Cyclone owners, a question

[nothungry3]

I have an idea to lay a cyclone in the dust box of my mark 7. I read a NASA analysis that said that there is no gravitational impact on cyclone performance.
Could someone lay their cyclone on it's side and give me their opinion of the effect on performance?

[Jack Wilson]

The motion the cyclone imparts on the air may not be effected by gravity; but once the particle escape, the need gravity to get into the collection barrel.

[BuckeyeDennis]

[quote="Jack Wilson"]The motion the cyclone imparts on the air may not be effected by gravity]

That is what I always thought too, but now I wonder. Those NASA guys are darned good physicists. I'll give it a try and report back. If I can find some sawdust, that is.

[BuckeyeDennis]

Well, it turns out that those NASA boys know what they're talking about. My cyclone bucket was about 3/4 full of sawdust, so I just dumped some out on the floor, and turned my cyclone cart on it's side. Here's the test setup.

[ATTACH]26273[/ATTACH]

Then I starting vacuuming up the pile. It went great at first, with the sawdust disappearing into the bucket.

[ATTACH]26274[/ATTACH]

But then the cyclone started backing up.

[ATTACH]26275[/ATTACH]

I turned off the vac, and then remembered that my bucket was still about half full after I had dumped out the test sawdust. So I figured that the cyclone worked sideways just fine as long as the sawdust had somewhere to go, but that it couldn't pack more sawdust into the bucket once it had filled up higher than the cyclone. So I completely emptied the bucket, and resumed the test, with a very high Hoovering rate to see if I could choke it again.

[ATTACH]26276[/ATTACH]

No problem at all with an empty bucket.

[ATTACH]26277[/ATTACH]

So the NASA guys are right, with one caveat. Under gravity, at least, your dust-collection bin can only collect dust below the neck of the cyclone.

[JPG]

Well, it turns out that those NASA boys know what they're talking about. My cyclone bucket was about 3/4 full of sawdust, so I just dumped some out on the floor, and turned my cyclone cart on it's side. Here's the test setup.

[ATTACH]26273[/ATTACH]

Then I starting vacuuming up the pile. It went great at first, with the sawdust disappearing into the bucket.

[ATTACH]26274[/ATTACH]

But then the cyclone started backing up.

[ATTACH]26275[/ATTACH]

I turned off the vac, and then remembered that my bucket was still about half full after I had dumped out the test sawdust. So I figured that the cyclone worked sideways just fine as long as the sawdust had somewhere to go, but that it couldn't pack more sawdust into the bucket once it had filled up higher than the cyclone. So I completely emptied the bucket, and resumed the test, with a very high Hoovering rate to see if I could choke it again.

[ATTACH]26276[/ATTACH]

No problem at all with an empty bucket.

[ATTACH]26277[/ATTACH]

So the NASA guys are right, with one caveat. Under gravity, at least, your dust-collection bin can only collect dust below the neck of the cyclone.

Surprised me!

Counter intuitive fer sure.

Curious what creates the force towards the narrower neck with right angle gravity.

Notice the multitude of rotations from 'top' to 'bottom'.

Your setup needed gravity to get the 'spoils' out of the way(below the neck).

Not shown is the effectiveness of debris removal from the 'exit stream'.


P.S. You need more screws in the bucket lid!

[BuckeyeDennis]

Surprised me!

Counter intuitive fer sure.

Curious what creates the force towards the narrower neck with right angle gravity.

Notice the multitude of rotations from 'top' to 'bottom'.

Your setup needed gravity to get the 'spoils' out of the way(below the neck).

Not shown is the effectiveness of debris removal from the 'exit stream'.


P.S. You need more screws in the bucket lid!

Hey, when I carefully apply JPW to each screw head with a Q-tip, and then shine each one with a buffing wheel on my Dremel tool, they add some serious bling to complement those nice tight joints on my cyclone cart!

But so much for the easy part. And shame on you for making me think hard this late at night! But I just can't resist an engineering challenge.

I notice in the photos that the dust spiral becomes more axial as it approaches the neck of the vortex cone. Indicating that the dust particles have substantial kinetic energy in the axial direction. Thus they will "shoot" into the bucket due to said kinetic energy, with no gravitational assistance required.

But why? Well, for starters, we know that the vac is sucking air out through the center of the tube at a high velocity. To the right, in the photos. Well, that air has to come from somewhere, and since all my pretty screws ensure that it cannot leak in through the bucket lid, it must therefore come from the inlet hose, ported through the outer diameter of the vortex cone, and cleverly offset so as to make the incoming air spin in the vortex cone. Which means that that the outer "cylinder" of air must rush furiously in the general direction of the bucket, to replenish the air that is being sucked up the "inner cylinder" by the vac. But since the "outer cylinder" of air is also spinning radially, the resulting centrifugal forces keep the heavier-than-air dust particles pushed toward the outer wall of the cone, separating them from the air stream that will be pulled into the "inner cylinder" and be exhausted to the vacuum. All of which is generally consistent with the observation of the dust paricles being "fired" into the bucket through the neck of the vortex cone.

Further, I would bet good money, but cannot prove that:
1: The angle of the vortex cone is optimized so as to maximize this effect, and
2: The NASA boys have some elegant mathematical tools that can prove their theory beyond a shadow of a doubt.

[JPG]

Hey, when I carefully apply JPW to each screw head with a Q-tip, and then shine each one with a buffing wheel on my Dremel tool, they add some serious bling to complement those nice tight joints on my cyclone cart!

