Fletty's new shed WIP ....or is it a retrospective??

A bit of progress today and the dust collector has been fired up in anger for the first time in weeks! I was hoping to have a system with the lowest denominator being the 125mm diameter choke point at the entry to the impeller BUT, to get me back into making shavings sooner, I'm going to have to continue for a while with some 1 X 100mm diam elements rather than the planned 150mm diam or 2 X 100mm.
The boom mounted duct...

Attachment 371782

.... for example, SHOULD be served by 2 X 100 mm diam flexies .... but a 125mm means that l can make stuff NOW :)!
l am still waiting for the 2 X 100 adaptors to use as line elements and to modify the machine outlets ...... but hey, what would I do next month if I already hand them?

fletty

Looking good Alan:2tsup:

Regards

Keith

Top idea with swing arm :2tsup:

Thanks for video link where can I get it here?

125 at the dusty am I understanding that right?

If so why don't we/you make a new resized to what you wish it to be? A bit of sheet metal work is all it takes. Happy to help.

Top idea with swing arm :2tsup:

Thanks for video link where can I get it here?

I bought mine directly from Rockler a few years ago. Lovely gear!

125 at the dusty am I understanding that right?

If so why don't we/you make a new resized to what you wish it to be? A bit of sheet metal work is all it takes. Happy to help

Not quite that easy. The entry to the impeller housing is 125mm diam plus a token flare, but impeller efficiency may be significantly reduced if the entry diameter intrudes too much into the involute and the blades then trap much less air. I've heard stories of 12", 13" and even 14" impellers being used on these generic DCs so a possible answer would be to see IF a larger impeller will fit and find one and then open up the entry hole BUT that still leaves a 125mm flexi duct after the impeller and fixing that is a much bigger issue.

Quote:

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Originally Posted by fletty

A bit of progress today and the dust collector has been fired up in anger for the first time in weeks! I was hoping to have a system with the lowest denominator being the 125mm diameter choke point at the entry to the impeller BUT, to get me back into making shavings sooner, I'm going to have to continue for a while with some 1 X 100mm diam elements rather than the planned 150mm diam or 2 X 100mm.
The boom mounted duct...

.... for example, SHOULD be served by 2 X 100 mm diam flexies .... but a 125mm means that l can make stuff NOW :)!
l am still waiting for the 2 X 100 adaptors to use as line elements and to modify the machine outlets ...... but hey, what would I do next month if I already hand them?
fletty

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It sounds like you are still working on duct area ratios which is incorrect - it takes 3 x100 mm ducts to carry the same amount of air as 1 x 150 mm duct at most DC pressures.

Quote:

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Digital temperature corrected anemometer with input actual area for volume measurement tested as an individual entity and then with upstream and downstream entities in series to check for transmitted disturbance.

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It would be useful if you quoted some actual flow numbers but what I also wanted to know were things like
What sort of anemometer was it? i.e. propellor based or hot wire anemometer?
What sort of air speeds were you measuring and what was the maximum air speed it could measure?
These questions are important because most hot wire anemometers can only measure up to 30m/s and in a 100 mm duct the air speeds might be greater than this.

Did you
- use a smooth wall test duct at least 1m long with a test port in the side of the test duct at the 500 mm into which the anemometer was inserted
- measure the air speed as function of radius across the test duct
- determine the air flow at each elemental radius
- integrate the air flow at each radial annulus.
If this is not done it will not give an accurate measurement of the flow.
Placing the anemometer in the end and in the middle of the duct and multiplying the resultant air speed by the area of the duct will give results that are incorrect by as much as 40% which is far greater than would be observed between different types of ducting.

Checking for radial variations of air speed is also important to detect turbulence.

Regarding the rockler flexy - I'm struggling to see how it can maintain a straight smooth bore once it is stretched even a small amount. Unless the material between the wire rings actually stretches it must fold creating wrinkles in the wall. If it stretches it must constrict slightly between the wire rings. A close up side on photo of it slightly stretched and fully stretched would be interesting to see.

Quote:

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Originally Posted by BobL

It sounds like you are still working on duct area ratios which is incorrect - it takes 3 x100 mm ducts to carry the same amount of air as 1 x 150 mm duct at most DC pressures.



It would be useful if you quoted some actual flow numbers but what I also wanted to know were things like
What sort of anemometer was it? i.e. propellor based or hot wire anemometer?
What sort of air speeds were you measuring and what was the maximum air speed it could measure?
These questions are important because most hot wire anemometers can only measure up to 30m/s and in a 100 mm duct the air speeds might be greater than this.

Did you
- use a smooth wall test duct at least 1m long with a test port in the side of the test duct at the 500 mm into which the anemometer was inserted
- measure the air speed as function of radius across the test duct
- determine the air flow at each elemental radius
- integrate the air flow at each radial annulus.
If this is not done it will not give an accurate measurement of the flow.
Placing the anemometer in the end and in the middle of the duct and multiplying the resultant air speed by the area of the duct will give results that are incorrect by as much as 40% which is far greater than would be observed between different types of ducting.

Checking for radial variations of air speed is also important to detect turbulence.

Regarding the rockler flexy - I'm struggling to see how it can maintain a straight smooth bore once it is stretched even a small amount. Unless the material between the wire rings actually stretches it must fold creating wrinkles in the wall. If it stretches it must constrict slightly between the wire rings. A close up side on photo of it slightly stretched and fully stretched would be interesting to see.

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Good grief Bob! I will try to answer your questions, concerns and doubts BUT please note that am claiming no particular insight nor knowledge of dust collection particularly with reference to woodwork. I regard dust collection, like sharpening and sanding, as necessary evils to achieve sustainable craftsmanship in woodwork. Dust collection, sharpening and sanding are not goals, they are means. However, there is so much misinformation and grandstanding included in the sources available to us that I decided to do what has always stood me in good stead through a long industrial career and that is to find out for myself. A lot of it is only minor detail and assumptions but, to me, the greatest folly that is being chased, the Holy Grail of Dust, is that some nominal 1000cfm of airflow "MIGHT" remove sub-micron dust? My knowledge of airflow and contaminants is that ONLY laminar flow can remove sub-micron contaminants and l doubt that any of us achieve laminar flow in any part of our extraction systems at ANY flow rates.
I purchased this anemometer ........

Attachment 371839

.... and used it to measure all flows at all current pick up points. My target was to 'at least' double what I already had, NOT to chase some numeric goal in which l had little confidence.
My then current extraction rate was 'adequate' ..... so twice that rate must be better? At some of my pick-ups, I was operating as low as 167cfm!
Your questions and comments re my working on incorrect duct area ratios misses the point that I am not designing a theoretical nor ideal system, I am trying to use what is already available and get back to woodwork. Simple area maths without any reference to skin friction nor surface area ratios shows that the area ratios of 100/125/150 mm diam are 1.0/1.56/2.25. So, in terms of base area, 2 X 100mm ducts are better than 1 X 125 but not as big as 1 X 150. Clearvue make a 150/2x100 adaptor so, in some parts of my network, I will be using 2 X 100.
Now to the Rockler 100 mm flexi. I will be using twin lengths of this where I am increasing my machine outlets from 1 X 100mm to 2 X 100 mm and yes, I am aware that this is not as big nor efficient as a single 150.
This is standard 100 mm flexi (s100f) static

Attachment 371840

....and compressed....

Attachment 371841

...both demonstrating a very corrugated surface.

This however is the Rockler 100 mm flexi (r100f) (externally) compressed showing the internal surface...

Attachment 371842

..... whereas this is r100f stretched by about 200% of the maximum 700% available showing the small degree of separation of the inner corrugations and the relative smoothness when compared to s100f in any state.

Attachment 371843


HOWEVER, the magic happens IF you cut the r100f to the right length. When the vacuum is applied, the Flexi (internally) compresses such that, in a straight line, both the inner and outer surface are smooth and the Flexi becomes rigid.

Attachment 371844

My interim system, probably in service next week, will have mostly 150mm backbone, some 1 X 100 r100f and some 2 X 100 r100f machine attachments but still with the 125mm choke point at the impeller face. Within the month it will be all 2 X r100f machine attachment.

Fletty

Thanks for the detailed reply and the pictures.

I won't clutter this thread with OT detail suffice to say that measurements of air speeds in narrow ducts made with a propellor based anemometers will not give correct results.
Any conclusions including that of the Rockler ducting arrived at about ducting with these instruments are likely to be invalid.
As I hate to see members wandering off on the wrong path I recommend members wishing to make, even relative, air flow measurements read Bill Pentz website about what instruments to use and how to perform the measurements.
I will write something a little more concise for one of the stickies in the dust forum.

Fletty, I made my own 2 into 1 units without blast gates before my CV days. You can have a lend to copy it if you want, PM me your phone number and I will arrange it.

I'm making sawdust again ........ :yippy:

........ but you really can't tell!

My deprivation is over. After far too many weeks, l can finally woodwork again. I haven't finished the DC soundproof enclosure and my machine connections are still 1 X 100mm flexies, but I can run some machines to help with the shed fit out.
As I noted before, the idea is to have all of my 'prep' machinery on wheels and moved into place under the boom only when in use.

Attachment 372003 Attachment 372004

The first cab off the rank today was the drum sander which l need to finish a new hardwood bench top for the shed. The sander will soon be converted to a 150mm diam pick up and so the 100mm in the pic above is only a temporary arrangement to keep me going. Even so, it worked very well. As an extreme test, I sanded a length of NSW scented rosewood which would normally send me spiralling into an asthma attack but, today ...... nothing!
Harking back to my old shed, the tardis, this is also the first time I have had the room to be able to completely unfold the sander base and use it as I had intended.

It's a good day, Fletty

Alan

Looks good.

I have a question regarding drum sander as I have never had anything to do with them. Is it's prime purpose rapid finishing or is it/can it be used for light thicknessing?

Regards
Paul

Quote:

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Originally Posted by Bushmiller

Alan

Looks good.

I have a question regarding drum sander as I have never had anything to do with them. Is it's prime purpose rapid finishing or is it/can it be used for light thicknessing?

Regards
Paul

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Hi Paul, that comes under the heading of 'bl**dy good question' !
I originally bought it to do light thicknessing on gnarly grained timbers that had a lot of break out on my normal thicknesser. After I fitted the segmented head to the thicknesser, that problem virtually disappeared overnight? I then found l was using it for light thicknessing/flattening of workpieces and assemblies that were too wide to fit into the thicknesser or too short to be safe in the thicknesser.
The job lm building up to today, is the flattening of a loose benchtop which is made up of strips of hardwood glued to an MDF substrate and will be about 600mm wide.
Also, as it 'abrades' rather than 'cuts', l can use it to thickness ACROSS grain. Although that sounds just plain wrong, it is really handy for instance if some clutz :B had messed up the domino settings and the pieces that made up a face frame didn't line up in thickness? That person, whoever they may be, could then run the whole face frame (750 X 1200) through the drum sander so that it long grain sanded or cross grain sanded all of the pieces giving a perfectly flat face frame.
The infeed and outfeed rollers that I added to it were particularly to help me do long double passes which l now do on all face and door frames.
I certainly use it as a flattener and thicknesser but the process seems to be too brutal to be regarded as a 'finisher'.

fletty

High Paul

the primary purpose of a drum sander is to remove the milling marks (small scallops) left by a thicknesser.

Then it can be used to come close to final sanding of flat pieces.

then it can thickness sand thin work pieces.

and thickness highly figured wood.


in an ideal world, the wood machining process would go
1st joint and thickness, plus any sawing to width
2nd through the drum sander to remove the milling (and saw) marks
3rd ROS to refine the surface

just be aware that the abrasive covered drum is probably as dangerous as the cutter head on a thicknesser, but much more accessible.

Thanks Alan ( and Ian). Luckily I don't have anywhere to put one nor the funds necessary. I may have to look up some of those plans for homemade drum sanders, but I wonder if they are sufficiently robust as I imagine there is a fair amount of pressure involved in the process.

