Moving the DC outside

[Ian Dobson]

Seeking advice from the resident experts.

I have a Carbatec 2HP DC on mobile castors which I've been wheeling around my garage workshop but am now looking at more permanent mounting options.

I have a very small rear yard behind the garage and am quite close to neighbours. Ideally I would get the DC outside, there is room to mount it protected under the eaves at the back of the garage but I am worried about noise affecting the neighbour and don't have room to build a full enclosure for the DC.

What I was thinking of is to leave the motor and impeller inside at the back of the garage, and run ducting to the bag/filter unit which would be mounted outside. My garage is brick but I can remove a small window pane of glass and replace with acrylic with a hole cut for the ducting. The ducting between the impeller and bag parts is currently 5" flex hose. I could do the DC mod on the input to the impeller (although don't see how it would be much use going beyond 5" on the input if constrained to that on the output side).

The other option is to do the full Generic DC mod and directly couple the impeller and collector sections with 6" input ducting, but then the bag/filter section would have to stay in the garage.

In a world full of compromises, can you advise which path would be the better one here?

At present I only have the DC for a table saw and my router table fence. These are connected through a 3m flex hose which I move between the machines as necessary. I might add a thickness planer in future. If I can get the DC permanently mounted then I would consider rigid ducting.

Thanks
Ian

[Lappa]

In this thread below, I was also contemplating having the motor/impellor inside and the filter unit outside the main shed.

http://www.woodworkforums.com/f200/separating-motor-impellor-filter-unit-210464

Alot of my questions were answered by knowledgable formites so it's worth a read.

In the end, I mounted the whole unit outside because I bought a shed only slightly bigger than the whole dusty assembly (1500x800x1900 - actually 2000mm) and was cheaper than building even a shelter for the filter alone. You can also see decibel readings I took as I had concerns re my neighbours. In the end, it was the best option for me with the minimal amount of stuffing around.

http://www.woodworkforums.com/f200/installing-dusty-wip-210746

[BobL]

I have a very small rear yard behind the garage and am quite close to neighbours. Ideally I would get the DC outside, there is room to mount it protected under the eaves at the back of the garage but I am worried about noise affecting the neighbour and don't have room to build a full enclosure for the DC.

A basic enclosure would only be ~250 mm wider, and ~125 mm deeper than the DC footprint.


What I was thinking of is to leave the motor and impeller inside at the back of the garage, and run ducting to the bag/filter unit which would be mounted outside. My garage is brick but I can remove a small window pane of glass and replace with acrylic with a hole cut for the ducting. The ducting between the impeller and bag parts is currently 5" flex hose. I could do the DC mod on the input to the impeller (although don't see how it would be much use going beyond 5" on the input if constrained to that on the output side).
correct


The other option is to do the full Generic DC mod and directly couple the impeller and collector sections with 6" input ducting, but then the bag/filter section would have to stay in the garage.
This is the one I would go for especially a full conversion to 6" between the impeller/filter can be done with 6" PVC enabling the impeller/filter to be separated from each other.


At present I only have the DC for a table saw and my router table fence. These are connected through a 3m flex hose which I move between the machines as necessary. I might add a thickness planer in future. If I can get the DC permanently mounted then I would consider rigid ducting.

Rigid ducting is superior from an air flow point of view especially if you are using 3m of flex. Try to keep and flex as short as possible although its not always possible.

[Ian Dobson]

I've been re-thinking through the options and now I'm considering putting the whole DC outside and directly coupling the impeller and collector sections as per the generic 2HP mod thread.


After measuring, there will be room to put a 1.5m x 0.75m colorbond shed in the space although it will be up against the neighbour's fence on one side so I will need to consider some acoustic deadening.
I was thinking of lining the inside of the shed walls with 18mm MDF, would that help with sound reduction? I won't have a lot of spare room for thicker lining or insulation material.


Also I don't want to cut a 150mm hole through the workshop (garage) brick work so I have two options to bring the ducting through from the DC shed. One is to go up through the eave soffit, into the roof cavity and then down into the workshop. This would allow me to have permanent overhead ducting in the workshop to the TS.


The other option is to remove a 450x450 window pane and replace with a ply or acrylic sheet with a hole cut for the ducting. This would be near ground level, would be a constant trip hazard and lose me some natural lighting. But it would be significantly shorter in length.


Does a 2HP (modified) dusty have enough power to cope with the additional length of the overhead option? (I figure an extra 3-4 metres of PVC 150mm ducting, mostly vertical, with some extra bends to go up and back down.)


Also with PVC ducting, do people usually use stormwater pipe or is DWV preferred?


Thanks heaps for your assistance.
Ian

[dai sensei]

I made my DC into a cyclone system mounted outside and then piped it in. I am in the process of installing a larger system but this one is still working pretty well

403349 403348

[Lappa]

Nice Neil. What unit did you use for the motor and impellor on top and did you make the cyclone yourself?

[dai sensei]

Nice Neil. What unit did you use for the motor and impellor on top and did you make the cyclone yourself?

I used my old 1HP unit and modified the intake to improve the suction. Yes I built the cyclone myself, I did a thread on it way back then, but probably gone now in the big clean up a few years back. It is still on my old web page from 2005, that I no longer keep and pay for so will probably disappear soon, but still there today http://www.dai-sensei.com/index.php?user1=neil. See under dust collection

[Lappa]

Ian, if you look at my build, I came in at the bottom then up the inside wall to the roof. Yours would be no different except your vertical would be on the outside wall.
I used DWV because the bends have a better radius but the DWV pipe I used is lined and weighs more than stormwater pipe. Not sure if all DWV pipe is lined? My DWV is approx 151mm ID while the stormwater is approx 153.5mm


403352 DWV pipe at the bottom


403350 Smooth stormwater interior
403351 Rougher DWV interior


If I did it again, I would use stormwater pipe but DWV connections, especially the bends. Funnily enough, the DWV straight connectors were cheaper than the stormwater at my supplier but it's best to check with yours.
However, if you were to use any sheet metal fittings (I used a 150mm to 125mm tapered adaptor and a 150mm flange ) they are almost dead on 150mm so they are loose in stormwater pipe but a reasonable fit in DWV pipe.

