Thread: Why isn't a 100mm dust port 100mm?

A sad but common story. My old 4 inch ports were also all over the place. I had two 1 HP dustys and even they had different sized fittings at the end of the flexy. Solved the problem with some standard 100 mm PVC pipe and fittings. PVC is easy to thermoform a bit larger than it already is.

I ended the 4 inch flexy with a piece of 100 mm pipe, expanding the pipe until the flexy would slip into it. Then I thermoformed/fiddled with the machine ports to get a 100 mm PVC straight connector (or a piece of expanded pipe) fastened to the machine. That way, the pipe at the end of the flexy always fit the new connector on the machine.

Suggest you start by seeing what fits best onto your flexy ... pipe or connector. Then use the other on your machines. For most of my machines the connector was a bit large, and I simply secured it in place with silicone. For one I needed to expand the connector. Made a form from a piece of pipe with duct tape wound it to make it big enough to match the machine ... heated the connector until it was very soft and forced the taped pipe into the connector.

The optimum solution for a 2HP DE is using 150 mm ducting all round

Have you read the "Generic 2HP DC Thread"? This thread demonstrates that using anything less that 150 mm ducting and opening up all the dust ports on the machines is like driving a V8 with a Mini Minor carby and exhaust system ie throttled.

If it is impossible to fit a 150 mm duct to a machines then 3 x 100 mm ducts will do a similar job, just leave the unconnected ducts nearby to suck up the residual dust that will be escaping from the machine

A single 100 mm duct at normal DE pressures can only move about 400 cfm and it takes 3 x 100 mm ducts to equal the flow of a 150 mm duct - there is no way around this problem.

BTW a 50 mm duct at normal DE pressures moves (in theory) about 60 CFM so it takes 20, 50 mm ducts t o equal the flow of 1 x 150 mm ducts.

BTW if you add a Thein collector you will actually reduce your flow rate even further. You won't even save on bag cleaning because few folks realize that whenever you empty your collector you must also clean your filter to maintain flow rates.

Thanks Bob, I think! I will try and get hold of some 150mm PVC and slowly work new ports onto my various machines. One thing I have learnt is to avoid as much flexible ribbed hose as possible so I am going to have to make lots of sketches of layouts etc. All my machinery (TS, BS, BDS, Thicknesser, DP) is on casters so moveable but space is v. tight and I need to determine an optimal setup so I am not always moving equipment.
Thanks again.

Originally Posted by John Samuel

A sad but common story. My old 4 inch ports were also all over the place. I had two 1 HP dustys and even they had different sized fittings at the end of the flexy. Solved the problem with some standard 100 mm PVC pipe and fittings. PVC is easy to thermoform a bit larger than it already is.

I ended the 4 inch flexy with a piece of 100 mm pipe, expanding the pipe until the flexy would slip into it. Then I thermoformed/fiddled with the machine ports to get a 100 mm PVC straight connector (or a piece of expanded pipe) fastened to the machine. That way, the pipe at the end of the flexy always fit the new connector on the machine.

Suggest you start by seeing what fits best onto your flexy ... pipe or connector. Then use the other on your machines. For most of my machines the connector was a bit large, and I simply secured it in place with silicone. For one I needed to expand the connector. Made a form from a piece of pipe with duct tape wound it to make it big enough to match the machine ... heated the connector until it was very soft and forced the taped pipe into the connector.

Hi John, I was wondering if you could explain what Thermoforming is and how it works?
thanks
Carlos.

Carlos,

Thermoformed simply means the shape is created by heating and forming the shape you want, then cooling it. PVC is a thermoformed plastic .... meaning PVC products are made by taking little granules of PVC, heating them and either extruding them through a die (pipe) or using injection moulding to make parts like wyes, bends and connectors. PVC products can be re-formed to a new shape by heating them, forcing them into the new shape and then cooling them in the new shape.

For instance, here is the overhead dust collection gear for my table saw. Note that the riser is a rectangular section of polycarbonate, a thermoformed piece of pipe (transition) is attached to that, and finally a standard PVC fitting is hooked up to the pipe. To make that transition (square to round) I made up a tapered block of wood the same size as the rectangular riser. The PVC pipe was heated in cooking oil until it was very soft, then it was forced onto the wooden block. Once it was forced onto the block and rectangular at one end, it was cooled with dripping wet rags. Once cool, it retains the shape you gave it.

IMAG0229.jpg

Another example can be seen on the spindle moulder below. The clear PVC sheet started out flat. A layer of oil was placed in an electric frypan and heated. The clear PVC sheet was dropped into the oil for a few seconds, picked up with tongs and laid over 6 inch pipe ... it "flopped" or formed around the pipe. Wet rags then cooled the clear PVC and voila, we have a perfectly curved section to make a transparent hood for the spindle moulder.
IMAG0128.jpg

The next pic is a bandsaw. The "plumbing accident" fastened to the back of the saw is made from 6 and 4 inch PVC pipe thermoformed (this time with a heat gun) to the desired shape.
IMAG0036.jpg

Thermoforming PVC is surprisingly easy, and it made the construction of the dust collection system much easier than any alternative. Nearly every machine in my shop has thermoformed PVC somewhere in its dust collection attachment.

Finally, here is a bow I made my grandkids. The arrow rests are made by thermoforming small pieces of pipe flat at first, then shaping them into arrow rests that allow the flight of the arrow to pass unimpeded between the bow and the rest. There is one either side because one boy is a leftie.
Arrow Rest.jpg

Thank heavens for PVC and for its thermoforming properties!