Then there is still the problem of where to put one. May have to give it a miss for now.

I am making a mental note of all the dust collection antics and storing them away to be regurgitated at a suitable time. In fact I recently purchased a simple cyclone for my two bag system, but cannot find the time to install it.

Regards
paul

:2tsup::2tsup::2tsup:

Looking good BUT no sawdust/shavings no sign of work :p

Carefull of following that sign up on the wall unless your doing it by eye of course.:;

I'm interested in seeing how you go about the 6" conversion on the sander

so am I.

perhaps it's time to break out (interpretation: find if I still have) my old hydraulics texts and revise boundary effects.

looking at the construction of the Jet [drum sander] dust shroud, expanding the 100mm outlet to 150mm will probably mean building a new taller rectangular to round transition to replace the existing shroud. The new shroud will need to flare from 100mm wide at the drum to 150mm wide where the round extractor duct connects.
I'm not sure that such a modification is warranted, unlike the cabinet of a table saw where you're trying to evacuate a poorly ventilated enclosed space, the shroud of a drum sander functions very much like the floor sweep on a vacuum cleaner.
and perhaps the higher velocity is not a bad thing.

Quote:

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Originally Posted by Sawdust Maker

I'm interested in seeing how you go about the 6" conversion on the sander

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Quote:

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Originally Posted by ian

so am I.

perhaps it's time to break out (interpretation: find if I still have) my old hydraulics texts and revise boundary effects.

looking at the construction of the Jet [drum sander] dust shroud, expanding the 100mm outlet to 150mm will probably mean building a new taller rectangular to round transition to replace the existing shroud. The new shroud will need to flare from 100mm wide at the drum to 150mm wide where the round extractor duct connects.
I'm not sure that such a modification is warranted, unlike the cabinet of a table saw where you're trying to evacuate a poorly ventilated enclosed space, the shroud of a drum sander functions very much like the floor sweep on a vacuum cleaner.
and perhaps the higher velocity is not a bad thing.

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Im really enjoying setting up my shed and doing what I love the most ....... trying something new and different. My concept of wheeling in the machines and 'plugging in' to both overhead power and dust extraction is driven largely by my space available but also to see if it works as a practical solution. I am most comfortable with a suck-it-and-see trial even though I know this will often cross over boundaries and limits defined by physics and other people having already tried things that may well also fail for me?
Another experiment last night after the heat had gone, the mozzie coils had driven the ravenous little bustards away and the Shiraz had softened showed that I have a fatal flaw in my 150mm DC outlet plan!
I WAS planning on using the Clearvue 150mm/2 X 100mm adaptors to be permanently 'moulded' into the shrouds on (particularly) the drum sander and thicknesser to provide the 150mm diam outlet and the rectangular transition to be the internal dust and dwarf pickup. I had made cardboard templates and was about to embark on surgery, cutting the shrouds, merging the 2 pieces, 2 pack putty etc etc but.....
As the night went on, the plan (and Shiraz) slowly melted away. The problem is that:

• the heads of both the drum sander and thicknesser rise and fall to do their jobs
• l have a high wall line but l lose some of that height in bracing the boom
• the only 150mm Flexi that I can find is quite rigid and decidedly NOT flexible
• ALL of which means that it will be too cramped and too much load will be put on the new shroud/s during installation and any operating adjustments.

I have pretty much decided to dump the 1 X 150mm outlets and settle on 2 X 100mm outlets on all of my machinery. Now, I know that 2 X 100's isn't the same capacity as 1 X 150 but for some of my machines (especially router table and disc sander) , 2 'lesser' outlets has many benefits.
So, a slight delay while I regather my thoughts and bits and pieces to continue.
fletty

Fletty, what about using 125mm flexy (available from Felder in Emu Plains)? It's very flexible. I know that brings in a new set of linkage problems, but probably no more than you were facing. The flow will restricted by the smallest choke point which would be at the machine - possibly even before the dust outlet. The cross sectional area is slightly less than half way between 4" and 6", so should yield an improvement.

