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

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.

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.

dustpickup.jpg
Ideally the junction between the 150 m and the attached cowl would be a bell mouth to which the cowl is added like this.
dustpickup2.jpg

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.

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

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

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

fletty

Originally Posted by Sawdust Maker

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

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.

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?

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.

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?

Yep

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

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.

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.?

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

image.jpg

Fletty

Originally Posted by fletty

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


Fletty

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 .......

image.jpg

... 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!

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