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  1. #76
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    FYI - For anyone interested, I posted a thread here on the problems I mentioned above with the new BS.

    Laguna 14-BX feedback wanted.

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  3. #77
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    I removed the 150mm to 100mm dual outlet fitting and grafted another low angle 100mm inlet into the 150mm feed for the BS. Ideally, I'm guessing, I should have separated it further back up the line, but this will have to do. I found a straight end 150mm to 100mm fitting at the local HW, made a sort of bell mouth insert that fits inside, this at least gives a better transition from the 100mm line into the 150mm BS DC line.

    Doing this has allowed me to remove almost 2M of 100mm flex, that has got to count for something.








  4. #78
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    This is not a debate about the pros / cons of removing tension on a BS blade, so I won't respond to any comments on this. As is common, this BS had a quick release blade tension lever - a nice long one. I know there are steps that you can take to indicate that the blade tension has been released, but instead, I added a micro-switch safety lockout, you simply cannot start the saw unless the Quick release lever is moved all the way to the fully tensioned position.


  5. #79
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    I like the micro switch installation.

    Pete

  6. #80
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    Good idea about the micro switch
    I've gone for a lo tech solution by hanging a piece of wood that says "Check Tensioner" from a piece of string on the "on switch"

  7. #81
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    Thanks Pete.

    Yes Bob, I had a bungee cord around the release handle and clipped across to the power button side protection bracket, but one day - I'm getting old - I might forget, and I would hate that blade to hook through the ceramic guides. Now it's just one less thing to do or think about, and another thing my wife doesn't have to worry about either.

    Mike.

  8. #82
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    Earlier in this thread post #52, I took a few pictures of the DC impeller housing with the intake / cover plate removed in order to measure the size of the impeller, it turned out to be 14.4" fan blade tip to tip.

    Also in post #52, I wondered about the impeller intake tube protruding into the housing and what effect it would have on the performance, some further readings suggest that it is to actually help get clearer air into the impeller. I also found a bit of a step in the intake, it also slips into the 150mm PVC as 150mm PVC is actually slightly larger than 150mm metal intake flange.

    I made a timber housing cover and flared the inside of the opening, while I was at it, the intake size was made slightly larger to match the inside diameter of 150mm PVC. With this in place I ran the DC and measured the current through the new naked opening, current was slightly less (250mA) that with the original intake. Unfortunately I could not test the static pressure.

    But every test indicates that the limiting factor is the impeller, due to the difference between the 60Hz design of the DC and our 50Hz supply and hence lower Impeller speed. For example, totally removing the Y metal impeller exit housing makes no difference to static pressure or current.

    As a matter of interest, the 14" JET impeller that Bill Pentz discussed has 1/2" taller blades. I know that Bill talked about initially running a larger impeller on certain HP motors, and reducing the height of the blades was suggested to still give some of the benefits of a larger impeller but also limit the maximum current. It's been a while since I read his writings so I could be slightly off here on that assumption.

    In any case, I'm happy that I have tried (maybe not as correctly as I should have) to see if there was any reserve capacity in this DC. I feel the next real step is to eventually go to a Cyclone with VFD. In the mean time, the only modification I have left to do is to make a chimney for the DC housing to get the exit vent above the roof of the workshop.

  9. #83
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    Quote Originally Posted by MandJ View Post
    Earlier in this thread post #52, I took a few pictures of the DC impeller housing with the intake / cover plate removed in order to measure the size of the impeller, it turned out to be 14.4" fan blade tip to tip.

    Also in post #52, I wondered about the impeller intake tube protruding into the housing and what effect it would have on the performance, some further readings suggest that it is to actually help get clearer air into the impeller. I also found a bit of a step in the intake, it also slips into the 150mm PVC as 150mm PVC is actually slightly larger than 150mm metal intake flange.

    I made a timber housing cover and flared the inside of the opening, while I was at it, the intake size was made slightly larger to match the inside diameter of 150mm PVC. With this in place I ran the DC and measured the current through the new naked opening, current was slightly less (250mA) that with the original intake. Unfortunately I could not test the static pressure.
    Less current means less air. What was the problem with the static pressure test?

    Interestingly I was talking one of my BILs today about this - he is a mechanical engineer and has done some work on impeller design and he was telling me about the importance of the gap between the top of the blades and the inlet port - distance x in picture A below.

