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Picture of Dust Sniper (quiet extractor system)
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DS cyclones.jpg
In this project we turn a bunch of old free stuff, including two old household vacuums into what is arguably the most useful and necessary of workshop tools: the dust extractor. But why stop there? Lets make a really fantastically effective dust extractor, one that is whisper quiet, never stops sucking or plagues you with blocked filters, one that is versatile enough to take dust from a variety of power tools, one that turns on and off on its own so you never forget, and most important of all, one that does a good job of extracting the small - most deadly - particulates from the air you breath... Step forth, 'The Dust Sniper'.

This project was borne out of my dissatisfaction with commercially available dust extractors. After a fair bit of research I purchased one of the more expensive 'quiet' workshop vacuums, and was not happy with its performance (I sent it back unused after taking a dB reading of it). In exasperation at the dusty noisiness of it all, and wanting to re-use materials and spend as little as possible, I began the Dust Sniper (DS) project. 

This DS ended up costing about £20 total. So it is possible to reused a bunch of stuff destined for landfill and end up with an aesthetically pleasing and useful tool-workbench. And of course we can learn loads about sound, cyclones and dust related jazz along the way. Because the DS's parts are mostly recycled, there is no comprehensive list of materials up front, instead I will give tips as we go along suggesting possible reclaimed bits that will do the job and where you might find them (if you don't care why we chose certain materials and just want a 'scavenging list', check out the last step).



My kingdom for some silent clean air

I'll throw it out there to begin with, most dust extractors are bad. Even the expensive ones, like the Festool, extract a continuing fee, needing regular bag and filter changes to keep working properly. The less expensive, well... lets just say they can be seriously bad for your mental and physical health, as you will find out if you follow along with this Instructable. 

The Dust Sniper (DS) is effective and very quiet - the two main goals I had when starting this project. It does, however, fulfil these requirements at a cost. Namely, it is very heavy and big (compared to your average canister style vac), so it won't be perfect for everyone. This isn't necessarily the disaster you might think though. In fact it can be darn right useful if we use the DS as a mobile work surface. That way we will end up with nice clean air, a quiet place to create our mad jazz, and a super sturdy, rollable worktop thrown in! Ideal if  you are still setting up a workshop, as I am.

 
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Step 1: Noise Loves Dust

Picture of Noise Loves Dust
We might not often think of noise and dust being co-conspirators, but they do help each other to cause workshop misery. Dust, particularly for those that do much woodwork with power tools, gets everywhere: in the air, in your lungs, and in the belts and bearings of our tools. Power tools, like an orbital sander, a jigsaw, a planer, or a router create a lot of dust, and without good extraction (sometimes even with it) the quantity of dust that gets into our tool's workings is enough to cause big increases in noise levels. 

Lots of noise is bad. As anyone who reads the FE blog will know, I am particularly fastidious about cutting down on noise (see for example, my quest for the quietest bandsaw). I can think of a load of good reasons for my desire for quiet tools, but probably the most important, and one that anyone using power tools should take seriously, may be gleaned from the following: 

"The first handicap due to noise-induced hearing loss to be noticed by the subject is usually some loss of hearing for high-pitched sounds such as squeaks in machinery, bells, musical notes, etc. This is followed by a diminution in the ability to understand speech; voices sound muffled, and this is worse in difficult listening conditions. The person with noise-induced hearing loss complains that everyone mumbles. High frequency consonant sounds of low intensity are missed, whereas vowels of low frequency and higher intensity are still heard. As consonants carry much of the information in speech, there is little reduction in volume but the context is lost. However, by the time the loss is noticed subjectively as a difficulty in understanding speech, the condition is far advanced." (p146 Engineering Noise Control)

Ok, so dust often equals more noise. How ironic that adding a dust extractor can be so noisy then. Lets leave 'noise' at that for now - for more noise related background and nerdy theory, checkout step 3.          

Dust is a serious problem. 

Actually aside from helping along hearing loss, dust can cause bigger problems. At this point I am going to go ahead and assume that everyone is comfortable with the idea that dusty lungs are bad and to be avoided. The problem is most people don't realise just how dangerous dust is, especially to us lone inventors, DIYers, and makers, who do not have the protection of government legislation, which enforces air quality standards* in factory and workplace environments.  

At home, people tend to use cheap and ineffective extraction systems and/or pathetically inadequate masks (or no protection at all). I must admit from time to time I have been guilty of this, not wanting the noise of the vac or being in a rush - very bad! The precautionary principal should definately apply here. Particularly until you have finished your DS, a good dust mask, goggles and ear defenders are your friends! For more info on dust and health check out this post on The Dangers of Wood Dust and this table of wood dust toxicity levels.

*It is interesting to note how these standards are constantly being raised, as more research is done on the effects of wood dust. See, for example, Jette B. Lange, 2008 "Effects of wood dust: Inflammation, genotoxicity and cancer"

Step 2: Cyclonic filtration - Overview

Picture of Cyclonic filtration - Overview
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The details, instructions, and measurements of the actual cyclones have been up on the Flowering Elbow website for some time. Rather than have them repeated here, check the cyclone build guide steps on flowering elbow. 
 

Step 3: Noise reduction - background information (and some theory you can skip)

Picture of Noise reduction - background information (and some theory you can skip)
So when I was building this, I spent a while researching about noise, sound and jazz, if you're into that kind of thing too read on... If you are a sound wizz already, look away. If you are bored easily and/or just want to hammer things together you can skip it too.

So what Is sound anyway?

Every school kid will tell you sound is basically the result of things getting excited and vibrating. Everything vibrates anyway, but if you do something like hit the table in front of you (assuming there is one), you change the way it vibrates and it passes on that vibration to the air. In the air we can imagine a series of high and low pressures, which in turn vibrate the internal gubbins of our ear - causing us to register what we call sound.

As with most subjective things in life we humans like to try and measure and quantify these vibrations. The quantity most often used to measure the “strength” of a sound wave is the 'sound pressure level' (SPL or sometimes Lp, not to be confused with 'sound power level') measured with respect to a standard reference pressure of 2 ×10−5Pa.  

SPL is expressed in dB (or Decibels) which are a logarithmic unit, so that for every 6 dB decrease in volume, the sound is perceived as being half as loud. 
 
Blocking out Nasty Sound (noise)

When an airborne sound wave encounters a solid blocking its path, it effectively bashes into it, the disturbance causes the solid to vibrate. This vibration is transmitted through the solid. Now on the other side, the surface acts as a new emitter by disturbing the air and producing a new sound wave. By this process the sound effectively passes through the barrier. The efficiency of the transmission depends on the physical properties of the solid in particular, its mass.

How much of the sound is blocked out? Well, if L1 dB is the sound pressure level on the noise source side of the partition and L2 dB that on the other side, then the Sound Reduction Index (SRI) or Transmission Loss (TL) is defined as:

TL = SRI = L1 - L2  dB  
 
The transmission loss, or SRI, varies with mass and frequency. In general the higher the frequency the better the sound is blocked, hence the higher the SRI will be. There are exceptions to this when partitions start vibrating at their resonance frequencies. More on that later, for now all we need to know is that:  

1. For precision work (or for special noises with a particular frequency content), the SRI index is quoted for particular frequencies, normally in octave bands.

2. For many purposes and for convenience, the SRI is quoted as a single number, which is the average SRI between the frequencies 100 – 3,150 Hz. The resultant sound level is then quoted in dB(A). (A) presumably standing for average. 

The Mass Law

The so called 'mass law' simply states that by increasing the mass of a partition, we increase the transmission losses or SRI of the partition proportionally. So mass is generally a good thing when we are trying to reduce sound (think about the useful properties of lead). The mass law however only applies to a given material, over a specific range of frequencies. It could be, for example, that a deep bassy noise (low frequency) travels through a panel with very little reduction in volume even when you increase the mass of a panel. Indeed it is often the case that low frequency noise transmission is more effected by the stiffness of a material.

Again, this all depends upon the material in question. A lead curtain's behaviour, for example, is essentially mass-law controlled over the entire audible frequency range. For a more geeky explanation along these lines, check out "Engineering Noise Control: Theory and practice, Fourth edition, David A. Bies and Colin H. Hansen (2009)" 

For us, the mass law is a good demonstration of the compromise we are going to make between light weight and sound reduction. "[We] should rule out the use of low density fibreglass (such as insulation batts used in house ceilings), as well as typical polyester blankets. In fact polyester blankets are likely to be completely ineffective." (Bies & Hansen, 2009 p 386). Although if we can compress them a lot and have them to hand anyway, it is a different story...

Building less symmetrical and more random please

As with double or triple glazing, it is important not to have all the panes the same thickness, as this accentuates the dip in the TL (transmission loss) curve at critical frequencies. The same goes for our purposes when we construct a double wall box. It is better to use different materials as well as thicknesses for the different layers. That way we will block out a broader range of frequencies.

While preventing resonance by mixing materials and shapes is good, it is also well worth incorporating an air (or foam) gap, which prevents the direct transmission of vibration. Vibration is easily transmitted to other materials by mechanical coupling - avoid if possible. 
 
