Thien Baffle Dust Extractor With Quick Change Bucket

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About: I enjoy working in wood and metal, doing overnight bushwalks, playing music, solving problems etc.

This project is inspired by Hector Acevedo's tiltable shopvac dust collector.

https://woodgears.ca/reader/hector/shopvac.html

Instead of tilting the top section, my design incorporates Matthias Wandel's foot lever idea for a quick and easy bucket release:

https://woodgears.ca/dust_collector/separator.html

The Thien Baffle was invented and patented by J. P. Thien: http://www.jpthien.com/cy.htm and it works amazingly well. It's big advantage is that it occupies a fraction of the space needed for a large dust collector or a conical cyclone.

Why Build it?

If you have ever tried collecting dust and shavings from woodworking equipment with a traditional vacuum cleaner or a shop vac, you know it is a losing battle because the filters block up too quickly.
This dust collector was made to collect the dust from a small band saw and a bobbin sander at my local men's shed. Both these machines have 40mm dust outlets on them, which should be within the capability of this dust collector.

It is obvious that a small – bore extractor like this can't handle machines with 100mm output pipes, eg. A Planer thicknesser or a big table saw, which need purpose built dust extractors.

The quick and easy removal and installation of the waste bucket is a huge bonus.

Step 1: Parts List:

1 round vacuum cleaner. If it is bagless like a shopvac, so much the better. (Mine wasn't)

1 plastic bucket for the Thien Baffle diameter 300mm, height 300mm (eg. a paint or tile glue bucket )

1 Strong plastic bucket 300mm dia x 400mm high to catch the dust

chipboard 20mm thick x 390 x 390 to create a surround for the dust receiver bucket

chipboard 16mm thick x 390 x 390 mm OR scraps of wood 210mm long x 16mm thick x 70mm wide to make a surround for the bucket
15mm plywood 390 x 390 for the baffle. (6mm thick would be fine)

300 mm dia circle of 10mm mdf with a 50mm hole in the centre (goes under the vacuum cleaner)

300mm dia circle of 16mm chipboard with a 50mm hole in the centre for the top of the Thien Baffle.

1 x 150mm pvc pipe 45mm OD (internal tube)

1 x 150 mm pvc pipe 60mm OD. (Inlet tube)

Wood to make the support for the inlet to the Thien Baffle

1 x radiata pine 100 x 200 x 20 (this is the block for the internal bag holder)

sheet metal 0.4mm x 120 x 170 bent to fit the vacuum cleaner bag

3.4 metres (11 feet) radiata pine, 70mm x 20mm

1 metre (39”) radiata pine 40mm x 20mm

2 x 70 x 50 x 38mm blocks for the front legs.

2 x 180 mm diameter wheels with through bolts (salvaged off an old barbecue)

6 x 10mm ID washers & 2 x 5mm spacers for the wheels

1 x 70 mm hinge.

1 metre of adhesive foam draft excluder 12mm wide.

Wood screws

PVA glue

Silicon sealant.

1 x Spring 220mm long x 20mm dia, 10g wire thickness

2 x 6mm eyebolts 60mm long with nuts and washers.

2 x 6mm x 40mm bolts with wingnuts, & washers

Step 2: The Thien Baffle:

Only basic tools are necessary, although a drop saw, drill press, band saw hole saw and jigsaw will make things easier.

I won't detail the construction of the Thien Baffle, because it is covered in all the links that I posted at the start of this Instructable, except to say:

