Page 4 of 7 FirstFirst 1234567 LastLast
Results 46 to 60 of 101
  1. #46
    Join Date
    Feb 2006
    Location
    Perth
    Posts
    27,757

    Default

    Quote Originally Posted by QC Inspector View Post
    Thanks Bob. I thought the 30m/s (first link) would be enough but perhaps by the fall when I'll need it the 60m/s puppies will have come down. Otherwise I'll just have to rely on accumulated wisdom and apply it wisely.
    A buddy of mine has a number of pitot tubes from commercial passenger jets (heaters in them don't work) that he makes into weather vanes etc. If inserted into the duct at at fixed point when needed and hooked up to a water column, would it be enough to show the flow difference between clean filters and dirty ones?
    Should be although I wonder if they might be a bit bulky and impact on the air flow?

  2. # ADS
    Google Adsense Advertisement
    Join Date
    Always
    Location
    Advertising world
    Posts
    Many





     
  3. #47
    Join Date
    Aug 2007
    Location
    Saskatoon, SK, Canada.
    Posts
    1,436

    Default

    Quote Originally Posted by BobL View Post
    Should be although I wonder if they might be a bit bulky and impact on the air flow?
    It's been awhile since I last saw them but they were approximately .75 in diameter and the "blade" holding them from the fuselage was the same or less thick and 3 to 4 inches long airfoil shaped and 4" to 6" from the fuselage. I was thinking that I would only insert them into the 6" or 8" main duct only when wanting to check the airspeed/suction and the rest of the time the duct opening would be covered.

    Pete

  4. #48
    Join Date
    Nov 2013
    Location
    Caboolture QLD AU
    Posts
    781

    Default

    I have been reading specs for the various clones of the typical 3HP DC that look like the HAFCO DC7 for example.

    There are so many, and I was wondering why there was so much difference between the specifications posted for these units, along with the results posted by owners.

    It appears that they were supplied with 12", 13" and 14" impellers - depending on brand name and cost - and output also depending (as always) on mains frequency, and quite often impeller size is not quoted! - I found the following.

    12" impeller: around 8" WC.
    12" impeller at 60Hz running at a manufacture quoted 9.6" WC.
    13" impeller around 9.8" WC.
    13" impeller at 60Hz running at a manufacture quoted 11.5" WC.
    14" impeller around 11" WC but
    14" impeller at 60Hz running at a manufacture quoted 13.9" WC.

    Which also explains the widely varying CFM ratings (fancifully manufacturing values not withstanding) Un-freaking believable.

    Interestingly - they quote 12" impeller - the same Static pressure and air flow for a single entry point into one bag, the older style Y connection into two sets of bags, and the newer style with motor and dual bag ducting in one case. I guess the basic case design was made for the 14" impeller? I wonder why new users to woodworking / dust collection get so confused, and this is just one type / configuration of DC.

  5. #49
    Join Date
    Feb 2006
    Location
    Perth
    Posts
    27,757

    Default

    The static pressure values will be for the impeller only - the size of the input duct is irrelevant because that is blocked during the SP measurement but it is critical when you want air to flow.

    The SP is not really the key figure anyway - what the manufacturers should supply is a fan curve.
    SP is an indication of how much air will flow with zero resistance but what is more important is what the flows are when the fan is restricted.

  6. #50
    Join Date
    Nov 2013
    Location
    Caboolture QLD AU
    Posts
    781

    Default

    Hi Bob, yes I understand all of that now, my point was that all of these units look exactly the same, and usually have the OEM model number as part of the rebadged model code, so you think you are buying the same unit, but many are just rebadged with a 12" impeller and apparently no other housing modifications in a physical unit designed for a 14" impeller, add the fact that they run slow over here at 50hZ and it's no wonder we get crap dust capture and even lower performance figures.

    A fan curve for a unit running a 12" impeller in a housing with impeller clearances designed around a 14" unit would, I imagine, take an even bigger performance hit.

  7. #51
    Join Date
    Feb 2006
    Location
    Perth
    Posts
    27,757

    Default

    Quote Originally Posted by MandJ View Post
    A fan curve for a unit running a 12" impeller in a housing with impeller clearances designed around a 14" unit would, I imagine, take an even bigger performance hit.
    Correct.

  8. #52
    Join Date
    Nov 2013
    Location
    Caboolture QLD AU
    Posts
    781

    Default

    A few years back when we purchased a 3HP DC on special at Trade tools, I knew nothing about dust collection or the dangers of dust, anyway, I never bothered to measure the impeller size, so today at long last I did. The DC in question is one of those rebadged Kufo UFO-102B that seem to be sold in one form or another by every man and his dog.




