Cyclone Rotation Question

[Travis Fatzinger]

Hi,

I was looking at a Oneida Left Hand C-650 cyclone.
http://www.oneida-air.com/inventoryD...-D46574885567}

I currently have a 2hp Jet 1182 with clockwise rotation. I was thinking about mounting it on top, or using a hose to connect the two.
Would the Left hand Oneida work with my clockwise rotation or would I need the right hand model?

Thanks,

Travis

Jet 1182.jpg

[Anthony Whitesell]

I'm pretty sure the inlet and the outlet have to be on opposite sides. The blower rotation will be setup to push the air out of the outlet, and the fan rotation determines the cyclone rotation which needs to be such that it pulls are in from the body inlet. Which puts the inlet on the opposite side. I have a C-950 and an Oneida blower (not set up yet, three years running) and the inlet and the outlet are on opposite sides.

[John K Jordan]

Would the Left hand Oneida work with my clockwise rotation or would I need the right hand model?

I don't know anything about Oneida. I installed a ClearVue and was deciding which "hand" to order based on my space. I asked them the same question. They said the rotation of the motor was determined by the impeller geometry and it was the same for either left or right handed intakes. This make sense since the cyclone intake is well above the updraft tube. If you look at a closeup of the ClearVue picture you can see how it is constructed.

JKJ

[Travis Fatzinger]

So that's one vote for it matters and vote for it doesn't?

After looking at the clearvue website it seems that they only sell one "twist" of impeller but sell both LH and RH models of dust collectors. So as suggested by JKJ it looks like it doesn't matter to Clearvue.

Also in thinking about it more, Oneida markets the Super Dust Deputy which only comes in one flavor, but it should work with any dust collector so I'm thinking it shouldn't matter.

However I found this on another forum:
"The link that you provide for the cyclone body doesn’t seem to work, but it looks like it’s item #SSX060000, “C-650 CYCLONE SEPARATOR – Left hand inlet”. If in fact that’s the cyclone you have, the Grizzly motor impeller combination won’t work well. The reason being is the direction of airflow has to change direction going from the cyclone through the impeller. In the Oneida separator, when air enters, it spirals around in a clockwise direction. The Grizzly motor/impeller that you link to moves air in a counter-clockwise direction; you can tell this from the shape of the impeller housing. You’re going to want a DC motor/impeller combo that’s basically flipped, like this Delta 50-850:"

I wonder if its a theoretical thing that doesn't matter too much in practice.

[Steve Peterson]

I recall seeing some comments on the ClearVue web site stating that there is a very slight improvement in separation efficiency if the dust enters with the same rotation as the impeller spins. Otherwise, there is a small amount of turbulence when the airstream needs to change direction as it enters the impeller. The general consensus was that the difference is not that great and you should just order the one that works best for your shop. I wanted the intake tube flat against the wall, so I ordered a right hand CV.

Steve

[Peter Kelly]

If you're mounting the motor, housing and impeller directly on top of the cyclone body, the flow of the cyclone needs to be oriented in the same direction as your impeller. For a clockwise turning motor / impeller, the cyclone inlet needs to be on the right side.

If you are using the cyclone with a dust collector connected with a flex hose and not directly above it doesn't matter which side the inlet on the cyclone is located.

This vendor sells both right and left side oriented cyclones at quite a bit less money than Oneida: http://cycloneseparator.com/store

[John K Jordan]

However I found this on another forum:
"... the Grizzly motor impeller combination won’t work well. The reason being is the direction of airflow has to change direction going from the cyclone through the impeller. In the Oneida separator, when air enters, it spirals around in a clockwise direction. The Grizzly motor/impeller that you link to moves air in a counter-clockwise direction; you can tell this from the shape of the impeller housing. You’re going to want a DC motor/impeller combo that’s basically flipped, like this Delta 50-850:"
I wonder if its a theoretical thing that doesn't matter too much in practice.

One fun thing about the ClearVue is you can watch it in action. The dust and shavings come in fast and are immediately directed towards the outside of the cone, well above the intake to the impeller. All the visible material swirls tight against the cone. You can't see ANYTHING in the center of the space. The material continues to spiral downward where it drops into the can. The alignment of the main intake from the ductwork is what determines the separation rotation inside the cyclone.

Several questions: Is there actually significant counter rotation within the impeller intake tube? Is the rotation of the central column of air in the center of the cone significant or is it at a relatively low speed? If any rotational speed differentials are present, exactly what happens at the point where they meet and how does it differ if the speeds are low rather than high, specifically, is there turbulence or does the stream simply slow rotation in one direction, move straight, then begin rotating in the other direction? And how does each behavior affect the overall efficiency. Without modeling or extensive experimentation, one guess is as good as another.

But another clues may be useful. Based on my experience with my filters and cleanout, almost nothing but an extremely tiny amount of extremely fine dust is pulled up through the central tube, through the impeller, and blown through the filter stack (assuming the cyclone is working correctly and there are NO leaks!). After emptying three 30gal drums of dust and chips there is probably not a teaspoon of powder in my cleanout box - I have had no need to clean it out yet.