But so much for the easy part. And shame on you for making me think hard this late at night! But I just can't resist an engineering challenge.

I notice in the photos that the dust spiral becomes more axial as it approaches the neck of the vortex cone. Indicating that the dust particles have substantial kinetic energy in the axial direction. Thus they will "shoot" into the bucket due to said kinetic energy, with no gravitational assistance required.

But why? Well, for starters, we know that the vac is sucking air out through the center of the tube at a high velocity. To the right, in the photos. Well, that air has to come from somewhere, and since all my pretty screws ensure that it cannot leak in through the bucket lid, it must therefore come from the inlet hose, ported through the outer diameter of the vortex cone, and cleverly offset so as to make the incoming air spin in the vortex cone. Which means that that the outer "cylinder" of air must rush furiously in the general direction of the bucket, to replenish the air that is being sucked up the "inner cylinder" by the vac. But since the "outer cylinder" of air is also spinning radially, the resulting centrifugal forces keep the heavier-than-air dust particles pushed toward the outer wall of the cone, separating them from the air stream that will be pulled into the "inner cylinder" and be exhausted to the vacuum. All of which is generally consistent with the observation of the dust paricles being "fired" into the bucket through the neck of the vortex cone.

Further, I would bet good money, but cannot prove that:
1: The angle of the vortex cone is optimized so as to maximize this effect, and
2: The NASA boys have some elegant mathematical tools that can prove their theory beyond a shadow of a doubt.

The way I 'see' it.

Inlet flow is essentially tangent to the tapered cylinder. This causes the flow to become circular inside the tapered cylinder.

Outlet flow originates within the cylinder at the end of the outlet tube which is near halfway along the cylinder axis. Thus the 'flow' is caused to move towards that mid point.

As the flow moves towards the midpoint, centrifugal force causes the angular velocity of the flow to increase. This is more effective with the heavier particles than the air.

After reaching the mid point, the air departs the 'flow' and moves towards the outlet pipe. Thus the air essentially reverses direction.

Meanwhile the heavier debris continues to spin ever faster due to the decreasing diameter of the tapered cylinder(truncated cone). It has inertia towards the small end and continues to move in that direction.

Here is where my gut instinct is failing me. What effect does the decreasing diameter have on that velocity towards the small end. I have to assume it is affecting the axial velocity positively or at least less than enough to negate the inertia in that direction.

Finally what effect does the debris suddenly expanding its diameter of rotation as it enters the bucket have?

Good Morning!

[BuckeyeDennis]

The way I 'see' it.

Inlet flow is essentially tangent to the tapered cylinder. This causes the flow to become circular inside the tapered cylinder.

Outlet flow originates within the cylinder at the end of the outlet tube which is near halfway along the cylinder axis. Thus the 'flow' is caused to move towards that mid point.

As the flow moves towards the midpoint, centrifugal force causes the angular velocity of the flow to increase. This is more effective with the heavier particles than the air.

After reaching the mid point, the air departs the 'flow' and moves towards the outlet pipe. Thus the air essentially reverses direction.

Meanwhile the heavier debris continues to spin ever faster due to the decreasing diameter of the tapered cylinder(truncated cone). It has inertia towards the small end and continues to move in that direction.

Here is where my gut instinct is failing me. What effect does the decreasing diameter have on that velocity towards the small end. I have to assume it is affecting the axial velocity positively or at least less than enough to negate the inertia in that direction.

Finally what effect does the debris suddenly expanding its diameter of rotation as it enters the bucket have?

Good Morning!

Yea, the tapering thing is where I ran out of theories as well. The can-lid style devices that you can buy give you a vortex with little or no cone shape. I assume that these also work, but probably not as efficiently.

It occurred to me just now that some taper may be necessay in order to maintain the velocity of the air vortex as it nears the bottom of he cone. The farther it goes down the cone, the more air has reversed direction and headed back up the center toward the exhaust. So with less air remaining in the outer air cylinder, necking down the diameter would be necessary in order to maintain the air velocity.

One other thought: I believe that the air vortex extends slightly into the bucket. If I let mine fill up to within an inch or two of the lid, when I turn on the vac some sawdust will get lifted into the bottom of the cone and swirl around down there. Then when I turn the vac off, gravity will indeed drop it back into the bucket.

[nothungry3]

Thanks for your help.
If I mount a cyclone in the upper portion of the Mark 7 dust box, I should have ample space below for chips. Agree?
Jack

[BuckeyeDennis]

Thanks for your help.
If I mount a cyclone in the upper portion of the Mark 7 dust box, I should have ample space below for chips. Agree?
Jack

No problem, the test was fun and educational for me as well.

I'm going to defer to JPG (aka Galloping Ghost) on the Mark 7 mounting issue. I've only seen those machines in pictures, but he has restored them.

However, I can tell you that the Dust Deputy instructions strongly warn against allowing any air leaks into the dust bin. I assume that this is because the resulting airflow would tend to draw dust particles back into the vortex cone, and out the exhaust.

When reading Dust Deputy reviews, I noticed that several reviewers complained that the manufacturer didn't include a gasket with the do-it-yourself cyclone kit. I didn't see this as a problem -- I simply applied silicone sealer to the flange before bolting it to the bucket lid. To stiffen things up, I bolted a large plywood disk to the underside of the lid, so that the thin plastic of the lid is sandwiched between the plywood and the cone flange.