  1. It is faster and easier to make the top and bottom pieces of the baffle out of a sheet of chipboard and carefully and accurately cut the hole for the bucket directly in them with a jigsaw. You may be able to see that in my construction the wooden ring that surrounds the bucket is made from 6 x 210mm pieces of 20mm x 70mm pacific maple cut to form a hexagon with a circular inside curve for the bucket, with extra wood pieces to create a square section 390 x 390. I know that this is the “long” way round. The angles on these pieces must be exactly 30 degrees each, or it will not fit together, and consequently, a drop saw was essential.
  2. The baffle itself is cut out of a square piece of plywood 390 x 390 x 15mm sandwiched between the hexagonal ring and the chipboard square that locates the bucket onto the baffle. The baffle could be much thinner, eg. 6mm, but 15mm is what I had. Because it is thick, I put a 45 degree chamfer on the edge furthest from the inlet to minimise larger shavings getting caught on it and interfering with air flow.
  3. The inside of the bucket should extend about 6mm beyond the outside of the baffle opening. This means that the baffle must be designed using the bucket dimenstions for reference. There must be enough room to run a ring of 12mm wide stick-on foam draft excluder around the outside circular edge of the baffle, so that the bucket seals on to it. In the photos you can see that the chipboard ring that retains the bucket is made from 2 "halves" with some short joiners. Normally this would be one piece
  4. To interface the Thien baffle section with the bottom of the vacuum cleaner, a chipboard disk fits inside the top of the bucket, and piece of 10mm mdf fits underneath the vacuum cleaner. This compensates for any discrepancy in the size of the vacuum cleaner and the baffle assembly. and provides a way to create a good seal between the baffle and the vacuum cleaner. This kind of setup will interface with any sized bucket - even a garbage can if it can withstand the vacuum.

Step 3: Modifying the Vacuum Cleaner:

Round vacuum cleaners usually have their inlets on the side, but the suction needs to be in the centre of the base, for the Thien Baffle. The side inlet is blocked (see photo) and a 50mm hole drilled in the centre of the base of the vacuum cleaner, to take a piece of PVC pipe 150mm long which protrudes 30mm into the dust bag and about halfway into the baffle area.

This vacuum cleaner had a plastic ring around the bottom with 6 castors on it. It came off easily when I cut through the ring.

Although this vacuum cleaner has a “final filter” to remove fine dust, (see photos) I felt that it needed a dust bag in case of overflow. Eg if the bucket fills up.

I threw the original dust bag away, but I have a supply of smaller dust bags which were spares for various (now dead) vacuum cleaners. Rather than buying a large replacement dust bag, I made a steel holder to fit one of these smaller bags, and installed it on a wooden block where the PVC pipe came through. (See Fusion 360 drawing & photos)

The wooden block was necessary because the bottom of this vacuum cleaner is slightly conical and the metal bracket wouldn't sit flat on it. There was a fair bit of chiseling and sanding to make the block fit.

I could have cut the entire bottom out and installed a chipboard disk, but I think that the existing shell creates a far better seal.

Either way, the dust bag must be able to be placed vertically over the inlet pipe. It can't slide sideways because the pipe protrudes into the bag about 40mm. There are 2 x 6mm wing nuts either side of the metal bracket to secure it.

Once the machine is up to this stage, it is worth testing.

With the Vacuum cleaner attached to the baffle assembly and the baffle assembly resting on the bucket, turn it on and suck up some dirt & shavings. Hopefully, the Thien baffle will put almost all of it into the bucket.

Step 4: The Trolley:

A critical dimension for the trolley is the size of the bucket.

The retaining lever should be horizontal when the bucket is in position which determines all the other trolley heights. (see Fusion 360 drawings).

The attached Png files don't display well online, but all the dimensions etc are very clear if viewed in "Paint".

The wheels came from an old BBQ and had through-bolts and nyloc nuts. I used washers & spacers to space them away from the side of the frame and to take up the extra threads to create minimal side clearance.

The side clearances need to be small, or the wheels won't sit vertically - the hub "bearings" are sloppy.

I didn't use castors, as this unit is designed to be stationary, not dragged around like a vacuum cleaner.

Construction is straightforward. - Glue and screws. The wood frame is 20mm thick, because that is what was on hand. This makes the trolley very light and easy to lift during construction & painting which helps.

If you opt for thicker wood, some of the clearances may need to be adjusted, eg. The clearance of the rear batten near the top of the bucket where the spring attaches. I had it on the front edge until I found that it ran into the bucket...

The eye hooks were made from old bolts. The spring was from my spring collection. Almost all the materials for this project were second hand, including the buckets, screws, fittings & the vacuum cleaner. The only thing purchased was the foam draft excluder..