"Acoustic isolation is generally accomplished by providing as wide a gap between the panels as possible and by filling the gap with a sound-absorbing material, while ensuring that the material does not form a mechanical bridge between the panels." (Bies & Hansen, 2009, page376)

Absorbing Sound

The nature of the surfaces on which the sound wave falls determines how much will be absorbed. Hard rigid non-porous surfaces like glass, marble or concrete, provide the least absorption and are thus the best reflectors. Soft porous surfaces and those which can vibrate absorb more of the sound. When sound energy is absorbed it is converted into heat energy, but this energy is very small so no need to worry about overheating caused by sound.

The amount of sound absorbed is proportional to the area of the material concerned. So if S is the sound absorbed and A is the area of the exposed material, we can say that S is proportional to A. In general this means that rough surfaces are better at absorbing than finely finished ones. Further,

 S = aA
 
where:  a is the Absorption Coefficient.

The Absorption Coefficient is a number always less than 1 (because it has no units, it is a ratio) and is small for a material that reflects most sound and large for a material that absorbs most of the sound incident upon it. It is determined by the amount of sound absorbed by a material divided by the sound energy arriving at the surface (so a = absorbed sound energy / incident sound energy). Just for interest the table below (from the Sengpielaudio website) shows a bunch of absorption coefficient values for various materials. As you can see, different materials are better or worse at absorbing different frequencies.
 

Floor Materials   125 Hz   250 Hz   500 Hz 1000 Hz 2000 Hz 4000 Hz
             
concrete or tile 0.01 0.01 0.15 0.02 0.02 0.02
linoleum/vinyl tile on concrete 0.02 0.03 0.03 0.03 0.03 0.02
wood on joists 0.15 0.11 0.10 0.07 0.06 0.07
parquet on concrete 0.04 0.04 0.07 0.06 0.06 0.07
carpet on concrete 0.02 0.06 0.14 0.37 0.60 0.65
carpet on foam 0.08 0.24 0.57 0.69 0.71 0.73
             
 
Seating Materials   125 Hz   250 Hz   500 Hz 1000 Hz 2000 Hz 4000 Hz
             
fully occupied - fabric upholstered 0.60 0.74 0.88 0.96 0.93 0.85
occupied wooden pews 0.57 0.61 0.75 0.86 0.91 0.86
empty - fabric upholstered 0.49 0.66 0.80 0.88 0.82 0.70
empty metal/wood seats 0.15 0.19 0.22 0.39 0.38 0.30
             
 
Wall Materials   125 Hz   250 Hz   500 Hz 1000 Hz 2000 Hz 4000 Hz
             
Brick: unglazed 0.03 0.03 0.03 0.04 0.05 0.07
Brick: unglazed & painted 0.01 0.01 0.02 0.02 0.02 0.03
Concrete block - coarse 0.36 0.44 0.31 0.29 0.39 0.25
Concrete block - painted 0.10 0.05 0.06 0.07 0.09 0.08
Curtain: 10 oz/sq yd fabric molleton 0.03 0.04 0.11 0.17 0.24 0.35
Curtain: 14 oz/sq yd fabric molleton 0.07 0.31 0.49 0.75 0.70 0.60
Curtain: 18 oz/sq yd fabric molleton 0.14 0.35 0.55 0.72 0.70 0.65
Fiberglass: 2'' 703 no airspace 0.22 0.82 0.99 0.99 0.99 0.99
Fiberglass: spray 5'' 0.05 0.15 0.45 0.70 0.80 0.80
Fiberglass: spray 1'' 0.16 0.45 0.70 0.90 0.90 0.85
Fiberglass: 2'' rolls 0.17 0.55 0.80 0.90 0.85 0.80
Foam: Sonex 2'' 0.06 0.25 0.56 0.81 0.90 0.91
Foam: SDG 3'' 0.24 0.58 0.67 0.91 0.96 0.99
Foam: SDG 4'' 0.33 0.90 0.84 0.99 0.98 0.99
Foam: polyur. 1'' 0.13 0.22 0.68 1.00 0.92 0.97
Foam: polyur. 1/2'' 0.09 0.11 0.22 0.60 0.88 0.94
Glass: 1/4'' plate large 0.18 0.06 0.04 0.03 0.02 0.02
Glass: window 0.35 0.25 0.18 0.12 0.07 0.04
Plaster: smooth on tile/brick 0.013 0.015 0.02 0.03 0.04 0.05
Plaster: rough on lath 0.02 0.03 0.04 0.05 0.04 0.03
Marble/Tile 0.01 0.01 0.01 0.01 0.02 0.02
Sheetrock 1/2" 16" on center 0.29 0.10 0.05 0.04 0.07 0.09
Wood: 3/8'' plywood panel 0.28 0.22 0.17 0.09 0.10 0.11
             
 
Ceiling Materials   125 Hz   250 Hz   500 Hz 1000 Hz 2000 Hz 4000 Hz
             
Acoustic Tiles 0.05 0.22 0.52 0.56 0.45 0.32
Acoustic Ceiling Tiles 0.70 0.66 0.72 0.92 0.88 0.75
Fiberglass: 2'' 703 no airspace 0.22 0.82 0.99 0.99 0.99 0.99
Fiberglass: spray 5" 0.05 0.15 0.45 0.70 0.80 0.80
Fiberglass: spray 1" 0.16 0.45 0.70 0.90 0.90 0.85
Fiberglass: 2'' rolls 0.17 0.55 0.80 0.90 0.85 0.80
wood 0.15 0.11 0.10 0.07 0.06 0.07
Foam: Sonex 2'' 0.06 0.25 0.56 0.81 0.90 0.91
Foam: SDG 3'' 0.24 0.58 0.67 0.91 0.96 0.99
Foam: SDG 4'' 0.33 0.90 0.84 0.99 0.98 0.99
Foam: polyur. 1'' 0.13 0.22 0.68 1.00 0.92 0.97
Foam: polyur. 1/2'' 0.09 0.11 0.22 0.60 0.88 0.94
Plaster: smooth on tile/brick 0.013 0.015 0.02 0.03 0.04 0.05
Plaster: rough on lath 0.02 0.03 0.04 0.05 0.04 0.03
Sheetrock 1/2'' 16" on center 0.29 0.10 0.05 0.04 0.07 0.09
Wood: 3/8" plywood panel 0.28 0.22 0.17 0.09 0.10 0.11
             
 
Miscellaneous Material   125 Hz   250 Hz   500 Hz 1000 Hz 2000 Hz 4000 Hz
             
Water 0.008 0.008 0.013 0.015 0.020 0.025
People (adults) 0.25 0.35 0.42 0.46 0.5 0.5
             

So you get the idea.  Armed with all that knowledge you are ready to scrounge up some free materials and get building, right?

Step 4: Enclosure construction - material choice & general notes

Picture of Enclosure construction - material choice & general notes
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On average, people in the UK trade their kitchen in for a new model every four to five seconds (I may have made that up) - that is a whole lot of kitchen worktops being thrown out and replaced. Indeed, composite wood counter worktop seems to be one of the most commonest things to pop up in skips here there and everywhere. That was of course, until I thought of using it to make part of the enclosure - being MDF'esque, dense, stiff and heavy, it should be a useful material for sound proofing. After looking and incredulously not finding any kitchen worktop for some time ("Credit crunch curtailed peoples propensity towards kitchenocide, discuss."), freecycle came up trumps and delivered an ample bounty of fire door material.

When I went to collect the two freecycle fire doors, they were actually getting rid of four of them (nice big heavy strong composite things), some kitchen worktop, and some useful bits of hardboard too - score! I ended up using some of these bits to make the DS and having plenty to spare besides. 

When it comes to making sound enclosures, those 'audiophiles' and DIY speaker builders are somewhat ahead of the game - by that I mean they are quite happy to try experimenting with unusual materials and techniques and also perfectly willing to share their experience and knowledge. We can learn a fair bit from their build techniques and material preferences.

Here are some things that speaker enclosure makers experiment with that you might be able to scavenge or otherwise get your hands on:

  • Plywood (without voids is best), mdf, hardboard, etc. All these laminated sheet materials are rigid and easy to construct into airtight enclosures - look out for them turning up in skips.
  • Plasterboard - Used extensively in construction, can be laminated with acrylic latex-silicone caulk to provide very effective damping.   
  • Sand. This is well known as a good dampener of sound, I used some of this in the DS and also to damp my bandsaw. Best of all it is free if you know where to look (a beach might be a start, though in the UK it is technically not legal to just take stuff off beaches).  
  • Oil based plasticine. This is the stuff that never really dries. I have no personal experience with this, but apparently it can be rolled into flat sheets and adhered to panels to damp sound.
  • Scrap steel, can be used to stiffen up panels, and to change their resonant frequency. angle iron makes excellent bracing because it can easily be screwed (and glued with damping glue).

General construction points:

  1. Use lots of glue to make joints air tight. The reason for this is twofold: one, so that we can control the flow of air leaving the vacuums and make sure it is filtered and clean, and two, so that no sound escapes. Even little cracks can make a big difference to the sound reduction index on an enclosure - think about a car window - opening it just a little makes a big difference to the noise you can hear outside.    
  2. Ensure straight well fitting edges - all gaps must be filled. 
  3. MDF and chipboard resonate at averagely 150-400 Hz, with the strongest resonances usually at 250-300 Hz. All materials when they vibrate produce sound waves, so If we don't brace it properly we may have small movements in sides of the DS, but because of the area involved even this could be quite loud. 
  4. We need to treat both structural borne sound (so called 'impact sound') and airborne sound. The first involves mechanically isolating any sources of vibration with the main structure of the enclosure. The second, ensuring that we have good rigidity and mass.
  5. As I already mentioned, when we add bracing to panels, we want to divide up the various panels into sections of unequal area. If not there is a chance that you will have several panels with a common resonance frequency that will combine (and sound loud).

