Thread: Mens Shed Dust Collection

Originally Posted by ronboult

With that number of gates surely an automated system is warranted!!!

Yep - I fully agree.

However,
- most machines are still required to remain Mobile i.e. all machines are not necessarily operated using the same power socket or on the same DC duct
- the state of the finances
- skills of the members,
- I've already spending WAAAAAY too much time on this system and I only ever agreed to set up a manual system.
It's not happening on this build.

Perhaps once they see the limitations they might look at setting machines in dedicated spots thus making it easier to automate. getting it automated.

Well finally we have a few machines connected up.

So far the RAS, 12" thicknesser, the 12" disc sander, and the small belt sander are connected.

Only the thicky is connected up what I would call "properly" i.e. full 6" connection.
There are still quite a few leaks but we were running all 4 of these machines simultaneously without any problem.

Were at the point where we just want to connect the machines up as quickly as possible and then we'll go back and optimise things.

Hi BobL
I am intrigued by the red and green balls. Does red down indicate beware this gate is open or does green down indicate the gate is open and ready for use?

Originally Posted by ronboult

Hi BobL
I am intrigued by the red and green balls. Does red down indicate beware this gate is open or does green down indicate the gate is open and ready for use?

The latter.

This is pretty geeky stuff about measuring air flow - you have been warned.

To measure the air flows on my DC system at home I used a couple of different hot wire anemometers which can measure air speeds up to ~30 m/s.
Unfortunately the air speed in some of the ducts reaches around 42 m/s so to measure these directly I used a old clunker Pitot Tube borrowed from my former place of employment.
My home system is also not that high above the floor so I can reach it easily with both the Pitot Tube and the hot wire anemometers, and also could readily adapt over size test pipes to slow air speeds down before using the slower speed anemometers

Now that the men's shed ducting system is almost finished I will have a go at measuring the air flows.
Here I will be poking measuring gear into ducting up to 3.2 m above the floor where using over size test pipes will be very awkward.

To measure the higher air speeds in situ I borrowed the Pitot Tube again.
I have posted pictures of this before but they have been lost so here they are again.

AirflowMeter1.jpg
As you can see its pretty old school ( purchased in 1966)and is actually a lecture theatre demonstration device.
Its a German Leybold instrument with a bowl of coloured water connected to a 1/2 U-tube with water pressure and air speed scales marked on it.
The two ends of the 1/2 U-tube are connected by two hoses to the Pitot tube show laying on the black cloth in the foreground.

Here is close up of the Pitot tube.
There are two tubes connected at the tip A where the inner tube is exposed into the air stream and sealed against the outer tube.
The outer tube has 4 holes at B which are perpendicular to the air stream, while A is directed into the oncoming air stream.
The pressure difference generated between A and B is proportional to the square of the air speed so it can be used to measure air velocity.
Because the tube presents a small profile to the cross section of the moving air stream, a Pitot tube (along with a hot wire anemometer) is one of the few ways of accurately measuring air speed in small cross section ducting. This tube is relatively large so is limited to ducting about 6" in diameter although it could be used at a pinch for 100 mm ducting.
PitotTube.jpg

The whole unit has to be held steady and level to make a measurement so the thought of toting this around 3.2m above the ground is not practice;.
However, the pressure measurement side of the apparatus (coloured bulb of liquid and the U-tube )can be replaced by a digital anemometer which is what I plan to do.

So all I should need to do is connect the two arms of the Pitot tube u to the two inputs to the digits anemometer and subsequently convert pressure into air speed.
Now all I will need to worry about is the orientation and position of the Pitot tube while the digital meter can be held in any position

PplusMano.jpg

I have already cross calibrated the two pressure measuring devices and here is the calibration curve.
The calibration gave ∆ Pressure to the power of 0.504 which is within 1% of the theoretical square root factor which I am please about.
It's not that accurate for air speeds below about 20 m/s where the hot wire anemometers are more accurate and will be used.
Calibration.jpg

Here's something I'm calling a "Giant Sucker" that I knocked up over the weekend to act as a mobile floor level dust collection point at the mens shed.