Even if the rotation of the impeller DID cause some rotation in the air in the vertical intake cylinder leading from the cone, I cannot believe it would make much if any difference in the efficiency of the separation. For one thing, as indicated by the cleanout observation, there is simply not much material moving in the airstream. If there was a large amount of material being sucked up through the impeller then (such as if the drum seal is leaking), yes, laminar flow and turbulence might be an issue. But almost all of what moves up through the impeller is air. By definition, then, no significant separation can take place near the impeller intake opening. Once the air stream approaches and enters the impeller intake I believe it will travel just fine through the impeller (and at an extremely high rate). The possibility of any counter-rotation below the impeller doesn't convince me that the performance would be affected. If anything, I suspect any turbulence at the entrance impeller intake tube might even improve separation by throwing some fines back into the spiral, but I'm just speculating here.

Two caveats here. One: my observations are based entirely on my personal use, of course. I primarily pull dust from the bandsaw, very occasionally from a Performax drum sander, a tiny bit from the lathe, and sometimes but rarely from my table saw. I also went to great pains to ensure my cyclone and collection drum were air tight. Two: this is based on the ClearVue (Pentz) design. I have been told that Oneida and other copied Bill's design but I have no personal knowledge of this and no idea if the other brands are constructed and work the same way. They do make it hard to see inside and watch them work.

cyclone_closeup.jpg

JKJ

[James Gunning]

From everything I have read, the airflow up the central tube does turn in the same direction as the flow induced in the cyclone. You can't see that, even in a Clearvue, because the excellent separation occurring in most cyclones removes the only visible particles that would remain to go up the center tube. The cyclone and impeller rotation "should" be the same. The reason is to optimize the airflow through the blower. In truth, if the air in the center tube is turning in either direction, some blower efficiency is lost. Just more if the rotation is not the same. A straight in, non-turbulent flow is the optimum situation. Some commercial cyclones employ air straighteners in the center tube to achieve this. Whether this is necessary for the cyclones we use as hobbyists, hard to say. Just to tinker, I plan to install an air straightener in my SDD to see if I can even measure any difference. I'll post the results when I do the testing.

If you install a long tube (say, longer than two feet) between the cyclone and the blower, I think (not sure of this) it would act somewhat like an air straightener, dampening the swirling effect in the center tube. Much like the recommendation to have a long, straight, smooth duct feeding into the cyclone to allow any turbulent flow to settle before entering the cyclone. Problem is the long tube connecting the cyclone and blower induces it's own losses due to the internal friction, and may be no better than just close coupling the blower and cyclone. If it's flex duct, the friction losses from the flex duct would likely cancel out any gain from the air straightening.

My guess is you can hook up a blower turning in either direction and probably get a good result. This is a pure guess, but I bet the losses due to turbulent flow in the center tube are no more than 5%.

[Randall J Cox]

Interesting. If anybody had a smoke machine of some sort and also the Clear Vue cyclone, the theories could be tested as that is the only one you can see through. Randy

[John K Jordan]

Interesting. If anybody had a smoke machine of some sort and also the Clear Vue cyclone, the theories could be tested as that is the only one you can see through. Randy

I thought about that! I've used smoke sticks before which don't put out much smoke. I wondered how I would get the smoke generated inside the cyclone It's easy to watch streamers of smoke when the air movement is slight but I wonder if smoke introduced at the intake would even be visible by the time it got to the vertical tube leading to the impeller fan. Without trying an experiment, I wonder if it would take one of the methods used in wind tunnels which all, I think, rely on a bunch of nozzles arranged in a line or grid. They do use smoke but sometimes fog (from a nebulizer) and other materials. I think what they use depends on whether they want to analyze the laminar flow on a surface (such as a wing) or the flow through the free air.

The easier thing might be streamers, such as lengths of yarn fastened to surfaces and to support wires. Might to take the darn thing apart though, so there would have to be a pretty good reason to go through the effort!

JKJ

[James Gunning]

The smoke sticks would be useful to check your installation for leaks. I've thought about getting some for that purpose.

[Tim Campbell]

Here's another vote for it makes no real difference.

I posted the results of testing I carried out a while back on the last post of this thread http://www.sawmillcreek.org/showthre...ing-up-already

[James Gunning]

I knew I had seen this someplace. Quote from Bill Pentz website: We can build our cyclones from these plans with the inlet on either the left or right, but you should build your cyclone for the best match with your impeller. The direction the air turns inside the cyclone is set by the inlet. For motors smaller than 2 hp turning a smaller impeller you can put the inlet on either side because my testing only showed about 0.1 amp difference with no measurable airflow difference. When I upgraded from the smaller blower to the larger 5 hp with a larger impeller I was stunned at the difference. The bigger impellers with larger motors generate a really fast moving spiral of air that needs to be turning in the same direction as the impeller, or the impeller has to overcome that direction of spin. This quickly spinning air when it hits the blower can cost up to 1 hp of overall performance if it is not turning in the same direction that the impeller is rotating. With a big impeller, I found the blower moved as much as a 33% more total airflow if the impeller turned in the same direction as the air coming into the blower. You need to specify if you have a left or right handed cyclone to make sure you get optimum performance.

It looks like this pretty much agrees with Tims testing results above. Sorry for the bold type, I intended to edit this before posting. Too quick on the button.