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  1. #16
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    Quote Originally Posted by MandJ View Post
    Thanks for that info Bob, I knew this was an older DC and I doubt it's capable of the figures you get with your unit.
    I'm going to do a test without the bags tomorrow. .
    It would also be interesting to run the impeller briefly with the rectangular Y that connects the impeller to the two bag housings.
    Be careful - I doubt this will happened but if the current goes too high you could damage the motor.
    You should be OK to run it for about 10s or so.

    It's a 90 bend but I have two 45 here ready to make a smoother 90.
    Chasing in progress.
    two 45º s make it a slightly longer radius rather than smoother but I think that's what you mean.

    Most 240V AC ammeters have a resolution limit of 0.1A and as the the working range is about 6 to 9.5 A, so all you have is 35:1 resolution.
    So rather than using current you may get more resolution by measuring pressure difference.

    Measuring pressure is tricky since it needs to be done consistently but if the pressure monitoring point is left fixed in the same location and orientation i.e. in the middle of the ducting just before the impeller then the relative measurements will have some meaning. The pressure will typically vary by more than 100 mm of water so using a ruler with mm markings on it you can get at least 100:1 resolution.
    If you want more resolution you can use a manometer with sloped arms so you can measure 1/2 or even 1/4 mm differences.

    These differences will be enough to tell you whether a specific port design or opening on a machine is better than another.

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  3. #17
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    Nov 2013
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    Caboolture QLD AU
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    Have been looking at the prices for a low cost manometer and pilot tube but still undecided at this stage. BTW meter has an accuracy of around 2% on 40A range.

    I will have to remove the Y piece anyway sometime soon as the dam thing has a small leak on the end of each seam. These crap filter???? bags appear to leak around the bottom seam as well. I'm sure you reported these DC shortcomings in testing you carried out. I'll take a picture if I get a chance. Again - glad it's outside.


  4. #18
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    Quote Originally Posted by MandJ View Post
    Have been looking at the prices for a low cost manometer and pilot tube but still undecided at this stage. BTW meter has an accuracy of around 2% on 40A range.


    So at around 10A the accuracy is thus +/-0.2A which is poorer than the resolution (0.1A) so all the more reason to work with pressure.

    BTW It's very easy to make your own manometer with a piece of clear PVC hose and a ruler

    I will have to remove the Y piece anyway sometime soon as the dam thing has a small leak on the end of each seam. These crap filter???? bags appear to leak around the bottom seam as well. I'm sure you reported these DC shortcomings in testing you carried out. I'll take a picture if I get a chance. Again - glad it's outside.
    Yep - that's exactly why DC's are better placed outside

  5. #19
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    Just a quick update. interestingly, removing the bags made almost no difference to the reading.

    I replaced the flex with 6" PVC and prior to fitting the final 90 bend the draw was 8.1A, fitting the 90 drops C to 7.6A, I'll have to make a more gentle bend with 45's and move the lathe further out from the wall for clearance - might make a difference?. Everything on the lathe is quickly adjustable so having a fixed position pickup is not a problem for the work SWMBO is currently doing.

    When it's not too hot and I feel up to it I'll measure it without the Y piece, I may have a manometer and pickup by then.

  6. #20
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    Converted the temporary 90 deg inlet into a bell mouth shape using a large desert bowl that was a perfect match for 150mm PVC. A heat gun, SWMBO in control of that - under instructions - and with bulk downward pressure I had a perfect copy of the plate shape in just a few minutes.

    With bell mouth mod the current went from 7.6A (unmodified bend) to 8.1A - same as without the modified 90 bend. As SWMBO wanted to use the lathe I crudely placed a piece of 1" square opening fine wire mesh protector over the entrance, current dropped to 7.8A. I'll have to come up with something better during the week.

    Bobl's idea/testing of a bell mouth really made a substantial difference - in the right direction - to Dust Collector current.

