Make your own extraction trunking?

[That would work]

I am thinking about making my own trunking from thin MDF (say). Making square/rectangular section box trunking that I can build up around and along corners on walls and ceiling in my workshop. Mainly because I think it will be neater, easier to install and will be a fair bit cheaper. I know that the 100mm inside diameter has to be maintained and that probably corners may need smoothing inside. Has anyone done anything like this? I should add its a small shop... 18'x8'

 

[will1983]

If you are time rich and cash poor then this is a good way to get the muck from where it is made to where you can get rid of it. However there is quite a bit of work involved.

If you do this I would suggest that you pre make all your bends, sweeps and junctions separate from the straight sections, you could do this quite quickly if you make yourself a few templates and use a pattern bit in your router.

I wouldn't bother trying to radius the inside corners with timber. I would just leave them square. If you really wanted to achieve the radius(ed?) cross-section I would machine some coved trim for the straight sections of ducting and then use thickened epoxy and an old tea spoon to form the fillets in the bends and junctions.

Also think about how you will get into the system to clear any blockages, lots of viewing windows and hatches/covers.

I think a quicker way would be to use 110mm soil pipe as this is fairly inexpensive and just about any junction or bend is available.

 

[SammyQ]

Kitchen extractor fan ducting is amazingly cheap and available in an astonishingly versatile range of fittings. Try round to rectangular, swept right angle...yada, yada...I believe wood/MDF 'pipes' would have too much friction or boundary effect to be viable for an extractor under 3hp. Kitchen ducting will be smoother, lighter, cheaper and more adaptable. I'm putting it in the roof of my new shed for my HPLV serving my hand power tools, bandsaw, sander and routers; all served by a Record DX2000 and cyclone..or is it 4000? Will check.
Sam

 

[Trevanion]

I don’t know why you’d want to bother making MDF pipes when steel spiral ducting is as dirt cheap as it is. I don’t think the flow would be anywhere near as good as a round pipe, especially on bends.

Sheets of MDF aren’t the cheapest thing in the world either.

 

[That would work]

Mmm... Soil pipe is cheaper than I thought!

 

[Jamesc]

As a ductwork designer in a former life there is no reason why mdf would not work. However a few caveats to advice given above.
Whilst pretty much any shape and configuration of duct will work - to some extent. To get the best from your system a few things to keep in mind.
The cross section of the duct should be kept consistent, changing the shape or size alters the airflow and can cause dust to be trappped in areas leading to blockages. This is particularly inportant in corners. The air going round a corner has to travel farther on the outside than on the inside if it has a sharp corner this will cause eddy currents which tend to slow the airflow and deposit dust in the corner. This slows the airflow .......
Do not put enaything in the duct such as turning vanes. These help on air only systems but will catch any stringy chips and quickly clog the duct.
Finally static. Whilst I don't subscride to the 'use metal ductwork or you will get sparks and burn your workshop down' shcool of thought, I have seen one incident where a factory system caought fire but that was more to do with what they were spraying in the area. A problem that can occur us static cling. Dust has a tendancy to cling to mdf. this layer of dust serves to slow that airflow which makes it deposit more dust and so it goes on. I have seen mdf dust hoods with well over and inch of dust clinging to them.
Sorry for the long post but I wanted to explain my points.
Regards
James

 

[Inspector]

It is basically what I will do for my system because the PCV here is $16Can to $24Can per foot for 8" and the metal is $10Can to $16Can per foot. Fittings are worse $$$. I hate MDF so planned on using plywood, thin for bends with thicker on the flat sides. It also occurred to me that I can incorporate blast gates into the wyes by having a sheet of aluminium sliding in grooves cut into the sides from the upstream side of the branch. That would make any upstream air when it is on, only have a slight dip to go over rather than the traditional branch with pipe and blast gate. Less turbulence and I would have to make blast gates anyway. I need the 8" equivalent because the DC is a 5hp cyclone drawing almost 2000cfm. There was someone here that posted pictures of ducting he made in another thread a few months ago so it has been done sucefully before.