[BobL]

If I did it again, I would use stormwater pipe but DWV connections, especially the bends. Funnily enough, the DWV straight connectors were cheaper than the stormwater at my supplier but it's best to check with yours..

Price depends very much upon how many they buy in bulk at the time.

The main DWV fittings I purposely buy are the 90 and 45 bends because they are available with greater radii - everything else I try to get as stormwater.
I use a lot of treaded inspection couplings and caps and as these are not available in 100 mm stormwater I buy these as DWV.

[Lappa]

Price depends very much upon how many they buy in bulk at the time.

.

That is obvious to all. I was comparing a buy of 1 vs 1 Bob

[Ian Dobson]

Thanks BobL and Lappa.

I've started my build with a slab pour for the DC shed. Looking forward to some clean air woodworking in the near future. I'll post some photos on progress as I go.

Ian

[Ian Dobson]

Resurrecting my old thread. For many reasons, I haven't made much progress on my dust collection project since last Summer. But I'm finally back onto it.

After building a small shed behind my garage workshop, I put the 2hp dusty in there and checked the noise level from the adjacent fence line. I don't have a fancy meter, but I do know that my neighbour wouldn't be happy with that arrangement.

So I am reverting to my original idea to put the bag/filter end of the dusty into the shed and leave the impeller in the garage. I am assuming the majority of noise will be coming from the impeller rather than the bag/filter.

The next step is to form some 6" PVC pipe into the appropriate shapes to connect each end of the dusty. Tonight I started on the impeller end (rectangle ~155x105mm). I whipped up a simple moulding form from scrap MDF and spent some time with the hot blow gun to get the pipe end into the right shape. My intent is to create a rectangular wooden flange and epoxy it to the pipe.

Here is the progress so far, I will post updates as I go.

[BobL]

After building a small shed behind my garage workshop, I put the 2hp dusty in there and checked the noise level from the adjacent fence line. I don't have a fancy meter, but I do know that my neighbour wouldn't be happy with that arrangement.

A fancy meter is not needed. The free sound pressure level meters available as Apps for mobile phones will give you an idea of any improvements you make. Human ears simply can't hear small changes in sound pressure so it is hard to tell if "this is better/worse than this".

What is your small shed made of? May may need to seal it properly, add some more weight to the walls and add a sound muffler/baffle to let the air out.


The next step is to form some 6" PVC pipe into the appropriate shapes to connect each end of the dusty. Tonight I started on the impeller end (rectangle ~155x105mm). I whipped up a simple moulding form from scrap MDF and spent some time with the hot blow gun to get the pipe end into the right shape. My intent is to create a rectangular wooden flange and epoxy it to the pipe.

Moulds/formers will form a better shape if they have a longer transition and quite rounded corners at the start of the transition.
Ideally the mould should starts off with a round end that fits inside the pipe and transitions to the square shape.
Unfortunately this produces a large area requiring even heating which is near impossible to do by hand evenly with a single heat gun.
This is why I place my Bell Mouth hood formers onto a lathe which improve the even-ness of heating.
424999

A coupe of other tips
Try rubbing wax (paste or from a candle) or oil to the former and the inside of the pipe to help it slide onto the former.
When I tried this with MDF I found it soaks up most of the lubricant which is why I ended used hardwood as the former.
Heat the former itself up to about 100º before heating the pipe.
I realise that not everyone can access hardwood of these sizes so you have to work with what you can get but even pine will be better than MDF.

[Ian Dobson]

> What is your small shed made of? May may need to seal it properly, add some more weight to the walls and add a sound muffler/baffle to let the air out.

> Moulds/formers will form a better shape if they have a longer transition and quite rounded corners at the start of the transition.
> Ideally the mould should starts off with a round end that fits inside the pipe and transitions to the square shape.
> Unfortunately this produces a large area requiring even heating which is near impossible to do by hand evenly with a single heat gun.

The shed out back is a 1.5m x 0.75m Colorbond garden shed, with no rear wall (it's bolted onto the brick rear wall of the garage). What do you suggest as the best material to use for adding weight/sound deadening to the walls?

I agree using a longer mould would make a smoother transition. But in this case it's a bit more complicated than a bell mouth as the vertical dimension (as shown in photo above) is 105mm which is smaller than the pipe diameter. A form that started to fit the round pipe and ended as the rectangle shape would have to be either made in multiple parts, or destroyed to get it out of the formed pipe.

In this case to keep things simple, after getting the end into rectangular shape, I have taken the pipe off the former, and reheated it (not at the very end, but from a couple of inches down), and used an oven mitt pressing from the inside to smooth out the transitions on each corner.

[russ57]

Shed insulation...
The main thing to block sound transmission is mass.
Line the shed with any dense material.
Acoustic plasterboard
Fire check plaster board
Lead
Lead loaded vinyl
Solid brick


The next step is to absorb sound.
Inside the mass layer, use acoustic insulation, rock wool, etc.
I think carpet may work.

I'm not sure of the acoustic properties of Styrofoam. (just checked one product, it has some value but probably not enough)

I'm looking at this:
Speedpanel.com.au

Of course, the dc needs to exhaust its air.

Rather than just an open hole, a baffle, or series of baffles covering the hole, will let the air out keeping most of the noise in.



Russ

[BobL]

The shed out back is a 1.5m x 0.75m Colorbond garden shed, with no rear wall (it's bolted onto the brick rear wall of the garage). What do you suggest as the best material to use for adding weight/sound deadening to the walls?
A plain Colorbond shed will ring like a bell. For weight I suggest using scrap MDF but anything solid with weight, plaster board etc Ideally the enclosure also should be near air tight and the the air escape via a baffled box.

My enclosure is also bolted to the wall of my shed.
I have Colorbond, 32 mm of Scrap melamine, 50 mm of Acoustic Rockwool and then 16 mm of Scrap MDF and then 50 mm of mattress foam. The reason for all this is enclosure is right next to my fence and the neighbours pool is immediately on the other side of the fence.


I agree using a longer mould would make a smoother transition. But in this case it's a bit more complicated than a bell mouth as the vertical dimension (as shown in photo above) is 105mm which is smaller than the pipe diameter. A form that started to fit the round pipe and ended as the rectangle shape would have to be either made in multiple parts, or destroyed to get it out of the formed pipe.
Yeah those ones are buggers to do because if a solid former is used as I suggest the former cannot be removed from the pipe!
The only way to do those with a proper transition is with a collapsible former


In this case to keep things simple, after getting the end into rectangular shape, I have taken the pipe off the former, and reheated it (not at the very end, but from a couple of inches down), and used an oven mitt pressing from the inside to smooth out the transitions on each corner.
Makes sense.

[tonzeyd]

Also take into consideration the machinery you have/plan on having. If you spend considerable amount of time chiseling or angle grinding or using a circular saw putting all your efforts into absorbing the sound a dusty makes, will have a limited effect on the number of times your neighbor will come knocking on your door.

Obviously something is better than nothing but for me when my thicky is on I just hope no one within 50m radius is trying to sleep.

[Lappa]

I made an inner and outer mould to form mine. Only used a standard heat gun and had no problems. Cant find the outer mould but it was just a rectangular hole in a 17mm piece of ply wood. The the hole was larger than the inner mould by two times the thickness of the pipe plus an additional 1 mm. I used the larger joint end of 150mm pipe.


425028425026

It was sealed and screwed into a timber flange. This is it fitted.

425027

[Ian Dobson]

A bit more context ... this is the back wall of my garage with the shed behind it. On the right is the boundary fence with my neighbour's outdoor entertainment area behind it.

My plan is to remove the lower fixed glass pane of the window and run the ducting through an acrylic sheet with a 160mm hole in it, then turn 90 degrees with a hole in the left side of the shed.

It's either that or try my hand at some brickwork, and the wall is full of obstacles including electrical wiring and water pipes, so I'm not very keen on that idea.

I'll do the 90 degree bend with a couple of 45's.

Any suggestions?

[BobL]

My plan is to remove the lower fixed glass pane of the window and run the ducting through an acrylic sheet with a 160mm hole in it, then turn 90 degrees with a hole in the left side of the shed.
Sounds like a plan



I'll do the 90 degree bend with a couple of 45's.

A large radius 90º bend will be better than 2 x 45º bends.

You'll need a way for the air and as little sound as possible to get out of the enclosure.

[Ian Dobson]

> A large radius 90º bend will be better than 2 x 45º bends

I'm not sure how I'd do that. DWV and storm fittings don't come in large radius bends. I could try filling the pipe with sand to stop it kinking, and then using the heat gun on it, but I don't have a mandrel bender for anything like that size and my heat gun doesn't cover a large area at any one time. I see there are large radius 150mm electrical conduit 90's (exxy $$$) but am not sure if they are sized to interface with 150mm stormwater pipe (160mm o.d.).

[BobL]

> A large radius 90º bend will be better than 2 x 45º bends

I'm not sure how I'd do that. DWV and storm fittings don't come in large radius bends. I could try filling the pipe with sand to stop it kinking, and then using the heat gun on it, but I don't have a mandrel bender for anything like that size and my heat gun doesn't cover a large area at any one time. I see there are large radius 150mm electrical conduit 90's (exxy $$$) but am not sure if they are sized to interface with 150mm stormwater pipe (160mm o.d.).

Sorry I should have provided more detail.

Standard Stormwater 90º bends look like this.
The bend radius is equivalent to the radius of the pipe - its called a 1R bend
425083

DVW 90º bends come in two sorts, a 1R bend the same as the stormwater and a 2R bend like this.
425084

My testing shows that 2R bends only lose about 1% of the flow whereas the 1R lose 7% of the flow.
It doesn't sound like much until you have to use a few bends and then it all adds up

[Ian Dobson]

Oh, ok thanks.

I had assumed that two 45 degree bends would lose less flow than even the 2R 90 degree bend. But if the 2R 90 will only drop 1% of the flow, that's easier to do (and cheaper too).

My impeller & motor will be in the garage, directly inside from the window. I had planned to mount these onto a vertical framework so the exit duct off the impeller can head straight out through the window without having to make any 90 degree turns.

Between the window and the shed I might need a 15 degree elbow so the pipe can enter the shed at the same height as the bag/collector input duct.

[BobL]

I had assumed that two 45 degree bends would lose less flow than even the 2R 90 degree bend. But if the 2R 90 will only drop 1% of the flow, that's easier to do (and cheaper too).
I also used to believe that until I tested it.
It turns out that a 2R 90º (blue on graph) bend has about the same resistance as 1 x 45º (red_.
The problem with the 45º bends is that they are not really smooth bends but 45º steps.
2 x 45º (green) is better than a 1R 90º bend (purple).


http://www.woodworkforums.com/attachment.php?attachmentid=412036&d=1494232380

Lots more data in this thread.
http://www.woodworkforums.com/f200/air-flow-calibration-measurements-213627/3
Anyone starting out building a DC system could benefit by reading this thread.

[Ian Dobson]

Thanks Bob, interesting reading & your expertise is most valued.

In my setup, the ducting we are talking about is on the output side of the impeller - ie the airflow is being driven into the bend rather than sucked out of it. Do you think that would make any difference to the result? (just thinking this may make a difference, as there is no vacuum force pulling the dust around the bend)

[tonzeyd]

Thanks for this Bob very insightful.

Are 2R 90 bends common? I don't recall ever seeing them at either Bunnings or loca ducting shop.

[BobL]

In my setup, the ducting we are talking about is on the output side of the impeller - ie the airflow is being driven into the bend rather than sucked out of it. Do you think that would make any difference to the result? (just thinking this may make a difference, as there is no vacuum force pulling the dust around the bend)

It doesn't make any difference. Air moves from higher to lower pressure - the air itself doesn't know whether it is being pushed or pulled - it just moves because of the pressure gradient.


Thanks for this Bob very insightful.
Are 2R 90 bends common? I don't recall ever seeing them at either Bunnings or loca ducting shop.

I would not recommend buying any PVC from Bunnings - way too expensive and very limited range.
Pipeco (same as Pipeonline) in Welshpool have most of these PVC fittings.

[tonzeyd]

Thanks Bob, will need to keep my eyes open for them next time i visit Pipeco.

I only use Bunnings when I'm in a hurry or if I only need a short length of pipe, obviously in an ideal world buying 6m lengths and having it sit around till i get around to expanding the ducting but I've got to share a house with one who'd rather not have it looking like an industrial warehouse (or junkyard for those who don't know what its intended purpose is).

[Ian Dobson]

I'm working on the bag end of the pipe now - a short journey back to high school geometry and trigonometry to calculate the required curve to interface two cylinders.

I'm sure there are online resources for this sort of stuff, but I enjoy nutting out stuff like this myself. Since I started woodworking a couple of years back, my high school maths has had quite a work out.

[BobL]

I'm not quite sure what you mean by "interfacing two cylinders"?

[Ian Dobson]

> I'm not quite sure what you mean by "interfacing two cylinders"?

Connecting the horizontal cylindrical 6" pipe with the vertical cylinder from the bag/filter unit.

I've cut out the pipe along the curve now, and the profile fits nicely. The next step on this component of the job is to cut the matching hole into the sheet metal, but I won't be doing that until I've got everything else ready to go as it'll put my dusty out of action until it's all reassembled.

[BobL]

Ah ha - thanks.

I would have done the same as you but I recently watched my mathless BIL having to do a similar thing joint with Al pipe and what he did was use a piece of cardboard formed into a cylinder and a pair of scissors - he just winged the first cut and then made adjustments until he had it - pretty quick really. Then he did the same and wrapped the cardboard around the Al pipe.

[Ian Dobson]

Sizing up the inside half of the unit so I can work out where to cut the hole in the window pane . I'll be able to move it closer to the window once the hole is there.

To avoid a 90 bend straight out of the impeller, I have turned the whole unit onto its side, but it's hanging off the original mounts. I am concerned that the motor bracket may sag over time and was thinking to address that by blocking up the motor with a short timber offcut underneath. Is that a good idea, or am I better off reverting to the original orientation and including the bend?

(I don't do metalwork, otherwise I would have fashioned a support bracket to connect straight off the motor casing.)

[BobL]

Looks fine to me but I would add 45º wooden braces on each side of the marine ply bracket.

[Ian Dobson]

Looks fine to me but I would add 45º wooden braces on each side of the marine ply bracket.

Yes thanks, did that already with the steel brackets which incorporate a 45 brace. They are painted black so are hard to see in the photo.

[QC Inspector]

If I remember correctly you can unbolt the housing from the motor and rotate it ninety degrees and bolt it back on. The motor will sit as it was made and the impellor outlet exits to the side instead of up. You need to remove the inlet, then the impeller to get access to the bolts in the end of the motor. When you put it back together you should seal the mating surfaces to prevent leaks.

Pete

[russ57]

I'd be putting a block /cradle under the motor. I'd think it would risk distortion in the blower housing otherwise.




Russ

[BobL]

I'd be putting a block /cradle under the motor. I'd think it would risk distortion in the blower housing otherwise.
Russ

The motor and impeller are not hanging off the housing, instead they're attached to a sturdy (3mm thick ) steel bracket attached to the ply upright. If anything the blower housing is hanging off the motor but it does that as supplied in the original fitting and the housing is much lighter than the motor.

I lightened up the photo so the motor bracket could be more easily see.
425278

[russ57]

The motor and impeller are not hanging off the housing, instead they're attached to a sturdy (3mm thick ) steel bracket attached to the ply upright. If anything the blower housing is hanging off the motor but it does that as supplied in the original fitting and the housing is much lighter than the motor.

I lightened up the photo so the motor bracket could be more easily see.
425278I can see clearly now the dust has gone ...
Yep, that should be fine I reckon.
IMHO.


Russ

[Ian Dobson]

Up until now I've been working through the problem of getting the DC outside (or at least the leaky bag and filter half of it) but had a bit of a blind spot on the inside implications of doing that.

My working space is one half of a double garage, and my primary dust makers are a table saw and a router table. The router table is set into the extension wing of the table saw.

This means extending ducting into the middle of the room as the table saw can't be located against a wall.

An overhead route from the impeller to the TS would be 2m up then 3m directly across and 2.4m down, with four right angle bends (plus 2m from the impeller out the window to the bag) ... from reading this forum that sounds beyond the ability of a 2hp modified dusty?

If pressed, I could put up with the inconvenience of running ducting across the floor, even then it would be at least 4m horizontal ducting inside, with two 90's, and 2m more outside.

How much flow loss will I get from the extra length of 150mm PVC? Bob, you say try not to go over 3m with a 2hp dusty, but I can't see how else to get the DC outside and I understand that is the #1 thing to achieve.

Also does pipe going vertical cause more of a loss than going horizontal?

[BobL]

How much flow loss will I get from the extra length of 150mm PVC? Bob, you say try not to go over 3m with a 2hp dusty, but I can't see how else to get the DC outside and I understand that is the #1 thing to achieve.

By "3m" I mean as short as possible.
It's not like that up to 3m its OK , and then at 3.1 m it drops of to "Not OK".
If you cannot keep the ducting runs under 3m then you have to live with it unless you go to a larger DC.
I usually recommend no more than 6m for a 3HP DC but my ducting run to my TS is 11m.

Unless the ducting ends with naked duct (i.e. not attached to a machine) attached to a BMH the biggest losses are always at the connection to a machine.
I would focus more on that than anything else.


Also does pipe going vertical cause more of a loss than going horizontal?
No real difference.

[Ian Dobson]

I have had some time to get back to the project today now that Christmas is over.

1. Removed the lower glass window pane and replace with acrylic/Perspex, with a corner removed and replaced with a ply panel with a 6" hole for the ducting.

2. Took to my shed wall with a jigsaw to make a 6" hole for the intake duct. I found a DWV 90 with a larger radius than the storm pipe. BobL I hope that's the type you were referring to.

3. Rather than continuing with my earlier idea of interfacing the 6" pipe directly with the bag/filter ring, I have switched to making a ply adaptor following Jonno's idea. Then I have made two 6" round pipe to rectangular transitions, to fit the impeller in the garage and the bag/filter ring in the DC shed. The idea here is that if I decide later on to put the impeller into the DC shed too (with a swag of additional soundproofing) then I can easily revert to the original DC mod design with the impeller and bag/filter directly coupled.