Step 5: The Inner Enclosure

The inner box will not be bearing much weight, and to make the space usage sensible, it is not a massive construction of fire door or kitchen worktop material. Check out the photos for build ideas. 

A Note on the Enclosure and Heat

"But won't the motors overheat if they are in an enclosure," I hear you cry. Hold on there, vacuum motors are something of a special case when it comes to cooling. They blast all the air that they suck in through the motor windings (after passing it through a filter to remove the dirt). So long as any subsequent filters (post-motor filters) remain unblocked, this system works perfectly, and means that vacuum motors can be much smaller than they would otherwise be, and wrapped in a convenient insulative plastic case. Incidentally, this is why vacuum motors make very poor motors if we try and re-purpose them for anything other than air moving applications.

For the DS this means that we need to keep a reasonable exit path open for the air being pumped out of the motor, and that we can expect warm to hot air to be travelling this path (step 11 & 14 deals with this). But it also means that we don't have to worry about trying to blow in cool air to pass over the motor, the vacuums themselves do a very good job of that already. Almost all vacuums are fitted with a heat sensitive safety switch, that will cut power if the motor is overheating. If yours has not, it is probably worth adding one, or finding a different vacuum to use. 


MDF warning:  

MDF is typically about 9% urea-formaldehyde resin, it is the stuff that bonds it all together. When we cut it to size we effectively pump out a load of particles of this stuff.  Dust is a big MDF hazard (read the first few steps for the lowdown on dust badness).  But there is another consideration, particularly if you are sensitive to formaldehyde, and that is the long term 'off gassing' MDF does. Formaldehyde-free MDF does exist, but if we are scavenging our materials one must assume the worst. In this design the 'off gassing' will hopefully be less of a problem as the inner box will be sealed in. In general though, you can control these emissions by finishing the surface with a veneer or a sealing paint, and this is a good practice whenever you make MDF things that will be in living areas.  

Lead warning

Lead is great! It can practically be 100% recycled, has fantastical blocking properties, and is comic book style heavy. Lead is not good however, inside the human body! A tiny bit inside, is way more than we want. Luckily it only really gets in there if we are careless. It is best to handle the stuff with thick gloves - you don't want to cut yourself with lead!  Wash hands before you eat after handling the stuff. Do not do anything that creates lead dust, unless you have the ultimate dust extractor (presumably you wouldn't be making this in that case!), are wearing a quality ventilator and goggles, and have a way of properly disposing of the dust.  I would advise against doing anything that might make lead dust, and really you don't have to because it is so soft - it cuts with tin snips. Don't be tempted to melt it, unless you have the correct safety equipment - the vapour is another way it can get inside you.

Step 6: The Inner Enclosure's Tortuous Path

After making a nice sealed box the problem is that we need to allow air to flow in and out (so that the vacuum can suck stuff up and vent its exhaust air!). If we have holes for the air to go in and out, it is a safe bet that noise from the vacuum's air chopping impeller is going to maliciously exploit them and fire sound out at you. That is, unless we create an elaborate maze in which the noise will get lost (bwahahaha), but which our friendly air will have no problem traversing. People (that is, an author of one of the more obscure books I read) sometimes refer to such a system as a 'tortuous path'.         

When we incorporate obstacles into the air stream, we add resistance to its flow. To maintain necessary airflow, most silencers have to increase the cross sectional area, so enough air can run through - making them quite bulky. This tortuous path or baffle system has the same problem.

There are many different designs to reduce sound that is transmitted through airflow passages: reflective, reactive, diffusive, depressive and active. Quick and concise description of different types of silencers can be found here.

For the dust sniper, the back of the inner box is where I made the baffle arrangement. I wanted to keep the two exhaust streams separate so it consisted of two paths, created by fire door off-cuts (produced while making the outer box). It ended up being damped by a sealed off panel of sand (see the pics and descriptions for build info).    

Another consideration is that sudden changes in air pressure can be noisy - the sound of a vacuum usually increases when we put a crevice nozzle on the end for example.  We can extend the changing pressure gradient though, by breaking the exhaust stream into a series of outlets - the same style of thing that you see on a big motorbike exhaust with lots of holes in.  

"Such a device has been shown to accomplish by itself, without any additional muffling, a 10 dB insertion loss in broadband noise in a steam-generating plant blow-out operation." (p434).

So that seems like a good idea, assuming the air coming out is making much noise...

Step 7: Assembling the Inner Enclosure

Lets put this inner box together (see photos).  The main challenge here is to make a very snug fitting front panel, which will have a tight seal, preventing sound from escaping.  

Step 8: The Outer part 1 - Housing

The outer housing wants to be quite robust, as it will be functioning as a worktop/ multi-use-surface. This is all good as I have a few thick, heavy fire doors to make it from. As a bonus when we make it massive, we are also helping to cut down the noise. I also have a quite delightful bit of scavenged teak to go on top (It was thrown out by my university's science department and matches my current workbench, which has a similar ancestry).    

As it is going to end up on the heavy side of hefty when it is all together, we are going to want some casters to get it mobile (ish - well like a gigantic lumbering titan of a thing at least). As with the inner box, it also needs to be as sealed up and tight as possible, with no weak points for sound to leak out from.  

To begin with I sized it up, based on the Sketchup 'plan' and got cutting. Being way too big to manoeuvre the doors through the bandsaw, and after some 'interesting' jigsaw antics, I borrowed my friend's mighty fine circular saw for the job. This worked very well in combination with a clamped on bit of wood, that I knew was straight, as a guide. 

Similar to the inner box. We can prepare the individual pieces as best we can before sticking them together. It is a good idea to leave the lid off for easy access until after we have finished all the insides.

Step 9: The Outer part 2 - Air Exit and filtration

After all that effort, we don't want to just blast out the air into the atmosphere. It is a happy coincidence that a filter, as well as removing very small particles that can kill us, is also a useful sound deadening material for the exhaust passage. This time fortune really did smile upon us, and a perfectly sized, HEPA filter fell from the gods (well, from our friend who works for a big pharmaceutical multinational who thinks nothing of skipping anything that is not made of purest, unmarred angel essence) into our gratefully receiving lap. This is not strictly necessary, as the vacuums have filters (though they are fairly pathetic in comparison) but certainly a welcome boon.

HEPA stands for 'High Efficiency Particulate Absorbing (or Arrestance, or even Air filter, depending on who your talking to)'.  Basically is is pretty much the best commercially available air filtration of the sort that relies on the air passing through a fine mesh which catches the dust particles.  

"The HEPA standard exceeds the MERV specifications because they are the only mechanical air filter with an efficiency of 99.97% at 0.3 microns. This makes them at least 50% more effective than other types of mechanical air filters." http://www.hepafilter-pro.com/Filter_Ratings.php  (For the grades of filter : http://www.filtration-engineering.co.uk/air_filter_testing.htm). 

So we have one of these babies to integrate into the DS. As this will be right by the air outlet, it needs to be heavily soundproofed to make our other efforts worthwhile. Now is the time to deploy the lead!

Step 10: The Outer part 3 - The Forbidden Cork Forest (or Air Intake Sound Proofing)

Unfortunately, despite the sound having to travel against the airflow created by the vacuums, the gaps needed for the air to come in will still leak a lot of sound.  As MahavishnuMan told me when I foolishly suggested the sound might be reduced by the inrushing air:    

"...in order to "suck up the sound", your vacuum would have to breathe in air at a higher velocity than what sound travels, which is 1,127 ft/sec at sea level and standard temperature and air pressure. Not only am I positive your vacuum doesn't suck at Mach 1, but if it did you would have a sonic boom loud enough to crack the box."

So yeah, we need to 'treat' the air inlets so that we defeat the escaping sound. For this purpose I am experimenting with what I fondly dub the 'Forbidden Cork Forest'.  It is crucial that we don't add much to the air resistance, which is tricky when you are introducing obstacles to block sound.  

The idea with the cork forest is that it will block sound with the sound absorbing 'trees' (the corks), while still presenting a smooth round aerodynamic surface for the air to pass through with minimal turbulence.
 

Step 11: The Cyclone & Dust Cabinet

Picture of The Cyclone & Dust Cabinet
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As the cyclones are transparent, we want to allow light into their area so we can see what is going on. I used some more of the nice 15mm thick acrylic for the side panels (see photos).

We can continue the theme of oak wood facing and make the control board and corner strut from some lovely scrap oak.

The cyclones themselves are the tallest part of this construction, and because we want the finished work surface to be no higher than our workbench, they need to sit below the level of the DS's floor. This is not a problem because the castors raise it high enough that I can still unscrew and empty the dust containers.

Step 12: The Top and Front

Because we are using the top of this DS to make our cool stuff, it needs to be nice. Some solid reclaimed teak will do nicely. I blogged about the origins of the teak worktop as I was doing it so I don't want to repeat it now. Enough to say it will be sturdy, help damp the sound, and provide years of service. To attach it, we don't really want to have a solid mechanical link, but instead use silicone-acrylic-latex caulk to bond it. This provides much better damping than screwing it.    

