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  1. #1
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    Default Beginner attempt at DC - thanks to forum members

    HI all, I'm new to the world of woodworking and here because my Wife has progressed with her interest in woodturning. She has been taking woodworking classes for a year or so and decided to get an old lathe to enjoy her newfound hobby at home. Sigh!

    I can suffer from severs sinus (slowly getting this under control after 60 years) and so decided to research the health and safety issues of wood turning, wood working in general and wood dust.

    Thanks to this wonderful forum and the intelligent and insightful discussions, I was able to come up with a workable solution - I know some will point out that it's not a good or ideal solution, but it's the best I could come up with for my wife in our current circumstances. Had it not been for forums like this I would have made so many major errors by not understanding the factors involved in collecting dust from a lathe and other machinery.

    My wife had found a WoodFast 280 (I know, it's old as) on a sturdy frame with various attachments and tools - it has not seen a lot of work and after pulling it apart and going over it with some TLC, it appears to be in perfect running condition.

    Now to the debated and difficult (if funds are limited) issue of the DC, ducting and air safety.

    After reading articles and posts from BobL, and many others including Billpentz's site, I decide to go for a 3hp dusty and not the 1hp or 2 hp friends had advised. A unit was available local to us - again an old design - but it was something we could afford at this stage.
    We have a 6x9 shed that's lined and insulated, one 6 x 3 bay is lined with fibre-cement sheeting and is sealed from the rest of the shed. This would be the location for the lathe, tools and various wood working equipment.

    I positioned the lathe so that the DC could be mounted close outside the shed (as others and BobL suggested) in a self contained cabinet which is sealed except for low mounted exhaust vents. Thick treated pine planks glued and screwed make up the base and this is mounted on six 75mm x 600mm steel box section tubes driven into the ground about 1/2 meter. This cabinet is constructed from (seems like tons) of 70 x 35 pine and covered in hardy flex fibre cement sheeting. Every joint is glued and screwed as are the FC sheets, later I plan to add internal sound deadening when time and funds permit, I constructed the cabinet to make sound proofing a simple add-on .

    The cabinet is about 100mm at the closest point from the main shed (stand alone to remove any mechanical vibration coupling) and this position allows me to run 150mm PVC pipe around 1.8M long almost straight to the lathe (as suggested in these forums, keeping it short and 150mm). I'm also following BobL's advise and will be making a bell mouth for the 150mm tube and mounting it close to the work.

    Luckily the wiring to the shed is a 30A circuit (single phase unfortunately ) and the run is very (seriously) heavy gauge cable. The 3HP DC (at start up - max current draw) hardly even flickers or dims an incandescent globe connected with the DC at the end of this heavy 240v run. The start/emergency stop switch is moved from the DC to the inside shed wall next to the lathe.

    A trial run and the sound outside is even lower that I had hoped for. Shed closed and standing outside near the DC, the noise of air being sucked into the 150mm port near the lathe (inside the closed shed) is louder that the DC. When 9m away and you can hardly hear the DC and no low freq rumble.

    I plan on fitting a powerful through the wall extractor (blowing in) on the opposite side of the shed to bring outside air in and across the 6 x 3 wood work bay towards the DC extraction port, this will auto run whenever the DC is running and of course can be switched on by itself for cross ventilation when needed, hopefully this will provide that desirable extra cross flow and help counteract the sheds negative pressure when the DC is running . Also making a small weatherproof box for the shop VAC and mounting it outside the shed, using this for metal drilling and general large shavings clean up.

    Who'd of thought that even making small things like pens on a lathe could be so hazardous to one's health, but then again, it involves very fine sanding with some hardwoods that can be higher on the list of problem timbers.

    Picture were taken at dusk and are a bit washed out.

    The 150mm flexible tubing (hanging by a cable) in the picture was for a temporary test and will be changed to mostly PCV when I make an adjustable solid holder and a bell mouth collector.