The next step is to get the external ductwork completed and flashed/sealed

At present I haven't even started on the 6" input side to the impeller, or ducting in the garage. I am trying to work one step at a time without totally disabling my DC for a long period in the process.

[Ian Dobson]

Test fit of the duct work. I still have to change over the bag/filter connection to the 'Jonno' adaptor.

I downloaded an iPhone DB meter and took some measurements.

Inside the garage ~46dBm with nothing turned on.
~85dbM with the impeller powered up and standing 1m from it.

Outside 1m away from the DC shed ~64dBM with nothing turned on. Our ducted A/C heat exchanger is about 3m from here and currently operating so it's noisier than usual.

With the DC on, I measure 85dBM standing 1m from the shed with the door open, and 78dbM if the door is closed. Currently I don't have any exhaust ports cut into the shed and there is considerable back pressure with the door closed.

I am surprised that the bag/filter is pretty much just as noisy as the motor/impeller.

Now to work on some sound reduction, or the neighbours wont be too impressed with my efforts. My shed is only 0.8m deep so there isn't a lot of room for thick absorbing batts. I could line it with thick MDF or chipboard and still have room to move to empty the bag and clean the filter.

[russ57]

To stop noise transmission, mass..
Line it with chipboard, mdf, carpet, lead sheet, concrete :)
A baffle around the air exit, at least, or better some sort of labyrinth, lined with noise absorbing material. Eg, carpet, acoustic batts, acoustic foam.




Russ

[Mobyturns]

I would be looking at fitting a vibration isolating "baffle" between the pipe and opening through the Perspex window pane. Its amazing how the pane can act as an amplifier for low frequency noise and also transmit vibration to the aluminium frame.

[Ian Dobson]

I have been working on noise reduction in the shed (which currently holds the bag/filter collector only, with the motor and impeller still in the garage)

I ripped some 4x2's down the middle and built a frame, then overlaid 18mm MDF sheets with the cavity filled with acoustic batts from Bunnings.

The batts are rather compressed as the frame is only 45mm deep - this will reduce the air trapped in the cavity and reduce the sound absorption effectiveness. However I am somewhat limited for space in the shed - as it is, the filter bag hits the MDF sheet on the roof and I am probably losing a little filtration area (and losing some SP from increased back pressure) as a result.

The sound measurements standing 1m from the shed door are now 68db with the door closed, and 73db with the door propped open a few inches (noting that until I build an exhaust baffle I need to run it with the door open a little).

This is down from 78db (door closed) and 85db (door open). The background noise in this location is 64db with the ducted A/C unit running, which it was pretty much continuously today being 42 degrees here in Melbourne.

So I am pretty happy with the reduction, and with the addition of an exhaust baffle should have a solution to keep the neighbours happy.

Tomorrow I will put the motor/impeller into the shed and do another sound test to see if that would be viable. If so then I will pivot to that approach, to reduce noise in the workshop and save some floorspace too.

At the moment I am still yet to modify the input to the impeller to 6" ducting so am not getting the airflow benefit of the mod yet. Will the increased air flow from that result in increased noise too?

[MandJ]

If you want to get an idea of how much noise is coming from the motor and impeller then just block the inlet, that eliminates most air flow noise. The main noise in the workshop (and you can hear it outside the closed workshop as well) is from the sound of air flowing into the intake ports - and that's with a 150mm bell-mouth intake which should have the least edge flow noise (as opposed to something with sharp non aerodynamic edges) Most noise from the impeller and motor comes from low frequency rumble which can make a cabinet resonate. Intake noise increases as flow rate increases. I'm running a 3HP DC, levels are around 86db with that port open and 64db with it closed, the Router table air intakes are even louder - those readings are from inside the workshop.

[Ian Dobson]

Today I reassembled the full DC inside the shed and took some sound measurements, again standing 1m away.

64db background noise (same as yesterday)
85db with the DC on and the door open a few inches
77db with the DC on and the door closed

Interestingly, that's pretty much the same as I had measured with no soundproofing and only the bag/filter in the shed, weird?!

Just to be sure, I split the DC back into its two halves again, and with only the bag/filter in the shed, measured 74db (door propped open) and 69db (door closed), pretty much confirming my previous measurements.

77db with the DC in the shed is too loud and I am running out of space to add much extra weight or baffling on the walls. So it looks like I'll be sticking with keeping the motor and impeller in the garage, and adding a baffle to vent the shed so I don't have to run with the door wedged open.

[MandJ]

Those readings are interesting? I assume that you had the intake ducted into the shed when doing the test above.

Here are my readings for a 3HP 4 bag DE mounted in a timber frame (lots of treated pine to cut down panel resonance) Fibre Cement clad housing - no other lining - no exhaust baffle.

Using a standalone dedicated noise meter.

Normal background noise at the moment is around 41dB.

DC cabinet door open @ 1m = 87dB - this door is one full side of the cabinet.

Door closed @ 1m = 62dB.

On the fence line @ 3m from DC cabinet (opposite side to the exhaust ports) is 58dB.

The side of cabinet where the DC exhaust exits @ 5m = 60dB, the fence line on that side of the cabinet is a further 11m away and the DC almost inaudible there.

Some of this noise with the cabinet closed is from the Intake port in the closed Woodwork shed. At 1m from the 6" intake port it is 87dB, the total pipe length to that first port from the DC is 1.8m.

We can run the DE at night and you can't hear it inside our house which is 3m from the DE cabinet. The cabinet is mounted in a long walkway between the WW shed and the house, this is not an ideal location as it concentrates and bounces any noise down that relatively narrow walk way.

[BobL]

Couple of comments.
Fibre cement is a very good noise suppressor - much better than sheet metal.

There is nothing absorbing the sound inside the enclosure.
Suggest a couple of layers old carpet on the floor and one on the ceiling.

A well made baffle should be much better at sound reduction than a crack in a doorway.

Check that the ducting running through the wall of the enclosure is not touching the enclosure wall.
Maybe when you had the DC inside the enclosure it was touching whereas before it might not have been?.
I cut my ducting holes 50 mm oversize and cut foam rings to bridge the gap.

[Ian Dobson]

Those readings are interesting? I assume that you had the intake ducted into the shed when doing the test above.