The front of the DS gets some handmade catches - which are actually really simple - to hold it in place and compressed against its bubble seal.   

Step 13: The DS Auto Switch

Picture of The DS Auto Switch
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So we want a switch that turns the DS on automatically when we start up our power tool, and then turns it off again when we are done making dust. Ideally it will switch on just after the tool, so that the starting current of the power tool is not exacerbated by the simultaneous starting of the dust extractor. And when the power tool turns of, we want the DS to stay on for a few seconds so that the hoses are cleared of any remaining dust. 
  
There are a load of different ways to approach the auto switch circuitry. Here, for example, is an auto switch that uses commercial current detector. The cheapest I could find the toroidal sensor component for  this was for $50 so this was out as far as I was concerned. I wanted to make it without buying anything, using the odd bits and bobs I had knocking about, so my design was a bit, hum, unusual. There are a load of alternative ideas for this in the resources section at the end.  

If you want to try out my design, instead of using a current transformer, which seems the standard approach, we use a reed switch, activated by a very small coil in the live power cable that supplies the power tool. The reed switch activates a relay, which in turn energises the heavy duty contactor, which is hefty enough to cope with switching both vacuums on or off at once. If you want to do it this way follow the circuit diagram below, nothing is too complicated, expensive or difficult. 

To make the coil, just wrap some 16 AWG (or fatter) magnet wire round something thin that is a similar size as the reed switch. I used the blank end of a drill bit, but be careful not to scratch the enamel insulation (something plastic or wooden is better). To begin with I didn't even use magnet wire, just standard insulated wire, as you can see in the pics, and it still worked OK. This way is not as sensitive though, because of the insulation gap. So if you want to use it with lower current draw tools as well, magnet wire is better.  About 13 turns is all you are likely to fit on the reed switch - that's fine.  

The capacitor bank in the 6V relay circuit adds a delay to the switch, so that the DS stays on for a few seconds after the power tool is turned off. Having a capacitor bank like this though, means that we need to add a resistor (or around 8KOhm) in series with the reed switch, to protect it from the inrush current when it is switched on (without it the reed switch will weld shut). If you wanted to be a bit more elegant you could put together some kind of 555 time latch circuit, but I didn't have any 555s to hand.  

If you just want a very quick and dirty solution, just having the reed switch activate the AC contactor worked OK when I tested it. You will not get any delay, and the motors will start together with this one, but it is very simple and it works (though how long the reed switch would last I can't say).   
    
Components (circuit diagram below click the 'i' in top left to get full size):

Reed Switch - just one of a bunch I had laying round. It is about 1" in length, glass body, the coil goes tightly round this.  
D1 - rectifying diode
D2 - rectifying diode
TR1 - a small step down transformer (to 6V) - time to use one of those 'wall warts' you have been saving. 
C2 - 6.3V 4700uF (but just use what you have in your scraps box)
C4 - 6.3V 4700uF
C5 - 6.3V 4700uF
DC Relay - 6V DC relay, a smallish low current thing is what you want.
Contactor - Heavy duty contactor, I found this on a thrown out saw - these are useful for NVR applications.
R2 - 8.2KOhm resistor, important for protecting the reed switch.
C3 - a 0.22uF 275V AC capacitor
R1 - 330 Ohm resistor  
B2 - a suitably beefy bridge rectifier 


Step 14: Controls and wiring

Picture of Controls and wiring
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Ok so here is where we end up with plenty of head scratching, checking, double checking, and re-checking again. Remember that this is mains voltage we are tinkering with so get some qualified help if you need it.

The control board is basically going to consist of:
a dumb plug socket (just a plain socket),
a control socket (what we plug the power tools into, if we want auto dust extraction)
A master on/off switch (this turns everything on or off)
A switch that toggles between on/off/auto one of the vacuums 
A switch that toggles between on/off/auto the other of the vacuums

Begin by making some real size sketches of how it might be on card and work from there. Of course, this control board would be a prime candidate for some laser etching. Anyway, preparing the board can be a classic woodworking task: we need to drill and chisel some holes that will fit our sockets, switches, and air inlets. Make sure to plan it all out carefully based on the switches you have acquired before setting mallet to chisel.    

At this stage I also added in a 16A trip switch (that I was given when a neighbour was replacing their consumer unit). The fuse in the plug should give protection anyway, but a little extra is nice. Once you have everything sorted, and tested carefully rout the cables and secure them so they are all neat and tidy.

Step 15: In Use, Evaluation, Maintenance

Picture of In Use, Evaluation, Maintenance
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Lets evaluate the DS in relation to the design goals which were: 

1) Effective removal of dust from hand-held tools and bandsaw 
2) Little or no noise
3) Provide strong but wheelable work surface

1) The removal of dust thus far is excellent. The dust is sucked up and separated by the cyclones into the collection barrels. Because the separation efficiency is so good suction remains very high - no regular cleaning filters or changing of bags required. Obviously the collection barrels need emptying occasionally, but being many times bigger than a bag or standard shopvac canister, this is an easy and infrequent chore. Thus far, I have only had to change a vacuum bag after I got carried away and let the barrel become full, which resulted in the dust quickly clogging up the vacuum bag and suction becoming very weak.  

So yeah, it might be worth me trying to make some kind of warning sensor that tells me when the collection barrels are approaching fullness to avoid similar problems in future. I already put a viewing window into one of the collection barrels, problem is that the static causes it to be obscured with dust, so that's little to no help. Some of you have already made some good suggestions on how to overcome this little problem in the comments. Of course any other ideas are very welcome...  

2) Noise wise I am better pleased that I expected to be. When the DS is all closed, shut up and operational, I can't really hear the noise of the vacuums at all! The noise of the air rushing through the hose is pretty much all that is audible. So jackpot on the sound front. I can't tell you how nice it is to be able to clear up the shop and suck up dust without a loud noise. It makes nice quiet, well balanced power tools more worthwhile ;)

Now bearing in mind  there are many differing and complicated techniques of sound measurement, the audiophiles may want to look away now. In a blissfully and probably horrifyingly simplistic manner, I used a mobile phone with an in-built 'sound meter' to do my measuring.

Sound of both vacs out in the open - 85dB
Sound of one vacuum in the open - 83dB
Sound of both in the DS - 61 (but varies a lot depending on where the end of the hose is situated - the air rushing in at the tip is almost the only precipitable noise) 
Sound of one in the DS - 55 


3)  The work surface is nice, functional, and sturdy enough to dance on. I do need to add a breaking mechanism to the wheels, so that I can lock it in place better.

Parting Thoughts

The DS has been a long project for me, with plenty of help, research and tweaks needed along the way. Still, it has come together in the end and with any luck this instructable will help you guys avoid some the mistakes I made. Already a number of you have said you will be making your own DS, so I look forward to feedback, build photos, and areas of development. If it improves the working environment (and health!) of one of you, my fellow makers, hackers and craftspeople, then great!

Hi, I love this project and I am starting to build myself what will probably be a much less sophisticated version using a single shop-vac (either 1.25 HP or 2.0 HP). Just a couple of things aren't quite clear to me:

1. Do the holes in the inner enclosure seal around the intake hoses somehow?

2. What is the purpose of the round holes in the outer enclosure above the HEPA filter?

bongodrummer (author)  Hack of All Trades4 months ago

1. Yes, the intake holes join up with some flexible hose.

2. Those are there so that I have the option to duct the exiting air straight to outside (good on hot days to prevent overheating in the shop).

Thanks for clearing that up! Optional outside venting sounds like yet another very good idea.

I scrapped my initial plans after the motor burned out in the old shop-vac I was building it around. It wasn't in the cabinet at the time, but it has occurred to me that wet/dry vacs cool their motors a bit differently to household vacs and might not do so well inside an enclosure.
ecarter111 year ago

Hi I love the idea of the cyclone and have made a mock up using plastic milk bottles.

I live in France and can't get hold of polycarb sheeting for the cone. Do you think that I could use transparent PVC instead.

Love the site

Ernie

bongodrummer (author)  ecarter111 year ago
Hi Emie, Thanks for the comment. We are actually just making a BIG new cyclone for the FE workshop, so go like the FE facebook page to stay updated on that (shameless plug)... 

PVC could probably be made to work, but is a bit nastier imho. It has a lower impact resistance than polycarb and is worse environmentally, but is a bit cheaper. I'm sure you will have ploycarb suppers in France. Maybe under a different name? have you tried searching for lexan?

Polycarbonate has a few other names like Lexan, Makrolon and Makroclear.


Hahob 1 year ago
Very nice build! But you used all that teak for that top:-( That stuff is precious. ....
ecarter111 year ago

Yes I can get lexan but not 0.75. Minimum 2.5mm thick, I might try this and use a hot air gun for bending it. What do you think?

bongodrummer (author)  ecarter111 year ago
I think you will struggle with this... I know from experience that DIY heat bending polycarb is tricky - probably possible if you have some decent jigs to hold it in place and form it around... If you try it use a small test piece and be careful to keep the heat exposure to a minimum or it will bubble and loose its clarity - I believe that has something to do with it absorbing atmospheric moisture when heated...

