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  1. #46
    Join Date
    Feb 2006
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    Perth
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    Quote Originally Posted by Baddabing View Post
    As stated, it is a cheapie off Ebay. I got it not so much to measure the CFM, because I have low expectations of accuracy. I wanted to measure the decline in performance as I added piping, junctions and flex hose. In particular, I want to see what I get at the machines. I assume that what I start with is what it is. Maybe what I can do is reduce the drop by minimisi9ng flexi & the need to reduce to 100mm where possible. Hope that makes sense.
    The prop type units can over estimate the flow by up to 50%. I would not even used them as relative measures of air flow as air flow in DC systems is typically non-uniform across the duct and very sensitive to to position of the sensor. Using the prop type units for decision making can lead to decisions that can make things worse.
    There's more detail i n DRAFT: FAQ - Dust Extraction (Practical Aspects) if you need it.

  2. #47
    Join Date
    Jan 2014
    Location
    Sydney Upper North Shore
    Posts
    3,214

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    If you create a jig that will hold the propellor unit at the same position at the pipe mouth and 90o angle, you will get repeatability. Sure the readings may not be accurate but they will be repeatable so comparisons can be made.

  3. #48
    Join Date
    Jul 2015
    Location
    Melbourne
    Posts
    92

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    Quote Originally Posted by Lappa View Post
    If you create a jig that will hold the propellor unit at the same position at the pipe mouth and 90o angle, you will get repeatability. Sure the readings may not be accurate but they will be repeatable so comparisons can be made.
    Good idea, at least it would be consistent

  4. #49
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    Jul 2015
    Location
    Melbourne
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    92

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    Quote Originally Posted by BobL View Post
    The prop type units can over estimate the flow by up to 50%. I would not even used them as relative measures of air flow as air flow in DC systems is typically non-uniform across the duct and very sensitive to to position of the sensor. Using the prop type units for decision making can lead to decisions that can make things worse.
    There's more detail i n DRAFT: FAQ - Dust Extraction (Practical Aspects) if you need it.
    Thanks Bob. I didnt think it would be super accurate, but probably not that far off either. I actually got it to measure the flow when I open up ports on my machines. I have a few different options and wanted to compare which gives a better out come on each one as I go.

  5. #50
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    Jul 2015
    Location
    Melbourne
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    92

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    Just read the link provided by Bob. Looks like I have blown $30. No real harm done. I will still see if I get any significant differences when opening ports & using Lappa's suggestion to knock up a jig which may give some comparative results, albeit inaccurate readings. I worked out a while ago, that perfection is not an option, but it would be good to make the best of what I have.

  6. #51
    Join Date
    Feb 2006
    Location
    Perth
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    Quote Originally Posted by Baddabing View Post
    Just read the link provided by Bob. Looks like I have blown $30. No real harm done. I will still see if I get any significant differences when opening ports & using Lappa's suggestion to knock up a jig which may give some comparative results, albeit inaccurate readings. I worked out a while ago, that perfection is not an option, but it would be good to make the best of what I have.
    Just make sure the jig is good and solid - (unless you have a cyclone) one slip and it will be in "teeny weeny pieces in the dust collection bags".

  7. #52
    Join Date
    Jul 2015
    Location
    Melbourne
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    92

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    Haha, yep I learnt that already. Nearly lost the anemometer down the pipe. When things happen, they happen quickly.

  8. #53
    Join Date
    Feb 2006
    Location
    Perth
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    Quote Originally Posted by Baddabing View Post
    Haha, yep I learnt that already. Nearly lost the anemometer down the pipe. When things happen, they happen quickly.
    A couple of my attempts at turning have been shredded by my DC. I screen of some sort can help.

    I'v been using mesh guards like this 25 x 25 mm SS mesh in front of my sander and lathe BMHs.
    Here you can see two guards, and inner and an outer - it doesn't look like it but it is the same size mesh..
    The inner guard reduces flow by ~4% while the outer one (being in slower air flow) one;y reduces flow by ~1%
    lathenew.jpg

  9. #54
    Join Date
    Sep 2014
    Location
    Castlemaine, VIC AUSTRALIA
    Posts
    34

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    Really enjoying the ongoing DC discussion here, very informative. Time permitting, keep it coming Baddabing.

    Cheers.

  10. #55
    Join Date
    Jul 2015
    Location
    Melbourne
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    92

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    I have been progressing slowly, am putting on a patio at the moment, so not much free time. I have gotten a bit more done on the ducting etc, and will post some pictures on the weekend. But i have a question. I received with my dusty a 3 hose attachment, which I removed so and hooked up 6" directly to the machine.
    I was thinking of using this attachment to run 3 x 4" hoses to my band saw, so I have 1 hose above the table, 1 hose below the table & 1 hose into the port on the bandsaw body. Is this a crazy idea that won't work? Here is a photo of the port. It would of course be connected to the 6" ducting run to my bandsaw.

  11. #56
    Join Date
    Jul 2015
    Location
    Melbourne
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    92

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    Quote Originally Posted by BobL View Post

    I'v been using mesh guards like this 25 x 25 mm SS mesh in front of my sander and lathe BMHs.
    Here you can see two guards, and inner and an outer - it doesn't look like it but it is the same size mesh..
    The inner guard reduces flow by ~4% while the outer one (being in slower air flow) one;y reduces flow by ~1%
    lathenew.jpg
    Thanks BOB, I will look at installing. FYI, my first attempt at making a bellmouth was pretty much a spectacular fail. I went about it a different way, trying to press the heated pvc into shape - didnt work. I will have to have a go at your method or make in wood. Cheers.

  12. #57
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    Jul 2015
    Location
    Melbourne
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    92

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    Ducting so far...Duct work.jpg

  13. #58
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    Jul 2015
    Location
    Melbourne
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    92

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    Sander with port removed. Sander post (2).jpg
    Attached Images Attached Images
    Last edited by Baddabing; 15th Sep 2019 at 10:37 AM. Reason: put up twice

  14. #59
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    Jul 2015
    Location
    Melbourne
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    92

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    The sander is a cheapie but works quite well. The 2" dust port was useless. The dust was supposed to follow the belt down, with a vac attached to suck. All that happened was the dust flew everywhere, and what dust did get down just clogged up. So I removed it all so the DC had a chance to capture. Snder pre.jpg

  15. #60
    Join Date
    Jul 2015
    Location
    Melbourne
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    92

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    I had a big gulp, so cut out the 4" and modified to 6". Added 6" pvc pipe and fibreglassed it in. On the inside, I formed as good a bell mouth as I could. It works extremely well, and all dust seems to get sucked up. I sanded a 6" scrap circle of mdf down to about half, with no dust anywhere around the sander. A massive improvement.
    Gulp 1.jpg Gulp2.jpg

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