Shop Vac / Thien Baffle modification

[DustySanders]

Hi, everyone - I hope this is of interest. I decided to try to modify my Ridgid Shop Vac, bought a few years ago from the local Home Despot, to include a Thien separator. I didn't want to go with a separate trash can model, because floor space is at a premium in my shop, and I move the vac around a lot. So, in the posts below, I'll show you what I have done. But first, a few things -

I tried my best to do this project "quick and dirty-" since I wasn't eve sure if it would work. And that rarely works for me, because halfway through I start liking the project, and wanting to do it "right." But I managed to keep this one pretty quick. And, of course, I now know how I would do it, if I decided to do it again.

In terms of quantifying my results, I did two things. First, I used a wind speed meter to measure the baseline performance of the vac. I found that it was drawing air in at a speed of 31 MPH, and blowing it out at a speed of 46 MPH. I attribute the difference to the lack of a really good seal between the top lid, and bottom bucket of the vac. Secondly, in terms of static pressure, I used the very scientific method of sticking my hand over the opening, and feeling how hard it sucked. I'd quantify it as "pretty hard."

Below, see pictures of the very common vac I started with.

[DustySanders]

I measured the inside rim of the lower part, and found it to be 16". I had the idea of using concrete form tube to make the body of the unit, and had noticed in previous projects that the Despot sells their form tubes nested one inside of the other, so I knew I would have a range of tubes to choose from. I ended up finding one that was a good match for the rim of the vac. In retrospect, I should have sized it to the top part, which had a groove that the cardboard fit into nicely. In the end, I cut some rings off of the tubes to use to help fit the vac to the tube, as well as to reinforce the main tube itself. The lower part of the vac was easy to get a good seal to.

I cut the tube pretty easily using the crosscut sled on my table saw, and rotating the tube around. It produced an OK edge, and it remained fairly square. I glued the pieces up using the vac to size it. I had also already cut two discs, one 1/4" plywood and one 1/8" masonite, to be the top and bottom of the Thien chamber, and I had them inside the tube to help keep it nice and round and stiff.

[DustySanders]

You will notice that the thing is pretty tall. This shop vac, like many, has the filter that hangs down below the motor, and I had to have room for that. So there is basically a tall upper volume that the filter sits in, separated from the lower cyclone part by a 1/4" plywood baffle with a hole in it. More on this later.

I bought some shop vac fittings to use to make a round to rectangular transition, as well as to hook the vacuum tube up to. I made a wood piece that ended up with the size and shape I wanted the inlet to be, and started heating up the parts hoping to push them on the form, and voila! perfect transition. It took me a few tries, and produced a kind of lumpy final product, but in the end, good enough.

[DustySanders]

More pictures of the inlet

[DustySanders]

For the baffle between the filter section and the separator, I used a piece of 1/4" plywood scrap. I cut a hole in it, made two other rings for support, and used a $4.00 , 4" bell-mouth that I bought from a supplier of speaker building parts that I found online. I set it so that the bottom of the bell-mouth was right in the middle of the chamber, vertically. The chamber ended up being just over 3" tall inside. I didn't do a whole lot of thinking about the size of that inlet, or the height of the chamber, to be honest.

I did get a nice smooth fit on the tube from the bell-mouth into the filter chamber, and used a round-over bit to make the "output" of that whole thing more like a bell-mouth. I also didn't bother with any kind of air straightener, because I think there is enough separation between the vortex chamber and the blower, and who knows what kind of flow patterns are happening inside that chamber, anyway.

Nothing really radical about the 120 degree baffle, although I did include a bolt for support.

[DustySanders]

I used some heavy-duty foil tape to make the inside of the baffle chamber slicker, and also used that to smooth the transition out of the inlet. We will see if the stray nail, screw, or chunk of wood I suck up will tear that up or not. You could easily use some of the aluminum flashing you can buy in rolls for the same thing, and it would be a lot tougher.

[DustySanders]

Finally, I used a piece of rubber weatherstripping to make the seal around the bottom of the separator and the lower part of the shop vac. I sealed up the original inlet of the vac with some tape. Now that I know that it works, I'll buy one of those expandable rubber plugs to put in there.
I used a couple of bungee cords to hold it all together, and tested it out.

I found that the outlet wind speed stayed the same, at 46 MPH. This makes me think I have not added a significant amount of turbulence or flow restriction. Amazingly, the inlet air speed actually went up by about 1 MPH, but it is probably within the margin of error for my testing methods. I think that what may have happened is that I have achieved much better sealing between the various parts than the vac had off the shelf, and that made up for any loss due to the added vortex. In terms of static pressure, I again stuck my hand over the inlet, and would still rate the suction as "Pretty hard."

So, I vacuumed up a pile of dust, and it seemed to perform as well as I remember the thing working before. It didn't make any additional noises, and was able to suck up some fairly big pieces of wood. As soon as I can, I'll try sucking up some jointer shavings.

One think I like about it, is that if I ever need to vacuum up something wet, I can just take my new midsection off, stick the hose back in the old inlet, and do the job. I do wish that I could have made the whole thing shorter, but I didn't want to change the filter arrangement. If you wanted, you could probably find a way to lower the profile of that chamber by making your own filter.

I think I'll give the whole thing a coat of paint, and use it for a while. If any major flaws show up, I'll be sure to post about it, but for now, I'm pretty pleased, and think this is something that other folks might want to try.

[retired2]

Dusty,

I must say that is a piece of work, and I meant that as a compliment.

I'm not surprised by your air flow numbers.  Shop Vacs can have 5x the static pressure of a typical 1-1/2 hp dust collector, so you can add a lot of friction loss before you will notice a change in the flow rate.

