Drop slot on Thien Cyclone Separator Lid?

[sportflyer]

As an experiment ,  I  temporarily stuck some 1/4 in  thick ply strips on my pail wall  in the drop zone  with double sided tape .  The length of the strips bridge the top of the cover to the baffle and approx 3/4 inch wide.   I am happy to observe that it improved the fine dust collection tremendously.  It seems that these "turbulators" work very well. See attachment .

[BernardNaish]

A useful experiment. It looks as though you are on to something here. I wonder what would happen if yours strips were angled down towards the slot? Again what would happen if the strips were thicker? Sorry - my mind is racing ahead of my concern for your work load.

[sportflyer]

A useful experiment. It looks as though you are on to something here. I wonder what would happen if yours strips were angled down towards the slot? Again what would happen if the strips were thicker? Sorry - my mind is racing ahead of my concern for your work load.

"angled down towards the slot "  Do you mean for example angled at  70 degrees  in the direction of air flow instead of my 90 degrees or you mean thick at the top and thinner at the bottom or both.

[retired2]

A useful experiment. It looks as though you are on to something here. I wonder what would happen if yours strips were angled down towards the slot? Again what would happen if the strips were thicker? Sorry - my mind is racing ahead of my concern for your work load.

"angled down towards the slot "  Do you mean for example angled at  70 degrees  in the direction of air flow instead of my 90 degrees or you mean thick at the top and thinner at the bottom or both.

I'm pretty sure he means angled the way I described it in my earlier post in thiis thread.  In that post I suggested the ribs be angled in the direction of the airflow.  So instead of your ribs being vertical they would be rotated, say 30 degrees.  Now as I pointed out in my post that creates a real fabrication challenge because they can't be flat because they need to follow the curvature of the drum.

[sportflyer]

A useful experiment. It looks as though you are on to something here. I wonder what would happen if yours strips were angled down towards the slot? Again what would happen if the strips were thicker? Sorry - my mind is racing ahead of my concern for your work load.

"angled down towards the slot "  Do you mean for example angled at  70 degrees  in the direction of air flow instead of my 90 degrees or you mean thick at the top and thinner at the bottom or both.

I'm pretty sure he means angled the way I described it in my earlier post in thiis thread.  In that post I suggested the ribs be angled in the direction of the airflow.  So instead of your ribs being vertical they would be rotated, say 30 degrees.  Now as I pointed out in my post that creates a real fabrication challenge because they can't be flat because they need to follow the curvature of the drum.

Yeah , that would be difficult to machine  properly due to changing curvature :( .  I wonder whether it necessary to follow the drum surface that accurately . Perhaps a little slop is OK ? I will see how much slop there is . Also now we are deflecting some of the sir directly into the slot and could possibly  churn up the stuff below the baffle .

[dabullseye]

well after watching the dust in my can i can see it swirling around circumference down to the bottom. i like retired2 half a dowel idea maybe it could be steamed into shape   

[phil (admin)]

First I tried beads of silicone glue.  You can do any angle you like and follow the contour of the can.  It didn't help.  I figured maybe it wasn't sticking up high enough or wasn't slick enough, so I switched to a rubber weather strip called I think a round seal or something like that.  McMaster sells it, it is self-adhesive.  Still didn't help.

While I was doing this testing I had my 16-32 drum sander.  You really need fairly large volumes of dust, and you need a way to accurately measure the bypass (I used a kitchen scale set to grams, and was measuring my vac bag).

Eyeballing better/worse for fine dust isn't going to get you anywhere.

Most of the fine dust that bypasses never makes it to the wall, it simply short-circuits the entire thing.  So I'm a bit dubious that anything you do to the wall is going to make a big difference where the finest dust is involved.

[retired2]

First I tried beads of silicone glue.  You can do any angle you like and follow the contour of the can.  It didn't help.  I figured maybe it wasn't sticking up high enough or wasn't slick enough, so I switched to a rubber weather strip called I think a round seal or something like that.  McMaster sells it, it is self-adhesive.  Still didn't help.

While I was doing this testing I had my 16-32 drum sander.  You really need fairly large volumes of dust, and you need a way to accurately measure the bypass (I used a kitchen scale set to grams, and was measuring my vac bag).

Eyeballing better/worse for fine dust isn't going to get you anywhere.

Most of the fine dust that bypasses never makes it to the wall, it simply short-circuits the entire thing.  So I'm a bit dubious that anything you do to the wall is going to make a big difference where the finest dust is involved.

