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  1. #1
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    Default Service trench in slab????

    Just signed up today to build a new house/shed combination and had to do up a proposed layout to work out where I want the doors and to make sure I can fit all my existing toys and goodies in there. No matter how I lay it out, I still find myself wanting to avoid having the DC hoses and power leads coming from above or across the floor. I haven't spoken to the concreter yet but I want to try for a trench with maybe lift-off sections of gang-plate level with the slab covering a trench about 150mm x 150mm square from the edge of the slab to the south or east where the DC will be in a cubicle outside the shed. It would only have to pass by the Hammer and go to the big bandsaw so it wouldn't be much more than about 5m long. Thinking this would reduce the length the DC has to pull by about 5 metres of up and down for overhead ducting.
    Looking for ideas - Has anyone out there ever done or contemplated this sort of set up ??????
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    Updated 9th of June

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  3. #2
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    I have a 2 m section of under floor DC ducting to my TS. It's one of the better things I have done in my shed and would do more of it if I ever did it again.

    Just be aware that if you are going to use 150 mm ducting you will need more than a 150 x 150 trench.

  4. #3
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    Quote Originally Posted by BobL View Post
    I have a 2 m section of under floor DC ducting to my TS. It's one of the better things I have done in my shed and would do more of it if I ever did it again.

    Just be aware that if you are going to use 150 mm ducting you will need more than a 150 x 150 trench.
    I was thinking of doing the same at one stage but I know myself well enough to realise I will inevitably change the layout of the gear now and then. I like the idea of being able to sort of 'pop-up' power, air and dust extraction any where near a given line through part of the shed. I was thinking of using 5" hose and because it would be reasonably close to the DC I should get much better extraction than I do currently. Just got a couple of ideas so I'm off to Google a little
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    Updated 9th of June

  5. #4
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    I ran 2 lines of dust collection duct to the centerline of the shop floor and positioned floor mounted electrical boxes near them with 120v and 240v in each. I'm in the USA so your electrical will be different, but the idea is the same. I haven't regretted the layout.

  6. #5
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    Quote Originally Posted by TTIT View Post
    I was thinking of doing the same at one stage but I know myself well enough to realise I will inevitably change the layout of the gear now and then. I like the idea of being able to sort of 'pop-up' power, air and dust extraction any where near a given line through part of the shed. I was thinking of using 5" hose and because it would be reasonably close to the DC I should get much better extraction than I do currently. Just got a couple of ideas so I'm off to Google a little
    What size DC do you have?

  7. #6
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    Quote Originally Posted by BobL View Post
    What size DC do you have?
    It's a common 2HP job - not sure of the cfm rating - inherited it from the old man. It does the job OK if I'm hooked up close enough but my main line is currently only PVC storm pipe (about 100mm inside diameter) and by the time it goes up the wall, across the shed and down to the machine through 4" flex, it just can't clear the jointer properly ( The Hammer is all 5" ports). Pretty sure if I can run 5" straight across the floor (ie: just below it in the trench) it should work well.
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    Updated 9th of June

  8. #7
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    Quote Originally Posted by TTIT View Post
    It's a common 2HP job - not sure of the cfm rating - inherited it from the old man. It does the job OK if I'm hooked up close enough but my main line is currently only PVC storm pipe (about 100mm inside diameter) and by the time it goes up the wall, across the shed and down to the machine through 4" flex, it just can't clear the jointer properly ( The Hammer is all 5" ports). Pretty sure if I can run 5" straight across the floor (ie: just below it in the trench) it should work well.
    Despite the manufacturers claims the CFM rating on the generic 2HP DC is about half what they claim and that is with clean bags and no more than about 3m of ducting. Overall they are well below any sort of reasonable spec for dust collection especially, as you say, at collecting over any sort of distances of ducting.
    Upgrading the ducting size to 5" won't help much because it poorly designed and so doesn't generate the volume flow that can take advantage of bigger ducting.
    There is also the possibility that the air speed in a larger pipe may be slow enough to allow the sawdust to fall out of suspension and it will further reduce the flow.

    You may want to take a look at this thread (https://www.woodworkforums.com/showth...generic+2HP+DC) where I discuss/demonstrate the ways of improving the performance of this DC.

    Sooner or later anyone is serious about dust control will need to go to a bigger DC and 150 mm pipe. That's why I figure anyone doing under floor service trenches should look at being able to accommodate the bigger pipe. It's no big deal to make the trench a bit bigger during construction but no one wants to get out a jackhammer afterwards.

  9. #8
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    Had a quick look at the thread (way too much there to read the whole thing!!!). Have noted the valid points you have made about the trench but for the DC's capacity\efficiency, I think I'll just upgrade to a bigger/better DC down the track.
    Waiting to meet with the concreter and see if he has any ideas on how to create the trench - I'm sure he would have done this sort of thing before. I've got my own plan of how to form the trench but he might have an easier (read 'cheaper') way I hope
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    Updated 9th of June

  10. #9
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    Quote Originally Posted by TTIT View Post
    Had a quick look at the thread (way too much there to read the whole thing!!!). Have noted the valid points you have made about the trench but for the DC's capacity\efficiency, I think I'll just upgrade to a bigger/better DC down the track.