I bought a small Rigid last year for my garage to vacuum out cars when they need it.  The static pressure (and noise) is so high I can barely use it.  It just sucks itself fast.  It's hard to vacuum carpet when the attachment grabs hold like a pit bull.  I've thought about cutting a hole in the hose to relieve some of the vaccum.

[DustySanders]

Thanks, R2 -
I ended up buying a "muffler" that Ridgid sells, from which I got the part that my hose attaches to. The other, working part of it fits the output of the vac, and makes a tiny difference in the sound - mostly in the high frequencies. IMHO, not really worth it, but as I said, I bought it for the connector.

I did about 20 minutes of vacuuming last night - the first time I ever rushed to the shop so I could vacuum - and opened the thing up to check it out. There is definitely fine dust getting into the top chamber, but the filter still has plenty of capacity. I vacuumed up some  dropped screws and nails, and a few chunks of hardwood, and the foil tape still looks fine. Of course, that will need to last a lot longer to really have proven itself, in my book. the dust in the bottom chamber is piling up around the sides, which I would expect. It isn't deep enough yet to really risk "scrubbing."    I'll report further in a few weeks, when I've had the chance to use it more.

[retired2]

I have the Rigid muffler as well.  It is useless as a muffler, but it serves a purpose as a diffuser.  Without it, there is a jet of exhaust air that if pointed in the wrong direction can blow a lot of unvacuumed dirt around.

Don't worry about your device performing perfectly, any separator is better than none.  In a woodshop a shop vac fills up in no time, and of course the filter gets choked with cake with nearly every use.

[BW68]

I have the Rigid 16 gal 5.0 peak HP with 1 7/8 hose. I did similar using 6 gal bucket to enclose the filter element and opening in the bottom to the separator mounted in Rigid lower section.  I get a lot of fine duct in the filter clogging it up.  lost so much suction over a couple of weeks time it is useless.  What has been your experience?

I have built a bucket separator dedicated to my table saw attached to a Shopvac 6.0 peak HP bought on CL for $20.  works 100x better,  and quieter.

bought my second shop vac at flea market for $5 dedicated to HF miter saw.  both vacs quieter and out perform Rigid from HD.  never have another Rigid.

Original question:  Seems to me the hose connection from vac to separator seems to act as a trap to keep fines out of filter.  Does any one else have this experience?
 

[retired2]

I have the Rigid 16 gal 5.0 peak HP with 1 7/8 hose. I did similar using 6 gal bucket to enclose the filter element and opening in the bottom to the separator mounted in Rigid lower section.  I get a lot of fine duct in the filter clogging it up.  lost so much suction over a couple of weeks time it is useless.  What has been your experience?

I have built a bucket separator dedicated to my table saw attached to a Shopvac 6.0 peak HP bought on CL for $20.  works 100x better,  and quieter.

bought my second shop vac at flea market for $5 dedicated to HF miter saw.  both vacs quieter and out perform Rigid from HD.  never have another Rigid.

Original question:  Seems to me the hose connection from vac to separator seems to act as a trap to keep fines out of filter.  Does any one else have this experience?

Let me start by saying I have no experience with separators attached to shop vacs.  So with that amount of experience let me say that I doubt a hose provides any trapping or separation.  The high sp and conveying velocity of a shop vac almost certainly brings all the waste from the pickup point into the separator.  Once there, it is either separated or not.  If not, it is going to wind up in the filter.   If the separator is separated from the shop vac by hose, I suspect the filter stays cleaner a little longer because you are separating twice, first in the bucket separator, and then again in the shop vac.  Now if I've misunderstood what you were describing, then what I just said may not apply or make sense.

[DustySanders]

BW68, I haven't used mine enough to really say, at this point. After about 20 minutes of vacuuming up everything from planer shavings to very fine dust that has been sitting on top of ducts in my basement, I definitely had some fine dust in the filter and top section, but it was no where near enough to clog the filter, and the vacuum was sucking just as hard as when I started. I'll be doing some work next week, and will report back then.

By the way, though, on the Shop Vac model, is the filter any shorter, or is it pretty much the same configuration as the Ridgid? I miss being able to stash my vac under my workbench.

[handyrandy]

Dusty,

I did my modification to my 12 gallon Rigid just over a year ago and had similar results. Not as clean looking as yours. See post elsewhere in this forum. http://www.jpthien.com/smf/index.php?topic=1210.0
What I have found over the last year, is that the baffle works extremely well. I have gone from banging my filter clean bi-weekly when in heavy use to once every 2-3 months. Before I had to replace the filter twice a year, now I haven't replaced it since building the baffle. All of the large sawdust or other stuff vacuumed up ends up in the bottom and is easily dumped. The inside of the chamber does get a fine coating of dust, but it does not affect performance. As R2 indicated, the muffler does little for sound, but does diffuse the exhaust air. My 1 7/8" hose with one wrap of duct tape fits snugly inside of a 2 1/2" dust fitting and doesn't come loose with the vacuum running and pulling it by the hose.

I am a tall guy and I like the height of my unit so I don't have to stoop to grab the hose and turn it on. I just drape the hose over the top when not in use. Still no clamps to hold it all together, the vacuum inside the unit does the trick when moving around. My one flaw is the inlet hose connection. I pressure fit the dust fitting in 1/2" ply to take the vacuum hose and sealed with silicone - the fitting does flex a bit. One recoat of the silicone allows it to flex but does not leak.

Randy   

[DustySanders]

Hey, Randy - your build looks good, I wish I had seen it before I started mine!

I have just about filled up the lower canister of my vac, and it is still performing very well. I probably would have emptied it once by now, and be due to empty it again, with the filter still down in that area. I'm planning to  see how many times I can fill and empty the bottom section before I have to clean the top filter.

Also, a lot of the Ridgid filters are washable with water, which might save you having to replace them as often.