Step 5: Assembling the Trolley:

TO ASSEMBLE:

Screw and glue the rear legs to the lower horizontal supports to make 2 "L" shapes, and Screw and glue these onto the side of the baffle assembly, with the horizontal pieces on the inside of the verticals.

Screw and glue the lower cross piece to the bottom of the horizontal pieces, ensuring that the horizontal pieces are parallel.

Screw and glue the lower rear batten in place.My lower batten was 40 x 20 x 390, with a filler batten underneath it for the hinge screws. You may like to use 1 x 70 x 20 x 390 and do cutouts for where it overlaps the horizontal legs..

Ensure that both horizontal legs are square with the vertical supports and parallel with each other.

Screw and glue the 2 x 480mm x 40mm x 20mm vertical side struts 95mm from the rear supports. They rest on the horizontal supports and are screwed in place at each end

Make the lever and foot pedal assembly and attach the hinge to it, as per the drawing.

Turn the assembly upside down so that the bucket can beheld in place by gravity.

Put the bucket in place, position the lever against the bottom of the bucket, get it straight, centred and level and mark the hinge screw holes on the batten at the back.

Drill the screw holes, and mount the lever onto the stand.

Put the bucket back, make sure it is evenly seated against the baffle, and find the spot where the eye bolt will fit – as close to the bucket as possible without touching it and without the spring colliding with it. Mark the position on the lever, drill a hole and install the eye bolt. I used a nut & washer each side of the lever to fix it in position.

Depending on how strong your spring is, find the right height to attach the upper batten and eye bolt, so that the spring tension maintains firm lever pressure on the bottom of the bucket. With this design, the spring is only 70mm from the hinge pivot, but the centre of the bucket is 235mm from the pivot. 235/70 = 3.4:1 If the bucket and contents weigh 6 Kg, then there needs to be at least 20KG of spring tension.

With the eye bolt at minimum adjustment, get a rough approximation for the batten position, screw (don't glue) it in place, and test it. If it works fine, you can glue it. With the eye bolt set at minimum adjustment, the nut can be tightened to provide extra tension if necessary.

It is much easier to fit the spring onto the eye bolts if the bucket is not in the machine. The lever will move up enough to make it easier to stretch the spring onto the eye bolt. If you find this difficult, loop a piece of strong cord through one end of the spring, and wrap the cord around some wood scraps for handles, which you use to pull the spring up & hook it over the eye bolt. (see photo)

To install the wheels, with the trolley on the bench, level it with a 20mm high batten at the back edge, and a 40mm high batten at the front edge. Measure ½ the diameter of the wheel up from the bench and make a mark in the centre of the rear upright. Drill holes for the bolts (mine were 10mm) and using washers and spacers, install each wheel.

Screw and glue 50 mm x 70 mm x 40mm spacers under the front of the horizontal legs to level it up.

Step 6: Final Steps:

PAINTING:

If you want to paint the machine, it's easiest to do this before the vacuum cleaner bowl is screwed to the Baffle assembly. The wheels and spring should be removed.

If you plan to paint it, DON"T use non-paintable silicon sealants (eg. acetal cure tile and bathroom sealant) on any part of the construction. I did, and the paint didn't adhere properly.

The hinge should be coated with metal etch primer before installation and undercoating, or left unpainted.

Screws can be countersunk and filled for a better finish, or removed, re-drilled and replaced with dowels after the glue has set on the joints. (Less filler required!)

TIP: A quick and effective filler: Bicarbonate of soda poured into the hole, super glue dripped onto it until the drips are soaked up. Wait 10 minutes, and it's ready to sand.

Once painted, the vacuum cleaner base, wheels & spring can be replaced, and the machine is ready for use.

This machine has been equipped with an adapter for a vacuum cleaner hose, but a larger hose could be fitted over the inlet if there was enough suction.

TEST RESULTS:

I had 169 grams of mixed sawdust/metal filings/wood chips etc, which I weighed, sucked into the machine, and re-weighed what went into the bucket. As you can see from the photos and the video, I sucked up 169g, of which 167 g went into the bucket. (98.9%)

How well the machine will separate very fine dust, I am not sure, but the 98.9% I got with sawdust and wood chips was surprising and encouraging.

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