    I mentioned in the previous post about different impeller sizes in these units and someone mentioned that the China made units / clones usually have a 12" impeller, a lot of the units I've researched have 13" and often quote that in the data sheet, others even quote 12" in the 5HP models, only a few quote 14" in the 3HP model specs.

    Anyway, just finished removing the front housing to measure it, my first thought was that it looked like a 12" unit, however on measuring the impeller, I find it is 366mm from blade tip to blade tip (14.4") and 358mm across the thick blade support base plate, which is 14", I'm happy about that.





    Exit port is not that smooth either, and has a lip, don't know if this restricts anything.


    However the metal inlet fitting sits inside my 150mm pipe, so there is a lip there for a start, the metal inlet also projects about 1/2" through the cover plate into the housing. I'm thinking a BobL modification on the inlet might make a bit of difference here?


    The motor has the correct lower speed listed for the 50Hz line frequency stated on the label.

  9. #53
    Join Date
    Feb 2006
    Location
    Perth
    Posts
    27,757

    Default

    Being a 14" impeller explains the good static pressure you are getting.

    Those ripples in the blades are interesting. I have heard of these being used to help to reduce noise as well as reducing material build up on the surface of the blades.

    How is the noise level on that DC?
    A mobile phone app will be able to measure it if you have one.

  10. #54
    Join Date
    Nov 2013
    Location
    Caboolture QLD AU
    Posts
    781

    Default

    These are the readings I just took from a dedicated sound level meter, haven't changed much in two years.

    Normal background noise around 42dB.

    DC enclosure cabinet door open @ 1m from the center of opening 87dB.

    Door closed same position @ 1m 62dB.

    On the fence line @ 3m from DC cabinet (opposite side to the exhaust port) is 58dB.

    From side of cabinet where DC exhaust exits (big opening) @ 5m is 60dB, the fence line on that side of the cabinet is a further 11m away and the DC almost inaudible there.

    In the shed at 1m from the 6" intake port I read 84dB.

    But you can stand next to the DC Housing and have a quite conversation, we are able to run the DC at night, neighbors did not even know we were running it.

    I never bothered to line the DC housing, that heavy fiber cement on the walls and door, glued to lots of timber frame work, and the housing base made of thick treated pine sleepers sitting on six 100mm x 100mm square steel posts, driven 1m into the ground, seems to keep it very quiet and absolutely free of vibration or drumming. Two years on and it's still as tight as a drum.

    Bob what are your thoughts on the intake projecting into the impeller housing?

    Mike.

  11. #55
    Join Date
    Feb 2006
    Location
    Perth
    Posts
    27,757

    Default

    Quote Originally Posted by MandJ View Post
    Bob what are your thoughts on the intake projecting into the impeller housing?
    I suspect it adds to the static pressure maybe at the expense of flow.
    But definitely with trying a Bell Mouth Inlet
    If you decide to modify it make sure you keep the original.

  12. #56
    Join Date
    Nov 2013
    Location
    Caboolture QLD AU
    Posts
    781

    Default

    The Band saw arrived, borrowed a trailer to pick it up (cost was going to be $220 to deliver it), three hours later, backed trailer straight into the end of the workshop and within a foot of where the BS will be installed, stood it up, moved to the correct position and unpacked it.

    Redid the 150mm hard line to the new BS.

    1st thought - people who design band saws are morons at dust extraction design!

    This new model has two 100mm dust extraction ports: As soon as I opened the lower door I knew the dust extraction design was a total fail. The top port is angled down at 45 deg and up very close to the lower guides a lower zero clearance insert and the top of the lower wheel cleaning brush. The lower port is 90 deg into the bottom of the cabinet, the lower port is vertically in line with the upper port.

    Both ports extract from the same lower enclosure.

    Now don't get me wrong, this dust extraction port design is brilliant - if the intention was:

    A: Stop you from opening the lower door with the DC running - I thought the door had jammed.
    B: Not remove any dust.
    C: Choke the DC so it doesn't have to do any work.

    There is no intake port or any real gap to allow any air to enter the enclosure.

    To further enhance the functional design, they placed a rubber strip down the side of the door so that it doesn't make a sound when you close it, and it makes a great vacuum seal.

    Having the door not make a noise when it's closed is more important that removing dust - who'd of thought!

    Seriously - the door sucks down so tight that it has to be really muscled to get it open with the DC running.

    It's a new band saw, so I don't want to cut into it at this early stage, for now, I decide to not use the lower port and use it as cabinet intake port , at least the door now opens normally with the DC running.

    The upper port is good, it has clear path to the upper guides etc. However as usual, there is no real extraction between the table and the top of lower guides, but it's simple to fit a pickup below the table, there is an unobstructed air path to the bottom of the table insert and the top of the lower guides, so the 2nd 100mm pickup will go here.

    Finally, I've just finished making a takeoff into the 150mm feed, this will be the 3rd 100mm fitting for above-table dust pickup.

