Before we start of:
The idea behind this handy air filter unit was to use materials you can only find in your homecenter. and prefferably you don't need to solder and make intricate wirings and such.
So far i think this has worked out. Let me know if you feel the same!
If you are interested in the schematics and sizing, this is available from my website: www.seamm.nl
Step 1: Design
So the idea is clear:
Use matererial from the home center and keep the fabrication limited to no soldering and complex wiring.
(I'm going full nerd in the next paragraph, excuse me)
The next step was thinking about other design constraints or challenges. I wanted it to be small, my own shop is small so therefore. And I would've liked if I could hang it like a dust filter cleaner unit and stand it on a desktop/workbench. And while i am at it; make it function as a fume extrator. This is handy for useing lacquer, welding and soldering.
So at first I needed to find and use a fan which doesn't require electronics and could be hooked up to a wall plug. The simplest and cheapest option would than be a 100 mm tunnel fan you put in your toilet for air extracting. These fans have a high flow rate and low energy consumtion (AC synchronous motor) but have a limited pressure capabilities
For the filter material I needed a fine mesh fabric and I came across a 'stove grease filter' material. The stuff which is in your 'extractor hood', 'afzuigkap' in Dutch. And for the fume extracting an active carbon filter.
Step 2: Cutting Stock
The first real fabrication step was getting the wood wheet material to size. I used a mitre saw and table saw.
Step 3: Rabbet Joints
The general frame of the housing is fitted together with a rabbet joint in the top-bottom piece. Those pieces are 18mm (3/4 inch). And the sides are 6 mm (1/4 inch). This way there isn't too much material in the the housing.
Step 4: Housing Assembly
The top and bottom pieces are glued to the thin side pieces. I drove in some small pin nails to help clamping and aligning. This is slightly easier but not required. After the glue has set the front sheet was put on the assembly, with the same procedure. When this was done the whole housing was assembled and when the glue was set it was suprizing sturdy given only the top and bottom are of standard thick sheets and the other parts are thin.
Step 5: Making Holes
So the housing is one piece now. I took one tunnel fan and measured the outside rim of the tunnel. I increased that measuring with 10% and drawn the hole I could saw with a jigsaw. In my cat the holes became 112 mm (4 1/2 inch).
Step 6: Wiring
So there are two fans. Both ran in my situation at 240 V AC. To make them work they needed hooked up in parallel.
If you dislike electrics skip the previous sentence.
So I placed one 2 wire cable between the motors. Hooked it up one side. Drilled a hole for the wall plug cable with switch. Feed that through. Hooked up the wall plug cable with the 2 wire cable in the same slot of one fan. On the same wire colors as the first fan to wire connection.
This way the motors are in parallel. This is similar as you would want to use the tunnel fan when you switch on the light in your toilet.
Step 7: Test
This step is very important.
This way you can validate if all went well. Before you test, check if there are no other machines running or hooked up to the electrical group you want to test the unit on.
Check if you have enough circuit breakers or an automatic one.
And press the switch.
If you worked neatly and safely nothing bad has happend; on to the next step.
Step 8: Support
On the inside of the top and bottom part I glued in a slat of 18 mm (3/4 inch) material to act as a support for the filter material and frame.
Step 9: Frame
The filter material will be secured via a retangular frame. This frame will be screwed on and 'clamp' the filter in place. The frame is made via a simple halflap joint glued in place. Screws or nails can be added as extra, this is not required.
Step 10: Filter Material
So the grease filter and the active cabon filter come in this fabrics or sheets. They need to be cut larger than the frame to be properly secured in place.
Step 11: Filter Assembly
As said earlier the frames are screwed into the housing. There where the support slats were glued in place. Four screws will do the job fine.
Step 12: Finishing
This step is totaly not important and only for your own visual comfort. I painted the MDF sides green.
After that I glued on 4 small blocks of wood to act as feet. On the front I put a cleat to be able to hang the unit to the ceiling.
And that concluded the Air filter unit. I have a video testing the fume extracting capabilities: