Thread: Dust extractor questions

Err . . . . . if the motor is pointed out the window, how do you plan to collect the sawdust?

A modified 2HP is borderline able to cope with most fine dust situations provided short lengths of ducting are used.
10 m of 6" ducting on a 2HP will reduce the flow by 16%
If 4" ducting is used the flow is only half that of the 6' and flow is further reduced by 26% if 10m of ducting is used
A Thein separator will reduce flow by ~25%

Machine -> separator -> motor -> window

I figure 99% of the dust will end up in the separator and the fine stuff can go out the window rather than clogging the filter bag/finding the gaps and making their way back into the air.

I realise the general advice is go big but buying a new dusty isn't really on the books so I'm pretty much limited to what I can do with what I have on hand.

What would be your advice on ducting run length and diameter?

Originally Posted by chemfish

Machine -> separator -> motor -> window
I figure 99% of the dust will end up in the separator and the fine stuff can go out the window rather than clogging the filter bag/finding the gaps and making their way back into the air.

99% of the dust is by weight but not 99% of the dust particles so in practice there will be a lot of fine dust coming out of the blower. I guess it depends what's in the area outside your send. If its a 5 acre lot then no problem. If it is a suburban back yard I would recommend using some form of filtering.

The separator will still reduce the air flow by about 25% - that means 25% more fine dust will not be captured/removed and so stay in the shed.

What would be your advice on ducting run length and diameter?

To maximise air flow and thus capture the most fine dust at source I would use a modified 2HP with no separator, no more than about 3m of 6" ducting and keep the filters clean. For a bit more performance I would suggest using a pleated filter.

Have you seen my thread on modifying the Generic 2HP DC?

You also have to be prepared for what happens when your Thein separator fills up. I'm using an 80L drum and it happens surprisingly quickly, for example after thicknessing just a couple of 1.5m boards. I doubt you want to just keep pumping all the chips and dust out the window wherever you are. If you are Ok with that, you may as well just ditch the separator and have an outdoor collection box.

I have actually read your modified dusty thread, along with a few other threads which seem to present multiple opinions about what is acceptable. Your thread was where I was starting to get my idea from though, the amount of flow dropoff from a filter bag seems pretty high and although a cyclone of some sort seems to eat a bit more flow I don't have to worry about it clogging/leaking dust. I also figure If I vent outside I won't have to cut up the dusty filter housing as I really don't have any sort of metal working experience.

3 metres is a pretty short run... might see what I can reorganise to cluster things together a bit more. The problem is the "workshop" is under the house and although large does has alot of posts that get in the way and as the walls are not 100% water proof I try to avoid sticking rustable things near them. The end result is things are spread out alot.

Might have to have a look around and see what connectors I can find that are 150mm, they seem much harder to source than 100mm stuff. If I can find some splitters I might be able to locate the dusty centrally and split it off in two directions with blast gates to shut off stuff not in use.

Originally Posted by chemfish

I have actually read your modified dusty thread, along with a few other threads which seem to present multiple opinions about what is acceptable. Your thread was where I was starting to get my idea from though, the amount of flow dropoff from a filter bag seems pretty high and although a cyclone of some sort seems to eat a bit more flow I don't have to worry about it clogging/leaking dust.

Sure, but I always assume folks will want to fully optimise their flow and to achieve this are prepared to keep their gear up to scratch.

A modified 2HP is absolutely marginal to begin with and the only way to keep it fully optimised is to
1) modify the DC according to the way I describe or similar
2) use 6" ducting all the way
3) keep the filters clean
4) don't use any form of separator or collector
5) Keep the duct length to 3m or less
If all of these are not done the flow rate will drop below marginal.
Sometimes this cannot be avoided so folks have to live with that but that is not for me to judge.

The 3 m or less of ducting spec is one I made up.
It keeps pressure and flow losses due to ducting length to <5%.
Folks can make up their own criteria if they wish.

Might have to have a look around and see what connectors I can find that are 150mm, they seem much harder to source than 100mm stuff. If I can find some splitters I might be able to locate the dusty centrally and split it off in two directions with blast gates to shut off stuff not in use.

The connectors are indeed pricey and are best sourced at irrigation ducting suppliers.

When I was building my cyclone systemI found that Total Eden was by far the cheapest for 6" pipe and fittings.

They have an outlet in north Brisbane and another on the Gold Coast.

www.totaleden.com.au

Originally Posted by safari

When I was building my cyclone systemI found that Total Eden was by far the cheapest for 6" pipe and fittings.

They have an outlet in north Brisbane and another on the Gold Coast.

www.totaleden.com.au

Cheers, I will have to check them out, apparently they are in strathpine which is only a 20 min run up the road from my place


Also cheers BobL for all your advice.