No, I haven't yet modified the intake to 6" ducting so was t able to connect it up for the test. When I did the test with the full DC in the shed, it was with a naked input, and the ducting into the garage was left in place but disconnected.

[Ian Dobson]

Couple of comments.
Fibre cement is a very good noise suppressor - much better than sheet metal.

There is nothing absorbing the sound inside the enclosure.
Suggest a couple of layers old carpet on the floor and one on the ceiling...

Perhaps I should have used FC as the internal cladding inside the shed rather than MDF?
I will try and find some cheap scrap/surplus carpet as internal lining.

[tonzeyd]

Hi Ian,

i suspect a couple of things that you could try to suppress noise further.

- Try caulking all the gaps, I built a compressor box a while ago, with acoustic foam and plywood. Because i needed to get the compressor in and out of a tight space i built it in a way that i can remove all the walls if needed to move the box at a later stage. When i tested it the first time noise levels was almost identical to what it was just sitting on the floor. Realised there were gaps everywhere caulked everything and remeasured and reduced everything by about 13 db.
- Also depending on how well your mdf fits together when you close the door, might be worth adding a few strips of rubber where they touch, as any vibrations would be transmitted directly to the outside.

Also these are amazing, they killed any vibration my compressor made, obviously might not be as effective with your concrete slab but could reduce by another couple of dbs

https://www.bunnings.com.au/whites-on-site-100-x-12-5mm-rubber-anti-vibration-mat-4-pack_p3961547

Also in terms of sound absorbing, you don't need much just enough to reduce the amount of energy bouncing around and compounding as the waves crash into each other. I suspect even if you stuff each of the corners with old jackets/clothing/socks etc it'll give you a good reduction in noise levels.

[MandJ]

No, I haven't yet modified the intake to 6" ducting so was t able to connect it up for the test. When I did the test with the full DC in the shed, it was with a naked input, and the ducting into the garage was left in place but disconnected.

if I read that correctly then there is a problem with your noise readings. With no ducting, you have to block the impeller inlet if you are going to test the noise level with the motor and impeller inside the DC cabinet, otherwise you are simply reading the intake sound level of the air being sucked into the impeller, when you duct the impeller into the shed, then you are actually reading the sound of the complete DC inside the cabinet.

[MandJ]

Sorry to go on about this but just to clarify post #54:

You are always going to have intake noise, it will change with the amount of air flow the DE is capable of, the type size and length of ducting and where the duct is within a machine - or not - and the shape of the duct intake.

So measuring that intake noise is a fruitless exercise when trying to see how loud the DC is inside an EXTERNAL cabinet. The intake sound will be contained - for the most part - inside the workshop, some will escape into the external DE cabinet and find it's way out the cabinet vent port, but in my case it's minimal. If you have a lot of low frequency noise from the impeller or resonance in the cabinet that can't be reduced then these and other noises have to be addressed with an exhaust vent baffle. I did't need any - that is another reason I heavily cross braced all interior surfaces, it breaks up internal cabinet reflections and panel resonances. Like I said, I don't use a baffle and I have no lining, but as BobL said, thick fibre cement is pretty dense, the reason I used it, but like most big panels they need to be braced to stop low frequency resonances. Everything was not only glued, but screwed down to within an inch of it's life, then sealed again with silicon sealer but silicon mainly for extra weather proofing more than sound reduction.

[Ian Dobson]

Thanks. I believe that blocking the impeller inlet with the whole DC in the shed will fail to take into account the noise from normal airflow through the bags. Currently the air duct into my shed ends at a rectangular transition which interfaces with the bag housing, and there is no straightforward way for me to connect this to the impeller inlet without making irreversible changes to the ducting. I might be able to run a 4" Flexi from the impeller inlet then internally back through the 6" ducting, at least that would remove the majority of air intake noise from the shed measurement.

[MandJ]

Then your smaller DC must substantially different than mine, the noise is made at the pick up and then reduces as it travels to the DC, my Lathe port produces 87 DB and travels only 1.8M to the DC intake, it is virtually inaudible from the DC housing, there is more intake noise coming through the walls of the shed than from the DC housing exhaust port

[Ian Dobson]

Then your smaller DC must substantially different than mine, the noise is made at the pick up and then reduces as it travels to the DC, my Lathe port produces 87 DB and travels only 1.8M to the DC intake, it is virtually inaudible from the DC housing, there is more intake noise coming through the walls of the shed than from the DC housing exhaust port

My DC impeller must be much noisier than yours.

I just went into the garage and measured the following, at 1m away from the DC motor/impeller, and 1m above the floor. (Note at present the impeller ouput is
ducted through the window to the bag/filter unit in the shed.

1. DC input connected to my TS with 3m of flex hose: 79db

2. DC input disconnected and naked: 85db

3. DC input plugged (with duct tape covering the input flange): 85db

With the input plugged and no air flow through it, there is no inrush noise from the port but the impeller is making more noise than with ducting connected. I expect there would be a lot of turbulence internally as the motor strains to drive air around the impeller loop, and the motor would be subjected to a much higher load resistive torque as a result.

This would very likely be at a different frequency to the inrush noise and your enclosure with the FC sheet cladding may be much better at suppressing it as such.

[MandJ]

Those readings are similar to mine - sound does not add up the way you think, adding the intake noise to the impeller/ motor noise will only show a very small increase, yet each can be deafening on there own - what I'm saying is that you can't measure the effectiveness of the DC housing with the complete DE "inside the housing" and measuring DB with the impeller intake port open (inside the cabinet).

Yes there is a difference in DE impeller noise (with the complete DE in the housing) and with the intake open and then blocked - but the way you are measuring it won't show the DE housing reduction correctly until you pipe the impeller intake into the WS - until then you are guessing how much remote intake noise will end up at the cabinet exhaust vent.

However I'll leave it at that and let you build it the way you think will work best, I know how annoying it is when someone (me in this case) harps on, and I'm sure you'll get it sorted one way or the other.

[BobL]

With the input plugged and no air flow through it, there is no inrush noise from the port but the impeller is making more noise than with ducting connected. I expect there would be a lot of turbulence internally as the motor strains to drive air around the impeller loop, and the motor would be subjected to a much higher load resistive torque as a result..

