Thien Separator Tophat for 55 Gallon Drum

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Project by BobAnderton posted 05-21-2016 04:46 PM 12318 views 13 times favorited 9 comments Add to Favorites Watch

I finished a tophat build that started with a 55 gallon drum based dust collector that Cincinnati Fan sells as the model 200s, see pic below, as a 2 stage collector. It had a 2HP Leeson motor with a 12.25” impeller and 6” inlet and outlets, which was an ok start, but its separation characteristics left a lot to be desired. It scrubbed the contents of the drum badly and passed about 1/3 of what went into the drum on to the filter bag. The manual even said to empty the drum when it was 1/3 full or it would start filling the filter bag faster. The bag was a 18 square foot bag of 5 micron knit polyester.
So, I figured this thing could really benefit from a tophat that would do a good job of separation, allow what went into the drum to stay in the drum, and that would enable putting a better filter on it since you’d no longer be sending everything to the filter. The inner cylinder with tangential inlet acts like the top portion of a cyclone. As the air spins around inside the dust is pushed to the outside walls by centrifugal force and then it drops down into the barrel through a 1.25” wide drop slot that runs 2/3 of the way around the circumference. The dust free air makes it to the center where the blower inlet takes it in. The baffle that sits between the drum and the chamber keeps the circulating air in the chamber from stirring up the dust that has already fallen into the drum.
I went with a design that didn’t deviate too far from what others have built before and shown both here and at the Thien baffle forum. My 6” round inlet hose transitions to a 3.5” x 10” rectangle using a floor register from Home Depot. The body of the chamber is 12” high, so the body is either a 2X high tophat based on the diameter of the 6” inlet, or 1.2X high based on the height of the rectangular inlet. Anyway, there is 2” of full circle that passes under the inlet rectangle. I used 0.093” (3/32”) PETG from McMaster Carr. 24×48” sheet was $26. The PETG is very flexible and was easy to form into the tube to go inside the rings. The interior space is a 21” diameter circle and the outside dimension of the wooden rings was 24”. I epoxied the PETG into the plywood form and then used silicon caulk around the outside to ensure a good seal. The outlet at the top of the separator is a 8” to 10” reducer also from Home Depot. It further tapers to 7” as it goes into the impeller housing.
I had some scratched 3/8” plexiglass that I’d curb picked that I used to make the actual baffle. By using clear material for both the sidewalls and the baffle I’m able to look through the side down into the drum and see how full it is directly. Around the top of the tophat I’ve got 3 hoist points and I have a 7:1 block and tackle pully I got from Amazon for $14 that I can use to pull the entire tophat up off the drum and tie off with a cleat. Inside the 55 gallon drum I’ve got a 55 gallon bag taped. When the bag/drum is full I’m going to nylon zip tie it closed and tip the drum on its side and pull the bag out. Haven’t gotten that far yet as I haven’t yet filled the drum the first time.
I used the 0.5 micron 300 square foot media 9L300NANO filter from Wynn Environmental. I made an interface flange for it out of plywood and added a gamma lid ring to the bottom of it with a 5 gallon bucket cut off at about 6” so I’ve got a screw on dust basin at the bottom of the filter. There is a write up at Wynn Environmental that shows how to do this.
The entire collector is free standing on top of the drum, which I think is a nice attribute because I can scoot it around if I need to. Right now I’m just running 6” flex to tools as needed as I don’t have 6” ductwork up yet, but you have to start somewhere.
It seems to work really nicely.

-- Bob Anderton - Austin, TX - Nova 3000 lathe, Alaskan Mark III mill, Husqavarna Saw

9 comments so far

View DocSavage45's profile


9071 posts in 4341 days

#1 posted 05-21-2016 05:40 PM

Hey Bob!

I like it!
I did something similar awhile back although I think yours is MO-BETTER! Been thinking about improving efficiency. Also a 55 gallon drum has pros and cons. Mine is outside the shop in a garden shed which has a ramp to get into it.

At present I don’t have enough suck to remove an adequate amount of dust and chips, but I have 50 feet of corregated 4 inch.

Have to put this on my shop to do list!

-- Cau Haus Designs, Thomas J. Tieffenbacher

View Jim Jakosh's profile

Jim Jakosh

27836 posts in 4604 days

#2 posted 05-21-2016 06:11 PM

Man that is stop shelf. Congratulations on that build. Very nice!!!!!!!!!!!

Cheers, Jim

-- Jim Jakosh.....Practical Wood Products...........Learn something new every day!! Variety is the Spice of Life!!

View BobAnderton's profile


315 posts in 4289 days

#3 posted 05-21-2016 06:52 PM

Thanks for the comments guys, much appreciated. Doc, I bet you could get a big improvement just from switching to 6” PVC pipe for the biggest part of your long run. The ASTM 2729 “sewer and drain” 6” pipe is about $20/10 foot length around here. Even if you keep the 4” fittings on your collector you’d eliminate the static pressure drop of your 50’ of 4” flex.

-- Bob Anderton - Austin, TX - Nova 3000 lathe, Alaskan Mark III mill, Husqavarna Saw

View DocSavage45's profile


9071 posts in 4341 days

#4 posted 05-21-2016 08:38 PM

Thanks Bob,

It’s in the works. Just need some money and time. :<))

-- Cau Haus Designs, Thomas J. Tieffenbacher

View bushmaster's profile


4181 posts in 3781 days

#5 posted 05-22-2016 03:40 AM

Nice well built project, and it works great I bet. I did something simuliar using a 45 gal drum. Re configured a standard 2 stage dust collector to thein principle. I orginally had a filter that looks like yours. I found it plugged up with dust, cutting air flow down and is a pain to clean. The commercial has a handle that you turn and it beats the pleats as you know. When I redid the system I located it all outside and vents outside. Full suction all the time, I would never go back to trying to filter the air, even here in the north. I had made provisions to do that in winter. Remote control to use when needed.

-- Brian - Hazelton, British Columbia

View MustacheMike's profile


263 posts in 3587 days

#6 posted 05-22-2016 11:34 AM

Very nice!!!

-- You can trust Mike -" because I will never pull your stash!" See my show weekly at

View Holbs's profile


2389 posts in 3528 days

#7 posted 05-22-2016 02:03 PM

Welcome to the Thien Baffle Tophat community. We all gather around our tophats on Phil’s birthday, grab some popcorn, chuck gallons of saw dust in our dust collectors, and watch the saw dust swirl around and around like a snow globe :)

-- The Carpenter Bee is derived from the Ancient Greek word wood-cutter "xylokopos/ξυλοκὀπος"

View helluvawreck's profile


32122 posts in 4365 days

#8 posted 05-22-2016 03:22 PM

That is a very creative design for a barrel top cyclone unit that is shop built.
helluvawreck aka Charles

-- helluvawreck aka Charles,

View david38's profile


3518 posts in 3842 days

#9 posted 05-23-2016 02:09 PM

looks great

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