Despite now having dust collection on most machines there's still plenty of uncollected saw dust generated with blokes using hand and power tools, and forgetting to open the blast gates etc.
At the end of each session theres a clean up time and stuff on the floor is swept into piles and pick up with a dust pan and brush.

Its basically a mobile 6" Bell Mouth hood on the end of a 1.6m long piece of PVC duct.
At various points around the shed there are a number of 6" flexies suspended from above and connected to machinery.
These connections are deliberately not fixed because the machinery may be moved around at short notice thus making the connections useful for other machinery

Now the blokes can connect the sucker to one of the flexies and just sweep the sawdust into the vicinity of the Sucker and then roll the Sucker back and forth over the pile of dust to pick it up.
IMG_1909.jpg

The cabinet section is made out of veneered MDF I collected after gutting the inside of a large kitchen cupboard for my niece so she could fit her large fridge into the kitchen of her new place.
The jarrah handle is made from veranda pickets being thrown out following my Bro's reno.
The bits of painted 6 x 65 x 65 mm angle acts as bracing plus adds low down weight to reduce the possibility of the Sucker tipping over.

The round piece of veneered MDF is surrounded by a strip of PVC and mounted off centre to the main PVC pipe.
Turning the handle to the left drops the BMH down to within 10 mm above floor level
IMG_1911.jpg

Turning the handle the other way lifts the BMH 60 mm above floor level.
IMG_1910.jpg

Here's a view from underneath.
IMG_1912.jpg

I'll try it out during the week and report back on how well it works.
Whether the blokes bother to use it will also be an interesting point.

Turned out great mate!

Originally Posted by BobL

Here's something I'm calling a "Giant Sucker" that I knocked up over the weekend to act as a mobile floor level dust collection point at the mens shed.

My "Giant Sucker" is a Great Dane, but I haven't managed to train her to eat sawdust yet.

The second 6" BMH has gone into service at the mens shed on the 6" belt sander.
IMG_1913.jpg

There's some positional adjustment so that it can swing out of the way to clear the line of the belt when long pieces of wood are being sanded.
Also for curved pieces being sanded on the roller itself.

IMG_1914.jpg

Quite a bit of dust gets carried around the back of the sander so it is important to extract some air from that region as well.

IMG_1915.jpg

The galv strap around the PVC fitting is a bit lightweight so I'm going to rebuild that part using 3mm steel strap.

Originally Posted by BobL

Turning the handle to the left drops the BMH down to within 10 mm above floor level

Wouldn't putting the BMH down to 10mm from the floor create a choke point?

At a rough estimate, I think that would give you an air intake area approximately half the cross section of the 6" duct.

Cheers

Doug

Originally Posted by doug3030

Wouldn't putting the BMH down to 10mm from the floor create a choke point?

At a rough estimate, I think that would give you an air intake area approximately half the cross section of the 6" duct.

Yes good point, 10 mm is a bit low as a min height, and if it significantly reduces the air speed in the pipe it will also not enable heavier stuff to stay suspended inside the duct
It's easy enough to adjust the min height by drilling another hole in the veneered disc so it won't lower as far.
I was going to pre-drill a series of holes in the disc so this could be experimented with - I may still do this
This will also reduce the max height the BMH comes up above the floor unless the hole in the PVC chimney is repositioned.
We'll try it out and see how it goes before we too many drill holes - you can see the disc already has some (incorrectly placed) holes in it.

Originally Posted by BobL

Yes good point, 10 mm is a bit low as a min height, and if it significantly reduces the air speed in the pipe it will also not enable heavier stuff to stay suspended inside the duct

I was wondering if 10mm was chosen to reduce the number of tape measures it can suck up.

At that height it would probably get the odd pencil.

Cheers

Doug

Originally Posted by doug3030

I was wondering if 10mm was chosen to reduce the number of tape measures it can suck up.

At that height it would probably get the odd pencil.

I didn't target 10 mm especially, it's the furthest the BMH can drop before the coupler that joins the BMH to the chimney hits the frame and prevents it going any further.
We really do want it to be able to pick up slivers and pieces of wood and waste that are normally swept up.

Latest report from the men's shed just sent to me by email.

Hi Bob, We gave your latest creation a run this afternoon.
Impressive. It worked like a dream.
Cheers.

FloorSweepMensShed.jpg