Homemade dust extractor and RAS dust collection discussion

[moorebens]

Have any of you built a dust extractor? Ive been looking at the build diary for the dust sniper, it looks very good but I wanted to simplify it and I was wondering if I could just build a big box, line it with some sort of sound proofing material and put the hoover in it.
I would then have a cyclon seperate from this.
My concern is if I can just join two hoovers with a t joint and will this double up on the power? will two 2000watt hoovers equal 4000watts
another question is if its safe to remove the switches from each hoover, extend the wire and mount them to the outside of the box?
If anyone has any experience building a ds id love to hear you story.
Regards

Ben

 

[Racers]

Hi, Ben

4000 watts of heat in a sealed box woun't be good and a 13A fuse is only good for 3120 watts so thats a couple of problems to start with.

Pete

 

[Paul Hannaby]

I built one using a couple of box fans with 600m3/hour flow rate each. I used a filter for one of the microclene extractors. The whole thing cost around £70

 

[9fingers]

Hoovers and other domestic type vacuum cleaners are not suited to continuous running and could well overheat in a workshop application where runs are longer and the airflow is more restricted.

Think before investing too much time/effort/cost in this type of solution.

Bob

 

[doorframe]

Hi Ben.

If your trying to do this on the cheap (and there's nothing wrong with that) then the source of your 'suck' is probably going to be a domestic hoover. Even the bagless ones have filters, and they need cleaning often. That's why cyclone separators are becoming ever more popular. They drastically reduce the clogging so maintain high performance. My own experiments with separators are here...

https://www.ukworkshop.co.uk/forums/dust-extraction-and-thien-separators-my-efforts-t60232.html.

I always prefer a homemade solution, so good luck with your build.

Roy

 

[adzeman]

I can concur with 9fingers, I tried with a domestic vac It lasted about 3 weeks. 1st week it ran OK 2nd week it would pack in for a few minutes then start again. 3rd week it would run for 5 minutes then pack in. Would start next day run for 5mins and then pack in again. Went down to local timber yard and bought an industrial vac for less than £100.00 off the shelf 6 years ago Still going strong. I installed a tubed sawdust chippings system 3 years ago which I am in the process of re-vamping. (not using the shop vac) Visited the timber yard today and noticed a new Draper Cyclone in operation looked impressive and a good buy.

A few guys are building there own Cyclones or converting there existing shop vacs on utube and this seems an acheivable project.

My immediate problem is dust from my radial arm saw it throws out tons of dust and all attempts to catch it to date have failed.

 

[Noel]

My immediate problem is dust from my radial arm saw it throws out tons of dust and all attempts to catch it to date have failed.

Mike, assuming your new extraction system has a decent enough draw build the usual box behind your RAS but with a venturi arrangement . I'll try and get a picture of mine when I get a chance. Should catch about 80 odd % of the sawdust.
Works well with a lower than usual fence so the dust has an easier route to the box/hood.

 

[Bluekingfisher]

Noel - sorry to but in, what is the venturi system??

 

[Noel]

Noel - sorry to but in, what is the venturi system??

It's just a method to increase air pressure in order to make the hood/box more efficient.

Typical box arrangement around the back of the pillar with extraction connected to the top side of the box. Then there's an sloped/angled board that leaves around a couple of inches of opening at the bottom. The slope helps deflect dust down to the opening and leaves a small gap where the air pressure and air movement is greatest:

Don't think it's anything new but it's a massive improvement on anything else I've used. Experiment to see how large or small a gap works best and at what angle. Made out of scrap and 40 odd minutes of fathing around, well worth it in my case.

As you can see there's a reasonably dust free "path" on the kerf line to the back of the box:

As mentioned, a shallow fence is important.

 

[Bluekingfisher]

Cheers Noel, I think I could manage that.

I'm no expert on dust collection but would the effect be greater if the dust port was lower down towards the opening at the bottom? or does the sloped back board assist the air movement coming down from the top of the collector where you have yours ?

 

[Noel]

Cheers Noel, I think I could manage that.

I'm no expert on dust collection but would the effect be greater if the dust port was lower down towards the opening at the bottom? or does the sloped back board assist the air movement coming down from the top of the collector where you have yours ?

