Looking for Trash Can Separator Pics

[Scott Myers]

Phil,

Thanks for the feedback. Yep, bet my wife will soon hear the dremel cutting the can.

As far as what causes the pressure drop; No, I don't believe it is leaks or anything of that nature, as least in my tests. I have a pretty extensive background in fluid/air flow dynamics and 2 certifications to that end with the fluid power society (For what its worth. That and $2 will get you a cup of coffee.) I've been working in industries that deal with this sort of thing for 25 years. Granted, I am normally working with much higher pressures and velocities, but the formulas and rules of thumb still apply. It's just a matter of turbulence and surface eddys from friction in the pipes and chambers. Lower air speed/larger tubes/laminar flows = lower pressure drops with a given amount of inches of vacuum and available CFM.

Bottom line; I just have to build it and report back as to how it works. Might require several mods along the way, but that's the way such things go.

[Phil Thien]

Phil,

As far as what causes the pressure drop; No, I don't believe it is leaks or anything of that nature, as least in my tests. I have a pretty extensive background in fluid/air flow dynamics and 2 certifications to that end with the fluid power society (For what its worth. That and $2 will get you a cup of coffee.) I've been working in industries that deal with this sort of thing for 25 years. Granted, I am normally working with much higher pressures and velocities, but the formulas and rules of thumb still apply. It's just a matter of turbulence and surface eddys from friction in the pipes and chambers. Lower air speed/larger tubes/laminar flows = lower pressure drops with a given amount of inches of vacuum and available CFM.

I got the impression from your statement that separator lids induce substantially greater losses than conventional cyclones. And that certainly is conventional wisdom. But my testing doesn't back it up. In fact, the losses from my separator lids have been very in line with what is quoted for typical cyclones.

Losses on the cheap plastic ones have been terrible, but mostly from the points I listed above. Sealing one up w/ hot melt glue resulted in an approx. 18% boost in CFM. But much of that vanished as the can began to fill. With less than 4 gallons of dust in the can, the CFM was back down to the starting point (I was using a blower w/o filter so no worry that the filter was blocked).

I look forward to seeing your progress on your dual-can cyclone. Don't leave is in the dark!

[Scott Myers]

Don't worry, I'll post the results. It will take me about a month to get to it. I've got a lot of other irons in the fire at the moment.

I believe the reason you haven't seen the pressure drops in your lids would be a complex math discussion to say the least. Might be it hasn't been run at high enough air flow yet to push it to that point. Who knows? Since I am not in the least interested in pulling out my fluid dynamic book and discussing Reylonds numbers, eddy currents, pressure, air layer stacking and a whole lot of other "fun" stuff, I'll just have to take your word on it on faith. Turning this into workable math has been done commercially in the past, which is of course how the cyclonic dust collector was born. I am sure all this is in a book somewhere. We could probably even get some of this data from cyclone manufacturers and back calculate into why and how your baffle works specifically. But I am not about to spend the time!!! Ugh.

As you alluded to, this "fun" math is why a cyclone collector makes a the same or much lower pressure drop than "bag house" type dust collectors, for the same air flow. (Now where is my fluid dynamics book?...)

Phil, out of curiosity, how are you measuring actual CFM flow? It's tough to measure accurately, to be sure, without special equipment. Estimated measurement can be done easily enough, but it would probably be 20% off.

A REALLY good resource is Bill Pentz's website on cyclonic dust collectors. He puts it in as close to layman's terms as humanly possible. Still enough data to make one's head explode.
http://billpentz.com/woodworking/cyclone/index.cfm

I got the impression from your statement that separator lids induce substantially greater losses than conventional cyclones. And that certainly is conventional wisdom. But my testing doesn't back it up. In fact, the losses from my separator lids have been very in line with what is quoted for typical cyclones.

Losses on the cheap plastic ones have been terrible, but mostly from the points I listed above. Sealing one up w/ hot melt glue resulted in an approx. 18% boost in CFM. But much of that vanished as the can began to fill. With less than 4 gallons of dust in the can, the CFM was back down to the starting point (I was using a blower w/o filter so no worry that the filter was blocked).

I look forward to seeing your progress on your dual-can cyclone. Don't leave is in the dark!

[Phil Thien]

...

I believe the reason you haven't seen the pressure drops in your lids would be a complex math discussion to say the least. Might be it hasn't been run at high enough air flow yet to push it to that point. Who knows? Since I am not in the least interested in pulling out my fluid dynamic book and discussing Reylonds numbers, eddy currents, pressure, air layer stacking and a whole lot of other "fun" stuff, I'll just have to take your word on it on faith. Turning this into workable math has been done commercially in the past, which is of course how the cyclonic dust collector was born. I am sure all this is in a book somewhere. We could probably even get some of this data from cyclone manufacturers and back calculate into why and how your baffle works specifically. But I am not about to spend the time!!! Ugh.

As you alluded to, this "fun" math is why a cyclone collector makes a the same or much lower pressure drop than "bag house" type dust collectors, for the same air flow. (Now where is my fluid dynamics book?...)

Actually, it is the other way around. The typical bag house DC starts at less than a .3" WC and as it approaches 2 or 3", it cleans itself. But cyclones for woodworking typically come in around 4-6" of WC. I think 2" is about the bare-knuckle minimum for a cyclone.

Phil, out of curiosity, how are you measuring actual CFM flow? It's tough to measure accurately, to be sure, without special equipment. Estimated measurement can be done easily enough, but it would probably be 20% off.

For CFM readings, I've used Dwyer gauges, weather-type anemometers, and abused a friend that has access to exotic gear through his employer. I am able to get to within 5-10% of JC's (Johnson Control's) gear with my Kestrel and some simple jigs I've built.

However, I don't often have a need for absolute #'s. Most often, I'm looking for relative (A/B) data, so I use the Kestrel and also have lately been experimenting with my ammeter, which may turn out to be the most accurate method of all for comparative analysis.

A REALLY good resource is Bill Pentz's website on cyclonic dust collectors. He puts it in as close to layman's terms as humanly possible. Still enough data to make one's head explode.
http://billpentz.com/woodworking/cyclone/index.cfm

Yikes. Many of my findings have been contrary to Bill's. If I had taken his site as gospel, I'd have never invented my separator lid. Nor would I have discovered the Dylos meter's application to woodworking, that led to the group buy, that ultimately debunked the myth that our shops are toxic wastelands filled with non-settling sub-micron dust.

Just wait until the world sees my new blower design, combining the CFM of a DC blower with the static lift or a shop vac. I can collapse that cyclone while at the same time I scare your neighbors with fog horn type sounds. Muwa-hahahaha!

[Scott Myers]

ROFL!!! Too funny. But how much HP will that require?!?!?!

[Mark Hubl]

Here are the ones I made for my shop. I am quite happy with Phil's design. I only used a twenty gallon can on the dc so I need to empty more often. I am intrigued by the top hat design. It would give me more capacity in the can and might be rigged to make emptying easier. I do notice lower cfm than without the can but it is still very effective. I fill it up with my lathe pretty quick and only notice significant scrubbing when it is getting full (bottom of baffle). It could probably use some tweaking but I have been on to other things. Always interested in what success' others have had though.

[Greg McCallister]

Here is my version with 6" duct. Also I have updated the can with a window started by Ron Wong on Phil's site.
I am currently working on changing the outlet to 6" and hopefully have some pics this weekend.