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Dust extraction and Thien separators. My efforts.

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doorframe

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I've had my Elektra extractor for a couple of years now. It's been stuck in a corner doing nothing. Last year I used it to
hoover up leaves and sucked up a large stone that smashed the impellor. It went back into the corner again! Same as this one....
EB extractor.JPG


Finally got around to repairing the impeller, which ended up out of balance, but was corrected by a presision placed 1 pence coin. Took ages to do but worth the effort.

Intention was to use the 2" pipework I got cheap, but this was a total failure. Although these type of extractor move a lot of air, they create only low pressure, and suck virtually no air through small bore pipes, so the bag just collapses. I was told by members here that's what would happen. Oh well... plan B!!

Decided to have a double system. I've got a huge Numatic vacuum that sucks fine through 2" pipe, so will use that piped around to various machines. Same as this one...
Numatic.jpg


My tests with up to 20 meters of pipe with T's and Elbows went very well. I'll use the Elektra purely for my miter saw station which has a purpose made dust collection hood covering both saws.

The trouble is, as has been mentioned before, all extractors lose performance as the filter clogs, so cyclones are a god send. Also worth considering, are Thien Seperators, which is the option I've chosen, if only because the construction is simpler and the building materials are more 'to-hand'. My next post will show my efforts.
 

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doorframe

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1st job, find a suitable receptacle (alright, a bin then!!). This will do nicely...
PICT0003.jpg


Now for some suitable ply to make the sandwich. I have a fair bit of 35mm laying around. Bit heavy maybe, but that's fine. A good session with the router and this is the result...
PICT0004.jpg
PICT0005.jpg


The lower section has a 10mm slot for the top lip of the bin, and on it's reverse is a 6mm slot for the side wall. The 270' dust slot is approx 30mm wide. The top section has a corresponding 6mm slot for the side wall, and 4 100mm cut outs to lighten the load. These cut outs were later covered on the underside with 2mm perspex.

For the walls I cut a strip around an old plastic drum....
PICT0006.jpg


Next the inlet and outlet holes and some 110mm soil pipe...
PICT0007.jpg


All secures together with some 6mm studding, and some thin insulation strip in the slot for the drum...
PICT0008.jpg
PICT0002.jpg
PICT0001.jpg


All of the above was pure guesswork regarding dimensions. I'm unaware of any scientific principles which may apply to Thien seperators, but have to say I'm delighted with the performance. After 2 bucketloads of sawdust were sucked up, 99.9% was in the bin. Only a tiny amount reached the bag. In fact, most of what is in the bag was already there! The assembled separator is surprisingly light considering the thickness of the 35mm ply.

I made 2 of everything during the construction, as I will be making a second seperator for the 2" pipe next.The only difference I might make is to have a thinner sandwich. If anybody has any thoughts on this I'd be very pleased to hear them, and I hope this project will be of interest to some of you.

Cheers,

Roy
 

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wallace

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Hi looks good to me, How is it connected to the bin, is it just the weight and the suction that keeps it in place?
Mark
 

cambournepete

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That's very interesting.
How high is the plastic part of the separator?
How far into the separator does the outflow pipe extend?
Why did you cut the four 100mm holes in the top - just for weight saving?
Why didn't you cut the middle hole at the same time?
Have you tried it with larger shavings to see if they fit through the 270 degree slot?

Sorry for all the questions, but I'm rather interested in this and might make one :)
 

JakeS

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Certainly looks less hassle to put together than a cyclone - and it's reassuring to know it works without careful calculation and measuring!

Do you have any idea how good it is at ultra-fine dust, the kind you see off MDF or from sanding? Does it get collected as well, or just (potentially, depending on your extractor) passed out into the air again?
 

beech1948

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PeterBassett":1hg9mtxq said:
Confused, what are the holes in the top for?
weight reduction I think. earlier in the thread the OP says he covered them with some type of plastic sheet....so also provides some visibility into the separator.

Al
 

doorframe

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wallace":33nfxhww said:
Hi looks good to me, How is it connected to the bin, is it just the weight and the suction that keeps it in place?Mark. Yes. I also added a 2mm foam strip in the slot to help seal to the bin lid.
cambournepete":33nfxhww said:
That's very interesting.
How high is the plastic part of the separator? Approx 15mm above and below the 110mm pipe + 2 x 6mm into routered slot.
How far into the separator does the outflow pipe extend? At the moment it will slide up and down. I thought I may need some adjustment to fine tune the performance, but it seems to make no noticeable difference where it is set. I have left it approx 40mm from the inside top.
Why did you cut the four 100mm holes in the top - just for weight saving? Yes, and as view holes so I could see if there was any turbulence or blockages. I'm amazed how smoothly the sawdust moves around. I could watch it for hours!!
Why didn't you cut the middle hole at the same time? This seperater is for 4", and the next one is for 2". Initially I just made the parts which were the same in both.
Have you tried it with larger shavings to see if they fit through the 270 degree slot? The sawdust / shavings I've used are from under my table saw, behind my mitre saws, from the routing for this project, and from a thicknesser. Everything went through the slot fine.
Sorry for all the questions, but I'm rather interested in this and might make one. You're welcome :) :)
JakeS":33nfxhww said:
Certainly looks less hassle to put together than a cyclone - and it's reassuring to know it works without careful calculation and measuring! I was quite relieved to discover that as well :lol:
Do you have any idea how good it is at ultra-fine dust, the kind you see off MDF or from sanding? Does it get collected as well, or just (potentially, depending on your extractor) passed out into the air again? I will find out and let you know.
beech1948":33nfxhww said:
The Thien separator is a very proven design and even has its own web site and forum.
Take a look at http://www.cgallery.com/jpthien/cy.htm.Al. Thanks Al :D

Does anybody know if it's possible to put a video clip into this thread, as the centrifugal action and the dust dissapearing through the slot are amazing to see.

Cheers,

Roy
 

doorframe

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The 2nd separater is now well under way. This one is using smaller pipe, (63mm through the separater onto a 50mm system). Initial tests (with the same height as the 110mm system) showed I wasn't moving enough air with the Numatic to create the centrifugal action, so as I suspected I need to reduce the height of the separater to match the pipe. I've cut the side wall down to 63mm + 15mm above and below + (2x) 6mm for the recessed slots in the ply sandwich. Will hopefully get gack in the shop later to test further, and will update.

Roy
 

doorframe

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Well that made all the difference. I think I've arrived at a 'general-rule-of-thumb' that the internal height of the top-hat should be no bigger than 15mm above and below the height of the inlet pipe. Works every bit as good as my larger seperater.

One thing that's become instantly obvious and needs to be my next job is a pressure relief valve. As this seperater is being run on a LVHP system (low volume high pressure) if the inlet is blocked it sucks and crushes the metal drum walls like they're made of paper!!! I found out the hard way. Some panel beating with a rubber mallet was applied!

Can anybody suggest a simple valve set up? I need it to install into the top section between the inspection holes.

Roy
 

Chems

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doorframe

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Thanks Chems. I can't quite incorporate it 'as-is', but will borrow part of the design if you don't mind.

Roy
 

Chems

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Not a problem, you can fit it anywhere inbetween your extractor and the separator it doesn't have to be directly on the Thein separator if that helps.
 

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