I found the port at the top to be the most effective. I got my high and low pressures mixed up with the air movement. The air moving from a wide area to a narrow area will decrease in pressure but increase flow, hence the port at the top.

Must be a picture about somewhere, ok, here's one:

So half the width will increase the air (or fluid, as in a carb) flow etc.

 

[9fingers]

Noel,

I'm thinking that the area A1 represents the hose and A2 the cross sectional area of your slot at the base of your taper.

Can you tells us what sort of ratio you have between these two - or just the csa of the slot and the diameter of your hose please?

TIA

Bob

 

[Bluekingfisher]

I'm sure there is a bit of engineering science or applied mechanics there somewhere but the hose at the top and the slot at the bottom is clear enough advice for me. Thanks again for the response.

I'll get onto my RAS collection box build now.

David

 

[adzeman]

Brilliant! is this what you mean? I recognise venturi as what they use on formula 1 cars to keep it on the ground at speed.

 

[Noel]

Hi Bob, the diagram was only to illustrate the principle (although in cylindrical form)but yes, you could apply it as you suggested.
The port is standard 4" and I suggest you just experiment with the size of the bottom gap and the angle of the board to suit your extraction system. I built various versions (as you can see I extended the sloping board to decrease the bottom gap) and this arrangement seemed best along with the low fence. As mentioned the angled board also deflects debris down to the gap. It also creates a "reservoir" above the gap which seems to be helpful and reduces the surface area at the bottom.
I tested each version by throwing sawdust at it, cutting various materials and most scientifically of all, creating little lines/piles of sawdust from the bottom of the box out towards the table to see how far up the line the dust disappeared. Nobel prize threatening? I suspect not......Not surprisingly the more I could hear the air passing through the gap the better it was.
Another non-Nobel test was to do a quick cut at night, switch off the lights and shine a torch around, you'll be amazed at how much airborne dust there is.
I've had it like this for a few years but I'm sure it could be improved.

Yep Mike, that's exactly it. As you say, similar ideas have been used in F1 and Champ Car/Indy Car to create negative pressure and hence downforce. Lotus and the old ground effect cars were famous for it.

Ben, sorry for the hi-jack, blame Mike...........I've changed the title to reflect both topics and it's also aid searches made in the future.

 

[Bluekingfisher]

Noel - This has been very useful, I think you are underestimating yourself there. It sounds like over a period of time you have tweeked and fine tuned your collection box. to gain best results. Had you not shared your experiments others, including me, would have had to spend a pile of time going through the same processes.

As a matter of interest, could you give rough estimations of the dimensions of the height of the gap and the angle of the back board.

I have a dust port on the top of my blade guard so I'll have to rig up the ducting to allow for the collection at the dust box and at the guard, although this doesn't seem to be too taxing a job.

Thanks again.

David

 

[adzeman]

Hi Ben it loks like I owe you an appology for the hi-jack of your post on using domestic vacuems. Please take this as an appology and hope there are people out there who could respond to your request that have built shop vacs or cyclone vacs.

 

[Noel]

Hi Ben it loks like I owe you an appology for the hi-jack of your post on using domestic vacuems. Please take this as an appology and hope there are people out there who could respond to your request that have built shop vacs or cyclone vacs.

Was only jesting Mike. I'm sure Ben will soon realise that some threads cover many topics.

Anyway, David here you go, dimensions etc:

Box is 430mm wide x 300 high x 280 deep. Deflector board sits at 17 degrees and gap is 23mm. The distance from the bottom edge of the deflector to the back of the box is 70mm. It's positioned so that the kerf line is central.

Someday I try rounded corners, keep existing box but have no gap at bottom of deflector and mount the Venturi "upside down" below the table and a few other tweaks.

 

[Bluekingfisher]

Noel - Thank you for this, as much fun as it is sometimes experimenting with different conotations, there are also times when an effective means of getting the job done is more important than my time spent tinkering.

Your advice has been invaluable, I now have a base to work from.

Thanks again.

David

 

[adzeman]

Work has stopped on my power tool cabinet due to this post. I started working out the dimensions last night and low and behold this morning you have put them on the site
As soon as back from the weekly shop will make a start and record in the work in progress section.