Quote:

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Originally Posted by FenceFurniture

Fletty, what about using 125mm flexy (available from Felder in Emu Plains)? It's very flexible. I know that brings in a new set of linkage problems, but probably no more than you were facing. The flow will restricted by the smallest choke point which would be at the machine - possibly even before the dust outlet. The cross sectional area is slightly less than half way between 4" and 6", so should yield an improvement.

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AND, there are already 2 pieces of 125mm flex in the circuit. Both the 'hinge' for the boom and the connection to the impeller are also 125mm flex and therefore already provide the lowest common denominator?

fletty

I am just musing about the loss in flow rates for the smaller diameter fittings.

My understanding is that flow rate is lost by frictional resistance. This can come about by size and smoothness of the inner surfaces of the pipe. Consequently that resistance is also dictated by the length of pipe. If the initial restriction of, say, two 100mm outlets quickly transitions to a 150mm pipe is there very much loss? It must be minimised at the very least and I think this is what you are trying to achieve.

This assumes that the outlet from the machine is an optimum shape. If this were a fluid there is a simple formula P1 V1 = P2 V2. We see this relationship with our garden hose and a spray/jet nozzle.

Having said that, we are talking about a gas laden with solid particles and it does behave a little differently.

Of course it would be preferable to have 150mm outlets starting at the machine, but we are not in a perfect world with infinite time :wink: .

Regards
Paul

Boom does indeed look good (although the hard 90º could be improved with a wider radius :)and I can really appreciate the problems with these sander.

The elephant in the corner with those types of sanders is the duct opening in the top shroud is not even 100 mm in diameter and there little one can do except rebuild the top cover on the sander to allow a 150mm duct to be connected.
However even a 150 mm duct will not fix the problems caused by the small gaps around such a machine

An alternative design to consider that still uses the existing outlet as follows.
This design is sometimes used is labs to vent spaces in open labs and is called an elephant trunk

The 150 mm ducting is already on the boom to which a shroud is added.

Locating the top end of the 100 mm duct immediately in front of and in the middle of the 150 mm duct entrance won't draw quite as much air as a hard connect but the wide shroud above the table should catch much more of the fine dust escaping around the sander.

Although I say the shroud should cover the table, if the shroud gets in the way it could be made a little smaller and still help collect the fine dust
The best place for the open end of the 100 mm duct will be in the middle but fixing this accurately would require some loose (sliding ?) connections to the shroud which will impede the air flow so I wouldn't worry about locating it too accurately. It could even protrude up into the 100 mm duct.

Attachment 372068
Ideally the junction between the 150 m and the attached cowl would be a bell mouth to which the cowl is added like this.
Attachment 372069

Making the 100 mm duct length as short as possible and being able to bring the cowl down as far as possible close to the table would be better.

Please note I have never measured the performance of this design but I'm confident it will capture more overall dust from the sander.
It will also be a bit easier and quicker to connect compared to a hard connection system.

[QUOTE ] the only 150mm Flexi that I can find is quite rigid and decidedly NOT flexible [/QUOTE]
Have you looked at this?
Accessories and Spare Parts | Clearvueoz.com.au

I was wondering whether an oval fitting on the machine might work
ie does it have to be round?

My twin drum sander, similar to this one

L129 | DS-25 Twin Drum Sander | For Sale Sydney Brisbane Melbourne Perth | Buy Workshop Equipment & Machinery online at machineryhouse.com.au

has 2 x100mm outlets, which would give you more flow than just a single one.

Quote:

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Originally Posted by BobL

... I can really appreciate the problems with these sander.

The elephant in the corner with those types of sanders is the duct opening in the top shroud is not even 100 mm in diameter and there little one can do except rebuild the top cover on the sander to allow a 150mm duct to be connected.
However even a 150 mm duct will not fix the problems caused by the small gaps around such a machine

An alternative design to consider that still uses the existing outlet as follows.
This design is sometimes used is labs to vent spaces in open labs and is called an elephant trunk

The 150 mm ducting is already on the boom to which a shroud is added.

Locating the top end of the 100 mm duct immediately in front of and in the middle of the 150 mm duct entrance won't draw quite as much air as a hard connect but the wide shroud above the table should catch much more of the fine dust escaping around the sander.