    ImpellerInt.jpg

    Somewhat counter intuitively if X is too small the flow is reduced because of significant turbulence in the region above the blades.
    If X is too large the static pressure won't be as good so optimising X becomes important.
    It's also important for the fan curve in general to get the right.

    Flaring the ends of the inlet as shown in B should help but I suspect if this is done X may need to be adjusted .
    Picture C is how the generic 2HP DC mod was done.
    On the stock 2HP DC there s no protrusion of the inlet into the Impeller housing.

    The value of X is something worth pursuing - something else to do when I get round to it.

    But every test indicates that the limiting factor is the impeller, due to the difference between the 60Hz design of the DC and our 50Hz supply and hence lower Impeller speed. For example, totally removing the Y metal impeller exit housing makes no difference to static pressure or current.
    On reflection I now don't expect it to make any or only a small difference.
    I may have hinted otherwise in previous posts but during a static test the impeller should be cavitating so will not be moving any (or much) air so the outlet back resistance has to be changed quite dramatically to see much of an effect.

    If you want to improve the performance you could always swap the SP motor for a 3P and a VFD and spin the impeller at 60Hz.
    Beware the noise increases dramatically and the added current draw may be too much for the motor.

  10. #84
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    Thanks Bob, that last point about swapping in a 3P and VFD was something I had been thinking about, and although I can get something lower in cost that the Clearview Motor and VFD, I'm thinking it may be better to save my limited resources for a Clearview MAX, especially if we end up adding a few more peices of equipment and therefore the need for extra ducting etc.

    As far as static pressure, my wife informed me that she needed to finish a lathe project that very evening - sigh! As I had mounted the manomerter to the wall inside the workshop and was running out of time, I just popped the original cover plate back on and set the DC back into the system. But as you say, I really think I'm just playing with minor gains / losses here.

  11. #85
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    Quote Originally Posted by MandJ View Post
    Thanks Bob, that last point about swapping in a 3P and VFD was something I had been thinking about, and although I can get something lower in cost that the Clearview Motor and VFD, I'm thinking it may be better to save my limited resources for a Clearview MAX, especially if we end up adding a few more peices of equipment and therefore the need for extra ducting etc.
    The VFD won't be wasted as you can use it in the ClearVue.

  12. #86
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    FYI - Again, for anyone interested, I received the second tyre and it fixed the problem, I've poster a couple of videos of the faulty lower tyre.

    Laguna 14-BX feedback wanted.

  13. #87
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    A few more pictures of the Bandsaw dust collection and thoughts on the air flow into the lower cabinet versus my below table dust hood. Now I'm likely going to get flack over this, but my results indicate that in my case this works.

    Like most of us, I can't accurately measure airflow, but I don't need an instrument to measure a substantial change in airflow to tell me when air is moving faster into a dust hood, I can feel it and hear it. In an ideal situation the main feed duct would be flowing enough air to support 3 x 4" ducts flowing at or near the CFM capacity for a 4" duct, however I'm sure that with this DC unit and ducting runs that my main duct is not flowing 1200 CFM at this end of the main 150mm drop.

    When talking about flow rate through the main duct, compared to the Lathe which is very close to the DC, I'm sure that I'm not running the same airflow when using this end of this main run. Both the Static pressure loss (difference) and the current drawn by the motor driving the impeller confirm it.

    Various testing with this below table dust hood indicates that with it in place I may not need as much DC from the lower cabinet. By further reducing flow into the lower cabinet I found that air flow into the below table Hood was substantially increased, furthermore, overall dust collection was even better.

    One of the big problems, and hence a balancing act, would be ensuring there is sufficient flow through the main larger ducting to ensure that the dust material I'm feeding from the BS does not drop out of suspension, and it (so far) doesn't - I will be monitoring this.

    I have continued to cut similar amounts of dark timber and record dust in the top and lower cabinets and the below table area. This latest configuration has been the cleanest so far when going over every nook and cranny with a spot light and wiping with a white cloth.

    NOTE: No top of table duct collection was used in following.