I still think you could find .75mm polycarb somewhere - try searching for 'polycarbonate film' rather than 'sheet' (or whatever film is in French...
Good luck let me know how it goes.
dcorbett4 years ago
WAY AWESOME!!! I loved the reed switch auto on/off idea. Plain to see you put some extra effort into this one.
Try ultrasonic for measuring the level in your bucket.
The transducer can be mounted at the top (to provide "analog" measurement), or on the side (use as ON/OFF or "dump alert").
bongodrummer (author)  dcorbett4 years ago
Thanks. I must admit I had to do some reading to find out about ultrasonic sensors, and the idea seems good. One concern might be the dust flying into the barrel interfering with the sensor's reading, while the DS is in use?

Sounds like it could be worth pursuing though. Any ideas for cheap/salvageable sources? My first thought was the car alarm doodars that clip on inside at the edge of the windscreen - probably plenty of them floating around at scrap yards or still in cars with alarms that have been permanently disabled or taken out. Would that be any good? Other ideas?

I still want to try the simple idea of using grounded antistatic bags over the viewing window (as MadScott and wingman358 suggested).
I have an idea(combined with top one and this one)
Using antistatic bags does NOT disrupt laser light,if the light is bright enough.
So combining laser tripwire(or multiple tripwires aligned to approx. level connected to Arduino or Raspberry Pi,or other analogue/digital measurement) with antistatic bags will be enough to keep sensors clean,and operable at the same time!
Using laser tripwire system is quite ideal.

Since the dust fills up,it blocks laser light.
It triggers alarm,like those alarm systems,when laser light is blocked.
It's good to keep it off-center because the dust falls down,to the center,so it may malfunction. (seriously you don't want to get annoying BEEEP every time you use Dust Sniper!)
Or maybe multiple tripwires installed on different level,with Arduino,can make dust level indicator.

The only problem is,dust can block laser even the level is low.
If it weren't for static,this idea could be used instantly.
nashton1 year ago
What a fantastic solution to an age old problem!

I currently have been researching dust extraction and have found the same problems as you did, Noise!

I will use your design to build my own DS as I fear a flash over may occur if I continue to work on my projects with the levels of dust currently in my workshop.

Many thanks.

Beetle.
bongodrummer (author)  nashton1 year ago
Cool. send me photos of your build and when your done - I would love to see!!!
dmon1232 years ago
Hi

Firstly, congratulation on a great project.

I have some questions if you dont mind. I am about to build something similar, but simpler. I have an Axminster vacuum (basically a hoover attached to a metal can!) and it is so loud... I want to build a basic box for it, sound proof it as best as I can and put on wheels so that it is mobile. So:

1) Heat should be okay as the filtered air comes out from under the lid (motor). Right?
2) The machine has a single hose for sucking in air (dust). In your machine, you have two separate baffle paths. Is this because you had two separate vacuum machines?
3) I plan to make a hole on the side for allowing me to connect a hose between the box and my tool. So that is how the sucked air comes in. I dont understand how your baffle gets the air out :-( Is it just the whole on the baffle's inside which allows the air to eventually make its way out? I dont see how you can connect a hose to the exit as there is no hose :-)
4) Also, why did you make the sand partition between the MDF and the metal sheet? Is this just for addtional sound proofing? If so, why not "wrap" the entire inner box with sand?
5) Finally, if I add a cyclone to the setup, where do you place the cork forest? Do you need one? If I dont end up using a cyclone, do I still need a cork forest? If so, where does it go?

Thanks so much in advance,
D
bongodrummer (author)  dmon1232 years ago
Hi David. Thanks for the comment... Wow, I didn't realise the i'ble was that unclear. Anyway here goes:

1. I'm not sure on your particular vac but heat shouldn't be a problem provided you have a sufficient path for the vac to suck incoming, and blow outgoing air - that's what cools the motor.
2. Yes.
3. Because the box is made to be air tight, the air only has one place to go once it has been ejected from the vacuum motor - ie. through the set of baffles and out the exit hole(s).
4. It was additional sound proofing I was experimenting with. I had run out of mdf by that point so it is made with the scraps I had - a thin piece of ply and a bit of sheet metal from an old microwave case. The sand sandwich works very well and It is worth having extra vibration damping in areas like this which the air is rushing through. As opposed to the enclosure box which is just designed to attenuate sound from the vac itself, the exit path is a bit more tricky: it cant simply 'enclose' the sound (because it need to let air through) so we want to absorb as much sound as possible with extra mass - sand is good.
5. If you use a cyclone I would be tempted to leave out the cork forest: the cyclone is already introducing resistance to the flow of air (effectively reducing your airflow), and it will also act to dampen sound (if made from polycarb). As to where to place it - that will depend on you enclosure arrangements - the 'cork forest' (hehe made me chuckle to hear other people using that name) is just another way to help attenuate sound in places that we need to leave unsealed for airflow. So in either case, cyclone or no, it could go right before the vac - but to be any use you want to build it into the structure of you enclosure. If you wanted you could make 2 cork forests to treat both the incoming air and outgoing air... Many options...

Hope some of that helps.
Bongo.
Legeir0073 years ago
Nice work. I am making a "Dust Deputy" now. Once I have that perfected, I will definitely be making a silenced system like yours. Thanks for the info!
bongodrummer (author)  Legeir0073 years ago
Thanks. Let us know how it goes. I demand pictures! ;)
fredellarby3 years ago
This DS ended up costing about £20 total.
We don't have £ here. Can we still do this?

Seriously, it beats wearing a dust mask all the time.
bongodrummer (author)  fredellarby3 years ago
Ha! No £ a? Well I should think if you can scrounge up some cup cakes or newly harvested brazil nuts or some such, you could get trading for what you need. Or just scavenge what you need in the first place. Trading is quicker though.

Yeah, dust masks suck bad.
Can you give the modifications needed to make it in $.
I can trade pop bottles for those.
I have a Whitworth hammer. Will that work for £ stuff?
bongodrummer (author)  fredellarby3 years ago
OK, but help me work it out, how many pop bottles = one $?
Actually, It would probably be easier if we worked in cups of tea if that's any good for you?
Sorry, coffee.

Cultural differences are so hard to overcome.
I guess those of us in the colonies are doomed to a life of dust.
ryangranado4 years ago
Great Ideas all around! I will be using your ideas ASAP. Lexian is a little harder to come by around these parts but I do know a great sheet metal guy who I think can make this for me in a jiff, if I can't get the materials my self.

Also, if you are really hung up on having some sort of indicator on when your cans are full, you have all the materials right in front of you. Just cut your barrels down the middle about 15mm wide and on the inside glue a strip of clear plastic all the way tru and you will have an indicator window right in them!

Keep up the great work!
This is only 20 USD

http://www.sears.com/shc/s/p_10153_12605_00924031000P
wiml4 years ago
Thinking laterally about bucket sensors: perhaps you could put a small tube into the collection bucket near the top, connected to some not-very-strong source of vacuum. When the bucket fills, the sawdust blocks the tube, making the pressure in the tube drop, which then ... um ... raises a flag, or triggers an electronic pressure sensor, or the like.

Or, alternately: isn't the interior of the bucket at below-atmospheric pressure? The tube could be connected to 'outside' air though a small hole. When the bucket is not yet full, airflow into the bucket keeps the tube below atmospheric. When the bucket fills past the tube, airflow stops. Let's see if I can attach a sketch of this idea... I can't decide if it'd be horribly finicky and impossible to implement, or if it would be perfect and elegant. :)

Electronic pressure sensors are around $15 new but maybe there's a good junk source for them...
bucket sensor.png
bongodrummer (author)  wiml4 years ago
Hi Wiml,
Interesting ideas, thanks! Things are complicated a bit because the storage barrels themselves are in a partial vacuum (which fluctuates depending on whether the end of the vacuum hose is blocked or partly blocked). It is necessary to maintain the seal on the barrel so that the cyclones work right. My feeling is that adding another 'not-very-strong source of vacuum' would open a whole can of worms (big malicious ones at that).
An interesting idea though, thanks for sharing.
jeff-o4 years ago
I wonder if you could put a small digital scale with a remote readout under the barrels. When the barrel hits a certain weight, you know it's time to empty it.

Any kind of optical sensor inside the barrel would be obscured just like the window, and other sensors are out because of the static. But yeah - weight would probably work.
How about using a simple, light flap and a cherry switch, along the inside of the barrel at the 'full' line. Have a spring on it so that it normally sticks out when the system is off. When the system is in operation, the flap will be forced against the side. If the flap doesn't swing back out when the system is turned off, something is blocking it, and the barrel can be assumed to be in need of emptying.
bongodrummer (author)  jeff-o4 years ago
Hay Jeff-o!

I am not sure I am understanding you with this. The barrels 'float' off the floor, so that the DS can be wheeled around. They are screwed onto the base of the cyclones - their lids are firmly attached so the cyclones and everything remain stable.