    Attached Images Attached Images

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  3. #2
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    Very well done . It looks like you understood the advice and did a great job within your budget

    Mick

  4. #3
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    Default

    Quote Originally Posted by MandJ View Post

    Thanks to this wonderful forum and the intelligent and insightful discussions, I was able to come up with a workable solution - I know some will point out that it's not a good or ideal solution,

    MandJ,

    There is always a better way, but what you have done looks pretty good to me. 3 HP dusty ... short run to lathe ... bell mouth inlet. Many of us would like a bigger impeller and/or motor (I would), but the acid test is the system's ability to grab the fine dust. What you have done looks like it will, so please post your experiences once you have the lathe running with the dusty.

    Cheerio!

    John

  5. #4
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    Default

    Looks good but the louvres on the vents on the side of the enclosure look a too small and will generate a significant back pressure on the collection of dust inside the shed. I'd be using something with a total cross sectional area of at least 1 sq ft. The smaller the holes or slots are the MUCH more of them there needs to be. If you want to use louvre vents that size there would need to be 3 or 4 times more than you currently have. I notice you have what looks like a foam? sealant around the door but this is not necessary and you could in fact have a deliberate 1/2" gap around the door.

  6. #5
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    Default

    Thanks to each of you for the replies, after some tests I realised there was a problem with the louvers and I had removed most of them already, just left the surrounds in place. I plan to do some type of flow testing and keep an eye for dust build up over time. I have a few spare Ampere meters laying around and I may fit one permanently just to keep an eye on changes to the fan load over time and with different port connections, not sure how useful that might be?

  7. #6
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    Default Cross Ventilation

    One thing I didn't mention in the first post is the wood working bay has a roller door, something we were going to remove, unfortunately this is the only side of the shed where the external DC cabinet could be located.

    This is why I sealed the DC cabinet door and placed the cabinet vent down low and as far as possible from the opening at the top of the roller door.

    To help solve any negative pressure effect of the DC and, due to its location, any chance of dirty air being sucked back into the shed, I installed a through the wall fan. The idea is to allow a large volume of air to come in through the rear wall of the shed, far removed from the DC. I tried a 500w 300mm unit but the noise was so loud that it was impractical.

    To get the airflow I was looking for but with reduced noise I decided to try a much bigger fan turning at a slow speed. To this end the only thing available was a 3 speed 600mm fan in a full steel housing and rated at 200watts. Gave it try and the results were what I hoped for, little noise for the volume of air moved and with the DC running there is a positive air flow out over the top of the roller door. It allows cross ventilation when running the DC and when the work is finished we can open the roller door and have the fan run on HI to quickly vent the small 6 x 3 bay. Much to my amazement ,this fan (on high) blows any dust or small particles lying on the floor, out the door when it's raised. As a bonus, on most days it should help cool the woodwork bay.

    For security, a heavy steal grill covers the rear opening in the wall. A large open frame encloses the opening and is covered in fiberglass flyscreening (large enough surface area to not restrict air flow) a protective weather hood stops any rain entering the opening.

    Here is a view of the fan in it's trial position, I have yet to trim / tidy the installation and mount the 3 position speed switch.
    Attached Images Attached Images

  8. #7
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    Craig

    Expert /Ex-Spurt/ -n. An "Ex" is something that has been or was. A "Spurt" is a drip under pressure.

  9. #8
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    Good work M&J

    Quote Originally Posted by MandJ View Post
    One thing I didn't mention in the first post is the wood working bay has a roller door, something we were going to remove, unfortunately this is the only side of the shed where the external DC cabinet could be located. This is why I sealed the DC cabinet door and placed the cabinet vent down low and as far as possible from the opening at the top of the roller door.
    One problem with this is that air coming out of a shed that has been through a machine and a DC is usually warmer than external air so it will immediately rise. One way around this would be to use a chimney to get the air past the opening above the roller door. Last week I drove past a skip with a beaut looking SS fireplace chimney which would be the sort of thing that would make a great DC chimney.

    To help solve any negative pressure effect of the DC and, due to its location, any chance of dirty air being sucked back into the shed, I installed a through the wall fan. The idea is to allow a large volume of air to come in through the rear wall of the shed, far removed from the DC.
    In your case a good idea and I can understand why you did it !