Although I say the shroud should cover the table, if the shroud gets in the way it could be made a little smaller and still help collect the fine dust
The best place for the open end of the 100 mm duct will be in the middle but fixing this accurately would require some loose (sliding ?) connections to the shroud which will impede the air flow so I wouldn't worry about locating it too accurately. It could even protrude up into the 100 mm duct.

Attachment 372068
Ideally the junction between the 150 m and the attached cowl would be a bell mouth to which the cowl is added like this.
Attachment 372069

Making the 100 mm duct length as short as possible and being able to bring the cowl down as far as possible close to the table would be better.

Please note I have never measured the performance of this design but I'm confident it will capture more overall dust from the sander.
It will also be a bit easier and quicker to connect compared to a hard connection system.

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I need to go to bed -- I'm 18 hours behind fletty

But, Bob, if I have understood you correctly, what you are suggesting should also work to collect dust from the overhead guard on a table saw


Need to draw some diagrams, but sleep beckons

Quote:

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Originally Posted by BobL

The elephant in the corner with those types of sanders is the duct opening in the top shroud is not even 100 mm in diameter and there little one can do except rebuild the top cover on the sander to allow a 150mm duct to be connected.
However even a 150 mm duct will not fix the problems caused by the small gaps around such a machine

An alternative design to consider that still uses the existing outlet as follows.
This design is sometimes used is labs to vent spaces in open labs and is called an elephant trunk

The 150 mm ducting is already on the boom to which a shroud is added.

Locating the top end of the 100 mm duct immediately in front of and in the middle of the 150 mm duct entrance won't draw quite as much air as a hard connect but the wide shroud above the table should catch much more of the fine dust escaping around the sander.

Although I say the shroud should cover the table, if the shroud gets in the way it could be made a little smaller and still help collect the fine dust
The best place for the open end of the 100 mm duct will be in the middle but fixing this accurately would require some loose (sliding ?) connections to the shroud which will impede the air flow so I wouldn't worry about locating it too accurately. It could even protrude up into the 100 mm duct.


[QUOTE ] the only 150mm Flexi that I can find is quite rigid and decidedly NOT flexible

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Have you looked at this?
Accessories and Spare Parts | Clearvueoz.com.au[/QUOTE]

I've bin thinkin'........
Bob, it seems to me that (at least) my drum sander doesn't have enough air space around the drum for a single top mounted spigot to effectively draw air and dust through? I gather that is why you believe that a 150mm in the same place wouldn't do much better?
It also appears that there is a mechanical action of the abrasive throwing dust out from under the drum before the airflow can trap it? So, IF I was to go for a 2 X 100 solution then I could run 1 of them to the existing outlet and run the other to an external manifold that runs the full width of the drum to pick up any 'flung' dust OR to a manifold on both external openings?
I was quite happy to rebuild the top cover for a single 150 outlet OR, more likely 2 X 100 outlets but it would be quite simple for me to mock up one or 2 external manifolds first. My concern would be that the manifolds would starve the centre spigot of air supply?
Thanks for the heads up and I will be placing an order on Clearvue for more adaptors and some 150mm Flexi as soon as my 'cunning kick' is restored :roll:

fletty

Quote:

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Originally Posted by Sawdust Maker

I was wondering whether an oval fitting on the machine might work
ie does it have to be round?

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Oval will work but not as well as round.
If the oval is made out of a 150 mm diameter round duct and squished down on one side to become oval the flow will tend to have the flow rates closer to the smaller than the larger dimension.
The reduction in flow rate is non-linear so a near circular oval will have little impact on flow, through to an extreme long narrow oval which will have very little flow
Sometimes beggars can't be choosers so anshallow oval made of a 150 mm round should still be better than a 100 mm round.

Quote:

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Originally Posted by fletty

I've bin thinkin'........
Bob, it seems to me that (at least) my drum sander doesn't have enough air space around the drum for a single top mounted spigot to effectively draw air and dust through? I gather that is why you believe that a 150mm in the same place wouldn't do much better?