    Picture to come.

  13. #57
    Join Date
    Feb 2006
    Location
    Perth
    Posts
    27,757

    Default

    Quote Originally Posted by MandJ View Post
    It's a new band saw, so I don't want to cut into it at this early stage, for now, I decide to not use the lower port and use it as cabinet intake port , at least the door now opens normally with the DC running.
    .
    If you are able to you can just leave the bottom door ajar. I would have had to defeat the door switch on mine to do that which is why I cut a hole for a vent in it. Of course I did it after the warranty had run out.

  14. #58
    Join Date
    Nov 2013
    Location
    Caboolture QLD AU
    Posts
    781

    Default

    Yes, exactly what I plan on doing, and as soon as warranty is up I'll mod it.

    I often wonder how many owners of various equipment just hook up the ports thinking thay are getting even half decent dust extraction. I also wonder if the second lower port was an afterthought when they went to the newer design with a full lower cabinet? Anyway it will work out great in the end.

  15. #59
    Join Date
    Nov 2013
    Location
    Caboolture QLD AU
    Posts
    781

    Default

    Just getting the layout sorted, ducting, under table and above table pickups not finished / installed yet.







  16. #60
    Join Date
    Nov 2013
    Location
    Caboolture QLD AU
    Posts
    781

    Default

    I have a few close ups of the 100mm 25 deg takeoff that I cut into the 150mm line to the BS, the end of that 150mm line has a standard 150mm into 2 x100mm fitting. As BobL indicated, at least 3 x 100mm ports are needed from a 150mm main in order to maintain flow - and I found that to be 100% true.






    I initially tested it with 2 x 100mm ports, motor current and static pressure confirmed that the DC was severely restricted, adding a 3rd 100mm port made a huge difference to current and pressure difference.

    As I side note: I made a much better sloping manometer with a big reservoir, it allowed me read the pressure directly. I have the manometer mounted on the wall inside at eye height, it's great for seeing differences in pressure with changes in ducting, flex hose, pickup fitting etc. It mounts on the wall next to the current meter and the two readings give me a real feel for how the DC responds to changes. Again, I was surprised at just how much difference there was between 2 and 3 100mm ports, I'd swear I could hear the DC breathe easy when the 3rd port is opened.

    Below: I've shown the temporary DC pickup I'm trying with the band saw, I won't know exactly what to do with the above and below table pickups until we do some test cuts. My wife is the woodworker, I'm the research assistant, designer, problem solver, repair and maintenance guy, just waiting for the next little cry - I mean call - of my name from a cute tiny person in the depths of thewoodworking shed.




    Below: This is one of the sleds I made for the Bench saw. We tend to cut a lot of small panels and pieces of timber. I couldn't go near this filthy dust makes before I built it into a moveable table and opened the bottom up for 150mm extraction, I mentioned that I made sloping internal walls leading into the into pickup and added 4 x 100mm air intake ports - I think I need one more - I removed the ridiculous 2" DC port and plastic lower blade pickup - its design made everything in the lower sawdust filled plastic blade cover, either return to the top of the table or spew out of the vents in the bottom and sides of the case - must be designed by the same people who did the dust extraction for the band saw.



    Anyway, the top slide has a 6mm thick polycarbonate lid, I have a clamp system inside for holding the work, I use a shop VAC mounted on the other side of the wall to pull air across the blade from the front LH side of the slide to the RH rear.




    This is my quick connect idea for swapping the DC hose form the bench saw port over to the down draft table port (built into the same moveable table as the saw). The fitting has two metal handles and it works a treat, takes just a second to swap over.

    I realize the blast gate should be high up to stop build up in this run when using the band saw, I'll shift it later when I get a bigger blast gate, for now it matches the 6" flex hose, I'll be sure to crack open this blast gate every so often.

    In use, not a speck of dust - anywhere - can't even smell the timber, don't need eye protection or a mask, and reduction in sound level is amazing - no ear muffs needed.

    Completely hands free so I'm happy letting my wife use it - yea I know she is capable, but I worry the same.

Page 4 of 7 FirstFirst 1234567 LastLast

Similar Threads

  1. For forum members only.
    By nt900 in forum FESTOOL FORUM
    Replies: 2
    Last Post: 1st November 2011, 06:55 AM
  2. How many forum members ....
    By Incoming! in forum WOODIES JOKES
    Replies: 16
    Last Post: 4th September 2008, 05:43 AM
  3. Forum has >20,000 Members
    By dai sensei in forum ANNOUNCEMENTS
    Replies: 13
    Last Post: 3rd July 2008, 11:42 PM
  4. u.k. forum members
    By jow104 in forum TRITON / GMC
    Replies: 1
    Last Post: 4th March 2004, 07:58 PM

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •