J. Phil Thien's Projects

I've been thinking about building a flapper as well, but blowing it out with a compressor (low pressure - maybe 35PSI) seems to work well. Plus, the baffle really helps keep things clean. I've seen several designs - here is one and another

Ken, you ask a good question. My statement was somewhat presumptuous. I wanted a trash can separator for several reasons:

- It is a big pain in rump attaching plastic bags to the DC. It involves duct tape as temporary holders and a metal strap that never wants to stay in place. A separator means I won't have to change bags but a few times per year. The plastic bags are not expensive, but not exactly cheap either.
- A separator protects the impeller from any large, foreign objects (screws, nails, gold doubloons)
- The DC filter will last much longer without large particles (shavings, chips) wearing away the inside

My primary concern is volume. I built a simple workbench and ended up with three trashcans full of shavings. Without a separator, I would have had to hang three new bags.

My DC is lousy at capturing fine dust. It only has 1.5HP, and with 4" ducting it will never move enough air for the fine stuff. That's why I use my ShopVac with a HEPA filter (and a stocking to slow the clogging) with my sander. Of course, you're using your separator with a ShopVac! So, in your case I can see why you want the better separation. If I built a separator for my ShopVac, I'd want it to filter as much as possible too.

Let me rephrase my statement: "And for the average woodworker trying to collect the larger shavings and chips, it's irrelevant whether the baffle efficiency is 97.2% or 98.5%.".

I made a baffle for the HF unit, which is about 1.5HP. The CFM ratings on dust collectors are generally worthless, but the amount of air it moves is more or less comparable to the JET unit. The trash can I used has a diameter of 19.5". 4" hoses, Wynn filter.

I used the same size for the "gap" as Phil used for the shopvac baffle. The inner circle has a radius 1 1/8" smaller than the outer circle. It works really well. But, I do have about 1/4" gap around the outer edge of the baffle. This makes it easier to put the lid back on without scraping the sides. I have no idea whether this gap size is optimal. The slot has to be wide enough for the chips to pass, but not so wide the dust gets sucked out. In addition to the system's power (CFM/ SP), the diameter of the trash can is also a factor.

I placed the intake elbow about 1/3 inset from the start of the radius, so I'm probably using only 90 degrees. Again, it seems to work really well. This is also an interesting variable to experiment with.

I think the design is very forgiving. I hope Phil has some real information he can supply rather than my speculations, but I wouldn't be overly concerned with the measurements.

Sounds like it would work. Venting outside is best of course, no clogging of bags/ filters and no particles escaping. Of course, living in California helps...I wouldn't want to do this in Vermont!

The only downside I see is that you're still putting dust into bags. Those need to be emptied/ replaced, which is cumbersome and can get expensive. Have you considered getting rid of the bags completely, and instead using a large 55 gallon fiber drum? I don't know if you can combine the two exhausts into one (to feed into the drum), but it might be possible to make a baffle with two inlets and one outlet.

BTW, if you this route, you've just built a "real" cyclone system, not a trash can separator..... Since you already have the motor/ impeller (which is the expensive part), you may want to consider getting a real cyclone. 3HP should be plenty for that.

One more question....Why does one bag on my dual bag setup have about 5 times as much dust in it than the other?  One side has about 3" and the other has about 15" full.
That's bizarre. Is it possible the cloth bag on top of the "full" plastic bag is cleaner, and is letting more air through? More dust/ air would flow to that side then. It could also indicate you have a leak. Try swapping the top bags and see if it makes a difference.

On my original trashcan separator/ HF unit combo, scrubbing was terrible. With the baffle, it's practically zero. The Delta 50-760, while no doubt a little better than the HF unit, probably won't give you any problems (as long as you add the baffle). The next level up would be a true 2HP unit (running on 220V). Based on the results so far (see some of Phil's posts), anything that runs on 110V shouldn't have scrubbing issues

On the HF unit, the bags clogged severely in a very short amount of time. These bags were rated at 30 micron, which falls in the category "sieve". The bag on the Delta is much better, but the surface area is only 20sq.ft. By comparison the Wynn cartridge has 100sq.ft. (poly) or 275sq.ft. (paper). You may want to look at the Delta canister model. JET, Grizzly and JDS also have some affordable canister DCs. I noticed a tremendous difference in the suction when I replaced the bags. Even now that the filter has been "seasoned" (i.e. plugged up), I still get adequate airflow. That wasn't the case with the bags. Again, it's not an apples-to-apples comparison with the Delta bag, but I'd keep that in mind if you're trying to maximize airflow.