I played with a duct friction loss calculator and there isn't much difference in static pressure losses with square compared to round and with making my own I can incorporate large radii corners to reduce losses even further. http://www.freecalc.com/ductloss.htm If you are going to the trouble of making your own ducts they should be 6" (150mm) equivalent as it can carry 2 1/2 times the airflow that a 4" (100mm) will, assuming you have a DC with a 6" (150mm) inlet.

I have no concerns about the static because it can't be worse than plastic pipes. Static is only an annoyance not an explosion hazard in a home system. If you want to you can paint the pipe inside and out with a static dissipating/anti-static paint used for floors and ground it. Downside is it is spendy but a gallon would paint the insides of a lot of ductwork. http://cliffsgarage.tv/articles/dustExplosion.html
http://www.woodcentral.com/articles/sho ... _221.shtml

Pete

 

[sunnybob]

Accepted that shop bought comes at a cost, but have you calculated the cost of ALL the materials, ALL the incidentals like electricity to run the machines to make it, wear and tear on the blades, screws and glues and supports, and of course your time.
Compare that to buy it, assemble it, and get on with something useful :shock:
Very often these totals all get overlooked in costings. I would be surprised if you saved enough to make the hassle worth while. :roll:

 

[Mike Jordan]

There are lots of things you can make for the home workshop that will serve you well and save money, think In terms of workbench ,saw bench ,shooting boards and templates of all kinds. This is not a bright idea but a massive waste of time and effort compared to installing the proper metal pipe work and fittings in a few hours. Like the soil pipe systems it will have zero fire resistance, take hours to do, and save very little cash while giving a second rate result.
A good maxim for all of us is to try to do a job right and then it only needs doing once.

 

[ED65]

That would work, you might like a peek at the dust collection system in the YouTube channel Stephen's 8x6 Workshop.
Shop tour shows some of the low-profile trunking he made: https://www.youtube.com/watch?v=gCtRWwvGHeY
And the vid that gives an overview of his extractor build: https://www.youtube.com/watch?v=4QgHnYNExPs

Inspector, if you get that far in the second video, a "pinny" and "Marigolds" may need translation: pinafore and rubber gloves

 

[Deadeye]

I think a quicker way would be to use 110mm soil pipe as this is fairly inexpensive and just about any junction or bend is available.

+1 for this. Plastic pipe is as little as £2.50/m - so about 6m for the price of a 9mm MDF sheet. If you're ducts are 100mm square, a sheet will do 7.2m (and that's ignoring kerf loss)...

 

[Inspector]

ED65 I understand the gent's tiny shop dictates all of what he does and commend him for exhausting the DC outside in the warmer months. It isn't a good idea in my opinion to reduce the 12 square inches of a round duct to 8 by making the duct 2"x4" when 3"x5" would give him the equivalent to the 100mm/4" round without a loss. The other thing I think is daft is to empty the dust in the box by scooping to out and dumping it into a bin inside the shop. :shock: The collected fines will be released to hang in the air for a few hours for your lungs to enjoy. :roll: He should go outside for that operation. Working in a shop that tiny would drive me batty especially after enjoying a bean filled dinner. :x

I didn't go far in the video, just looked for the pertinent stuff but do understand the pinny and Marigolds (they are sold here too) references. We do get British shows here and have since I was a kid. :wink: Monty Python, On the Busses and a little later, Benny Hill coming to mind among the earliest I remember. :shock: You have probably had the same with our shows like The Beachcombers. So we have both been culturally polluted to some extent and didn't know it.

 

[Trevanion]

+1 for this. Plastic pipe is as little as £2.50/m - so about 6m for the price of a 9mm MDF sheet. If you're ducts are 100mm square, a sheet will do 7.2m (and that's ignoring kerf loss)...

You can get steel spiral ducting for about £3.50-£4.00/m, where they nail you on the money is for bends, blast gates, and saddles.