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Correct - also the abrasive action heats the dust and air significantly. Fine dust acts like a gas so when carried in heated air it will rapidly rise away from the sides of the drum.

Quote:

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It also appears that there is a mechanical action of the abrasive throwing dust out from under the drum before the airflow can trap it?

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Yep

Quote:

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So, IF I was to go for a 2 X 100 solution then I could run 1 of them to the existing outlet and run the other to an external manifold that runs the full width of the drum to pick up any 'flung' dust OR to a manifold on both external openings? I was quite happy to rebuild the top cover for a single 150 outlet OR, more likely 2 X 100 outlets but it would be quite simple for me to mock up one or 2 external manifolds first. My concern would be that the manifolds would starve the centre spigot of air supply? y

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Thats right!

- My guess is there is relatively little flow from the existing sub-100 mm sander port (what is it's ID BTW?), maybe something like 200 CFM.?
- Running two 100mm ducts from a manifold above the sander will generate about 350 CFM for each duct for a total of about 700 CFM.
BUT
The 700 CFM now has to drag all the dust from further away which it won't be able to do for the bigger dust particles leaving them to clog the drum making it less efficient.
A 200 CFM extraction direct from the sander where the dust is formed is still probably worth retaining ing because it is capturing (especially the bigger particles of) dust at source.
Less flow at source is sometimes more valuable than more flow further away from the source.

The question is what to do with the remaining suck.
Adding a 100 mm duct to a manifold above the sander will draw no more than 350 CFM for a total of 550 CFM.
Two 100 mm ducts above the sander will draw 700 CFM, plus the 200 CFM from the sander for a total of 900 CFM.
To achieve this 900 CFM the 100 mm ducts would have to be joined to the 150 mm duct with at least 2 Y junctions and a reducer.
If all 3 100 mm junctions were to come together at the same point there will be a reduction in flow, maybe 800 CFM.
While the multiple Y junction design would be idea the 3 100 mm ducts and junctions will take up a lot of space and now you need to connect 3 ducts connecting into the 150 mm snorkel or elephant trunk every time the sander is used.
My design is unlikely to generate 900 CFM - maybe 800 CFM (but importantly 200 or maybe a bit less of that comes direct from the dust source) and it only uses one simple 100 mm connection.

BTW if you decide to use that design the end of the 100 mm duct poling up through the 150 mm duct should have a sharp edge rounded on the inside edge to make a sort of bell mouth or trumpet like exit.

Quote:

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Originally Posted by BobL

- My guess is there is relatively little flow from the existing sub-100 mm sander port (what is it's ID BTW?), maybe something like 200 CFM.?

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It's not too bad actually. 100.03 OD and 94.3 ID BUT the grate is a horror!

Attachment 372095

Fletty

Quote:

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Originally Posted by fletty

It's not too bad actually. 100.03 OD and 94.3 ID BUT the grate is a horror!


Fletty

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Oh dear,
The difference between 100 and 94mm is surprising
The 6 mm difference represent 13% reduction in area but it represents ~18% reduction in flow!
By the time the grating is taken into account it will be under 200 CFM.
I would definitely remove the grating.

The narrow gaps around the drum is not going to help either

I hit the wall today. Like many other ventures, reorganising a workspace requires going backwards first. Racks and storage places need to be unpacked and the contents scattered until their new 'home' is built/rebuilt/purchased/decided. I have added a further complication in that I am reusing the material from the old racking to make new storage spaces and so the 'stuff' has nowhere to go until the racking is built.
A few weeks ago this pic .......

Attachment 372433

... which is background detail from another pic, showed my main storage which was finally cleared today. To give you an idea of scale, the lowest bay immediately behind the DC contained an antique full-size mahjong table and 3 chairs .... something I had forgotten until I hauled it all out today!
Shortly after this revelation I realised that I couldn't move. I was surrounded by homeless 'stuff', old racking, workings for new racking, (literally) a wheelbarrow full of books and no clear path forward, absolute hell for an OCD. I had to clamber out .... and go for a walk.
After regathering my thoughts via the medicinal consumption of a SUPERB G&T (Bombay Sapphire!), I rejoined the fray.
Paul has suggested that cleaning up the mahjong table may be worthy of a thread in its own right ...... tomorrow is another day, especially if today really was the low point?

fletty

Some days are like that, I sometimes just decide to have a day off and think about things.

