Thread: Converting drum sander to 4" outlet.

Is this an open end drum sander? Not sure I'd be cutting holes in castings on something cantilevered like that, I'd be worried about losing stiffness and the drum not staying parallel. Pics would help.

Drilling/cutting holes in the side shouldn't effect the stiffness of the cantilever. If you look at some of the steel beams in use, they have large holes cut/fabricated in them, my idea works in principal very similar to an open web steel beam. Admittedly the engineers have worked out the maximum load allowed on something like that.
I feel that in my experience of 40+ years in steel fabrication, that the unit will still be more than solid enough to allow the 3 X 30 mm holes to be cut out.
Someone else might say different, but till then this is what I'm aiming for.
open web beam.png
Kryn

I'd like to see some photos before commenting.

Where the cross marks are, is where I'm proposing to put the holes.
Still undecided whether to put 25 or 30 mm holes, as I don't know what would happen if too much air was drawn in?
DSCF0386.jpg
The top section roughly done to see if it's going to work. Will change it later to a bell mouth, if it works OK, as I feel that would improve it better still, I hope.
DSCF0387.jpg
Any comments appreciated
Thanks for looking,
Kryn

What sort of a DC is this machine being connected to?
You probably don't want to hear this but anything less than a 6" duct all the way to and through a DC is needed to manage the dust from this machine.
but let's park th

Another thing to be aware of is that 25 - 30 mm holes are not going to draw a lot of air so you might need lots of them to create enough flow.

Then you want them to be as close as possible to the edge where the dust is escaping .

In that case I suggesting starting with holes on the places I have marked with circles on this photo.
If that doesn't work I would then make more holes at your "crosses"

You also might want to consider making a cowling that covers the holes and comes down to about 25 mm above and workpieces.
KBsander.jpg

While you are making the hole see if you can make the CS on both sides?

Thanks for that information Bob
What sort of a DC is this machine being connected to.
Currently a 2 HP, will be upgrading later as money becomes available. Also have mounted the outlet of the DC direct to the cyclone section of a std 2hp unit.
You probably don't want to hear this but anything less than a 6" duct all the way to and through a DC is needed to manage the dust from this machine.
Am planning on 6" all the way through the shed, once the extension is done.
but let's park th ??

Another thing to be aware of is that 25 - 30 mm holes are not going to draw a lot of air so you might need lots of them to create enough flow.
Thanks, this is what I needed to know.
Then you want them to be as close as possible to the edge where the dust is escaping.
In that case I suggesting starting with holes on the places I have marked with circles on this photo.
If that doesn't work I would then make more holes at your "crosses"
I might do both, cut the whole section out, just leaving the webs in place, for strength.

You also might want to consider making a cowling that covers the holes and comes down to about 25 mm above and workpieces.
Will do that also, will make it about 50 mm radii, I presume that you mean 25 mm above the work piece?
While you are making the hole see if you can make the CS on both sides?
When you say "make the CS on both sides?" is that as in countersink, to give a better airflow???
What sort of gauge would I need to get hold of to work out if this is working more efficiently, or would it be a visual testing improvement??
Thanks again,
Kryn

Originally Posted by KBs PensNmore

Thanks for that information Bob
What sort of a DC is this machine being connected to.
Currently a 2 HP, will be upgrading later as money becomes available. Also have mounted the outlet of the DC direct to the cyclone section of a std 2hp unit.
You probably don't want to hear this but anything less than a 6" duct all the way to and through a DC is needed to manage the dust from this machine.
Am planning on 6" all the way through the shed, once the extension is done.
but let's park th ??

That was meant to be "but let's park it there for now".

[QUOTE]I might do both, cut the whole section out, just leaving the webs in place, for strength.[QUOTE]
OK - I guess you can always block them off if they start to leak dust.

You also might want to consider making a cowling that covers the holes and comes down to about 25 mm above and workpieces.
Will do that also, will make it about 50 mm radii, I presume that you mean 25 mm above the work piece?

yes

When you say "make the CS on both sides?" is that as in countersink, to give a better airflow???

Yes.

What sort of gauge would I need to get hold of to work out if this is working more efficiently, or would it be a visual testing improvement??

Oh boy, that's a can of worms if I ever saw one. Unfortunately you can't buy a simple gauge and wave it in the general direction of the ducting and hope for it to make sense. To start with have you got a spare couple of days to get the hang of doing the air flow measurements properly

An air speed gauge that will measure accurately will cost about $150. then you need to set up a test duct etc etc.
Have a read of this link
DRAFT: FAQ - Dust Extraction (Practical Aspects)

Now this is not a perfect solution but it is one that will tell you the direction that the air is flowing and that is really important because that's where the fine dust goes.

get yourself some wool or cotton and cut up 25 mm lengths and make up a tracer ribbon as you see in this post.
Tape that ribbon to the edges of the current openings and take 2 photos with the current setup with the drum running (no need to sand wood), with DC on, and with DC off.
Then do the mods and tape pieces of tracer ribbon to the edges of the cowling, holes etc.