Or did you mean putting the scales inside the barrels? That might work, if they were inside some kind of plastic bag - but then again the partial vacuum created would probably disrupt readings...
Ah, true. I forgot that the barrels were connected to the cyclones. Perhaps with a short flexible tube (flexible ducting?) between the two it would work.
bongodrummer (author)  jeff-o4 years ago
A bit of flexible tube would get around that yes, although there is another problem with the weighing method, that was pointed out to me on one of the forums. That is, the material sucked up is often of very different density. Between different woods and plastics, and different shapes (ie shavings, fine dust, etc.) the weight of a barrel can apparently vary a lot.
I was thinking of that. And yeah, if you're sucking up plastic and metal along with the wood then it could be a problem. But really, they shouldn't be mixed in the first place (sawdust can be used for other things!) And as for different density woods, unless you're doing a lot of work with ebony and cocobolo, I doubt it'll present much of a problem. In most cases, people will be using oak, pine, maple, and poplar. Set your threshold for a bucket full of oak sawdust and you'll be good to go!
bongodrummer (author)  jeff-o4 years ago
I am not sure we can assume wood density is so homogeneous, but you are definitely right about keeping materials separate (one of the reasons I wanted two collection barrels). I have no first hand experience, but I can quite easily imagine the shape of the particles would make a fair difference though. I know a barrel load of shavings from the power planer feels lighter than say 3/4 of a barrel of proper sanding dust - I haven't actually weighed it, so I am just going from my feeling here.

But also consider: my Handbook of Hardwoods claims the weight of European Oak usually falls in the range from 640kg/m3 to 820kg/m3, having an 'extreme but possible' range of 600 to 900kg/m3. And that is within one species. Pine is often round 500kg/m3. That in mind, I think density issues would be worth considering with the weighing approach. If you calculated in a good safety margin though, I expect it would work fine as an indicator - barrels don't have to be full before we empty them after all.
It's true, the barrels don't have to be full. So, you'd make a "best guess" estimate of what weight the barrel should be when it needs to be emptied. Then over the course of a few "empties" you could adjust the threshold up or down accordingly. I think you'd find the weight would, on average, be about the same assuming you use the same types of woods and processes on a regular basis.
bongodrummer (author)  jeff-o4 years ago
Agreed.
Pazzerz jeff-o4 years ago
I guess with all the problems with densities, the best thing would be to do what we do every time we vacuum the house: Visually check the container and empty it prior to use. A bit old fashioned, but it works.
adambsmith4 years ago
bongodrummer,

Thanks, again for the great write-up. I've just bought some Lexan and am trying to build my own cyclone dust extractor using the information in you;r write up.

You wrote that you are using a hot melt glue gun to glue together the lexan when it is rolled up. I have been trying this but I an finding it very difficult to squeeze the glue out, and roll the plastic up into the right shape before the glue sets up hard again. Do you have any glue-related hints?

I have been debating using some epoxy resin (Araldite). I've have great results with this before, and it allows more working time, but I haven't tried it on lexan. Do you know if Araldite would work?

Thanks,
Adam
bongodrummer (author)  adambsmith4 years ago
Hay Adam,

Good stuff.
In regards to the gluing, it is best to roll up the shape you want first. Once it is in the correct position, hold it there with a little masking tape. Now for the inside of the cone (I presume it is the cone you are struggling with?), you can peel back a little flap, and run the glue gun's nozzle inside the seam, making a nice long bead. Let the flap close and press the parts together. Should work well like that. For the outside seam, I did it in stages - undo a bit of masking tape near the top, pull back making a flap and inject some glue under it, hold together till set, then move on to another bit, etc. When you are done and the cone shape is secure, you can run one continuous bead along the outside seam, to ensure air tightness.

Of course all this would be easier if you can borrow an extra pair of hands for a few seconds to hold the cone for you while you glue it.

As you mentioned you will have bad luck applying the glue then trying to wrap up the shape, because the glue will have set before you have it aligned correctly.

I am not sure about araldite, I have a feeling that it might eat away at the Lexan, and/or make it brittle and discoloured - if you want to try it, best bet is to use some offcuts you don't need first and see what it does.

Hope that helps, any more questions, just ask. Take your time with it and let us know how it goes.
mauriceh4 years ago
You wrote:
" Quick and concise description of different types of silencers can be found here."
The HERE seems to be intended to be a link.
But, it does not work
bongodrummer (author)  mauriceh4 years ago
Ooo, my first missing link. Well spotted, thanks - it got lost in a copy/paste edit somewhere along the way. Have removed it as it was a pdf hosted at http://www.silex.com/pdfs/ which does not seem to be responding any more. Will try again tomorrow, and replace if working...
bongodrummer (author)  bongodrummer4 years ago
Link working again and fixed in the ible - http://www.silex.com/pdfs/blower%20technology.pdf
brainmist4 years ago
Glad to see someone addressing noise and its hazards. You might also throw in that excessive noise exposure can lead to hypersensitivity to loud sounds (meaning you can no longer tolerate sounds you once ignored), distorted sound and diplacusis (one ear hears pitches differently from the other), and tinnitus (ringing), which gets louder and more sustained the more damaged the ear is. Hearing aids do not cure this: they just amplify the incoming sound, then send it through the damaged, distorted ear.

DIY-ers face an unrecognized risk; because no one oversees their safety, they may be exposed to chemicals without adequate ventilation, which can also increase hearing loss, both on their own, and in combination with noise. Carbon monoxide and other asphyxiants, solvents (such as you might find in carpentry stains and varnishes, cleaners, degreasers, etc), and pesticides can all increase your risk.

If you have a hobby that's noisy or fumy, keep things ventilated, get regular breaks, invest early in hearing protection (much, much cheaper than hearing aids!), and start getting your hearing tested on a regular basis. Even a fairly basic screening (by an audiologist) can indicate the early signs of hearing loss. Find an audiologist who knows something about hearing conservation for best results, and explain to them your concerns. And recreational noise affects hearing too; if you can turn it down, turn it down!

Maybe I should do a hearing loss prevention instructable...
bongodrummer (author)  brainmist4 years ago
Thanks for the info - go for it and write an instructable, I can add a link from this one ;)
kibukun4 years ago
Everything is better with lasers!
bongodrummer (author) 4 years ago
The latches don't fall, but yes, small wedges are a good idea. In face I had already put one on at time of publishing, will do the other three when I get round to it.

Bearing in mind that the big filter comes after the vacuum's filters, and has an absolutely enormous surface area, it should be in there a good long time (at least a number of year). I can see the vacuums wearing out before the filter needs changing. When the time comes, it will be a case of unscrewing the lead sheeting that holds it in, pulling it out and putting a new one in.
If you want a float that might actually work, then I would recommend you put a handle on the float and then vibrate it, watching the point at which it settles. I actually imagine a circuit/motor that jiggles the float handle while the dust collection was proceeding, so that the ping pong ball doesn't get buried.

Once the ping pong ball hits a certain height, then you hit a limit switch and turn on a light, or a buzzer, or just check the handle position occasionally.

You would only need the float to check the last 20-30% of the collection bin height.

Nice instructable.
Sorry, difference in dialect. Where the latches fall is where they strike the door. Also called hatch dogs aboard ship.
While true the filter will last for some time, no reason to make it difficult to remove. My personal opinion and experience is to make it as simple as possible for maintenance. KISS, is always a good principle.

A bit of a laugh. Last time I told someone I'd do something when I got around to it, he promptly handed me a rountuit. A wooden circle with rountuit written on it. I've since passed it on.
0_0

That...is brilliant. I must make a rountuit. And carry it with me always.
srilyk4 years ago
This is an *excellent* instructable. Well written, good photos.

As far as a 'fill sensor', you have a couple of options:

1) a float like you have in your toilet - maybe using a ping-pong ball or something like that. I'm not sure how well this would work, but if your bins are in a fixed position, this may be a more ideal solution.

2) a scale - just grab a few springs and a maybe lever and a bin full of sawdust. Mark points for empty, full and maybe a few intermediate marks. If you use the lever style you could have a dial, or you could just hook a marker to the spring and have a linear gauge.

Those are the two things that popped into my mind first. HTH!
bongodrummer (author)  srilyk4 years ago
Hay Srilyk,
Thanks for your kind words, and suggestions.
I think 1) would be tricky, because there is still the problem of actually seeing the ping-pong ball or whatever you put inside the collection barrel. I am afraid I don't really understand idea 2). A scale would be nice - but how to prevent the lever from just being berried by the sawdust? I'm sorry, I probably completely misunderstood this one?
OP said: "...it might be worth me trying to make some kind of warning sensor that tells me when the collection barrels are approaching fullness... I already put a viewing window into one of the collection barrels, problem is that the static causes it to be obscured with dust, so that's little to no help. "

There are at least two approaches to solving this problem. Either fix the static cling issue or try some other sensor idea.

Static charges form typically due to the triboelectric effect (think socks on a carpet). Since plastics are on one end of the triboelectric series and glass on the other, I would try replacing the window with glass. I'm no expert but glass might avoid a static charge accumulation.

Furthermore, since static charges accumulate only on an insulating material, you might try grounding the surface with a grid of wire. The grounded wire would neutralize any charges, thus avoiding static accumulation.

Check out http://en.wikipedia.org/wiki/Static_electricity specifically the Removal and Prevention of Static Electricity section for more ideas.
Maybe you can cover the window with a snippet of antistatic bag that a lot of electronics components ship in: http://en.wikipedia.org/wiki/File:Antistatic_bag.jpg
I think what srilyk means is a float in the barrel which would actuate a switch. Personally, I think it wouldn't float on the sawdust but be buried. The scale would probably be better. Think of a balance scale with the barrel sitting on the pan. Or you could rig a spring balance. As the barrel gets heavier it drops until it trips a limit switch, barrel is full, empty it. Of course you'd have to use flex hose for your connectors then.
Hopefully this image helps give you an idea.

