up all the chips that are flung about by machinery, but remember that they don't represent anywhere near the same health risk from the finer dusts.

Originally Posted by BobL

Good summary John

Thanks, Bob. I had a good teacher.

I hear you believe me.

That said.... my combo - the fence for the spindle moulder with the 90 mm outlet is cast iron.

I can't even imagine what I'd have to do to open that up to 150mm.

The jointer / thicknesser - would be much easier - the 90 mm outlet is a plastic moulding that fits onto the square metal folded chute - so removing the plastic moulding opens it up to around 150mm square - which means just fab something to make it round...at 150mm

The saw - well with a 2 inch rubber hose under the cabinet.... - that will likely never make it to 6 inches...well at least not in any way I can think of at the moment, no doubt it could be done if one were determined enough to engineer something...

I can imagine that if I could think of a way I could open the saw cover underneath to a 150 dia - and create a 3d cloud file drawing and get a 3D printer to fab something in plastic that would just bolt on and work a treat.

VFD = Variable frequency Drive - (I'll need to research that bit - whats it do - spin the impeller faster or according to the load of dust or something? I didn't see VFD on the Clearvue web site as an option).

Thanks for summarizing it... I am getting the picture in my head now...

I will get there eventually - it might have to be one step at a time... I need the 3 Phase to run the combo machine...(So can't really avoid that cost) and I can get all the power points put in on a 15 amp circuit.... so I can run a clear view once I get it.

I have the room for a 8 inch duct along the roof...and to drop 6 Inch down to the machine...

Cost (surmountable) and neighbors/noise....might be my only issue but again I can sound proof the whole shed and lean too for the cyclone given time and a slowly slowly catchee monkey approach for finances.

I will get there - but it might be over a period of time...

Unless I sell something to finance it all upfront...

Anyone in need of a Kidney?

6 inch, & 1000CFM at the source and 4000 fpm in the duct to keep the fines suspended.

Its likely eventually that my 2nd 3 Ph machine will be a drum sander - which will be dynamite for fine dust creation, so it definitely will have to be hooked up to a decent dust extraction system with 6 inch duct....so it makes sense to go for a 8 inch main with 6 inch feeds to the machines.

Is there a significant fire risk difference, between using PVC and say galv metal sheet for ducts?

Just don't want to burn the joint down If I can avoid it.

I did read the bit about running a copper wire inside plastic PVC duct and bringing it out to earth via a sealed gutter bolt or similar to try and avoid static electrical discharge within the PVC duct.

I've learned a lot on the last couple days from this thread - mucho appreciated to all who have chipped in.

Originally Posted by Timless Timber

I hear you believe me.
That said.... my combo - the fence for the spindle moulder with the 90 mm outlet is cast iron.
I can't even imagine what I'd have to do to open that up to 150mm.

That port is basically a chip collector and meanwhile the majority of the fine dust just rises up with the warm air a moulder generates and fogs the area above the moulder.
I'd still connect to the 90 mm with a 100 mm hose and at the same time position a 6" duct above the moulder to help collect fine dust. Maybe consider making a shroud that hangs from above to help collection.

The saw - well with a 2 inch rubber hose under the cabinet.... - that will likely never make it to 6 inches...well at least not in any way I can think of at the moment, no doubt it could be done if one were determined enough to engineer something...

Where there's determination there are often interesting solutions.

VFD = Variable frequency Drive - (I'll need to research that bit - whats it do - spin the impeller faster or according to the load of dust or something? I didn't see VFD on the Clearvue web site as an option).

Originally developed to better match the speed to the load in pumps and air cons etc, but in a DC there is not much of a load imposed by sawdust compared to the amount of air moved so the VFD is not used for this purpose

@ 1000 cfm x air density of 0.075 lb/cuft = 75 lb/min or 34 kg/min
20" thicknesser, x 4.8 m/min * 1 mm pass = 0.0024 m³ at 1000 kg/m³ = 2.4 kg/m
So the weight of the sawdust even in the heaviest load is about 7% of the weight certainly its no more than about 10%.
(BTW This reminds me of one of the ultra clean air labs I help design which had fans that moved 11 m³/sec - thats 13 kg/s or 800 kg a minute of air. I think it was a 24HP motor with a 1m diameter fan.)

The main reason for using a VFD on a cyclone is that is can spin the impeller faster (ie 60Hz instead of 50Hz) and get 20% more volume throughput.
The other is the soft start capability so that a 4HP motor can start up and run on a 15A circuit - normally this would be a 20A line for single phase.

Its likely eventually that my 2nd 3 Ph machine will be a drum sander - which will be dynamite for fine dust creation, so it definitely will have to be hooked up to a decent dust extraction system with 6 inch duct....so it makes sense to go for a 8 inch main with 6 inch feeds to the machines.

Depending on how long the drum is you might be better off using 3 or 4 x 4" ducts

Is there a significant fire risk difference, between using PVC and say galv metal sheet for ducts?
Just don't want to burn the joint down If I can avoid it.
I did read the bit about running a copper wire inside plastic PVC duct and bringing it out to earth via a sealed gutter bolt or similar to try and avoid static electrical discharge within the PVC duct.

I was going to use my favorite forum word again (Bollocks).
The risk is so low for a static electricity caused fire that it is not worth worrying about.
If you want 8" you will have to use something other than storm or sewage PVC as it does not come in 8" diam

One more (OK maybe dumb) question...

Reading Bill Pentz web site he speaks about the option with his sons kits of rolling sheet metal cyclones left to right or right to left for right hand and left hand blowers / impellers, but mentions difficulties & friction losses getting electric motors to spin backwards and left handed impellers...

This got me to thinking about the effect downunder of the Coreolis Effect

This force causes moving objects on the surface of the Earth to be deflected in a clockwise sense (with respect to the direction of travel) in the Northern Hemisphere and in a counter-clockwise sense in the Southern Hemisphere. Rather than flowing directly from areas of high pressure to low pressure, as they would in a non-rotating system, winds and currents tend to flow to the right of this direction north of the equator and to the left of this direction south of it.

;-

and whether any significant %age increase in performance could be gained from cyclones if the air circulated the way the corelois effect naturally made it want to go (anti clockwise)?

I mean I understand that use of a VFD can increase rpms of the engine from 50 - 60 htz and gain 20% increase in flow rate of air!

What %age might be gained IF an engine could be wound to spin anti clockwise and an impeller specially built to work anti clockwise?

Is there anything significant to be gained %age wise by working with the laws of gravity in the southern hemisphere as against them?

Will the dust settle out faster/better.

Curious mind...
Sorry if its the dumbest question ever asked...
I've been known to question even Einsteins special theory of relativity....so - I guess I worry too much about little things.
Sometimes the dumbest question ever asked is the one never asked.
And - "it's all about the Journey" so I'm having a damned good look around is all!

Originally Posted by Timless Timber

Is there anything significant to be gained %age wise by working with the laws of gravity in the southern hemisphere as against them?

none, the coriolis effect is significant in an atmospheric cyclone but negligible in an atmospheric tornado.

Maybe workshop cyclones should have been called tornados?

Last night I was dreaming about making a timber "barrel" style cyclone (tornado?) with wooden (Sheoke) stave's and iron hoops...?

I get excitable after too much coffee - even in my sleep!

See if I can walk off the excitement down at the woodshow...

Tornado as a description / name for them sounds far better to me... now if Bob designed it - should it be called a Cock Eyed Bob?...Or if Willie Nelson chipped in, a Willy Willy maybe - ohh what the heck - why not just call it the obvious - a dust devil!

Originally Posted by Timless Timber

... now if Bob designed it - should it be called a Cock Eyed Bob?...Or if Willie Nelson chipped in, a Willy Willy maybe -

or "Bob Eyed Cock"

Originally Posted by Timless Timber

Last night I was dreaming about making a timber "barrel" style cyclone (tornado?) with wooden (Sheoke) stave's and iron hoops...?

You could make it from bending plywood and put a nice veneer on the outside. I'm not certain how it would be to shape the cone with it but I'm sure others on the forum that have played with it would know.

Pete

If it had a properly coopered barrel dust collector on the bottom to match the staved tornado part above, might really be something! Not as much fun to watch as the clearview tho. I reckon I could pay for the clearview, if I set up seating and charge the local kids 10c ea to watch the sawdust swirl around inside.

Knowing them, one would video it with his Iphone and upload it to youtube with a 5c pay per view arrangement link on his website... Kids today!

Well the wood show was certainly fun!
Meeting Bob L - that capped it off for me - what a thorough gentleman!. Nice to put a face to a forum name.

I brought back some brochures and business cards of suppliers I will be needing to talk too in future for various bits and pieces too and found a couple small items while I was there.

I enjoyed myself - got turned around twice and couldn't remember which way was in, and which way was out......went into Beyond Tools and drooled over the NEW Robland Machines... started wondering if I should trade the old X 31 on its newer brother, there's not THAT much different on them... well the sliding tables different - but a LOT of the parts are identical, just different color paint. Thinking I could upgrade the old gal with spare parts from the newer ones maybe...

Lots to think about - left in a bit of a daze.

One consideration for me - is where to put a cyclone, so it doesn't feed fine dust back inside the shed OR as importantly annoy the neighbors (with dust &/or sound).



As you can see the shed is in the back corner of the block a meter off both back fences. The front of the sheds a 5 meter electric roller door, so essentially the whole front is open when working inside for light and air unless it's raining.

The side closest the house has a personal access door and 2 windows.

The rear wall is fully enclosed as is the back wall with no openings.

My neighbor to the left or behind the rear gable where the shade cloth is - has a pool and outdoor BBQ area.

The neighbors to the rear of the property are a string if units.

The neighbors the other side of the boat and truck are also units - but a fair bit further away.

So I am in a quandary where I would locate the cyclone... so as to annoy as least people as possible and also prevent dust coming in the front roller door or windows and door.

If I put it behind the rear gable wall - near the pool neighbors, I fear the fine dust might coat the surface of their pool as it settles out of the air.

Predominant southwesterly breeze comes from this direction so dust will likely want to go toward the front roller door maybe more so than towards the pool if I am lucky - but that's bad for me if not the pool neighbors.

If I put it between the side / rear wall near the units... i worry the noise will get me in strife if not the fine dust on their cars - because the units are quite close.

If I put it between the house and shed - well it might send dust in thru both windows and personal access door.

So the amount of dust and noise exhaust emission for me, is a BIG consideration!

Anyone have any wise council/experience in this area?

I have neighbours with pools on two sides - its not a problem.

Remember the stuff that comes out is invisible and floats on hot air for hours so if there is even a slight breeze that will be enough to stop it settling.
If it is a really still still day then you may want to think about waiting but it won't be for long as this is Perth we're talking about!

Here's where I would put it

Thanks Bob - that was my thoughts too!.

I was thinking eventually a sound proofed enclosure would hold the CV, a compressor, and diesel genset for occasional use when the power goes out, - all on that side.... Poor neighbor that side's really gonna cop it - but what can you do eh?

I figure if I get a decent sized compressor - it won't be running long or frequently, so little real noise nuisance value.... the CV only when the machines are running - again I have some control over what times I do that (during the day mainly - I can do set out or finish work hand sanding or gluing and cramping up etc at night).

If at all possible I want to keep the neighbors happy.