Thread: Moving the DC outside

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.

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.


IMG_0983.jpgIMG_0521.jpg

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

IMG_0980.jpg

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?

Originally Posted by Ian Dobson

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.

> 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.).

Originally Posted by 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.).

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
STORMWATER_BENDS.jpg

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

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

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.

Originally Posted by Ian Dobson

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).




Lots more data in this thread.
Air flow calibration measurements
Anyone starting out building a DC system could benefit by reading this thread.

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)

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.

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.

Originally Posted by 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.

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.

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).

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.

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