Page 9 of 21 FirstFirst ... 456789101112131419 ... LastLast
Results 121 to 135 of 314
  1. #121
    Join Date
    Feb 2012
    Location
    Rosslyn Park, Adelaide
    Posts
    182

    Default

    Thanks Doug. I was counting on a lot of smaller openings with the Table saw, so will review, taking your comments into account.

    Regards

    Bauldy.

    P.S. Some years ago when I first bought my bandsaw and very ignorant of this topic, the first thing I did was to seal every gap I could assuming that would help the DE work better!

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





     
  3. #122
    Join Date
    Feb 2006
    Location
    Perth
    Posts
    27,756

    Default

    Quote Originally Posted by doug3030 View Post
    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
    AND provided a bell mouth hood is used as the opening.
    If not, a naked 150 mm duct will reduce flow by a 10% which is why it always worth having more area than the cross section of the ducting in use.

  4. #123
    Join Date
    May 2010
    Location
    Not far enough away from Melbourne
    Posts
    4,200

    Default

    Quote Originally Posted by BobL View Post
    AND provided a bell mouth hood is used as the opening.
    If not, a naked 150 mm duct will reduce flow by a 10% which is why it always worth having more area than the cross section of the ducting in use.
    That is of course assuming that you are talking about one of the few machines which is big enough to connect a round 150mm diameter dust port, let alone stick a bell mouth hood on the end.

    Cheers

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

  5. #124
    Join Date
    Feb 2012
    Location
    Rosslyn Park, Adelaide
    Posts
    182

    Default

    Starting to look at doing the modification. Cleaned the machine up and took some measurements. It is a Ledacraft DC1500T. It has a rectangular connection from the Impellor outlet to the Bags. The pipework is 153mm x 117mm internal measurements as best I can measure. This appears very close to a 150mm dia pipe, which was presumably the idea.

    IMG_5940.jpg

    IMG_5941.jpg


    So, it is not as restricted as many of these type DC's are. So two questions:

    1) Given I already have the equivalent of 150mm of exit area, is the length of curved rectangular pipe causing enough restriction to bother modifying?

    2) If it is, while I suspect it is preferable to turn the unit 90deg so the air enters axially, it would be a lot easier to just bolt the rectangular flanges together in the current direction they are

    oriented. Does the difference warrant some sheetmetal work rather than a simple bolt job (and new support for the motor)?


    Please note I will be opening the inlet to 150mm, but did not want to start pulling things apart until I had all of my planning done.

    Regards

    Bauldy

  6. #125
    Join Date
    Feb 2006
    Location
    Perth
    Posts
    27,756

    Default

    Quote Originally Posted by Bauldy View Post
    1) Given I already have the equivalent of 150mm of exit area, is the length of curved rectangular pipe causing enough restriction to bother modifying?

    2) If it is, while I suspect it is preferable to turn the unit 90deg so the air enters axially, it would be a lot easier to just bolt the rectangular flanges together in the current direction they are

    oriented. Does the difference warrant some sheetmetal work rather than a simple bolt job (and new support for the motor)?
    In terms of Xsectional areas the duct has 117 x 153 = 17901 mm^2
    In comparison a 150 mm diam pipe is 17671 mm^2,

    However the 150 mm pipe has a wall perimeter of 471 mm whereas the rectangular duct has a perimeter of 540 mm,so more surface ares to provide drag, and being asymmetric it will have slightly more drag between the narrower (117 mm) sides.

    In practice the flow performances will be so close together that it shouldn't matter that much so I would leave it alone at this stage.

    The only difference between my mod and this machine is then that the air coming out of the impeller is doing a 90º turn but it is a nice wide radius turn so it will have a minimal impact.

    So concentrate on expanding the entrance to suit 6" ducting and see if you can incorporate that reverse bell mount.

  7. #126
    Join Date
    Feb 2012
    Location
    Rosslyn Park, Adelaide
    Posts
    182

    Default

    Thanks Bob. My impellor is listed as 300mm in the specs (haven't opened it up yet). presumably apart from the 150mm inlet that will be the limiting factor. Is 300mm standard on most of these?

    Regards

    Bauldy

  8. #127
    Join Date
    Nov 2015
    Location
    Pinjarra Hills, Brisbane
    Posts
    12

    Default

    Hi Bauldy - does it look like you can reverse the side the motor is on the blower?

  9. #128
    Join Date
    Dec 2008
    Location
    Hobart
    Posts
    153

    Default

    Quote Originally Posted by BobL View Post
    I removed the whole (300 mm diam) front, and the outlet, off the Impeller and the motor then drew 6.2A or 1.97HP.

    So it is a 2HP motor when it is moving its max amount of air but I doubt it will be delivering 2HP even when the inlet is increased to 6". In a perhaps counter intuitive manner motors on impellers will draw less current and thus develop less HP when their air flow becomes restricted. To counteract this a DC manufacturer who knows what is going on supplies an over rated motor. The disadvantage of this is that if these motors are run with an opened impeller the additional current draw can overheat the motor. This is why BP suggests not running an open impeller for too long.

