|Forum topic by Absinthe||posted 06-26-2011 08:45 PM||6786 views||0 times favorited||15 replies|
06-26-2011 08:45 PM
I am starting this topic merely to discuss the hows, whys and wherefores, as well as qualification and quantification for some of these things.
After doing some research, it would appear that people use several different strategies for dust collection. Everything from, NOTHING, to some wild multistage hybrid systems that are so far beyond my budget I can’t really even consider them.
It would appear that simply using a shop vac, or blower with bag filter is frustrating at best because the filtration clogs up fast and suction pressure goes away… seems counterproductive. And the ultimate in better than nothing.
So at the very least, some kind of chip collection needs to happen. There are a few pre-made and home made bucket, barrel or can toppers that by virtue or the inlet going sideways and the outlet sucking from the center, separates most solids but still allows dust/fines to hit the filters. This is pretty much the internal design of most shop vacs and specifically my huge-ass Genie shop vac.
Then comes the new internet holy war :D mini-cyclones and Thien separator.
The mini cyclones seem to fall into a few camps. The strict Pentz based cyclones, which I think the only non-homemade ones are the Clearvue Mini and some other brand that I don’t think is actually sold anymore. Homemade ones seem to either settle for close-enough or take painstaking steps to get it dead on. Sometimes these include a funnel and other times it is simply a long column. It seems from my reading that the 6” Pentz one (for shop vacs) is a compromise from the recommended 5hp 18” serious one (and the 8” one that am building will no doubt be a compromise as well). In this same area is the smaller Oneida Dust Deputy, (I will have one to play with shortly) and it looks cool. One of the suggested configurations involves running two in series, which may be an effective idea for keeping the most dust/fines out of the filters. But, where does one draw the line? How many smaller ones in series is as good as one large one. I have seen numbers such as the big industrial ones built for the AG industry with an 85% efficiency to what Pentz claims as “low 90’ %” from his modifications and calculations.
The Thien separators tend to essentially be focused on a baffle below the out let. The proper Thien baffle appears to be based on a 240° drop slot in an otherwise fully blocking disk. I assume this works by merely not allowing the solids to reemerge near the outlet by trapping them below. I believe delta has a ‘Vortex’ which appears to be a dome added on to their drop box (though as far as I have heard, not offered as a retrofit or upgrade. Interestingly enough, this appears to be a dome that is convex toward the outlet. This has raised some ideas to me. It seems that some separators are complete and others are based on the bucket/can toppers and simply adding the baffle to it.
Terms like ‘good enough’ and ‘less expensive’ ‘just as good’ and things like that are hard to truey quantify or qualify. Granted, when you look at Pentz stuff, he obviously has the scientific data and measurements and general laws of physics to cite. However, in other things all I usually see are purely anecdotal. I also don’t see too many people that have both systems and some way to compare the results.
OK, now I have shared everything I have internalized so far. I have ordered one of the Oneida Dust Deputies (the small one with the buckets). I am also in the process of building an 8” Pentz based one. I will also make a couple different Thien based baffle barrel topper ones. One of the things I want to try is using an 8” vent cap as a baffle with a 4” outlet centered inside it, with the input at some level below it. My hypothesis on this is that if air rising across the conical cap should slow enough to drop out material before coming into the output area. Not sure how that will work, but if it does well, it would be reproducible with off the shelf items.
Another thing I have seen are tapered ducting reducers. At least from the pictures the ones that go from 8 or 6 to 3 or 2 and have a long straight part. If these are long enough to have that 3:1 top opening to bottom opening with the 1:1.64 top opening to cone length they might make for another off the shelf starting point for small home use cyclones that meet the Pentz ratios. Along with some plastic soda bottle’s that share similar shapes I will experiment with these as I get a hold of them.
If you have read this far then you are either a masochist, or you share my interest in this area. What I am looking for at this point are some ways to measure the effectiveness of one over the other. I am also curious of a combination between the two. Perhaps the use of a Thien baffle either in conjunction with or replacement of the air ramp in a Pentz style cyclone. As well I am interested in other shapes used for the baffle or even simply the air ramp without a following cone.
Anyway, this is more of an invitation to conversation than a specific question. I plan on playing, but I am not promising to do it all in a timely manner. :)