Originally Posted by OtakiriLad

Thanks Bob, I think! I will try and get hold of some 150mm PVC and slowly work new ports onto my various machines. One thing I have learnt is to avoid as much flexible ribbed hose as possible so I am going to have to make lots of sketches of layouts etc. All my machinery (TS, BS, BDS, Thicknesser, DP) is on casters so moveable but space is v. tight and I need to determine an optimal setup so I am not always moving equipment.
Thanks again.

My shop too is space limited.

One thing that helped in my shop was to standardise connections. Every machine has a 6 inch pipe sticking out of it. Every piece of flexy that connects to the machines has a straight connector at the end. That way any flexy can connect to any machine ... which is handy occasionally ... especially where machines are wheeled around a bit.

Thanks all. Attached are photos of addons to my BDS but in ignorance of the real size of ports on the DC I made them from 100mm PVC. I will now re-do in 150mm.

I like the principle of flexi John and will incorporate your suggestion.

CheersIMG_1777.jpgIMG_1778.jpg

Nice fab work OtakiriLad

Looking forward to seeing the 150 mm versions.

I wouldn't seal the 150 mm ones up so tight, the ports need to be able to breathe to generate the air flow to collect the fine dust.

Very professional looking fabrication!

I wish mine looked half as good.

I have been thinking about how I would tackle using a 150 mm duct on a belt sander. My main concern is that a cowling around the end of a small belt is IMHO too constrictive to air flow. A possible simple solution would be to just locate a bell mouth hood in the position I show here. This will generate much more air flow than the standard cowling and pull much more fine dust from the air than otherwise. You could even use the existing holes on the belt sander stand to clamp the hood in place.

Sanderhood.jpg

Originally Posted by BobL

I have been thinking about how I would tackle using a 150 mm duct on a belt sander. My main concern is that a cowling around the end of a small belt is IMHO too constrictive to air flow. A possible simple solution would be to just locate a bell mouth hood in the position I show here. This will generate much more air flow than the standard cowling and pull much more fine dust from the air than otherwise. You could even use the existing holes on the belt sander stand to clamp the hood in place.

Because it works so well I'd be inclined to do something similar to my linisher ... https://www.woodworkforums.com/f200/m...66/index2.html

It should not be too tough to make a hood that allowed greater airflow, and to incorporate a section of pipe that runs along the returning belt (underneath). The section drawing air from the retunning belt was the last piece of the puzzle for me. It works.

It should also be possible to make the top part of the hood removable if sanding a piece of wood longer than the belt was a requirement.

A bell mouth hood achieves almost 50% more projection distance and about 15% more flow compared to a big gulp type hood.
John, I see your setup does not transit smoothly into the port behind so it will have a lower performance for very fine dust but my guess is you probably have so much suck that it doesn't matter, but folks with smaller DEs should think seriously about what type of ports are used.

A 50% greater projection distance is another way of saying the air speed at distance x perpendicular to a big gulp hood is achieved at about 1.5x for a Bell mouth hood. The greater the projection distance the better a hood will at capturing the fine dust.
The bell mouth also doesn't get in the way as much as a wide hood.
A big gulp can of course be added to the outside of a bell mouth but the increase in performance is so minor it's not worth worrying about

Originally Posted by BobL

A bell mouth hood achieves almost 50% more projection distance and about 15% more flow compared to a big gulp type hood.
John, I see your setup does not transit smoothly into the port behind so it will have a lower performance for very fine dust but my guess is you probably have so much suck that it doesn't matter, but folks with smaller DEs should think seriously about what type of ports are used.

A 50% greater projection distance is another way of saying the air speed at distance x perpendicular to a big gulp hood is achieved at about 1.5x for a Bell mouth hood. The greater the projection distance the better a hood will at capturing the fine dust.
The bell mouth also doesn't get in the way as much as a wide hood.
A big gulp can of course be added to the outside of a bell mouth but the increase in performance is so minor it's not worth worrying about

Agreed. But who suggested a Big Gulp? Clearly that would be nonsense on such a machine. The only place I used one was on the drill press, and then only because I wanted a fast solution.

I was suggesting a hood a bit like the pic below, with a section of pipe running down the returning belt.
IMAG0184.jpg

OtakiriLad has done such a nice fabrication job on the 4 inch port it seemed to me that he would likely have little trouble making a nice hood that projected further from the belt than the existing beast so he opened up a bigger area through which to draw air ... he could make the entry of the hood either bell or ramp shaped in timber or thermomoulded PVC.

But you are right about my hood being suboptimal. It was supposed to be a prototype, but worked so well I decided to leave it in place for a while. One day I'll do another dummy spit and ignore the queue of jobs to catch up on my workshop improvements.

How does this sound ... the existing white hood is made of timber and MDF. Thought I would make a new one (when I get around to it) with flat top and bottom sections again, (which would be the sides on OtakiriLad's machine) and instead of a 45 degree ramp on the hood to thermomould a piece of PVC to a curved ramp that guided the air back to the pipe. It would be almost like a transition.

One day ... some day ... maybe ...

Originally Posted by John Samuel

Agreed. But who suggested a Big Gulp? Clearly that would be nonsense on such a machine. The only place I used one was on the drill press, and then only because I wanted a fast solution.

The big gulp is just what I saw on the video - looking at it again that was indeed for a drill press.

OtakiriLad has done such a nice fabrication job on the 4 inch port it seemed to me that he would likely have little trouble making a nice hood that projected further from the belt than the existing beast so he opened up a bigger area through which to draw air ... he could make the entry of the hood either bell or ramp shaped in timber or thermomoulded PVC.

Yep - that's the key to gathering up more air.

But you are right about my hood being suboptimal. It was supposed to be a prototype, but worked so well I decided to leave it in place for a while. One day I'll do another dummy spit and ignore the queue of jobs to catch up on my workshop improvements.

Mee toooo.