It would definitely be nice to mount the trashcan on the DC platform. I have a small shop myself, can't argue with that. I've seen people put a structure over the motor instead, and mounted the trashcan to that. It looked awkward getting it down to empty it, but it did save some space.

I was discussing the baffle design today with another woodworker, and there are some interesting things to try.

One problem with Dust Collection in general is the tradeoff between velocity and volume. For chips, you want velocity. For fine dust, you want volume. With the smaller DCs like the one from Harbor Freight, 4" is about optimal. A 6" pipe would be better for the fine dust, but the chips would get stuck. This could be used to an advantage on the trash can separator, by making the inlet 4" but the outlet 5" (or even 6" - whatever fits on your DC). Since we have a sealed system, increasing the pipe size will cause a drop in velocity, which is exactly what we want to further reduce scrubbing.

Again, this is a tradeoff. Even though the fine dust is very light, you still need some velocity. So don't reduce your trash can lid to just the rim  :)

An outlet of 5" precludes the use of PVC, but 5" metal fittings are readily available at the local home center. 5" hose is not as common as 4", but not too difficult to find on Amazon or Grizzly.

Increasing the outlet size may not make too much of a difference on the smaller systems. And for the average woodworker, it's irrelevant whether the baffle efficiency is 97.2% or 98.5%. But, with larger impellers and motors, this could be important.

Bas.

I'm impressed a DC that small actually pulls enough air to work, especially with a trash can separator. I wonder - would it be possible to hook two of them up in parallel? I.e. have two outlets on the trash can? That way, you could run a larger pipe for the intake without losing too much velocity.

It may not be that difficult to change the design. A 6" outlet that splits into two 4" branches ought to do it.

Bas.

Regarding the placement of the elbow - yes, it would probably be better if it was situated at the start of the outer rim. But, the baffle was added to an existing lid. I had originally placed the elbow at an angle so that it would spew the dust against the side of the trash can, to reduce the velocity and get the dust to drop quickly. With the addition of the baffle, that's no longer needed, but the elbow is locked in place. I was worried that because of the angle, the dust would lose too much velocity to travel the full distance to the drop slot, so I moved it slightly forward. I do have a small insert in the elbow I can remove (this is a 3" piece of PVC pipe). Hopefully, this will further improve things.

I'm using a big trash can (40 gallons). I don't want it to fill up all the way, since it will be too heavy to carry out. The extra room made it a little easier to construct as well.

I might build another lid one day, it's pretty easy to do. I know of several other people that are working on one as well, I'll ask them to post the results here.

I built my own trash can separator, using particle board for the lid. It's a 40 gallon can, metal, with the hoses attached to the lid via PVC fittings. The dust collector I'm using is the Harbor Freight "2HP" model, with a Wynn cannister. My shop is pretty small, the longest run I have is ~25 feet.



The results of the separator (without modification) were so-so. At first, I still had to empty the bag as often as the can, the "scrubbing" was awful. By tweaking the size of the pipe inside the trashcan, I was able to improve this slightly, and now I could fill up the trash can twice before having to empty the bag. Better, but not great.

I built the baffle from your design out of some particle board (5/8"). Probably overkill, but it made it easier to seat the dowel spacers, and I also happened to have some left over from a previous project. Construction was very simple using the pictures posted on your web site. A router, a Forstner bit, glue and screws: DONE!



The results are nothing short of spectacular! I haven't done any formal testing, but 95% (if not more) of the dust now stays in the trash can. Only the very fine dust ends up in the bag. And it is MUCH easier to empty the trashcan than emptying (or replacing) the bag. Getting the metal buckle around the bag can be a tricky job, only having to empty the bag once a blue moon is a real lifesaver! In the pictures below, the trash can is about 2/3 full. The dust in the bag is minimal, maybe 2 cups (if not less).




I can't believe what a tremendous difference this modification has made. The two hours I spent making it (including cleanup and shopping for the materials) will be recouped within a couple of weeks simply by not having to hang a new bag. Thanks for sharing the design! You should definitely pursue your patents, or at least recover some of your investment by selling plans on building a better separator.

Bas.