There is actually less load on an impeller motor when there is less or no air going through the impeller. This is demonstrated by the much lower currents drawn by an impeller motor when the impeller is blocked.
What happens is the air remaining in the impeller just goes around and around.
The more air that passes through the impeller then more work the motor has to do.

3m of flex will reduce the air flow substantially and the flex itself will absorb some nose so the SPL measurements in steps 1 - 2 above makes sense.

Measurement 3 is curious as it should be the quietest of the the 3.
It sounds like the motor impeller combo is itself vibrating.
It could be a motor bearing?
It would be interesting to see what the SPL measurements would be if you could dampen the vibe on teh impeller by attaching/hanging/placing some weights on the impeller.

[Ian Dobson]

There is actually less load on an impeller motor when there is less or no air going through the impeller. This is demonstrated by the much lower currents drawn by an impeller motor when the impeller is blocked.What happens is the air remaining in the impeller just goes around and around. The more air that passes through the impeller then more work the motor has to do.

Ah, ok that makes sense.

I've only ever had the one DC so if there was something unusual with the noise or vibration then I might not be aware of it.

I just tried starting it up and pressing in various places around the case to see if I could significantly reduce the sound, no real benefit there. (I presume you were referring to the casing rather than the actual spinning impeller there.)

It does vibrate quite a bit when first starting up but settles down when its up to speed.

I've attached a short video clip, if that helps at all (was taken with the DC connected by 4" flexi to the TS - haven't started work on the infeed ducting yet.)

[BobL]

Ian - I finally got to watch the vid - the noise made by your impeller does not sound right to me and the start up noise it makes is I think a hint as to what might be going on.
It could be that one of the impellers is bent, or a tad longer than the others and this was corrected for by balancing but that means it will produce a different noise than an impeller that has all even length blades. Unless it is something that is clearly visible then fixing this is not easy and it is often just easier to replace the impeller.

You will need much more force than hand force to make a difference.
Try carefully clamping bricks either side of the impeller exit.

It could be the orientation of the impeller/motor.
Try removing the exit ducting and standing the impeller back up on its base and compare that to the SPL with it hanging from the side.

A bracket between the impeller exit and the base of the stand might help.
427929

[Ian Dobson]

what I'm saying is that you can't measure the effectiveness of the DC housing with the complete DE "inside the housing" and measuring DB with the impeller intake port open (inside the cabinet).


Ok. Another set of test. This time I rebuilt the whole DC in the shed, and ducted the input back through into the workshop. As I currently have 6" ducting between the shed and workshop, and a 4" intake to the DC, I did this by running my 3 metres of 4" flexi internally up the 6" ducting. So airflow is definitely restricted but the intake noise is moved out of the DC shed.

73db with the DC on and the door closed
75db with the door open a couple of inches to allow exhaust
81db with the door open fully

Also I measured the intake noise in the workshop at 75db, I imagine its going to be significantly higher with a full 6" duct and unrestricted air flow.

So with the door fully closed, 73db vs my original 77db with the naked input. But with the door open a crack, 75db vs the original 85db measurement, a significant reduction.

After all that, with the door closed and the full DC in the shed (73db) vs only the filter/bag in the shed (68db) is still a significant difference (I am presuming with a proper baffle the end result will be much closer to these figures than with having the door open a crack.

I am going to pick up some freebie carpet offcuts and line the walls, then measure again. If I can get down to 70db at 1m from the shed, then I'll put the whole DC into the shed which will keep the garage quieter!

Also regarding motor noise, I turned it back upright and it doesn't change the vibration significantly. As Bob points out, I may well have a slightly unbalanced impeller or a noisy motor bearing. I don't know how to fix those short of replacing them, and I don't really want to buy another 2hp DC knowing how poor they are at actually collecting all the fine dust. Unfortunately a 3hp unit won't fit in my shed space so I will make the best with what I currently have.

[MandJ]

IMHO a 6" pipe with a bell mouth intake will likely be quieter than a 4" intake, usually the smaller the intake for a "given flow rate from a DE" the louder the intake air noise - forcing XX flow rate through smaller and smaller intakes creates higher intake air speed and noise- up to the point - then it drops off as flow rate chokes down.

[Ian Dobson]

I got some old rubber-backed carpet tiles and lined the shed with it, including the roof. (Note double stick carpet tape doesn't hold on roof and walls, I will have to get myself a tube of construction adhesive and try again.)

That brought the noise level outside the closed shed down to 70db.

Then I realised that my free download sound meter app has been measuring unweighted decibels and most of the noise is low frequency rumble. So I upgraded it to measure weighted dbA (weighted for human hearing perception), and measured the noise level as 62dbA outside the closed shed. That seems intuitively correct, I don't perceive the noise as overly loud myself.

Ok, I'm now comfortable with finishing the full DC 6" mod and keeping the motor/impeller in the shed too.

Next step is to make a MDF exhaust baffle and a frame to mount the motor/impeller unit.

[MandJ]

That's better, I just assumed that the app would be dbA. Thanks for the update.

[Ian Dobson]

I've revised my plan with the DC configuration. Rather than building a frame to lift the motor up to the same height as the bag unit input, I'm now going to keep the motor section lower down and connect the two pieces together with 6" ducting.

This works better with my shed configuration as it was going to be a very tight squeeze with the way I've mounted the baffle box internally

I have turned the motor 90 degrees so that the input can come in directly from the side wall of the shed, this saves a 90 degree elbow.

Also I turned the bag mounts 90 degrees so the section facing the shed door doesn't have a mounting pole on it, that will make bag changes much easier. By doing this, I am also cutting out and enlarging the original bag inlet area.

[BobL]

I've revised my plan with the DC configuration. Rather than building a frame to lift the motor up to the same height as the bag unit input, I'm now going to keep the motor section lower down and connect the two pieces together with 6" ducting.

This works better with my shed configuration as it was going to be a very tight squeeze with the way I've mounted the baffle box internally

I have turned the motor 90 degrees so that the input can come in directly from the side wall of the shed, this saves a 90 degree elbow.

Also I turned the bag mounts 90 degrees so the section facing the shed door doesn't have a mounting pole on it, that will make bag changes much easier. By doing this, I am also cutting out and enlarging the original bag inlet area.