That's disappointing Phil, but thanks for all that testing.  If you are right about the by-passing talc never making it to the outside wall, my guess is a bellmouth outlet pipe simply makes matters worse.

Another thing that I was starting to worry about is the frictional losses that might accompany a washboard separator wall.


Back to the drawing board!

[sportflyer]

 I am not aiming for perfection . My main interest is balsa dust since that is what I generate the most . Those vertical strips seem to help .

[BernardNaish]

I mean angled at 70 degrees in the direction of air flow. I was thinking the dust would be "screwed" downwards. I would have thought thin battens were flexible enough to twist and follow the curved wall. You might even be able to use balsa wood if it were coated with a hard finish. If this proves impossible then changes in the width, thickness and spacing of the vertical battens may be the only variables that can be tried.

I think the rectangular section of your battens could be why you are getting different results from Phil. Washboard ripples are quite different from an abrupt castellation. There are all sorts of possible turbulent flows around the "square" edges. My "lash up" bin has quite acute changes in angle of the stiffening indents around its circumference. Not at all like corrugated roofing. This does remove fine dust. Cannot say how much because I have not measured it but a significant layer of fine dust sits in the bottom of my bin every time I empty it.

What we are trying to do is slow up the very fine dust so that it will fall downwards through the slot. It has little mass so are we trying to "draw" the energy out somehow? The micro turbulent flows across abrupt changes in section might do this. Of course r2 is right to remind us that this will be at the cost of air velocity.

Another thought! Are these particles so small as to be attracted to electricaly charged plates. The words electrical precipitators floated slowly in so I searched and found: "An electrostatic precipitator (ESP) is a filtration device that removes fine particles, like dust and smoke, from a flowing gas using the force of an induced electrostatic charge minimally impeding the flow of gases through the unit." Just a thought.

Electronic postage or kitchen scales are remarkable accurate – not laboratory standard but good enough particularly if comparing before and after.

[retired2]

The difference in results being reported may have more to do with the particle size than separator design.  Sanding dust from one wood species can be different than from another.  Is it dust or is it talc, like drywall dust?  Is there a technical difference between the two or is it just our individual perception? 

[BernardNaish]

Yes r2 is right about standardisation. However sportflyer has a specific need and has found an improvement, albeit subjective. Some quick weighing with and without the ply strips should quickly establish if he is on the right path for his application.

[phil (admin)]

The difference in results being reported may have more to do with the particle size than separator design.  Sanding dust from one wood species can be different than from another.  Is it dust or is it talc, like drywall dust?  Is there a technical difference between the two or is it just our individual perception?

That is a good point.

I'm not convinced that fines separation can be improved by doing anything at the wall.  I don't even care much about what is at the wall.  It is the stuff that is so fine that it won't hug the wall, or which bypasses altogether (never enters rotation) that is plugging the filters.  You can't even see it at the concentrations that exist in the separator or pipe, but it is there.

When I was working on trying to improve fines separation by various additional baffles and modifications to the wall, at my darkest hour of frustration, I reached out to Steve Knight who uses his ClearVue for his CNC operation.  I asked what kind of separation he was experiencing.  He tired of plugged cart. filters, he said, and built a bag house.

More research (talking to manufacturers of industrial gear and also users of hobbyist cyclones) made it abundantly clear that my notions about what conventional cyclones could accomplish were way off.  Most of those ideas were based on what I had read in woodworking forums.  I later realized much of that stuff was posted by guys that barely used their shops, or may even have been sock puppets.

But the reality is, sanding generates enough "sanding smoke" that cart. filters plug pretty quickly.

So far I haven't figured out a way to improve things.  People ask me if I have something up my sleeve, that I haven't told anyone about.  Nope, I've got nothing.  I've tried all sorts of stuff, more than you can imagine, and found nothing.

[retired2]

That's a pretty discouraging report Phil, and even if you had "something up your sleeve" I worry that it might be so specialized that it would only work well for powdered waste.  If it didn't also handle planer shavings, it would be of no interest to me.  And I could not afford to give up even a few more CFM's to a separator that creates additional losses in order to capture powder.

There may be a few people who work exclusively in powder producing tasks, but my guess is the vast majority of us hobbyists jump from one machine task to another; one minute we are producing big shavings and the next we are sending sanding dust into the air.

I couldn't justify the time or cost of setting up multiple specialized dust collection systems.  I need a single system that is a "jack of all trades", if it is a "master of none" then so be it. 

And everytime I think I should buy a Wynn filter for my setup, I think about how easy it is to clean my bag filter when it gets too much cake.