The float would work like the one in your toilet, attached to a switch or valve or something. I don't know if it would have a tendency to get buried in dust, though, so I'm not sure how well it would work.

For the scale idea you would attach the springs (or whatever) to the outside of the bin, or to a plate underneath it. Taking apart (or searching Google for parts of) an old spring powered scale should give you some pretty good ideas.

I just had another thought. After reading your blog it looks like you're not too scared of electronics - you could probably find an old digital scale (maybe on freecycle?) and wire that up to either light up a bulb or just cut off your vacuums - can't use up a lot of filters if you can't suck any more ;)
scale-stuff.png
macrumpton4 years ago
Very nice build.
I wonder if it would be possible to use some active noise reduction that would electronically invert the vacuum noise and use the result to cancel out the existing noise like the fancy Bose headphones do.
bongodrummer (author)  macrumpton4 years ago
macrumpton,
Nice idea. I did have a little look at that, but was initially put off both by the few things I read that mentioned the technology was expensive my lack of knowledge in this area. As it was I wanted to make a sturdy bench anyway, which fit well with the kinds of sound reduction used. Perhaps someone who knows about active noise attenuation could chime in here? It is worth investigating - maybe with the know-how a noise cancellation circuit could be put together relatively cheaply?

If you wanted to go 'all out' something like that to cancel out the noise of the air rushing into the end of the hose (which is the only real source noise when the DS is running), might be cool - if a little overkill.
A couple of thoughts:
Rather than figure out the intricacies of active noise reduction circuits, I think that getting a fairly cheap set of NR headphones or earbuds and just rewire the outputs to a small amp and speaker set (an old car radio and speakers should do) might work.

Also you comment about the intake noise made me realize that most of the noise (besides the motor) is from air turbulence, and doing things like making smooth transitions in and out of the areas where the air is being pumped might help quite a bit.
karnold704 years ago
Completely awesome use of second-hand parts. Can hardly wait to make one of my own.
GordieGii4 years ago
Would this (http://www.leevalley.com/en/wood/page.aspx?p=30282&cat=1,42401) still be considered just a drop box?
bongodrummer (author)  GordieGii4 years ago
In my view, yes. Ok, it has a twist, in that the inlets are angled, but lots of fine dust will still come through. The spinning air inside will jostle up whatever is already in there a lot, every time you turn on the extractor. Don't get me wrong, it will certainly help, collecting about 85% of the waste material - that is a best case scenario, at low airflow rates. So it depends depends on what you connect it up to - the higher the airflow, the less useful it would be. According to Bill Pentz's research, at around 1000 CFM all the fine dust will get through, making it basically useless.

So yeah, it might help depending on your system, but is certainly not ideal.
guy904 years ago
Spot on! thanks for the instructable
pbbehrens4 years ago
Great design and instructable. What do you think of extending its use by adding a downdraft table that would replace the top or fit over the solid top for dust free sanding! A shallow box with a perforated top that attaches to the vacuum would do the trick. Of course, it would have to be very, very quiet, too.
mcr25824 years ago
Amazingly detailed how-to! I wanted to share a similar "sound crystal" solution I used for my air compressor sound box. I used metal pipe, but I really like the cork idea!

http://www.artifacturestudios.com/blog/archives/985
JohnTrevick4 years ago
I was looking for a similar unit and ended up getting this:
http://www.leevalley.com/en/wood/page.aspx?p=63013&cat=1,240,41065

$45CND, nice package, no fuss.

bongodrummer (author)  JohnTrevick4 years ago
Yep, that auto switch looks reasonable. A lot more expensive than making your own. But it maybe worth it for some who are not confident with the mains wiring or cant get help with that aspect.
This instructable is a thing of beauty, thank you sir!
Fantastic instructable!!!! Way to go!

It looks like some of your components were 3D modeled? Can these be uploaded or did I miss that here?

_jp
bongodrummer (author)  jordan.pollard4 years ago
Hi Jordan. Thanks for the kind words.
It 3D style diagrams, on all the cyclone making steps were actually done after I had prototyped the cyclone (the first one was quite different from the second, though the finished forms were the same). So really they were just there to serve as cutting diagrams for reader of this ible.

If you like I can upload these, I think. Give me a little time to gather them all into a zip file though.
That would be great. I would love to convert them to CAD and would happily share them back so anyone with a CNC or Laser cutter can cut them out.
mauriceh4 years ago
For years I have wanted to build a "better" whole house , built in vacuum system.
Here is an example of what I have now:
http://www.eurekacentralvacs.com/content.php?page=boss

Typically these are:
NOISY
Use expensive ( and hard to find) paper filters
And, worst of all: Send the exhaust air out of the house.
For someone who lives in a cold climate, this can be a horrible extravagance.


You have inspired me to revisit this project.

Thank you!
Edgar4 years ago
All Rhinitis-suffering Gizmo builders in the World salute you, indeed, a great concept, and a Public Service!

Maybe Ponoko will take up the challenge of making a laser-cut box for the Sniper, I'll give them a few lines of e-mail...

Very good.
Spokehedz4 years ago
Bravo! This is the kind of thing that you want to see on Instructables!
Andsetinn4 years ago
This is a nice writeup, with lot of details and knowledge. Great job.
WOW! this looks so good i may have to show this to the pastor of Towy Community Church. Pete T Snr
Atarimark4 years ago
Bravo... nicely done.
jeff-o4 years ago
Very nice work. My little workshop is in desperate need of some dust extraction system, as I have many different saws and sanders. I also like working with maple, which is apparently rather bad for me.

My biggest issue up to this point was the noise of a regular shop vacuum extraction system - I typically work at night when the kids are sleeping, and while I can't use all of the tools (no router or miter saw after 8pm!) I can get away with using my sanders, band saw and scroll saw. These all make tons of dust, and without proper dust extraction I've been using either a face mask or (time to wince) holding my breath.

But this... this may be just what I need. A quiet dust extractor! I've got a noisy little shop vac that belches dust when used on its own. But if I convert it with mufflers and a cyclonic system, it may just become useful again.

I'm definitely going to have to read this whole instructable tonight when I have more time. The whole "version 1/version 2" thing is a bit confusing (I don't really want to see what doesn't work...) but I think there's more than enough info here to get my own dust sniper up and running.

Many thanks!
bongodrummer (author)  jeff-o4 years ago
Jeff-o, my friend, I had to laugh at the breath holding. That might make you feel better at the time, but... It's funny because I have done it in the past - comedy foolishness.

I know what it is like to have a curfew on noisy power tools. I can't use any of the loud'ns after 6pm, for fear of driving the neighbours mad. This had led to some interesting ninja style modding for some of them (you should (will not) hear my pillar drill), and a full blown quest to shut my bandsaw up (still ongoing). And obviously the dust sniper is one of the key ones needed for most of the other tools, so it really does make sense. It is also just nice to know I can use the DS to clean up and make the shop tidy late at night, even if I can't use some of the others...

Agreed, I will look at the mk1/mk2 thing and see if I can simplify, guess I thought someone might avoid my pitfalls that way.
Let me know how it goes,
B.
Oh, I totally understand why the mk1 pictures were included, as they are a valuable learning experience. But yeah, clearly indicating which ones are correct and which are not would be helpful. Perhaps move the mk1 images to the end of each set of photos?

I bought a whole roll of sound absorbing foam for a different project, so I intend to deaden the sound in my workshop a bit with that. But yeah, it's hard to kill all the sound. It sure would be nice to have a quiet vacuum to clean up, too!
bongodrummer (author)  jeff-o4 years ago
Jeff-o, you were so right. I had a read through and that did need tweaking. I have rearranged things a bit, changed a bunch of text, and even added in an extra step. I think it is a lot clearer now, so thanks for the heads up. It is hard to see the difficulties sometimes when you are so close to a project.
peterwales4 years ago
What a thoroughly well researched and presented article. All we need now is for Flowering Elbow to start making and selling these to those of us that do not have the time (what do you mean 'don't be so lazy' - who said that?) to make our own.

Swix4 years ago
wow! nice job! ;]
MadScott4 years ago
Well done!! My dad and I built a cyclone system for his basement shop years ago and found out a couple of things that you may or may not have trouble with:

1.) Heat buildup. If you put a vacuum in a soundproof box, you have to provide cooling air for it or the motor will heat the enclosure...a lot!

2.) Static electricity. Until we ran a bare grounding wire through a lot of the plastic tubing, it was possible to get a stunning shock from the static buildup that the flowing air and dust.
bongodrummer (author)  MadScott4 years ago
Hay MadScott,
Interesting points. The enclosure does heat up, which is expected, but only to tolerable levels as we have good exit pathways for it. The motors are in no more danger of overheating, because the are cooled by the fresh air they themselves suck in.

In fact, this is how vacuum motors can be so 'overspun' and 'undersized', for what they are. They rely on the fresh air that they suck in, which is put through a filter and them blasted through the motor itself. Incidentally, that is why they make terrible motors if you try and repurpose them for anything other than air moving applications.

Someone on Hackaday made just those points as well, and mentioned adding a heat sensor. Both vacuums have a heat sensitive switch, designed to cut power if the motor is overheating, so I am not too worried about that. One concern I had was with the enclosure's structural stability, with with all the heating and cooling they are doing. But, I think composite materials like mdf and particle board are really quite stable and reliable in this respect - so far so good...