    I wanted to see how much sawdust was actually left and the pattern of dust on the table. I will next need to video this to see more of what's going on as I don't really see much while sawing. Most of what is left on the table appear to be chips, but as always, I'm sure there is more that I can't see, that is why there will always be above table pickup near the blade and upper guides.

    So as before, I resawed a 300mm long 200mm high piece of timber in two, then cut both in half so that I ended up with 2 @ 150mm long x 100mm high boards and cut an 3mm veneer from each board.

    All pictures are taken with a flash, it appears to show the most sawdust in the pictures.

    Results of cutting - again I KNOW it's not a lot of timber:

    Picture below shows the top of the table. There is no trace of any fine dark coating on the upper guides, only the underneath of the guide shows any signs of fine brown timber dust. Again, NO DC pickup was used here for this test.



    The two pictures below show no dust has spilled over onto the ducting - YET - obviously not a long enough cut to do that, and nothing on the motor or base. Yes that is a quick and dirty filter on the lower port, and yes, I know it reduces flow and I did this on purpose to keep sawdust out of that low "temporary" intake AND restrict flow.



    Note: I have a white plastic strip glued to the frame covering the foot brake opening, this strip sucks down and covers the opening, but it in no way restricts the foot brake operation. Again this goes against the normal recommendations of opening up the cabinet - BUT - because of the intentionally restricted air path into the lower cabinet, I don't want any dust from the table above flowing into the lower cabinet through this largish opening, and there is quite a strong air flow through this slot.



    Below: Under table pickup in place - not a trace of dust can be seen anywhere underneath the table with that in place.



    Pictures Below: Pickup removed shows a powdery dust trail that ends exactly where the top of the cutout starts in the Pickup hood that I just removed. There is nothing behind the table insert cutout, there is nothing ANYWEHRE behind the lower guides.

    Notice the dust line on the top lip of the lower housing, a fraction below that is where the cutout in the pickup hood finishes, there is nothing below where the pickup hood finishes.

    NOTE: What looks like dust further out below the table is dirt and smudges in the grease that covers most of the lower table, I have not removed it as yet, that grease on the bottom of the table, I recoat it when I clean up before the next test, it helps make the dust flow very obvious.





    Notice the dust trails are mainly on the exit side of the blade and pulling dust through from the cut. I notice - where the airflow is shadowed by the blue blade guide assembly and the blade - that you can see a very fine dust layer being left behind on the surface (reduced air flow over shadowed surfaces).



    Below: Side view, guides are clean, there is no dust, and again anything that looks like dust at the back of the table is caused by the effect of the flash angle on the grease and my grubby prints.



    Below: If you look closely, you can see a very fine sign of dust on the zero clearance plate. Not a trace of dust anywhere else.



    Four photos Below: Not a trace of dust inside the cabinet.

    NOTE: I have intentionally reduced airflow into the lower cabinet to allow more of the available air to be pulled in through the below table dust hood, there is virtually nothing getting past that hood and into the lower cabinet, the lower cabinet DE port is "almost" redundant.









    Below: Would like some thoughts on this - is it common? There are tiny "chips" that come from the blade as it flexes onto the top wheel, there are none inside the top cabinet only in the top door lower ledge, it's like they flick out towards the door, or there is also some fan effect from the blade helping them drop towards and into the door recess? Now this has always been there and it cannot be pulled from the blade with the DC. it has nothing to do with reduced dust pickup into the lower cabinet, it does this with full flow to the cabinet port and the door open. I know pine is bad for sticking in the blade gullet (it did), and it seems this dark timber is the same, it's blackwood?





    Finally - I'm thinking of trying a larger pickup diameter pipe for the below table ducting and hood - and modify it as BobL suggested, to catch overflow from the table when cutting big wood. That would overcome the effect of the restricted path of the lower cabinet and restore available flow back into the main duct, it may even work a little better?


    Thoughts!

  14. #88
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    Default Filter Bags.

    One of the reasons I fitted a manometer and ampere meter permanently to the workshop wall was to monitor DC system loss due to dirty filter bags.

    Had the first chance to see this over the past two days when compared to readings with clean bags. My wife did about an hour turning a "small" bowl on the lathe, the pressure dropped from the normal 6" at the lathe - cleaned and washed bags - down to 5.5" after she had finished.

    Current also dropped slightly as it followed the loss in pressure. This morning it was exactly the same as the night before, I ran it for a while checking everything and it didn't budge, but after another 30 minutes on the lathe it's down to 5.2" for a total loss of 0.8".

    Static pressure with closed gates has only dropped about 1/4" inch from 10" to 9.75", most likely due to less air being pushed through the bags with a closed intake when compared to an open blast gate, so less apparent effect?

    It will be interesting to see how fast it continues to drop, or if it levels out for a while. Obviously I can't notice any real difference in performance, so I'm thinking around 2" might be when it's time to clean the filters? A cyclone is sounding better every day.

    BTW I did check for leaks. I had been running the DC for around an hour before anything was done on the lathe, the reading only changed as lathe work progressed.

    The readings have been the same for the past month while testing and adding extra ducting across the workshop and testing various pickups. I have recently been working on the bandsaw pickup and had noticed a very slight change after using the bandsaw for all the test cuts, it appears that adding the large amount of sawdust that came from the lathe work into the filter bags really made it obvious.

  15. #89
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    Default BS dust pickup - random thoughts.

    I've been thinking about the fact that BS owners throughout various woodworking forums have been complaining about the poor dust collection designs of bandsaws for a very long time, and lately I have joined the chorus, but now I'm wondering if I've been a little too harsh?

    The DC port is usually located in the lower cabinet, therefore most of the initial attention has been given to opening up the lower cabinet in order to allow sufficient air intake to match the average 4" cabinet DC port, at the very least doing this as a starting point.

    Opening up the cabinet is obviously driven by the fact that our dust collectors can move a lot air at low pressure through a sufficiently large opening - say 4" and above - but cannot generate enough suction to do so through smaller openings. With a small workshop DC system with blast gates and various takeoffs, we should be concerned with matters like having enough airflow through the main ducting back to the DC, this is due to the need to hold dust in suspension and not have it fall back down vertical rises or build up in sections behind closed blast gates and ducting etc.

    Most bandsaws have very restricted DC intakes below the blade and lower guides, so opening up the lower cabinet by leaving the cabinet door ajar, or adding a 4" or larger intake port into the lower cabinet will only serve to further reduce, or even stop any dust pickup through the small pickup opening - more air into the cabinet from another less restricted intake will result in less air intake through the existing tiny intake slots. And because of below table designs, like the normally large space between the small DC intake opening and the table insert, there will be virtually nothing pulled through the guides, let alone the timber cut behind the blade and through table insert plate, therefore we end up with even more sawdust below the table and onto the floor.

    It's possible that the manufacture may be relying on blade fan effect to help pull dust into the restricted lower cabinet DC slot, although I feel this effect would be somewhat diminished after passing through the timber and lower guides. With even less intake through the supplied pickup slots, it likely results in the dust further fanning out and spreading over the guides, cabinet and floor.

    Is it possible that restricting the cabinet intake is the only way manufactures could force these tiny built in dust pickup openings to work in any fashion at all. I doubt manufactures are the slightest bit concerned about the effect this design and resulting port restriction has on our workshop dust collector or ducting, and are only concerned with, within the design constraints of the BS, getting some dust pickup into and removal from the lower cabinet.

    To sum up: Open the door and you get more air into the cabinet, you will see less dust into the lower cabinet, it looks cleaner and the DC gets more air into the main duct, but now you get even more sawdust being thrown out between the top of the cabinet and the table. This is why it's stated on the forums by the guys who already know this, you must also add a below-table pickup of some kind.

    BTW: In our BS, the top cabinet pickup slopes down externally to create a straight air flow path up towards the opening at the bottom of the lower guides and blade, it also pulls air over the wheel brush and a blade zero clearance insert inside the cabinet - at first glance it looks good. The big problem here is a tiny 3.5" x 0.5" slot for total air pickup / intake, it opens below the bottom of the lower guides and continues down a bit next to the blade, sound familiar?

    Also in this model they added a footbrake, doing that left a 3.5" x 3/4" opening that's bigger than the 3.5" x 1/2" slot for dust collection pickup. I'm guess because of this, they had to find a way to block air flow through that foot break opening, I believe it was just simpler for them to add a second dust port next to the footbrake opening and as a bonus they get to sell it as a feature - we've added a second dust port for even better ----. They also get a bit more of the sawdust that normally drops to the bottom of the cabinet because of the restricted low air volume out of the top port, again the cabinet looks cleaner and this appears to be what most owners / reviewers focus on, they open the lower cabinet and show a moderate amount of wood dust and comment on how effective the DC is?