Looks very tidy.

Not a biggie because you save a 90º elbow which probably cancels out the following. Usually this arrangement will have some small flow losses because the rotational flow of the air in the impeller is not in the same plane as the bag housing.

It will be interesting to see what SPL you get with this setup.

[Ian Dobson]

It will be interesting to see what SPL you get with this setup.

Silly question, but how do you measure SPL?

I can make up a u-tube manometer easily enough, but not sure how to hook it into the duct work, or whether the inlet duct needs to be blocked off when taking the measurement.

[BobL]

Silly question, but how do you measure SPL?
I can make up a u-tube manometer easily enough, but not sure how to hook it into the duct work, or whether the inlet duct needs to be blocked off when taking the measurement.

SPL = Sound pressure level - its the "quantity" for which dB is one of the "units".

Manometers measure regular "pressure" , units are things like Pa, psi, bar, etc

[Ian Dobson]

SPL = Sound pressure level - its the "quantity" for which dB is one of the "units".

Manometers measure regular "pressure" , units are things like Pa, psi, bar, etc

Thanks Bob, silly me, you were talking about flow loss in the previous paragraph then mentioned SPL and I misinterpreted that as referring to static pressure level, i.e. WC"

I will need to get new 6" shed inlet ducting in place before I can measure the noise level again. The new entry point needs to be much lower down so I enlarged the old inlet cutout into a long rectangle and made that the output vent from the baffle box.

Also I need to convert the impeller input over to 6". Not sure how to do the reverse BMH at present ... my largest roundover bit is 1/2" and I haven't turned anything on a lathe in 30 years. I am thinking of a long session with rasps or a sanding drum, but hard to get a consistent profile all around.

[BobL]

Also I need to convert the impeller input over to 6". Not sure how to do the reverse BMH at present ... my largest roundover bit is 1/2" and I haven't turned anything on a lathe in 30 years. I am thinking of a long session with rasps or a sanding drum, but hard to get a consistent profile all around.

1/2" is better than nothing.

[Ian Dobson]

The 6" input to the impeller is now installed. I'll fabricate a manometer and take some hard measurements plus redo the noise level check after I get it back into the shed. It certainly seems to be moving a lot more air now.

[Lappa]

The next problem maybe that is in fact moving too much air for a single filter to cope with. I’ve added another filter to my modified 2hp and my flow has increased somewhat over the single filter.

[Ian Dobson]

No room for a second bag in my shed, but I could swap the bag for a PF if that decreases the back pressure?

[BobL]

No room for a second bag in my shed, but I could swap the bag for a PF if that decreases the back pressure?
Yes it will decrease back pressure and filter will last longer before clogging.

[Lappa]

No room for a second bag in my shed, but I could swap the bag for a PF if that decreases the back pressure?

No room for a other filter in my shed either so I ran a pipe outside into a 200 litre drum with a Thein filter

[Ian Dobson]

Ok, I've finally got the DC back into the shed. I had to partially disassemble it to turn it 90 degrees through the door now that I've reduced the space inside with the soundproofing.

I've attached a few photos showing the DC, the baffle box and its exhaust port.

When I fired it up for a few minutes I can see some tiny dust trails starting to appear around the bag ring where it's leaking a bit so I am very glad it's not in the workshop any more!

Last night I cobbled together a U-tube manometer from a few scraps and measured the static pressure (with no flow) at the impeller input as 7.25" WC with the bag ring connected up. It was 7.75" with the impeller output unhooked which surprised me as I thought the bag/filter would be more lossy. (Please tell me if I haven't measured this properly - refer photo.)

I don't have an anemometer to measure the CFM - can it be inferred from the static pressure and 6" duct size or does it need to be measured directly?

Measuring SPL will have to wait until I get the input ducting back through the window - although to my ear with the door closed sufficiently quiet. There does seem to be a small amount of resistance still in the last inch or two of closing the door - hope I've made my baffle output large enough. The exit is about four times the 6" duct area although the dampening material on the walls eats into that a bit on the inside.

[BobL]

When I fired it up for a few minutes I can see some tiny dust trails starting to appear around the bag ring where it's leaking a bit so I am very glad it's not in the workshop any more!
:2tsup:


Last night I cobbled together a U-tube manometer from a few scraps and measured the static pressure (with no flow) at the impeller input as 7.25" WC with the bag ring connected up. That's about right. The most I have seen on a 2HP DC is ~8"


It was 7.75" with the impeller output unhooked which surprised me as I thought the bag/filter would be more lossy. (Please tell me if I haven't measured this properly - refer photo.) I'm surprised you measure any difference in SP as there is no flow. It's only when there is a decent flow that a pressure difference will develop.


I don't have an anemometer to measure the CFM - can it be inferred from the static pressure and 6" duct size or does it need to be measured directly?
Yep it needs to measured directly.

[Ian Dobson]

I've plumbed the intake back to the workshop.

SPL at 1m now measures 63dbA ... a great result as the measure with the door closed before I installed the baffle was comparable, so the baffle is doing its job well.

Glad that's finished!

Next step is to devise an internal duct plan, that's a whole different topic so I will close this thread here. Thanks for all your advise and assistance, especially BobL, MandJ, and Lappa.

[SuperB15]

Those readings are interesting? I assume that you had the intake ducted into the shed when doing the test above.

Here are my readings for a 3HP 4 bag DE mounted in a timber frame (lots of treated pine to cut down panel resonance) Fibre Cement clad housing - no other lining - no exhaust baffle.



Sorry to but in on thread but was interested in statements around Fibre Cement.
This I realise was used on outside of enclosure. Would it have been 6mm think FC?
Could it be used inside (in same 6mm thickness) an enclosure to successfully reduce sound and as alternative to ply or MDF?

[BobL]

Sorry to but in on thread but was interested in statements around Fibre Cement.
This I realise was used on outside of enclosure. Would it have been 6mm think FC?
Could it be used inside (in same 6mm thickness) an enclosure to successfully reduce sound and as alternative to ply or MDF?
Yes - anything with a bit of weight and rigidity helps - but it needs to be well supported (eg sturdy wooden frame) so it can't flex otherwise it can act as a drum head and transfer the sound out the other side.

[SuperB15]

Ok thanks Bob