  11. #10
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    TTIT, have you spoken to the Builder/Concreter yet......I think the trench idea is good but may involve a fair bit of extra dollars.

    The concrete trench may involve better reo configuration. Slab can get away with just sheets of reo mesh in a continuous plane when it is a flat floor but once you introduce steps in the slab there may have to be more substantial reinforcing bar around the trench as it introduces weak points.

    I think it would be more than just making the F35 (I think) wrap around the trench. I am not a concreter but I would be interested in the Builder's response to the extra work involved in the trench.

  12. #11
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    Here is an idea for the placement of your "trench" under the slab. If you are using, as BobL has suggested large diameter PVC ducting, I would lay the pipe "under the slab" by digging it into the ground/fill then just bring up a short piece of tube, the same size as the under ground piece, where ever you want. Doing it this way you are only penetrating the 100mm of concrete. If you were to make a box then pour concrete around it...yada, yada, yada, more expense and time. Just bury the tube with its penetrating vertical bits and then lay the plastic sheet, reo mesh that would have to be cut to allow the penetrations. Cover, of coarse the penetrations, then pour the concrete. Easy piesy

    The only other thing I would implement is a way to clear the pipe under the concrete should it get blocked. If you are building on a rise you may be able to make use of the slope to get at the pipe from natural ground level. Just something to think about
    Just do it!

    Kind regards Rod

  13. #12
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    Quote Originally Posted by chambezio View Post
    Here is an idea for the placement of your "trench" under the slab. If you are using, as BobL has suggested large diameter PVC ducting, I would lay the pipe "under the slab" by digging it into the ground/fill then just bring up a short piece of tube, the same size as the under ground piece, where ever you want. Doing it this way you are only penetrating the 100mm of concrete. If you were to make a box then pour concrete around it...yada, yada, yada, more expense and time. Just bury the tube with its penetrating vertical bits and then lay the plastic sheet, reo mesh that would have to be cut to allow the penetrations. Cover, of coarse the penetrations, then pour the concrete. Easy piesyThe only other thing I would implement is a way to clear the pipe under the concrete should it get blocked. If you are building on a rise you may be able to make use of the slope to get at the pipe from natural ground level. Just something to think about
    pretty much what I did, but I'm on level ground. the one time I got a serious blockage it was a bit of hassle to clear, but if it isn't too bad I can hit it with a blast of compressed air in the intake and send the chips or whatever flying on to the separator.

  14. #13
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    Quote Originally Posted by chambezio View Post
    Here is an idea for the placement of your "trench" under the slab. If you are using, as BobL has suggested large diameter PVC ducting, I would lay the pipe "under the slab" by digging it into the ground/fill then just bring up a short piece of tube, the same size as the under ground piece, where ever you want. Doing it this way you are only penetrating the 100mm of concrete. If you were to make a box then pour concrete around it...yada, yada, yada, more expense and time. Just bury the tube with its penetrating vertical bits and then lay the plastic sheet, reo mesh that would have to be cut to allow the penetrations. Cover, of coarse the penetrations, then pour the concrete. Easy piesy

    The only other thing I would implement is a way to clear the pipe under the concrete should it get blocked. If you are building on a rise you may be able to make use of the slope to get at the pipe from natural ground level. Just something to think about
    Quote Originally Posted by bridger View Post
    pretty much what I did, but I'm on level ground. the one time I got a serious blockage it was a bit of hassle to clear, but if it isn't too bad I can hit it with a blast of compressed air in the intake and send the chips or whatever flying on to the separator.
    The problem here guy's is that I want other services in the trench as well like power and compressed air and want them to exit the trench wherever I please. I'm prone to 'redecorating' so having a pipe pop up in a fixed location isn't what I want (but may have to settle for if the cost of the trench is too high )
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    Updated 9th of June

  15. #14
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    Quote Originally Posted by TTIT View Post
    The problem here guy's is that I want other services in the trench as well like power and compressed air and want them to exit the trench wherever I please. I'm prone to 'redecorating' so having a pipe pop up in a fixed location isn't what I want (but may have to settle for if the cost of the trench is too high )
    a trench covered with a plank has other disadvantages. unless the fit is perfect wheeled carts will hang up there, and it will have a load limit which maked moving heavy things a pain. a few dust ports well distributed plus a box of fittings and hose works best for me. cluster that with floor mounted electrical outlets and air hose on an overhead reel and you can easily pisition a mobile machine in most any location in the shop

  16. #15
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    Just a couple of thoughts...

    A raised timber floor over the slab would be easy underfoot and offer whatever configuration of DC, AC and air you can imagine. You'd need to alter the FFL of the slab of course.

    Alternatively, a swing gantry with DC, AC and Air could get you to almost any location (albeit, only one location at a time)

    John

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