    As I mentioned above, it's been suggested for years on these forums that the correct place for main dust collection on a BS is between the table and the top of the lower frame, and if you can get it right, well I'm stoked at how really effective it can be. A correctly designed pickup will pull a high volume of air directly over the guides, the blade, and a surprising amount out of the timber cut through the table slot. The lower cabinet pickup becomes almost redundant, this leaves more available air for below table and importantly some above table pickup.

    For the manufacture, implementing dust pickup like this would likely be an expensive and somewhat difficult design problem, especially considering the need to allow for tilting the table and the structural integrity needed for supporting the cast iron table carrying some heavy timber with a relatively small lower frame area. The pickup would likely need to be on the outside of the BS cabinet and would have to be easily removable for blade changes and lower guide adjustments, and either adjustable in some way or need a separate changeable pickup for when tilting the table.

    As has always been the case, it's up to us, the owners, to come up with a solution and one that does not restrict us when using our BS. As I said at the start, I feel that I've been a bit too harsh with my criticism over BS manufactures and their DC solutions, especially considering the problems they face when dealing with costs, design constraints and what the new BS purchaser will accept or more importantly - pay for.

    Thoughts, flames, tar and feather?

  16. #90
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    In another thread I mentioned trying a smaller cyclone on "ONE" of the exit ports of my 3HP dual bag dust collector, this was to test the loss compared to dust bags having done only a few hours of small bowl turning.

    You can see the testing Lappa is doing on his 2HP DC here: The Generic 2HP DC

    On this DC, the main exhaust from the impeller housing splits from 160 mm into two smaller square connections, each equivalent to around 135mm round.

    My thoughts are that as I'm only dealing with 50% of the flow rate in each exhaust port, a smaller cyclone would be less lossy that when it's connected at the input to the DC and flowing air from the main 150mm feed line, I tested this before and the loss was crazy at over 4"

    Why do it? I posted before that I cannot afford to purchase a big cyclone, and I'm no longer able to fabricate one. However I can build a small simple cyclone and I have room for TWO in place of the twin DC bags in the External DC enclosure.

    The loss of flow through the dust bags from turning two small bowls on the Lathe (including sanding) is around 1.3 inches of vacuum and 500ma of current, but it will get down to a loss of 3.4" and 1.5A.

    Although dust collection is still effective @ 1.3" loss, I can hear and feel the reduction in flow rate, by the time a 3rd bowl is turned the flow is getting too low for my liking. So with the reduction in vacuum and current as a starting point I removed one set of bags.

    DC - all bags connected and fully seasoned from sanding and turning two small bowls.

    7.6A and 4.2" of vacuum at the lathe intake through a 150mm bell mouth.

    Bags on one side were removed: 8.32A and 5.4" of vacuum. Other side still has dirty bags.

    Bags on one side replaced with a Cyclone:

    8.1A and 4.9" Vacuum, and the loss through that port will now stay the same regardless of how much turning we do.

    NOTE: The test cyclone set up has a 90deg bend at the exit port of the DC, this is bad for flow, so results could be slightly better.

    I'm hoping to see a similar increase with a second small cyclone on the other DC exhaust port.

    This looks promising, the only thing I need to check is how much dust escapes the cyclone - I'll test that with a particle counter in the next week. Next is to install it correctly and do another test, the cyclone has 150mm ports in and out, it's small enough that I can fit two in the external DC housing in place of the dual bag set up.

    Fingers crossed that further testing confirms my hopes for this, if output is pretty clean then I'll make a second cyclone and say goodbye to cleaning dust bags.

    I realise that I miss out on the advantage of large object protection for the impeller by not sucking through a cyclone on the intake side, but tests have revealed that individual removable screens on the bell mouth intakes are not as lossy as first thought, so no big deal for me.

    As it is now, with the cyclone on one port and slightly dirty bags on the other, it's back to that nice intake roar at the lathe, even with a second blast gate open (don't normally do that), but it was hopeless if I did that with both sets of bags after a short amount of wood working.

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