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I always wondered what in the world Powermatic was thinking when they switched to that mustard yellow or gold.  I much prefer the green. 

I would suggest making the area of your rectangular inlet a little larger than the area of the round.  7x4 is very close, so it probably isn't critical, but the HVAC industry says rectangular duct is less efficient than round, and somewhere I found they recomment a 10% size increase for rectangular duct to avoid additional line losses.  Since a separator takes a big bite out of your blower's performance, you don't want to add any more loss than absolutely necessary.

"Tall and skinny" probably isn't the best, but remember you are trying to put the waste stream against the outside wall and over the drop slot.  If the rectangular opening is too wide or oversized it allows waste to enter the separator too close to the exhaust pipe, especially if you use a bellmouth whose wide flange draws in air from a larger diameter.  So, you have a couple competing objectives to consider, and they also have impact on the optimum diameter of your separator.
OK, so I am now in the design phase for my top hat separator. because of height restrictions, I am planning on a single height unit. I plan on following retired2's design pretty closely, but from what I have found from testing my collector, I can use 6" pipe for the main run. I plan to transition that round into a rectangle for the top hat inlet, and I'm wondering about proportions of that rectangle.

The six inch pipe has an area of 28.27 square inches, so I could pretty much match that if I transitioned to a 7 inch tall by 4 inch wide inlet. Obviously, I could make the rectangular end of the inlet in any variety of proportions to equal the cross sectional area of the round duct, and I am wondering what people's thoughts are on what the ideal proportion would be.

It would seem to me that the closer to square the proportions get, the more it is like a round inlet, so I would lose some of the benefits. On the other hand, I know that there are ideal proportions for duct work, and tall and skinny isn't among them. So, do we say, as in life, all things in moderation? What do you all think?

Oh - by the way - in regards to the air straightener question - I have been in contact with the people who make the Vortab flow conditioner mentioned in another thread.
They think their product will work for our use, when I hear back from them in regard to cost and distance from the impeller, I'll let you all know.

BTW, retired 2, I am jealous of all of your nice old green Powermatic equipment. I bought mine after they switched to the current mustardy gold.
I want to be able to collect the soot in dry form. With DPFs you get it trapped within tiny holes in the cordierite structure and DPF wouldn't really work well as a retrofit. Filter based designs literally suck as they will get clogged.

as nucww said- we can try making it with non flammable material. I can also try to integrate electrostatic capture to the setup.

Anyone who wants to collaborate on the experiment? I am going to start this 5th May and see how this goes... Thoughts welcome!
quick thoughts:
The diesel exhaust temperature (>500F from google) could burn up or melt the typical thien baffle materials.  So make it out of non flammable materials suitable for your exhaust temperature.
The soot may be sticky and collect on the perimeter of the collector, so be prepared to clean it a lot or make it out of something soot doesn't stick to.  The added friction may also degrade the collection performance with time.
The back pressure of the baffle may increase the exhaust pressure and reduce the efficiency of the diesel.
Unique application, be careful.  Who knows, what you develop could be the next device we see on trucks.
If it does stick to a common, cheaply available product, make the air spin within a cylinder of the stuff and pass the soot through it, and throw it away when full like a filter but air flow is open.
A seperator/cyclone generally gets the bigger chips/dust and the filter catches the small stuff.  It sounds like you need a diesel particulate filter on the exhaust.
Thien Cyclone Separator Lid Discussion / Thien Soot separator? Please help, newbie!
« Last post by zwandy on April 25, 2017, 12:51:09 PM »

I have a old/vintagelike static diesel generator, whose exhaust points towards the entry of my house. These particles are solid and have choking hazard if breathed in for too long. From whatever papers/online info I read, the particles are 2-10 microns in size, and coming out with speed 20-30 m/s from the exhaust.

With your experience please help me as a community n00b.  ;D

-Can I use Thien generator to segregate the black carbon particles into a chamber?

-Would this be bad for the engine? since this design doesn't interface directly with the engine.

My engine is such that even after maintenance it would still produce carbon based smoke after a few days. Hence thinking of applying 'Thein' to it.

I am going to do some experiments and share results.

Thien Cyclone Separator Lid Discussion / Re: Introduce yourself...
« Last post by zwandy on April 25, 2017, 08:37:39 AM »
Hello hive!!

I'm a long-term amateur interested in dust capture... I am also a researcher who's trying to understand pollution and hazards of various types! 

Lovely to meet everyone here.
Another benefit of a new floor is it is much easier to keep clean.  I have a pretty nice dust collection system, but there are still times when it is easier to let everything go to the floor and clean it up later.  For that I have a strategically placed floor sweep and a 24" push broom.  Works very nicely and it doesn't require me to do much bending over.
Thanks, Retired2. I think that making a top hat will likely be easier than taking out the ramp, or at least be more the kind of work I like to do, so I'll probably go in that direction now. Part of the reason I was thinking about keeping the collector as much "as-is" as possible was that the configuration, with the intake close to the ground, worked well for ducting in the location I have chosen for the collector. But last night I had an idea of a good way to make it work with the high input of a top hat on a barrel, so there is one less reason to not do it the right way, with the blower up top, etc.

That being said, I'm about to embark on a major shop improvement project, specifically casting a new, flat and level floor.  The existing floor is untroweled concrete that looks to have been poured over unlevelled dirt, and I've run out of flat places to put tools... Once I get that done, I think I might find that a whole different arrangement of my workspace is possible, so I'm not going to finalize my dust collecting plans until I get that finished, and see what it feels like. It is exciting but frustrating because I have to wait a bit to work on any of it, but at least I can enjoy reading this forum and planning as much as I can in the meantime. I'd post pictures of my shop as is, but I'd have to include warnings for the faint of heart; it is hardly the operating room a lot of you guys are able to maintain!  ;D

Schreck's advice was kinda what I remembered, but I wasn't certain enough to tell you to rip out the ramp.  Thinking more about your plans, I want to clarify and change some of what I advised in my previous message.

If I'm clear about your configuration, you are "pushing" your waste stream into the separator rather than pulling it as I do.  Nothing wrong with that, but it reaffirms my advice that air straighteners would be of no value, that is unless you meant to place them before the blower inlet, then they could add to the efficiency of your fan.

With regard to a bellmouth, it would smooth the air exiting your separation chamber and possible add a few CFM to your performance.  Even a coffee can exit can be made more efficient if it siits on a wood collar that is thick enough so that the corner of the exit can be rounded over.  Even a crude round-over formed with a wood rasp is better than a sharp corner.  Hope what I'm describing makes sense.
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