    Increasing the pressure inside a room is usually done to exclude external dust from entering a room but in general, venting a dusty room or enclosure by pulling on the dust is more effective than trying to push it.
    If air is extracted from a shed using a fan, effective shed venting is best done with external air coming from a number of small openings in the walls opposite the fan. Locating the vents up high near the ceiling and down low near ground level is the way to go rather than just relying on a single opening like a door or window which tends to generate a tunnel of clean air between the single opening and the fan but it may leave other areas of the shed unvented.

    For security, a heavy steal grill covers the rear opening in the wall. A large open frame encloses the opening and is covered in fiberglass flyscreening (large enough surface area to not restrict air flow) a protective weather hood stops any rain entering the opening.
    You may not notice it but the fibreglass screening will reduce flow and will also eventually clog and further reduce flow. I'd suggest using a coarser screen.

  10. #9
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    Hi Bobl, thanks for the input, when building the system I tried to overcome most of the points you raised. The DC outlet is about 3m past the roller door and blowing in the opposite direction from the door. The room we used for woodworking was already completely sealed except for a gap at the top of the roller door and now the DC suction port and a 600mm fan intake down low in the rear wall.

    The air coming over the roller door is still strong blowing in your face at almost a meter from the door. The internal door to the rest of the shed has a surprising amount of resistance when opened for at least the first 4 to 5 inches due to the pressure and air flow from the woodwork room. !
    feel sure that the only air getting into the shed is via the rear fan, but again something I will keep an eye on.

    The woodworking machines are paced/moved near the shed opening (roller door) and with the intake fan running there appears to be no dust flow back into the rear of the shed (where the intake fan is mounted) still something I will keep an eye on.

    I agree with your assessment of the fly-screen material, it was the only thing I could find at this time and will be replaced when something better comes along - still need to stop the midges though. To compensate for flow I made the external housing around the fan inlet quite large, it extends about 500mm out from the shed and a minimum of 500mm away from the intake on all sides, the surface area of the mesh is 5 to 6 times the inlet size, hopefully the reduction in airflow is small.


    An ongoing chore around the home is replacing old fly screens and cleaning serviceable ones, I imagined that with high air flow, this screen would need cleaning often. I made the frame that holds the screen easy to pop off and clean with a hose.

    I opened the DC cabinet (wearing a mask) and even with the little turning my wife had done there was the telltale sign of fine dust from the timber on a tissue wiped on the DC housing. I rechecked the tightness of the bags and they were tight with no puckers, glad it's not in the workshop.

  11. #10
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    Default Sound levels

    Just did a few sound level tests.

    Normal background noise is around 41dB at the moment.

    DC cabinet door open @ 1m 87dB.

    Door closed @ 1m 62dB.

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

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

    Some of this noise with the cabinet closed is from the Intake port in the closed Woodwork shed.
    1m from the 6" intake port reads 87dB, total pipe length from the DC is 1.8m. Intake wind noise travels out over the top of the roller door and is also transferred through the metal roller door.

  12. #11
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    Current measurements.

    This unit is supposed to be a 3hp DC, however after reading Bobl's testing of an imported unit (Taiwan in this case) and how the industry in general tests them I'm not surprised with the results.

    I haven't checked with the filters off as yet but I was interested in some general measurements. First the motor spec plate. 240V, 50Hz, 15A, I know this was a unit designed for 60Hz as the CFM rating is down from the same unit sold in the US. God knows what that 15A current rating means as that would be close to 5HP if it did that.
    At power up the unit draws close to 48A @ 230v

    The mains voltage drops from 244v to 230v at power on. This is at the end of a 56m run fed via a 35A breaker in the fuse box at the front of the property. There is also a 25A breaker on the shed, however that breaker will hold 60A for a second or two before it trips and has not done so yet. I'm happy with that and it's up to full speed very quickly.

    The first reading was with everything connected and comprised of:

    A short 7" length of smooth wall flexible 6", 1m length of 6" PVC pipe, 600mm length of 6" smooth wall flex and then a 90deg fitting, currently the dust pickup and mounted really close to the lathe work.

    Reading was 7.3A which is around 2.3hp

    The idea of the first 7" length of flex was to isolate any vibration from the DC coming in through the shed wall via the PVC pipe. I was reading another of Bobl's testing posts and he mentioned turbulence near the DC fan at the intake could be a problem, this makes sense.

