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  1. #61
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    Bob,

    Two thoughts occurred to me today (rare indeed ... one a week is normally pretty good).

    First, was creeping around the web and saw this machine New 2011 Oltre FM300B 1 Bag Dust Collectors in Malaga, WA Price: $495 <28839> for $495 incl GST. It would be interesting to hear your opinion on this machine, especially regarding optimising it, if you have an opinion. It looks as it it would be easy to directly connect the impeller and motor to the bag housing, and it has a cartridge as standard. What a pity we can't trust the manufacturer's airflow claims.

    Second. I followed McPete's idea of the DC-7. It is a 3 HP machine, but the blurb does not give the impeller size. Do you know anything about this machine? Even when halved, the flow looks OK, as does the price ... but is halving rated airflow enough? I'm assuming it has a 6 or 7 inch inlet under the triple inlet.

    Cheerio!

    John

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  3. #62
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    Feb 2006
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    Perth
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    Quote Originally Posted by John Samuel View Post
    Bob, Two thoughts occurred to me today (rare indeed ... one a week is normally pretty good).


    First, was creeping around the web and saw this machine New 2011 Oltre FM300B 1 Bag Dust Collectors in Malaga, WA Price: $495 <28839> for $495 incl GST. It would be interesting to hear your opinion on this machine, especially regarding optimising it, if you have an opinion. It looks as it it would be easy to directly connect the impeller and motor to the bag housing, and it has a cartridge as standard. What a pity we can't trust the manufacturer's airflow claims.
    It's a generic 2HP unit with what looks to me to be a slightly smaller (square - as opposed to rectangular) impeller outlet. If is is smaller, then in a modified form it's not going to make even the same CFM as the units with there rectangular outlets.

    Second. I followed McPete's idea of the DC-7. It is a 3 HP machine, but the blurb does not give the impeller size. Do you know anything about this machine? Even when halved, the flow looks OK, as does the price ... but is halving rated airflow enough? I'm assuming it has a 6 or 7 inch inlet under the triple inlet.
    It's either 6" or 8". The limitation to flow is not the impeller it's the use of 6" ducting which limits the flows to ~1250 cfm with clean bags/filters and its downhill from there.
    One could use 8" ducting as a trunk line and then use 2 x 6" ducting on machines - but that is not necessary.

    All the flow rates claimed are usually
    - without bags/filters/ adapters
    - with a fully open inlet to the impeller (i.e. no 4" adapters etc)
    - they do a single point measurement in midstream and make no allowance for pipe friction.

  4. #63
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    Interesting to see your modifications.

    It may also be interesting to look at some of the oversease full line catalogues that are lying arround here somewhere.

    Like most things, we do not see half the products offererd overseas.

    One thing that is very interesting ....one of the catalogues shows a range of dust extractors much as we find them sold here and much as the oridinal dust extractor shown here....BUT next page there is a range of dust extractors, made from, more or less the same parts but looking very much like the post BobL mods dust extractor.

    It is also interesting to look at the differences between the cheaper generic extractors and the more expensive units offered.

    The unit in the original post just looks inefficient with its crude transitions and small diemeter pipe.

    Some of the better extractors have more streamlined parts and larger connecting pipes OR fabricated square ducts.

    As I may have mentioned elsewhere, I have a couple of 1.5 Hp rated extractors that look just like a 2 hp unit and claim and seem to perform as well as the better 2Hp units.
    Mine are more refined in the blower housing, have smooth transitions and come with a 6 inch corigated duct.

    Maybe they are similar extractors but the motor rating is more honest.

    One thng that may be noted.....as the efficiency of the blower and such is improved, air flow may increase while current drawn drops......a natural exectation from increased efficiency.

    another thing...look at the pictures of the impeller.....note that the inside corners have been cut off the blades.....I expect this is to reduce stuff being caught on the corners.
    The impellers in my machines are straighter, heavier and the inside corners of the blades are straight and square.
    note that the inside diameter of the impeller is 5 inches and while there is a 6 inch incomming flange there is a 5 inch restricter plate.
    I have always intended turning up an anular cone to streamline this transition.

    As for the bulseye finger guards...these came in a few years ago......when we first started to see these extractors offered in volume in this country, none of them had these finger guards.
    One of the US magazines, did some testing on these devices and concluded that they effected the air flow quite badly and where best cut out.....appart from the fact that stuff gets caught in them.

    The latest extractors we see have the motor mounted between two bags and the blower housing built in the same housing as the bag hoops..thus no connecting duct.
    These extractors seem to produce much higher flows that the older style bagged extractors....but one would expect sme improvement just from running two upper bags and two waste bags on a 2 hp blower

    cheers
    Any thing with sharp teeth eats meat.
    Most powertools have sharp teeth.
    People are made of meat.
    Abrasives can be just as dangerous as a blade.....and 10 times more painfull.

  5. #64
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    Your post brought a question to mind that I did not realise I wanted answered til now! What effect do corrugations have on efficiency of air flow?

    Dean

  6. #65
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    Corigations have a dramatic effect on air flow.
    They produce turbulence along the edge of the pipe...some people say its like reducing the diameter of the pipe...but it is worse.

