Part 1
I wanted to re-edit this video with a new voiceover, as the original version involved me mumbling foolishly to camera. Preparation it seems, as with cooking and making in general, is an important oversight, and just as applicable to voiceovers.
I was given an old workshop extractor which came without a filter. The original would have used a bag, and I had fashioned one from an old bath towel, which was not filtering to a decent standard. After emptying the drum and removing the old inlet, I went about attaching a soil pipe which I had cut to fit upon the outer edge of the drum.
To create the inlet’s shape, I cut the profile of the drum from MDF, screwed this onto the soil pipe and used a band saw or even a large coping saw to follow the line. I did not have a band saw, and did this in another workshop.
Newer shop vacs use a method to create vortexes by offsetting the inlet, helping avoid directly blasting the filter with sawdust. I wanted to try recreate.
Using a scrap piece of metal, which I will use to reposition the new hole, I traced the shape of the inlet, cut it with the jigsaw, including the drum itself, and attached it using several bolts on either side.
I then used contact adhesive to join the inlet to the new rim of the new opening, and then hot glue to seal any gaps. The fit was not perfect but a combination of the two made for a strong gap free seal.
The soil pipe then needed a step down adaptor to fit the hose. I padded the gap using draught excluder, which produced a snug fit however some tool stores do supply soil pipe adaptors.
I made a custom HEPA filter, by dismantling a shop bought one and attaching it to a MDF ring and disc.
At the time of filming, I had the chance to cut these out on a CNC router, which would have looked a little like this. These rings are a little larger and for a new extractor I am currently building from a piece of large galvanised air duct I salvaged from a skip.
The CNC machine both cut the shapes and rebated the space for the filter to be glued, however it is possible to achieve this using a hand router or even a jigsaw.
The original filter bag for the vac would have probably only reached 1 micron filtration, but this HEPA certified filter can remove up to 0.3 micron particles. I would also recommend using gloves if handling a HEPA filter, as they are composed of fibreglass which is a skin irritant.
After removing the rubber gasket, I used cardboard jigs to hold the filter in position, and contact adhesive to glue these together. Hot glue created a more permanent seal, however you could use expandable polyurethane glue.
In the original video I also attached a smaller inlet however I never use this and it was pointless. There I am, mumbling about it.
In addition to the HEPA, I bought a chip extractors filtration bag, which are normally made from non-woven polyester, to add an additional protective layer and increase the working life of the HEPA filter.
The final modification involves several holes being drilled into the bottom end of the drum, and a small piece of clear plastic glued within, using contact adhesive. This will allow me to monitor the capacity of the bin without lifting the lid.
Part 2
Procedure
1. Test velocity of air intake
2. Open and clean Extractor
3. Remove outer filter
4. Cut filter fabric to a smaller size
5. Install baffle, close extraction, seal and test velocity at intake
6. Make lid clamp.
I began talking to camera without realising the directional microphone was not turned on. I’ve done this so many times now, I’ve decided to buy a small length of fibre optic wire to attach onto the LED light behind the microphone and point the other end towards myself, as a glowing visual reminder.
In any case, this means I can use a podcast microphone bought specifically to record voiceovers.
I am going to test the velocity of the extraction at the inlet point using the affordable Chinese anemometer I’m holding in my hands.
The velocity reading was roughly 10 meters a second.
After unwrapping the hazard tape to reveal the filter bag covered in a fine grey dust. I donned a dust mask, vacuumed this off using the numatic vacuum cleaner and checked the HEPA cartridge underneath, which still looks quite clean.
I went about emptying the drum of the sawdust it had collected and gave that a quick clean as well. This is always a messy task and I should figure out a way of fitting a collection bag within it at some point.
The filter bag which is intended to prolong the working life of the HEPA cartridge, is made from a portable chip extractor filter which I had cut down, however not enough. I trimmed a little more to neaten the flange, preventing it disturbing the airflow and to make space for a baffle I was about to add.
A baffle forces particulates in the air to move in towards the collection point of the extractor.
I use cable ties to hold the bag in place, beneath the HEPA cartridge and placed a cylindrical hoop, made from an old tom-tom drum to check the spacing. This is what I plan to use as a baffle around the filter, with the hope that its smooth surface will help or improve the cyclonic effect from the inlet.
The drum’s diameter is about 40cm, and after taping up its existing holes, I use a few dabs of hot glue to hold it temporarily in place.
Once that had dried, I replaced the lid upon the drum and sealed it using hazard tape, and prepared to compare the difference cleaning had made.
Cleaning the filter has improved the velocity of the air by around 2 meters a second. After a few months of use, I will open the extractor to visually check the filter.
I’m going to also add some clamping latches, to replace the hazard tape. The drum is a little battered, and the lid needs to be aligned to minimise any gaps.
I began marking the lid into quarters, avoiding the handles, switch, power cable and inlet. When I was happy with this, I doubles checked the spacing with a piece of string the same length as the circumference of the bin, which I cut into quarters before marking the final positions.
I am using a thick off cut of laminated birch ply, which I mark against the drum estimating the spacing of the M8 insert nuts I will use.
These are cut to size with my table saw sledge, roughly 90mm long. I then trimmed an angle off the blocks, with my tapered angle jig. This tapered surface will sit against the drum angling the insert nut slightly away from the lid.
After marking where the inserts positioning, I drilled out holes the same size at their narrowest end, and then used a cone cutter to taper the hole. This will helpl prevent the birch from splitting.
I drove the inserts in, with a cut down allen key but hand twist the final distance to prevent over tightening.
I gave these a quick hand sand, marked the surface I was to glue, and then traced their shapes out against the bin of the extractor. Within this silhouette I drilled two holes, and de-burring the breakout from in inside.
I apply contact adhesive to the birch blocks and extractor drum, allowing the glue to become tacky after a few minutes before pressing them together. The bond is instant, but I drilled some shallow holes and places screws on cupped washes to hold them in place.
I am now going to make the hooks with which to hold the lid down. I am using some scrap pieces of aluminium, which were cut from an old apple G5 computer. The curve will fit over the lip of the lid, and the width will help apply ample clamping pressure. I test one piece before cutting the rest which I tried to do with the table jigsaw, but that failed, and I don’t like cutting aluminium with an angle grinder, so I resorted to using the hand held jigsaw.
I didn’t like cutting the aluminium with an angle grinder, so I resorted to using a jigsaw hand held. The pieces are then shapes on the edging sander, their holes drilled and small spacer blocks glued to the underside. I drilled holes through these as well, and used them to clamp the lids, using the pressure and some additional squeeze clamps to hold everything in place until the glue has cured.
The following day, I gave these a sand curving the corners, and used them to finally clamp the lid down.
