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  1. #106
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    Several people have PMed me about the generic 2HP DC mod, especially how this thread is a WIP and cluttered with additional info, and said they would like to see the mod summarised into one or 2 posts.
    So here goes.

    Start by removing the large impeller intake flange and use it as a template to draw a replacement (size and screw locations) onto material, as per the white piece in this photo.
    The Generic 2HP DC-6inchinlet-jpg
    You can use sheet metal (as per photo) or MDF for the replacement flange,

    The hole in the middle of the flange is NOT the OD of the ducting but OD + OD/2, so for 6" ducting the hole is ~9" in diameter
    An adapter flange is then made from some thicker material the central hole of which has an curved edge opening that is OD on the outside to OD + OD/2 on the inside.
    This is known as a "Reverse Bell Mouth Port"
    My adapter flange as shown in the above photo is made from 32 mm thick Melamine.

    On the inside it looks like this - this is not a REVERSE bell mouth port (air flows from narrower to wider opening) but a normal Bell Mouth Port (air flows from wider to narrower opening) as used to collect dust while turning. The curves are the same for both ports


    Cross Section wise Bell mouth ports looks like this - in this case the machine cavity is the impeller cavity
    6" port upgrade for a 15" Thicknesser-bellmouthport-jpg

    Here is another view showing the step for smooth transition of the 6" duct to inner curved edge.
    The Generic 2HP DC-joinedup3-jpg

    To be theoretically correct I should have used thicker (37.5+ mm) melamine but it is not critical as long as there is a nice fat curved entry way - in the case of the 2HP impeller no wider than OD + OD/2 otherwise the performance of the impeller will be compromised..

    The above will no little to improve the air flow unless the following is also undertaken.

    Remove the whole impeller from the DC and remove the outlet flange (usually plastic)
    Make a stand and outlet flange adapter that will enable the impeller to be held up close to the filter bag housing like this

    The Generic 2HP DC-combo2-jpg
    Above is how I did mine but it could just as easily be made using MDF like this one below by Jonno
    5in Flex or 4in DWV pipe?-image-7-jpeg

    With the outlet flange adapter molter to the filter bag housing the hole in the bag housing can then be accurately marked out.
    Remove the outlet adapter flange and cut out the opening with a thin kerf cutting wheel on an angle grinder
    The Generic 2HP DC-hole-jpg

    Block up the old round filter bag housing inlet - this is how I did mine.
    The Generic 2HP DC-holepatch-jpg

    Finally seal everything up as air tight as possible using an appropriate sealer.
    You may need to use foam or rubber gaskets to fill large gaps.

    The air flow obtained with this mod is a significant improvement over the original DC and well worth doing.

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  3. #107
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    BobL

    Thanks for the neat summary of how to do the mod. I'm keen to have a go at modifying my DC3, but there's a fair bit of effort involved. For the effort I'll put in, I wonder if it might be worth modifying a DC7 instead. Do you think I'll get improved performance applying your mod to a DC7 instead of a DC3? And if so, is there anything you would do differently if you were modifying a DC7 instead?

  4. #108
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    Quote Originally Posted by WoodyNZ View Post
    BobL
    Thanks for the neat summary of how to do the mod. I'm keen to have a go at modifying my DC3, but there's a fair bit of effort involved. For the effort I'll put in, I wonder if it might be worth modifying a DC7 instead. Do you think I'll get improved performance applying your mod to a DC7 instead of a DC3? And if so, is there anything you would do differently if you were modifying a DC7 instead?
    I agree it is a lot of work but the improvement in flow is well worth it.

    I haven't made any measurements of a DC7 but my assessment of that DC is that it should (after throwing away the silly 4" intakes) in stock form already pull 1250 cfm through 6" ducting.
    That DC will also have a better fan curve that a DC3 - this means when placed under load it will continue to pull air whereas the DC3 will lose comparatively more flow. This is really important as it means longer ducting can be used with a DC7 of similar system. A DC3 should not be used on long ducting runs

    Improvements can be made to a a DC7 but it won't improve the max flow very much as the limit to flow is determined by the use of 6" ducting.
    However, if you want to have a go at improving a DC7 I would look at the following.
    Bell mouth entry into the impeller.
    Improving the flow at the curvy Y connection between the impeller and the bag housings.
    In more recent designs this is done as follows - i.e. remove the Y connection altogether.
    CT-003VB-1PH.jpg

    The bigger DCs can also make use of 8" ducting and move even more air (i.e. 1400+ CFM) but this is only really useful if you want to be able to extract dust from more than one machine at the same time.