    I'm guessing the crude way the mesh is attached is disrupting air flow over the bell shape inlet.
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  7. #21
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    Quote Originally Posted by MandJ View Post
    Converted the temporary 90 deg inlet into a bell mouth shape using a large desert bowl that was a perfect match for 150mm PVC. A heat gun, SWMBO in control of that - under instructions - and with bulk downward pressure I had a perfect copy of the plate shape in just a few minutes.

    With bell mouth mod the current went from 7.6A (unmodified bend) to 8.1A - same as without the modified 90 bend. As SWMBO wanted to use the lathe I crudely placed a piece of 1" square opening fine wire mesh protector over the entrance, current dropped to 7.8A. I'll have to come up with something better during the week.
    Bobl's idea/testing of a bell mouth really made a substantial difference - in the right direction - to Dust Collector current.
    I am surprised it makes that much of a difference but there you go!

    I'm guessing the crude way the mesh is attached is disrupting air flow over the bell shape inlet.
    Yeah it would be better if it was inside the hood itself.
    Also the hood rim should be about double that size
    Probably more significant is the hard 90º bend behind that. Mine has just enough room for a 2 x 45º bend between the lathe and the wall.
    There is a reason why velocity stacks are as tall as they are.
    What would make the bell mouth work even better was if 500 mm of straight duct before the bend.
    This is a design/installation aspect that all lathe owners should consider when installing lathes.

  8. #22
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    Quote Originally Posted by BobL View Post
    What would make the bell mouth work even better was if 500 mm of straight duct before the bend.
    This is a design/installation aspect that all lathe owners should consider when installing lathes.
    I'm guessing the idea is to keep turbulence to a minimum for some distance before the hood and any change in direction in pipes as big a radius as possible.

    I wish I had room for a straight inlet length but two 45's will only just fit here as well.

    Quote Originally Posted by BobL View Post
    Yeah it would be better if it was inside the hood itself.
    Also the hood rim should be about double that size
    Probably more significant is the hard 90º bend behind that. Mine has just enough room for a 2 x 45º bend between the lathe and the wall.
    Thanks, when I make the final bell mouth I'll make sure it has a wider flange, now I just need to find stronger mesh to mount inside.

    I've at lease seen some positive difference with just a few simple changes so I'm definitely going ahead with dropping the single 90 and making one from two 45's.

  9. #23
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    Default 2 year on and now some upgrades.

    I'm in the process of running 6" PVC ducting across the workshop to where our new band-saw will be located - the first new piece of equipment we have bought, we decided to save up and get something decent that we would want to use, instead wasting money on a second hand unit that, because of limitations, we would end up using only if we really had to.

    Managed to get quality 150mm 45 deg bends for $7.06 each, 6M of stormwater pipe for $49.00 and a couple of massive 45 deg Y junction for $24.39 ea. A few of the places I rang wanted more than $25.00 for a 45 deg bend. Gumtree had a few second-hand 45 bends for $15, so $7 was heaven to my almost nonexistent finances.

    I figured it would be better running 7 meters of 150mm ducting than running 3 meters of flexible 150mm tube (really 142mm inside from what I've seen), not to mention having the tube on the floor to keep its length to just 3m or the cost of the coiled gold. Having decided to extend the small (short run) existing 150mm system, I then decided to add a second extra drop down the opposite wall for a moveable work bench with the following items:

    I managed to get 4 fabulous industrial castors worth around $80 each for just $12 each, all lock in both roll and swivel - steel gear type interlock on the swivel. Made a very chunky / strong moveable work bench (using those castors) and it holds a number of built in items. I built my old Bench saw (was on a crappy steel stand) into the right half of the bench and a sanding / down draft box with grill insert (350 x 350mm) into the left side of the bench. Both have 150mm PVC ducting that exits down low on the RH side of the bench, there are two 45 deg (angled up) fittings bolted there so I can quickly connect either port to the system DC with a short 1/2m of 6" flex. I'll use a quick connect to run either via a dedicated port on the main ducting run, that run exits next to the bench. I've made a 150mm exit port in the bottom of the saw housing and fashioned a full sloping interior leading down to that 150mm exit point, no place for sawdust to gather now. Added 2 x 4" intake holes high on the opposite side of the saw cabinet and a smaller 2" in the far lower corner, down low to pull air across the furthest part of the sloping interior floor (40 deg slope). There are another two 4" holes with grills that I can open up if I find I need more intake capacity. Can't test it until we get that 1/2m of 150mm flex.