The other trick is to use an lighted incense stick and wave it near the holes and see what happens - take a video - with drum running and DC on and off. You will see more if you apply intense side lighting like an LED torch so the light is at right angles to the air flow.

The other thing is to use a manometer and connect one end to a downstream point in the ducting. As the hood starts to breathe better the pressure difference should drop.

I read somewhere that the barrel needs some reasonable closeness to the edges to remove the dust off. If the gap is too large, the dust "clings" to the barrel as it rotates and doesn't clear for the next rotation.

One mod I saw was to put an aluminium angle close to the offside of the barrel (downside of rotation) on the inside (back) of the cowling. This created turbulence which increased the cleaning action.

KB, how did you cut that big hole on a curved surface so accurately?

That's what I did on my belt sander.
I used SS from a clothes dryer drum. I use SS for lots of things around the shed I have got through about 5 drums worth over time.
OTTop.jpg

KB, how did you cut that big hole on a curved surface so accurately?
I just cut a short piece of 100 mm pipe about 25 mm long, tried super glue to hold it in place but didn't hold. I just ran a pencil around the edge and cut it out on the scroll saw all from the inside, after I cut off the piece of tube on the bandsaw. It was then a matter of a bit of file work, didn't have a half round, so I just used a small flat Bastard File. When you cut on the scroll saw, it'll melt back together. I used a very course blade, try some double sided tape and a bit of thin ally top off Coffee, Milo can or similar to help separate the plastic. Where I cut through the Carbatec label, it went easily and didn't weld back together, which is why I suggested the ally tops.
Kryn

I've posted this diagram before


Before drilling holes in the bridge frame, can I suggest you look closely at how air currently travels into these sorts of drum sander.
The main source of make-up air will be from in from of the pressure rollers and from below the drum in the sections not in contact with the board being sanded.

Dust thrown onto the pressure rollers by the sanding drum will be pressed down onto the board and not really become airborne. This is where commercial drum sanders differ from home made jobbies -- the home made units typically do not have pressure rollers.

Drilling air inlet holes in the bridge frame risks reducing the volume of air passing over the pressure rollers and entering the dust shroud from beside the board being sanded.


A modification with could be added to the diagram above is a deflector -- similar to that on BobL's linisher -- designed to interrupt the laminar flow associated with the sanding drum, which would divert dust en-trained with that laminar flow into the dust extraction system.

My experience with the mens 24" shed drum sander has been ordinary.

When I did a quick and dirty assessment of this the sander, despite the full grunt of the Clearvue behind it and 2 x 100 mm ducts the air flow with a 12" wide pice of wood passing through the sander was < 200 CFM.
I wanted to cut a 150 mm opening in the top but with the machine still under warranty I didn't do that instead I will, eventually make a completely new cover for it

What I found was that bugger all air entered the sander (B and A in diagram below) especially through the smaller gap between the wood and the sander cover plate.
On that diagram that meant air flow A and B was almost non existent.
The drum does drag air (C) around from B to A - not so much where there is wood but where there is no wood passing through the machine - this scavenges and allows fine and visible dust to escape out of either side of the wood.

Breaking the C flow does make a lot of sense but unless D and E are increased there is no way that enough air will enter the sander.
The gaps at A and B should ideally be made bigger but failing that openings at F & G will at least manage the fine dust a little better.

DrumSanderdustcollection1.jpg

Here is before and after of the mens shed setup

DSoriginal.jpg
IMG_1916.jpg

An improvement was observed with less fine dust escaping but some visible dust was still clogging the belt and the drums and I need to spend a a bit more time on it.

Originally Posted by BobL

What I found was that bugger all air entered the sander (B and A in diagram below) especially through the smaller gap between the wood and the sander cover plate.
On that diagram that meant air flow A and B was almost non existent.
The drum does drag air (C) around from B to A - not so much where there is wood but where there is no wood passing through the machine - this scavenges and allows fine and visible dust to escape out of either side of the wood.

Breaking the C flow does make a lot of sense but unless D and E are increased there is no way that enough air will enter the sander. The gaps at A and B should ideally be made bigger but failing that openings at F & G will at least manage the fine dust a little better.

Attachment 413950

Bob this diagram you speak of didn't load

Originally Posted by KBs PensNmore

Where the cross marks are, is where I'm proposing to put the holes.
Still undecided whether to put 25 or 30 mm holes, as I don't know what would happen if too much air was drawn in?
DSCF0386.jpg
The top section roughly done to see if it's going to work. Will change it later to a bell mouth, if it works OK, as I feel that would improve it better still, I hope.
DSCF0387.jpg
Any comments appreciated
Thanks for looking,
Kryn

I would like to know if the machine came with the rubberised feed belt or where can I get one. Cheers Peter



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