Just another question, If I need to split the 6" down to two 4" lines how much of killer will building a small MDF box with the 6" line going in and 2 4" connectors coming out be, basically a home made version of the clear vue splitter.

http://www.clearvuecyclones.com/supp...ransition.html

Originally Posted by chemfish

Just another question, If I need to split the 6" down to two 4" lines how much of killer will building a small MDF box with the 6" line going in and 2 4" connectors coming out be, basically a home made version of the clear vue splitter.

http://www.clearvuecyclones.com/supp...ransition.html

Not that much because the 2HP is not drawing the full capacity of the 6" pipe anyway
However, all the small killers add up very quickly to be big killers on small systems.
The Cleavue splitter is designed for their higher pressure bigger flow system and will be a bigger killer on something like a 2HP system.

To optimise flow the way to do it is to use a 6" Y fitting.
Perth_Irrigation-107.jpg
There is version of these filttings comes with a 4" side duct and the straight thru 6" which can be reduced to 4" with a "Level Invert" adapter.
stormwater-3_m.jpg

To really get the most flow out of the 6" duct, when reducing to 4" ducting, 3 x 4" ducts should be used.
Like this


These 6" to 4" adapters can also be using 2 Y's and 2 level inverts so it starts to get expensive
or a single Y can be modified like this

Originally Posted by BobL

Not that much because the 2HP is not drawing the full capacity of the 6" pipe anyway
However, all the small killers add up very quickly to be big killers on small systems.
The Cleavue splitter is designed for their higher pressure bigger flow system and will be a bigger killer on something like a 2HP system.

To optimise flow the way to do it is to use a 6" Y fitting.
Perth_Irrigation-107.jpg
There is version of these filttings comes with a 4" side duct and the straight thru 6" which can be reduced to 4" with a "Level Invert" adapter.
stormwater-3_m.jpg

To really get the most flow out of the 6" duct, when reducing to 4" ducting, 3 x 4" ducts should be used.
Like this


These 6" to 4" adapters can also be using 2 Y's and 2 level inverts so it starts to get expensive
or a single Y can be modified like this

Cheers again, at around $10 a connector cost was the main reason I was considerign a DIY approach to the splitters. If I was to modify some connectors up how hard is it to get a dead smooth transition from the pipe to the connector? do you just cut it close enough, shave the sides down with a rasp till it's a decent fit, glue it and use silicone to fill any gaps?

Originally Posted by chemfish

Cheers again, at around $10 a connector cost was the main reason I was considerign a DIY approach to the splitters. If I was to modify some connectors up how hard is it to get a dead smooth transition from the pipe to the connector? do you just cut it close enough, shave the sides down with a rasp till it's a decent fit, glue it and use silicone to fill any gaps?

Not sure what you mean, maybe draw something up and lets have a look.
The most important things to avoid are any internal surfaces or steps that are perpendicular to the air flow

One way to make the lowest resistance transitions is to first make a tapered box that transits from a square or rectangular cross section with cross sectional area of 28in² at one end, to the other end pot the box which has two square or rectangular cross section ends each with a cross sectional are of 12in², (the 28in² and the 12in² correspond to the cross sectional area of 6in and 4: ducting respectively.
Then using a spreadsheet called "Duct evolution" (check on google) to design and then make up square or rectangular to round cross sectional transitions to suit 6 and 4" ducting.



At this stage you are probably saying ? and $10 a connector starts to look cheap unless more than about half a dozen are needed and then it maybe worth doing all of the above and setting up jigs etc to make your own.

Originally Posted by BobL

Not sure what you mean, maybe draw something up and lets have a look.

Sorry, I mean in your last example with the additional 4" pipe splitting off the y connector. I've never manually branched something round off of something else round before, especially so on an angle which seems like it would require a couple of compund curved cuts to be made. I was wondering how did you go about getting a good fit between the two components.

Originally Posted by chemfish

Sorry, I mean in your last example with the additional 4" pipe splitting off the y connector. I've never manually branched something round off of something else round before, especially so on an angle which seems like it would require a couple of compund curved cuts to be made. I was wondering how did you go about getting a good fit between the two components.

I found that making up 45 degree branches in 4" off a 6" line to be pretty simple. Here is one example from the new bandsaw.

aaaBack (Finished).jpgaaaThree way junction.jpg

The old bandsaw is identical, as below.
IMAG0036.jpg

All I did was to cut an undersize hole in the 6" pipe. Then the 4" pipe was cut at 45 degrees, and a flange put on the 45 degree end by heating the end in oil and pressing it onto a soup bowl and then a breadboard. Then you heat the edge of the hole in the 6" pipe with a heat gun and force the 4" pipe through from inside, forcing the wall of the pipe with a hole into the shape of the flange. Finally, the 4" pipe is glued and screwed (small self tappers) into place and the seam smoothed over with silicone.

There are lots of ways to make these fittings. This approach was used because I am comfortable working with PVC, and because it was dirt cheap and fast.