Say TWW wanted a run of pipe along one 18ft wall and an 8ft wall, 3 lengths of 3m pipe would do that for about £33 from Dust Spares, obviously you'd want a 90 degree bend in the corner so that's another £5, for arguments sake he plans on using the extraction line on 2 machines and a sanding station, he'd need 3 saddles at £15 a pop and probably another length of pipe at £11, He'd also want 3 blast gates at £16 each. A couple of end caps at £5 each as well and you're £152 into a top-grade extraction line. Obviously, there would be Flexi-hoses and the like added onto the price again but you'd need these with anything else anyway.

It sounds like a lot of money but really it doesn't really lose much value, pipes are pipes and fittings are fittings at the end of the day. Also quite easy to adapt and re-use the pipes elsewhere if you expand at all etc... Once you cut up the MDF for the ducting it's instantly worthless.

 

[Inspector]

I was given a price today for 8" pipe and comparing it to the Dust Spares 200mm pipe I would pay 2.5 times as much. The only difference between the two is I would be buying 22 gauge and not Dust Spares's 24 gauge material. I think I'm getting ripped off living in the colonies.

Pete

 

[sunnybob]

What have you got that requires 8" pipe?
I go to woodyards that have that size on 12 ft computerised panel saws.
Why cant you use 6" or even better 4"?
I have 2 1/2" that copes with a lunchbox thicknesser output.
And as far as metal thickness goes, lighter is better when it come to cutting and lifting above your head :roll: =D>

 

[Inspector]

It is a Clear Vue Max Cyclone. 5hp, 16” impeller and I got the 3 phase motor to drive with a VDF ( variable frequency drive) so I can over speed it to 66 hertz. That will pull 2000cfm at the end of the duct. Not the usually advertised flow using just the impeller without ducting or filters. I want to be able to capture all the dust from the lathe, run two machines at the same time, for a downdraft table and who knows what in the future. Always wanted a stroke sander.

The reason for 8” is to carry the airflow. A 6” pipe can only flow about 1,200cfm maximum and 4” maximum is 450. I will open the machines to 6” ports and not use 4”. A second port can be opened for air scrubbing or I can turn the speed down. Main duct will be 8” with a mix of 8” and 6” drops as needed.

I am not using metal duct. I only mentioned the price here is more costly than in the UK and the rest of Canada for that matter. I will be making square ducts as I said earlier in the thread and yes they will be even heavier than metal or PVC.

I want to do everything possible to capture the under 10 micron dust and that requires volume. Read Bill Pentz. :wink:

Pete

 

[That would work]

+1 for this. Plastic pipe is as little as £2.50/m - so about 6m for the price of a 9mm MDF sheet. If you're ducts are 100mm square, a sheet will do 7.2m (and that's ignoring kerf loss)...

You can get steel spiral ducting for about £3.50-£4.00/m, where they nail you on the money is for bends, blast gates, and saddles.

Say TWW wanted a run of pipe along one 18ft wall and an 8ft wall, 3 lengths of 3m pipe would do that for about £33 from Dust Spares, obviously you'd want a 90 degree bend in the corner so that's another £5, for arguments sake he plans on using the extraction line on 2 machines and a sanding station, he'd need 3 saddles at £15 a pop and probably another length of pipe at £11, He'd also want 3 blast gates at £16 each. A couple of end caps at £5 each as well and you're £152 into a top-grade extraction line. Obviously, there would be Flexi-hoses and the like added onto the price again but you'd need these with anything else anyway.

It sounds like a lot of money but really it doesn't really lose much value, pipes are pipes and fittings are fittings at the end of the day. Also quite easy to adapt and re-use the pipes elsewhere if you expand at all etc... Once you cut up the MDF for the ducting it's instantly worthless.

Interesting, very little price difference in steel ducting and soil pipe. Perhaps this is the way to go on this.
Mine will be a very small system, I have a used Axminster extractor (the small one that doubles up the bag and the filter). I am intending to have it sat under my bench. I will Tee out of the extractor with one one metre run going to a bandsaw with a blast gate. In the other direction ducting will go along and around a 90 degree corner, Tee off to my lathe (blastgate), round another corner and along the wall going past sawbench (blastgate) and ending at my planer thicknesser. Probably 9m of ducting.