    I also noticed the inner diameter of the area where there are no impeller blades is only 125 mm. This would then be the maximum optimum inlet size for this impeller. Using an inlet bigger than this may not generate the expected flow. While I have it open I might knock up a 6" inlet and see what happens.

    The Generic 2HP DC-2hpdcimp-jpg

    Hi BobL

    I am about to modify my 2HP dusty. Does the 125mm gap between the blades (same on mine) mean that the impellor would be most efficient with a 125mm (5 inch) inlet rather than a 6 inch one? If so how much more efficient do you reckon. I will only have about 4 metres of ducting from my dusty to the my machines. Would any increase in efficiency gained by optimising the inlet be lost by using 5 inch ducting rather than 6 inch.

    Cheers
    Mike

  10. #129
    Join Date
    Feb 2006
    Location
    Perth
    Posts
    27,756

    Default

    150 mm is significantly superior to 125 mm ducting.
    Provided the fan can physically move that much air, at the same pressure generated by a fan, a 150 mm duct can move about 3 times that of a 100 mm duct, and 1.72x a 125 mm duct.

    In theory if the impeller can generate 8" of WC it matters naught what the size of the entrance to the fan is. You need to remember that most of the fan pressure is generate by the outermost tips of the impeller so provided that is covered and does not let too much air get past it that is what will generate the pressure

    Now what really matters is the "fan curve", Flow rate V pressure. Where this matters is as ducting/bag/machine resistance is applied can the fan counteract this and maintain a flow.
    The size and design of the generic 2HP impeller will produce a relatively weak fan curve compare to a bigger more carefully designed setup.

    You also need to remember that in my mod that uses a reverse bell mouth hid the opening is even wider that 150 mm.

    So to summarise, I'd say the slight loss in efficiency from opening up the impeller intake is well and truly over come by the ability of 150mm ducting to move more air.

  11. #130
    Join Date
    Dec 2008
    Location
    Hobart
    Posts
    153

    Default

    Thanks BobL

  12. #131
    Join Date
    Feb 2012
    Location
    Rosslyn Park, Adelaide
    Posts
    182

    Default

    Quote Originally Posted by randlalfnasalfn View Post
    Hi Bauldy - does it look like you can reverse the side the motor is on the blower?
    Yes, I believe so, although not sure to what effect?

    I could also mount the motor/blower assembly directly to the bag housing and remove the section of ducting, but this would take a fair bit of extra work.

    Bauldy

  13. #132
    Join Date
    Dec 2003
    Location
    lower eyre peninsular
    Age
    74
    Posts
    3,577

    Default

    Yikes Ive read this, slept on it read it all again, fasinating and very informative,
    But, now here will prove weather I'am, blind/stupid/combined/ or ???
    but there is no mention of cyclones....I thought they were the ants pants or bees knees or warblers whiskers.

    comments please or provide artillery to shoot myself
    I would love to grow my own food, but I can not find bacon seeds

  14. #133
    Join Date
    Feb 2006
    Location
    Perth
    Posts
    27,756

    Default

    Quote Originally Posted by Tonto View Post
    Yikes Ive read this, slept on it read it all again, fasinating and very informative,
    But, now here will prove weather I'am, blind/stupid/combined/ or ???
    but there is no mention of cyclones....I thought they were the ants pants or bees knees or warblers whiskers.

    comments please or provide artillery to shoot myself
    The reason I started this thread and undertook the conversion was because the generic 2HP DC
    - is probably one of the most common DCs in DIY sheds
    - when modified and using 6" ducting has at least a hope of approaching 1000CFM
    - will run from a 10A socket (not everyone even has 15A let alone 3P power)

    Most Cyclones added to existing DCs end up restricting the flow of air through the system and this thread was about increasing the flow through what is already a marginal system.

    To be efficient cyclone and impellers have to be properly matched which is not a task for the average DIY.

  15. #134
    Join Date
    Dec 2003
    Location
    lower eyre peninsular
    Age
    74
    Posts
    3,577

    Default

    BobL, you are a legend, simple clear answer, thank you. What more could a man ask for? well maybe one lives in hope but I think I know where you would draw the line Bob.
    I would love to grow my own food, but I can not find bacon seeds

  16. #135
    Join Date
    Apr 2010
    Location
    Murray Lands SA
    Posts
    221

    Default

    Hi Tonto,

    The thread is TWO horse powered dust extractors and how to improve them.

    Cheers Barry

Page 9 of 21 FirstFirst ... 456789101112131419 ... LastLast

Similar Threads

  1. generic BAS 350 questions
    By corbs in forum BANDSAWS
    Replies: 7
    Last Post: 10th July 2010, 10:04 AM
  2. JET versus generic brands
    By Phil Mailloux in forum GENERAL & SMALL MACHINERY
    Replies: 15
    Last Post: 28th March 2008, 12:22 AM
  3. Another 'fix' for Generic 14" BS
    By Bodgy in forum BANDSAWS
    Replies: 0
    Last Post: 10th August 2006, 07:48 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
  •