    THEN things get much much worse when you bend a corigated pipe....UM and that is the point of corigated pipe.

    If you want to maximise air flow, avoid corigated pipe where ever possible.

    I have a single dust extractor dedicated to my saw bench..its stands right at the end of my side table.....around a meter away from the main dust port.
    I replaced corigated in this rig both on the lower dust port and the overhead guard, years ago and the increase in air flow and improvement in dust capture was dramatic.

    Replacing a meter of corigated, most of which was straight, made a significant difference.

    On this rig the lower duct has only about 8 inches of 100mm corigated to proide a flexible union and a couple of feet of 3 inch corigated to serve 2 x 3 inch ports on my overhead guard.

    For best air flow we want straight and smooth...if we want efficient bends, we want them wide and smooth.

    Avoid corigated hose wherever possible.

    cheers
    Any thing with sharp teeth eats meat.
    Most powertools have sharp teeth.
    People are made of meat.
    Abrasives can be just as dangerous as a blade.....and 10 times more painfull.

  7. #66
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    Thanks Soundman. I suspected it was not good but wanted to know for sure.

    Dean

  8. #67
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    A few members have asked me about modifying their generic 2HP unit and I refer them to this thread but though it would be useful to link in Jonno's budget mod of the same machine shown here.
    https://www.woodworkforums.com/f200/5...v-pipe-172455/

    You need to scroll into that thread a bit to see the mods.

  9. #68
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    Default

    I always thought this thread should be made a "sticky"

    It would make Bobs life easier for directing people to the thread!

  10. #69
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    Quote Originally Posted by legin View Post
    I always thought this thread should be made a "sticky"

    It would make Bobs life easier for directing people to the thread!

    Done

  11. #70
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    Apr 2010
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    Default Diagram Needed

    Quote Originally Posted by Trav View Post
    Is there any particular science in where to locate the hole in the bag housing for the new adaptor flange? And is the size of the hole solely determined by the length of the arc that corresponds to the size of the impeller outlet?

    Trav
    And is the size of the hole solely determined by the length of the arc that corresponds to the size of the impeller outlet? ?????

    I am thinking about this, but all I am getting is angles dangles squares
    and etc.

    How about a simple diagram to clarify?

    Cheers Barry

    ps Great thread

  12. #71
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    Quote Originally Posted by mannum3 View Post
    And is the size of the hole solely determined by the length of the arc that corresponds to the size of the impeller outlet? ?????

    Correct.

    The position is also important with the inside of the "impeller to bag/filter housing" flange meeting at a tangent to the bag housing since this provides the smoothest transition for the air flow.
    I made the flange a little longer than the tangent point so there was enough of a lip for it to be able to be bolted and sealed to he bag housing.


    The Generic 2HP DC-2hpdc-jpg
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  13. #72
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    Default Thanks BobL

    All OK now (a picture is worth a thousand words)

    Cheers Barry

  14. #73
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    I may attempt some of these modifications myself, having just bought the Gasweld branded unit of the same parentage.

    Disturbingly though, both the collection and filter bags are calico on my machine. Great filtration indeed.

  15. #74
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    Quote Originally Posted by McPete View Post
    I may attempt some of these modifications myself, having just bought the Gasweld branded unit of the same parentage.

    Disturbingly though, both the collection and filter bags are calico on my machine. Great filtration indeed.
    Get a plastic one for the bottom bag. It's important to be able to see how full it is and not let it get more than 2/3rd full before it is emptied.

    Before modifying any DC the best thing you can do is put the DC outside the shed or in an air tight enclosure that is vented outside the shed - then it doesn't matter if the bag is calico.

  16. #75
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    Jan 2012
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    East Gippsland, Victoria
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    Default Changing 2HP Carbatec DE and ducting to 6" set up

    I have been reading and following the DE posts, including Bill Pentz's site, looking at ways to upgrade my 2 HP Cabatec DE until my eyes go blurry. I'd love a Clear Vue but that would be divorce and my friends are already calling me obsessive and crazy. My main uses are a SCMS and a table saw. I have tried to make a shroud for the SCMS but with the current 100 mm PVC duct, that is of course only partly successful, even with panels that block off the mitre angles.

    Bob, I know the machinery outlets are the main issue and modifying these are a high priority, however, the current project is to swap the duct to 6" PVC and modify the DE as per your design (or Jonno 2000's wooden adapter 16 June 2013). Luckily, I can duct straight from an outside garden shed almost directly to the SCMS and only a short run along the floor to the table saw. My main query is which is more important, having a straight final run into the DE or avoiding 90° bends? If I set the DE outlet facing up, I can get about 1500 mm from inlet to the shed ceiling. I can either focus on a longer run with 2 x 90° bends or a shorter run with 4 x 45° bends. With a upwards facing DE I need a 180° loop. Or, I could point the inlet downwards and have a shorter run to the holes in the wall but also with sharp bends. I am planning on just connecting 6" flexible duct to the table saw when I use the it as it is only a short and fairly straight run.

    Any comments gratefully received.

    David
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