    A bigger DC does have the advantage of being able to rapidly vent a shed after the last dust making activity. However, I think there are better and cheaper solutions to general ventilation and that is to use high capacity exhaust fans (like squirrel cage fans) that run at low power. I have two of these in my shed. The one high up in the ceiling above my TS us only 1/4HP but pulls over 1000 CFM (unrestricted flow).

  5. #109
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    Stupid question. For the 37.5 mm radius on the bell mouth port, did you guys just use a large 38.1 mm round-over bit? Find much use for such a large bit outside of making bell-mouth ports ? I have a generic carba-tec 2hp dustie that I would like to improve the performance of (my friends identically spec'ed JET 2hp seems to provide much better flow / suction) and want to perform these mods.

    My other question is; could I make a large rectangular duct between the impeller housing and filter bag housing instead of raising the impeller housing to but up to the bag housing and get the same benefit? I need my inlet at ground level anyway so would only be running more ducting to get it back down in any case.

    What sort of % improvement in CFM did these mods generate?

  6. #110
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    Quote Originally Posted by DomAU View Post
    Stupid question. For the 37.5 mm radius on the bell mouth port, did you guys just use a large 38.1 mm round-over bit? Find much use for such a large bit outside of making bell-mouth ports ?
    I turned mine up on on a lathe. I glued together several layers of MDF and screwed this to a Face plate and turn the opening and radiused ip on the lather. I made up a cardboard template of the curve and kept removing stuff till it agreed.
    A round over bit will be very useful.
    If you really want to improve your duct collection you should use bell mouth hood ports on ALL you machinery so you will get to use it more than once.

    Removing wheels is maybe ok as a longer term storage solution but otherwise it is a PITA.
    My testing showed that DCs that are moved around a shed are always the leakiest because they suffer from movement.
    The best place for a DC is outside a shed anyway.

    My other question is; could I make a large rectangular duct between the impeller housing and filter bag housing instead of raising the impeller housing to but up to the bag housing and get the same benefit?
    That will generate an unknown amount of turbulence. that is equivalent to adding a chip collector - expect a 20+% or so reduction in flow.

    I need my inlet at ground level anyway so would only be running more ducting to get it back down in any case.
    Why? do you intend to use existing ducting - if so read on.

    What sort of % improvement in CFM did these mods generate?
    Obviously you did not read the thread all the way through - go back and read it - its all there.

    Remember you MUST use 6" ducting and where possible open up the ports on your machinery to 6" to make it work properly.
    If all you modify is the DC and you leave single 4" ducting / ports on your system you might as well not bother modifying the DC.
    It takes 3 x 4: ducts to equal the flow in a single 6" duct - so you could use 3 short lengths of 4: feeding into a 6" duct and get the same flow.
    On a TS that could be 1 x 4" on the regular duct port, one on a custom made 4" port saw guard, and one to another 4" port on the cabinet or just hanging out in the breeze to collect escaping fine dust.

  7. #111
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    Thanks Bob. I've had a better read through the whole thread. Very interesting. Thank you.

    I'll have a bit more of a think about the direct mount vs ducted setup from the impeller to the housing.

  8. #112
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    Hi Folks
    Yes, it's true. I have sinned, doubly in failing to extract my wood dust and the digit to do something about it. The time for redemption has arrived.

    I read through this thread and others and resolved to do the work but then.... I came across this <http://www.timbecon.com.au/extraction-safety/dust-extractors-filters/2hp-industrial-dust-extractor> and it seemed to have a lot in common with the modded 2HP DC. At first sight I thought manufacturer might have been reading this thread. As the intro reveals, I am a novice in these matters so I thought I'd ask. Is this a goer or have I missed something?