The static electricity is noticeable - in that the little viewing window I made in the collection barrel is always obscured because dust is stuck to the inside of it by static. I haven't had any shocks yet though, and I have had plenty of opportunities for them. I think this would be more of an issue in particularly dry climates (not like Wales), or when there are ungrounded metal sections?

Apparently some grounded aluminium foil tape wrapped/stuck to things and can eliminate most static. I haven't seen the need, though I might end up doing something, just to put my mind completely at ease - according to most well researched opinions I have seen it is unlikely to present much risk. A guy named Rod Cole has written an excellent and extensive article in Fine Woodworking on this (an edited version is available here).     

"...if you choose to use PVC ducting in your home shop, the risk of an electrostatic explosion due to the ducts is, at worst, extraordinarily small. From the research papers I have read, this risk is essentially zero."
 

Did you end up doing anything to prevent the shocks in you and your dad's basement system? Thanks for the comments, B.  

Humidity is occasionally your friend in woodworking - in the cold, dry winter of Michigan there's not much left. We joked about the fire potential but the real problem was the huge pain-and-annoyance factor.

What we wound up doing was both crude and effective; we simply glued some bare wire inside the pipe (this was a small system - total pipe run of maybe 12-14 meters in small sections), and also grounded the wires in the flex hoses and it seemed to work.

I very much like the aluminum tape solution Brent Dugan provided on Bill Pentz's page:

http://billpentz.com/woodworking/cyclone/ducting.cfm#StaticElectricity

but with moving air and particulates it's always going to be some kind of a problem.

If you really wanted a challenge, you could track down some aluminized film (such as that used in the shiny emergency blankets) and use that on the viewing ports since similar materials are used in packaging electronics components.
bongodrummer (author)  MadScott4 years ago
Ooo, nice idea with the viewing ports- is that the stuff they make the antistatic bags from?
Yes, it's all a plastic film (usually polyester) that has a microscopic aluminum coating on it - just like reflective sunglasses lenses. The emergency blankets have a thicker layer but if you can find some good semi-transparent electronics parts bags, you'll get the same effect. I'd put some conductive material along one edge and ground it - if nothing else the charge dissipation gradient along the surface will provide some interesting effects.
bongodrummer (author)  MadScott4 years ago
Great. I will have to give that a try... Will let you know how I get on when I get round to it.
Dr.Bill4 years ago
God what a nice Instructable.
Very well written and photo documented.
I would like to see something like this marketed for home/workshop use.

Central vacuum cleaners make a LOT of noise to the point where they have to be installed in garage. Yours could be installed Anywhere in the house.
racastro624 years ago
Wonderful! I cannot say less than this. An extremely detailed and science-proofed ible.
Thanks a lot for such a good work!
sphegdave4 years ago
Amazing job on this. I'll be borrowing your cork forest and torturous paths for a quiet server enclosure/coffee table.

You probably added a couple years to my life as well with the mention of the dangers of airborne dust and MDF offgassing.

Best of luck in winning that laser... you deserve it!
Probably the best Instructable that I've seen in a very long time. If I had the resources to do this, I would in a heartbeat; I hate noise!
Bravo.
Fantastic piece of work. Well done.
vectorges4 years ago
This is great. I have one suggestion and one comment. Comment - I would like to see more dimensions and explanation on cutting the acrylic pieces. I haven't gone through Bill Pentz/s stuff yet (or again, since I got lost there a couple of years ago).

Suggestion - What would you think of a wood ecto-skeleton ( more like some braces) ? Wood might be easier to fabricate, and it would reduce stress on the clear pieces. The horizontal pieces could be be plywood, then braces attached to them. With some fancy joinery it could even be steam-punky.

Great write-up. Easy to understand. Fine job
bongodrummer (author)  vectorges4 years ago
Vectorges, I think you have found yourself a project - I can't wait to see the steam-punk ecto-skeleton, version - sounds awesome! That could be a real workshop feature. The centrepiece of a proper mad-inventor style shop....

I will try and have a look at this today, and add in some dimensions etc.
bongodrummer (author)  bongodrummer4 years ago
Vectorges, I have added a cutting diagram with dimensions on, for each stage of the cyclone construction (the last few pics in each step). Should be of use to anyone building it as the geometry is quite crucial. Peace.
rimar20004 years ago
Fantastic work!!! Thanks for sharing.

I need one ot these, but it is too much work for me. Maybe a simplified version...
bongodrummer (author)  rimar20004 years ago
Thanks for that. You could defo make a simplified version. For ages I was just using a vac with a one cyclone, single barrel job - that is a lot better than just a plain shop vac. Though the DS is lots better again, luxury...
I suppose "defo" stands for "definitely", right? (I speak only spanish, pardon. I typed define:defo in Google). 

Yes, I understand your ptoject is better, I'm not objecting it, just  saying that for me is a hard work.

bongodrummer (author)  rimar20004 years ago
Haha, sorry, no more slang from me sir. Yes, defo is slang for definitely.
Agreed about the work, the worst thing is when you want/need to use a dust extractor when you are making it...
smessud4 years ago
Too many details for one reading. I will have to come back and read again.

All parts (cyclone effect and sound dampening) are extremely interesting and very well detailed.

One question. In "step 7, Absorbing sound", there is a table of absorption index. I see that some values are greater than 1. Could you explain how it is possible?

Thanks again for sharing so much.

bongodrummer (author)  smessud4 years ago
Ah.. OK, glad you picked up on that, I have been searching about, and looking over the lecture notes that I got the more spurious sound absorption ratings from. How they came up with figures higher than one, I can't understand either, as the absorption coefficient should be a ratio of sound energy absorbed over the total amount of sound energy arriving at the surface.

So a perfect absorber should be 1 and a perfect reflector 0. If the absorption coefficient = 0.3, just for example, 30% of any sound arriving at that surface is absorbed. However, as my 'Environmental Science in Building’ textbook informs me, the sound coefficient does not consider how that absorption takes place. So a funny example of a perfect absorber (a=1) would be an open window.

None of this explains how a could equal more than one. So I went looking.... I found one possibility here (along with a more comprehensive table of sound coefficients):

"The absorption coefficients that are typically published for acoustical materials are found using the reverberation chamber method. This method yields random incidence absorption coefficients, which are not percentages. Normal incidence absorption coefficients are percentages. The two are often confused in the literature. A material that has a random incidence absorption coefficient of 1.22 is simply a better absorber relative to a material with a random incidence absorption coefficient of 0.67 for the same frequency band, all other factors being equal. The numbers should not, however, be treated as an indicator of the percentage of sound absorbed by the material." by Savant aka Jeff D. Szymanski


We seem to be experiencing a classic problem of comparing numbers that have been determined through different methods, bad idea. So for now I have removed all the spurious values as well as the ones that don’t check against a table published in my building science book (which look to be more valid). Best I can do for now – perhaps a sound engineer can chime in and explain how a “Musician, with seat and instrument, per person” can have an absorption coefficient of 11.5. Most likely that it was just some shoddy typing, that I unsuspectingly and, rather foolishly, copied <how embarrassing >.
 
dchall84 years ago
I have never before rated any Instructable as "Best Ever," until now. This was fantastic!

I do have a comment, though.  In step 2 you said the container was spherical.  It isn't but that drew my attention to the paragraph.  You said:

"It does this by accelerating it round the outside of a spherical container, so that the centrifugal force acting on the mass of the dust particles forces them to the outside. Thus, in a helter-skelter stylee they go down a chute, while the air reaches a 'turn around point' and moves away up the central inlet."

The second sentence would lead the reader to believe that physics acted in an unpredictable manner.  I would set it up a little differently and say it like this:
It does this by introducing the dust filled air to the cyclone chamber via an inlet mounted tangentially to the cylinder at the top. This air inlet causes the heavy dust to circulate around the outside of the container by centrifugal force. Once the dust is spinning around the edge of the container, the rest of the air inside is relatively dust free. Gravity pulls the heavy particles down into a conical shaped container where the cone shape creates a cyclone with higher centrifugal air speed. The higher air speeds in the cone will keep the heavy particles against the side of the container but also force smaller particles to the side.  Finally gravity pulls the dust into a large settling chamber where the air is suddenly almost still. The clean air with the dust particles removed is sucked out axially through the center of the upper chamber.

That has more words but is more descriptive of how it works.  I'm not sure you need your air ramp inside but it probably is amazingly effective. 

As for keeping track of how much dust you have collected in the settling bin, I would try using a dip stick. Drop the stick into the bin. If it falls to the bottom, the bin is empty. If it stops sooner, then it has dust in it. Mark the stick with Empty and Full indications or 1-9 markings so you know when to empty the bin.
bongodrummer (author)  dchall84 years ago
Hay Dchall, Thanks so much for the feedback, it is always humbling to find that people are reading my words so carefully :-s

I will indeed reword that step - quite right about the spherical jazz., foolish me.

As for the air ramp inside, I believe it helps smooth out the airflow by preventing air entering the 'upper body' from being hit by air spinning round the chamber. It would work without, but not quite as well.

The dip stick idea is intriguing. It would be a technical challenge to have it sealed (the storage barrel needs to hold a vacuum). Did you have anything in mind? I guess some kind of tight fitting rubber o-ring....

Thanks again, B.
Dr. Pepper4 years ago
AWESOME. Whatch out dust, here I come!