"some days you the bug,
some days you the windshield"

Got that same feeling here Fletty! Actually had it for weeks!:C

I had about 20 drawers that I had never put handles on and then I built another small bench for my
small jet lathe and put drawers in that - a whole 11 of them. So now 30 plus drawers needed handles.

Emptied the drawers, put handles on and then just said "Bugger it!" Still haven't done anything useful as
other jobs have reared their ugly heads. However, there is hope!! This little episode of yours has lit the fuse!!

That reminds me - I really should put handles on the cupboards in the kitchen

Alan Darrell from OTGA had the same problem re-drum sander and he cut the top and fitted a wide mouth fitting which connected direct to the hose it improved suction 100%

Its a daunting task Alan its like moving or redecorating, which is in essence what you are doing, it bring about memories, thoughts long buried, tasks ahead the mind runs wild with all sorts of thoughts. Until like Ian said about bug or windscreen, the matter is to choose which you are.

OR Think about just leaving it all and returning to WORK.:;

I can see the garnd kids and you enjoying great times in there.

To return to fletty's drum sander and it's dust collection ...

my suggestion

Quote:

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Originally Posted by ian

To return to fletty's drum sander and it's dust collection ...

my suggestion

---

This is somewhat akin to sucking up a milkshake trough a large straw with the end partially blocked.
The gaps around the drum are just too constrictive and short of rebuilding the whole of the upper part of the sander not very much air will flow though those gaps.
It is still worth collecting some air from the top pipe but the lack of flow means more fine dust will escape from the gaps at the sides.

Quote:

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Originally Posted by ian

To return to fletty's drum sander and it's dust collection ...

my suggestion

---

Thanks Ian,
Ive been experimenting with 2 pack epoxy putties to to create the bell mouths and fairleads needed for an arrangement like the one you have suggested. I will probably make 2 new covers using the base of the existing cover, and 2 replaceable top decks. One top deck will have 2 X 100 mm outlets connected via 2 flexes to a single 150mm duct and the other will have a single 150mm rigid duct grafted directly onto the current base. As this 150 mm duct is wider than the base lm going to use the outer sections to draw air from outside of the housing and the centre, much larger, portion to draw air through the current base. The first can also be used to trial BobL's venturi and canopy suggestion.
Im also getting more and more entranced with the opportunities provided by 3D printing and IF I get my act together, it would be more than just feasible to 'print' and sell replacement drum covers for all of the drum sanders on the market.
It's an exciting World out there!

fletty

Quote:

---

Originally Posted by BobL

This is somewhat akin to sucking up a milkshake trough a large straw with the end partially blocked.
The gaps around the drum are just too constrictive and short of rebuilding the whole of the upper part of the sander not very much air will flow though those gaps.
It is still worth collecting some air from the top pipe but the lack of flow means more fine dust will escape from the gaps at the sides.

---

I've been struggling to keep up with all my subscribed threads of late. Not sure if you made a sketch recommendation. If not what would or how would you recommend this be done. If you have already said what post do i need to go back to

Meanwhile I'll try and do some catch up

Ok just found it

Dave TTC
Turning Wood Into Art

Quote:

---

Originally Posted by BobL

This is somewhat akin to sucking up a milkshake trough a large straw with the end partially blocked.
The gaps around the drum are just too constrictive and short of rebuilding the whole of the upper part of the sander not very much air will flow though those gaps.
It is still worth collecting some air from the top pipe but the lack of flow means more fine dust will escape from the gaps at the sides.

---

unfortunately, it is what it is.

in these sorts of drum sander, the drum is only supported at one end, the drum frame is a casting and if anything my diagram shows more space between the drum and the housing than exists in practice. I suspect that most of the make-up air enters from the ends of the drum either side of the work piece.

I know that all the ledges inside my sander are caked in fine dust.

what if you had 2 x 4" ports on the housing