    Cheers
    Mark

  9. #113
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    Quote Originally Posted by Genomey View Post
    I came across this <http://www.timbecon.com.au/extraction-safety/dust-extractors-filters/2hp-industrial-dust-extractor> and it seemed to have a lot in common with the modded 2HP DC.
    Those DCs have been around for some time (well before this thread) and are also available from other sources.

    There's this 1HP model https://www.carbatec.com.au/dust-con...kg-67-42-45-cm
    And these (expensive) 3 and 2HP versions https://www.carbatec.com.au/dust-con...aces-de-50-850
    (I have the 3HP version)

    The impeller on the 1HP DC is too small to overcome very much back pressure so it is never going to move much air.

    The claimed flow rate on the 2HP Timbecon unit will be better than a generic 2HP DC but the actual number is still highly optimistic so divide by 2 and you will get close to reality.
    If you do that you get about 875 CFM which is what I measure on the modified generic 2HP unit.

    Advertised flow rates for most commerical DCs are measures using an so called industry standard test.
    This test is for the impeller only (no filters/bags.ducting machines), and on top of that the test is incorrect in the way the measurements are made.
    I also doubt the claimed static pressure but I would be happy to measure one if someone can give me access.

    I also disagree with the advertising claim that static pressure is the best way you should decide on whether to purchase. The only valid performance spec is the fan curve - flow rate across a range of pressures. Some fans can generate good static pressures but suck (as in poorly) when any sort of back pressure is applied. Back pressure, caused by filters, choked ports, long ducting and junctions, is the Achillies heel of cheap fans but this is the reality of dust extraction that needs to be overcome in a wood work setting.

    One small difference with the mod in this thread versus the Timbecon unit is the Bell Mouth Inlet to the impeller.

    Despite all this, if you are going to purchase a 2HP DC then the Timbecon unit will save you time in converting.
    OTOH, at $599 it may be still worthwhile to purchase the generic 2HP (!$350) and perform the mod yourself - after all its not that difficult and can be done using some MDF.
    The rest of the funds can be put into 6" ducting and junctions which is not that cheap.
    Of course if you have the readies then go for it but if it was me Id be looking at a 3HP unit.

    TIP.
    Its much better to have the motor underneath (lower COG) and the ducting on top. This allows for a longer straight entry into the impeller. Ideally you would like 750 mm of a clear straight run into the impeller am then a gentle long curve to the rest of the shed. When the motor is on top this efficient entry cannot usually be managed when the ducting comes in from underneath.
    I suspect the motor on the Timbecon unit can be flipped over

  10. #114
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    Has anyone got a source for 160mm ID smooth bore flexible hose? The only stuff I have found is $182- /m food grade stuff and the only supplier of grey non food grade smooth bore 160mm i found says they won't be getting any more into the country (was about $84/m but only sold in 20m rolls). They have 150mm ID which would make connection problematic I think but again it's only sold in 20m lengths. I only want 4m or so.

  11. #115
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    Quote Originally Posted by DomAU View Post
    Has anyone got a source for 160mm ID smooth bore flexible hose? The only stuff I have found is $182- /m food grade stuff and the only supplier of grey non food grade smooth bore 160mm i found says they won't be getting any more into the country (was about $84/m but only sold in 20m rolls). They have 150mm ID which would make connection problematic I think but again it's only sold in 20m lengths. I only want 4m or so.
    No, but I bought my 150 mm flexy from Carba-Tec and it is all plastic. The reinforcing plastic rod is where the internal groove normally is for wired products, so it is not perfectly smooth, but is pretty good. I am happy with mine.

  12. #116
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    Quote Originally Posted by DomAU View Post
    Has anyone got a source for 160mm ID smooth bore flexible hose? The only stuff I have found is $182- /m food grade stuff and the only supplier of grey non food grade smooth bore 160mm i found says they won't be getting any more into the country (was about $84/m but only sold in 20m rolls). They have 150mm ID which would make connection problematic I think but again it's only sold in 20m lengths. I only want 4m or so.
    This topic should really be in its own or similarly related thread otherwise you will not get many readers/responses.

    ClearvueOz (Accessories and Spare Parts | Clearvueoz.com.au) and many other places will sell 150 mm ny the meter.

  13. #117
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    Many thanks for the thoughtful and comprehensive response Bob. I hear what you say comparing prices and performance. I wasn't expecting 1750cfm with everything attached and I'm pleasantly surprised by your estimate of 875cfm and the same measured rate for the modified generic 2 HP unit. What got my attention was the horizontal connection of the impeller and bag housings and the 6" intake for the impeller. I will try to find out if I can, as you suspect, flip the motor to get the ducting topside.

    By way of background, my workshop machinery and usage are not that extensive with a SCMS, Triton Router Table and a random orbital sander being the primary dust generators - not at the same time, of course. At this point I'm seeing 3 connections to the DC. Two fixed for the SCMS and Router and one flexible hose switchable between sander and shop vac attachments. I have the usual residential power issues being yet to definitely establish the amp rating for the power into the shed but it looks like 15A.

    Converting would have dollar as well as time costs. It's not beyond my skills but $230 is the price of not having to test them too much or tool up for the reverse bell mouth - if you see what I mean. I fear this might be taking us OT but I hope there is some use in it for others.

    Thanks again mate. It's appreciated.

    Cheers
    Mark

  14. #118
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    Quote Originally Posted by Genomey View Post
    Many thanks for the thoughtful and comprehensive response Bob. I hear what you say comparing prices and performance. I wasn't expecting 1750cfm with everything attached and I'm pleasantly surprised by your estimate of 875cfm and the same measured rate for the modified generic 2 HP unit. What got my attention was the horizontal connection of the impeller and bag housings and the 6" intake for the impeller. I will try to find out if I can, as you suspect, flip the motor to get the ducting topside.
    I should measure that horizontal connection next time I am at Timbecon as not all machines with these these connections are that much more efficient that those that don't use this.
    If the horizontal connection is less than the area of a 6" duct then it will still restrict the flow.

    By way of background, my workshop machinery and usage are not that extensive with a SCMS, Triton Router Table and a random orbital sander being the primary dust generators - not at the same time, of course. At this point I'm seeing 3 connections to the DC. Two fixed for the SCMS and Router and one flexible hose switchable between sander and shop vac attachments. I have the usual residential power issues being yet to definitely establish the amp rating for the power into the shed but it looks like 15A.
    The whole electrical power thing is never ending. I'm fortunate to have two separate power lines running to my shed, one is a 20A line and the other is 35A. I tend to run the DC on one line and machines on the other.
    Even when doing metal work (e.g. welding, 15A) and it's hot outside, so running the air con (10A), and the compressor goes off (15A) it's still OK

    Converting would have dollar as well as time costs. It's not beyond my skills but $230 is the price of not having to test them too much or tool up for the reverse bell mouth - if you see what I mean. I fear this might be taking us OT but I hope there is some use in it for others.
    Sure I can appreciate this.

  15. #119
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    "Remember, it is necessary to ensure you get enough air into the cabinet. YouTube is full of videos showing blokes blocking all the holes in the cabinet, thinking that will help their dust collection when it does the opposite."

    Does this mean that the equivalent to 150mm is sufficient? Is there any advantage or disadvantage in having more area, and if so is their an optimum? My tablesaw probably has enough openings, but I could open up my bandsaw a bit so curious about how much.

    I presume at the opposite side of the cabinet to the DE connection is the best location.

    Regards

    Bauldy

  16. #120
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    Quote Originally Posted by Bauldy View Post
    Does this mean that the equivalent to 150mm is sufficient? Is there any advantage or disadvantage in having more area, and if so is their an optimum? My tablesaw probably has enough openings, but I could open up my bandsaw a bit so curious about how much.
    Best thing is to let in as much air as your DC will pull out. the same cross section as a 150mm pipe is ok provided it is in one big hole but if it is in a series of smaller openings each opening will let in less air than it would proportionate to the larger opening and the sum total may not be enough. you may need double the cross section to get sufficient flow if all the inlets are smaller, maybe even more. There is probably no real harm in opening up the cabinet as much as safety and structural integrity allow, provided the collection port draws enough dust in and is located close enough to the source of dust.

    Quote Originally Posted by Bauldy View Post
    I presume at the opposite side of the cabinet to the DE connection is the best location.
    If by that you mean a cross draft across the area where the dust is being created then yes.

    Cheers

    Doug
    I got sick of sitting around doing nothing - so I took up meditation.

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