    Tested with just the 7" length of flex gave the same reading of 7.4A.

    I removed the short flex, flared the metal intake flange slightly and got a really good fit with 6" PCV.

    With filter bags and new intake coupling, about 7" long, the current was now 8.7A @ 242V which if I calc correctly is around 2.7hp. So that short bit of pipe was a real problem.

    Current was the same with the DC cabinet door open or closed so my enlarged cabinet vent is possibility not a limiting factor at the moment but without proper air flow tests I likely won't know for sure.

    Current with 1m intake pipe and 15deg bend running into the shed was 8.5A.

    Current when 600mm of 6" flex connected went back down to 7.4A.

    So the next thing to tackle is getting some better flex OR trying to do away with it. It's clear plastic flex with a spring steel spiral reinforcement - it supposed to be 6" but in between the spirals I reckon it's closer to 5". It does not collapse under suction even with the pickup blocked . Anyone know if there is something better?

  13. #12
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    Quote Originally Posted by MandJ View Post
    SNIP ...

    So the next thing to tackle is getting some better flex OR trying to do away with it. It's clear plastic flex with a spring steel spiral reinforcement - it supposed to be 6" but in between the spirals I reckon it's closer to 5". It does not collapse under suction even with the pickup blocked . Anyone know if there is something better?
    Carba Tec sells grey 6" flexy that does not have steel spiral. Rather it has a PVC reinforcing spiral moulded in and this reinforcing runs between the external spirals, making it smoother than the flexy with wire. It likely is not as flexible, but from what I gather, it has lower losses.

    Cheerio!

    John

  14. #13
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    Quote Originally Posted by John Samuel View Post
    Carba Tec sells grey 6" flexy that does not have steel spiral. Rather it has a PVC reinforcing spiral moulded in and this reinforcing runs between the external spirals, making it smoother than the flexy with wire. It likely is not as flexible, but from what I gather, it has lower losses.

    Cheerio!

    John
    Thanks John I'll look them up now.

    Mike

  15. #14
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    With nothing connected and clean bags mine draws ~9.3A as the bag gets dirty current drops to ~8.9A

    Quote Originally Posted by MandJ View Post
    A short 7" length of smooth wall flexible 6", 1m length of 6" PVC pipe, 600mm length of 6" smooth wall flex and then a 90deg fitting, currently the dust pickup and mounted really close to the lathe work. Reading was 7.3A which is around 2.3hp.
    For comparison purposes, my run to my lathe uses
    - 1 m of ducting
    - 1 x large radius (1 x 45 and 3 x 15º) 90º bend,
    - 1 x ( 2 x 45º) 90º bend,
    - 1 x 15º bend
    - 2 m of ducting
    - 400 mm of flexy
    - 1 x safety grate ( 1' x 1 " SS mesh)
    - 1 Bell mouth Hood
    8.5A
    Removing the bell mouth hood drops the current by 0.1A

    So the next thing to tackle is getting some better flex OR trying to do away with it. It's clear plastic flex with a spring steel spiral reinforcement - it supposed to be 6" but in between the spirals I reckon it's closer to 5".
    5" ducting is limited to ~700 cfm so it will really be worth your while chasing something better.

    Is your 90º bend a single fitting?

  16. #15
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    Quote Originally Posted by BobL View Post
    With nothing connected and clean bags mine draws ~9.3A as the bag gets dirty current drops to ~8.9A



    For comparison purposes, my run to my lathe uses
    - 1 m of ducting
    - 1 x large radius (1 x 45 and 3 x 15º) 90º bend,
    - 1 x ( 2 x 45º) 90º bend,
    - 1 x 15º bend
    - 2 m of ducting
    - 400 mm of flexy
    - 1 x safety grate ( 1' x 1 " SS mesh)
    - 1 Bell mouth Hood
    8.5A
    Removing the bell mouth hood drops the current by 0.1A


    5" ducting is limited to ~700 cfm so it will really be worth your while chasing something better.

    Is your 90º bend a single fitting?
    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's a 90 bend but I have two 45 here ready to make a smoother 90.

    Chasing in progress.

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