    I've almost finished a big mitre slide with integral clamping for the bench saw. I'm fitting a large 1" thick clear Perspex lid to look through and enclose the entire slide, we mostly cut small stuff on the bench saw, so this will stop all that high speed dust coming from the blade and escaping into the workshop. I'll have a 4" suction port on one side and an intake port on opposite side.

    The sanding station / down draft insert port is 350mm x 350mm and will have a big bell mouth built in below the table leading up to the insert recess, I'm currently making a number of pop in attachments / hoods that drop into that recess, these are for various tools that we will use on this bench.

  10. #24
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    Nov 2013
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    Default DC output dropping over the past 2 years.

    The DC suction has slowly reduced over the past 2 years, bags were close to half full when I opened up the external DC housing, time to empty them. My wife does a lot of pen turning and making small bowls, so not a huge amount of larger material in the bags. Importantly, after 2 years of use, there is not a trace of dust build up on the walls, above the door next to the lathe (where forced cross flow air exits) or the shelf above the lathe, nor the rest of the workshop. Anyway, I measured the DC current and it had dropped from 8.1A down to 6.4A.

    I dropped one of the lower bags and current went up to 7.6A with a corresponding big upward change in suction. Emptied both bags, (wearing my hazardous vapor rated dusk mask) and cleaned out he DC enclosure (a few rags, two bucket of warm water, detergent and a little elbow grease), thank God that DC is not in the workshop.

    Hosed out the bags, soaked then in warm water and detergent for an hour, rinsed and dried, looked like new.
    Ran the DC with no bags connected, and current was 8.1A, tested with the DC enclosure door open, same current, fitted the washed and dried bags and current was exactly the same, so current went from 6.4A to 8.1A after cleaning bags.

    I then added a 45 deg Y near the lathe to feed the new 6m of 150mm ducting that hangs from the ceiling and runs across the workshop, there are 4 x 45 deg (90) bends in that system, and a 2nd Y at the other side of the workshop, along with two blast gates. The current with the extra DC pipes and blast gates closed was still the same with the first original port opened, (the lathe) interestingly, with two blast gates open current went to 8.3A, with 3 open it dropped to 8.1A.

    I know I should make a manometer and measure properly, but this has been a big effort (I'm old) and had to do it on my own, one day I'll make one and figure out how to use it and interpret the readings . In the mean time, we wait for the new band saw to come, at least I now have the band saw ports sitting there ready.

  11. #25
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    Default New DC run for Bandsaw and temp BS outlet.

    Temporary take off for the bandsaw, until we get the BS, there is no way to be 100% sure exactly where it will reside, so this rough takeoff will allow me to test it, do some cutting and then decide on the final pipe fittings and flex size and number of connection needed.









  12. #26
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    Default Short run DC to Lathe and NEW Y take off

    View of the existing 150mm connection from the back of the DC cabinet to the lathe and the new Y take off fitting for the rest of the shed.


  13. #27
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    Default New run from the lathe Y to the ceiling.

    Ideally, there should be a long run between the two 45 deg bends but I don't have room, at least it's not a hard 90 fitting.


  14. #28
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    Default The new outlet for the moveable bench.

    Moveable bench under construction.

    There is a blast gate at the end of this outlet, ideally it should be close to the takeoff point to stop dust build-up in this run. but the gate is made for flex hose and is 142mm not 150mm, so I fitted it to the end. I'll just remember to crack the gate open every now and then with the DC running to keep it clear.


  15. #29
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    Default 150mm outlet from the Down draft fixture built into the bench.


  16. #30
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    Temp guard around the Blast gate is to protect the metal slide.

    Two 150mm ports, one from the down draft bay and the other from the bottom of the Table saw.


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