Cyclone issues - shavings won't drop?

[John Lifer]

The problem is not with a leak, I really don't think you will find one. The problem is the design of the cone vs the flow. As others have hinted at, you have too high a flow to drop out the particles. From my view, the cone is too long in relation to the diameter. If the velocity of the air remains too high at the wall of the cone, the chips will not fall out of suspension. The larger the diameter, the slower the velocity of the air and the chips would slide on down as gravity would be larger component than the axial rotation.... I note you cut flow and things started dropping. Until filter loads up, you might have to do this.

[Bob Wingard]

If you want to be certain that there' no leak in the chip bin ... take it out. Put a small (6") disc made of non-porous material on the bottom of the cyclone ... tape it up thoroughly to keep it in place and to seal any leaks. Turn the system on, and try the same pieces that won't fall out of suspension now. If they go right to the bottom of the cyclone, you have a barrel leak ... if they still stay in suspension, it may be "normal" for your system.

[Michael Dunn]

Has anyone seen the CV video demo where the guy sucks up a 25' tape measure into the cyclone? I'm pretty sure it was a CVC. The tape measure dropped immediately. I know some have followed my cyclone install. Mine is sheet metal so I can't see what's happening. All I know is that there is a ton of chips in my steel trash can beneath my cyclone. I kind of wish I could see it. 1. Because that would just be awesome and cool. 2. So I could know if mine is doing the same thing.

I'm so tempted to try the tape measure trick. It shouldn't damage anything, right? Maybe I'll use my 16' Fast Cap tape.

I'm certainly no expert here, but those pieces you fed into the system were quite small. I can't imagine that the force of gravity is stronger than the air movement in the cyclone. Try something heavier. I can't imagine small wood chips or even large wood chips from a planer would be able to just drop while the air is still moving.

My $.02.

[Michael W. Clark]

If the cyclone is working with dust, I would let it run. These peices you are putting in are very large with respect to the cone discharge diameter. In addition, they are also very light. It is easy for them to get caught up in all the air currents at the bottom of the cone, especially with no other loading. You will have swirling in your barrel, the vortex continues past the cone, the particulate drops out (slung to the outside of the barrel) and the clean air goes back up the middle. This is important, becaue if you fill your barrel to the top, you will get re-entrained material pushed into the filters, especially the small stuff.

Mike

[Cyrus Brewster 7]

If you want to be certain that there' no leak in the chip bin ... take it out. Put a small (6") disc made of non-porous material on the bottom of the cyclone ... tape it up thoroughly to keep it in place and to seal any leaks. Turn the system on, and try the same pieces that won't fall out of suspension now. If they go right to the bottom of the cyclone, you have a barrel leak ... if they still stay in suspension, it may be "normal" for your system.

I just tried this with the sane results - so no leaks in the bin. Thanks.

edit: not pun intended with sane but...

[Cyrus Brewster 7]

I'd for this reason be slow to tear too much apart or form too firm a view that there is a problem until you run it for long enough to properly check whether or not you are getting significant amounts of dust and chip carry over into the filters. i.e. into the drop out drawer at the bottom of your filter stack. Maybe talked to CV too.

ian

When I woke up I thought the same thing before I read this. To extend the intake would require moving a cabinet that would encroach on the only place I can store a full sheet of ply (20' x 20' shop). I am going to let the system run, get results and go from there.

Funny how when one gets involved, knee deep, in a project, that the thoughts (or frustrations) involved sleep right next to you. My wife will be happy when it is all done.

[Michael W. Clark]

When I woke up I thought the same thing before I read this. To extend the intake would require moving a cabinet that would encroach on the only place I can store a full sheet of ply (20' x 20' shop). I am going to let the system run, get results and go from there.

Funny how when one gets involved, knee deep, in a project, that the thoughts (or frustrations) involved sleep right next to you. My wife will be happy when it is all done.

Straight on the inlet is helpful, but the main thing is that you do not put a horizontal elbow counter-current to the rotation of the cyclone. Elbows in other directions will have much less of an impact (if any) on the efficiency.

Mike

[Cyrus Brewster 7]

If the cyclone is working with dust, I would let it run. These peices you are putting in are very large with respect to the cone discharge diameter. In addition, they are also very light. It is easy for them to get caught up in all the air currents at the bottom of the cone, especially with no other loading. You will have swirling in your barrel, the vortex continues past the cone, the particulate drops out (slung to the outside of the barrel) and the clean air goes back up the middle. This is important, becaue if you fill your barrel to the top, you will get re-entrained material pushed into the filters, especially the small stuff.

Mike

Mike... I was getting started on enlarging the hood of my jointer to 6". When I opened the plate I noticed a pile of chips/dust in the dead spot. I scooped them in a container and fed them into the system about 25' from the cyclone. The cyclone worked as I that it should have - a little swirling around (previously stuck by static) until a handful went in. Everything dumped right into the bin.

Everyone else... From the posts that Ian linked from the CV forum and from what I seen posted here (thanks), what I witnessed at first was normal. Because I wanted to check for leaks (even tough I was confident I did not have any), I only sparingly put material into the system (PVC shaving - bad, and a light piece of poplar - bad) so I would not clog the filters on my first go around.

The fact that the Clearvue is, well, clear, is a double edged sword. If I could not see what was going on I would have saved quite a bit of time tinkering around these past two days and would have been able to relax with some BBQ and a cold beer.

As I stated earlier, I will be adding a gauge on the exhaust side of the blower so I can visually see when the filters need to be cleaned. I will also be taking notes on what is going into the system - material being cut (MDF to wood), duration of cutting (as best as I can estimate), gauge results, dust run lengths to each machine, etc. It most certainly will not be anything scientific, but I am hoping to get a "feel" for my system. Maybe I will change a thing or two... or maybe I will finally just get to woodworking and forget about shop setup for a while - it has been going on for almost two years.

[Cyrus Brewster 7]

Straight on the inlet is helpful, but the main thing is that you do not put a horizontal elbow counter-current to the rotation of the cyclone. Elbows in other directions will have much less of an impact (if any) on the efficiency.

Mike

I actually read this somewhere else (made sense) so was not worried with the elbow going down.

[Clay Crocker]

Cyrus,

I think that may be normal. I have a Super Dust Gorilla (metal cone, so you can't see what is going on inside) and every once in a great while my compound miter saw will send a small off cut into the cyclone and I can hear it rattling around inside the cone. Sometimes I have to shut off the cyclone motor to get the offcut to drop into the drum. Clay

[ian maybury]

That sounds like a good move Cyrus. Please report if you can manage it.

One to be cautious about is testing the cyclone with the outlet at the bottom of the cone blanked off. It may function in this situation, but watching and reading about cyclones suggests that the drum pays a significant part in dropping out chips and dust. As in the swirling and downwards moving flow is maintained right down through the hose. The solid material really only drops out when this flow (which carries it) expands into the space at the top of the drum and slows right down. Which explains why they prefer to have a little empty space always left above the chip fill.

I have a long (roughly 15in) clear connecting hose between the cone and the chip drum, and the swirl (or at least the movement of dust and chips in it) is visually obvious right down the full length of it. It all suggests that the spin is pretty intense. Since air 'stuck' to the wall of the hose seems to be moving down into the drum, there presumably must be a balancing flow of air moving back up the centre of the hose and up the centre of the cyclone into the fan inlet tube. Pretty amazing really that it's able to maintain such a structured flow in this situation, and maybe a reflection of just how much energy/velocity gets concentrated up in it.

One thought I've had is whether the corrugations on the flex hose matter or not - or whether a smooth walled (hard to organise - we rely on the flex of the corrugations to lift the top off our chip drums) hose would help. The corrugations might conceivably help 'screw' debris down it's wall if they match the direction of spin of the cyclone, or oppose if not. (as in my own case) They may not matter, in that fast moving air has a way of forming stationary boundary layers that in effect 'fill' surface irregularities (at the expense of reducing the effective diameter of the port or whatever) when it enounters surface roughness.

That the direction of spin of the fan matches the layout of the cyclone is by the way something else to check if it seems to be acting up....

ian