Bagging the sawdust/chips (keeping the bag in the barrel)
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The Shop Fox cyclone I have has an aluminum insert that fits inside the drum.
Grizzly sells one, but it's not cheap.
Grizzly sells one, but it's not cheap.
Most Cyclones that come from the factory with a bagging system will implement one of two approaches.
1) An insert drum or frame set within the bag. These models may or may not ship with an external drum. The frame or drum insert remains IN THE BAG and must be removed before the bag can be discarded. My JDS Cyclone-II shipped with such a frame and it was just a pain in the butt -- and a mess -- to remove from a bag full of sawdust and wood chips!
2) A bag lined canister (think your household trashcan) with a vacuum line that draws a greater vacuum between the bag and canister. The vacuum is designed to be greater than the vacuum within the bag region, this prevents the bag from becomming inverted and -- along with it's contents -- from being sucked into the impeller and clogging the exhaust filter(s).
The reason the vacuum line is needed is due to the fact that it is almost inevitable that some air will, over time, find its way into the voids between bag and canister (just the act of inserting a new bag will leave behind trapped air). Over time this opens an avenue for even more air to find its way in both during the cyclone's run as well as each time the unit is cycled. Without an internal frame set within the bag itself, the air trapped between the bag and canister will lead to the bag becoming increasingly inverted during cyclone operation due to the vacuum within the bag, eventually drawing the bag and its contents into the impeller and contaminating your cyclone's exhaust filter(s).
I can speak from experience that frames inserted within the bag are a royal pain in the butt. Since I don't need to bag my waste (I recycle it into flower beds) I replaced my original JDS (Cyclone-II) 40-gallon frame with a reinforced Rubbermaid Brute trashcan (33-gallon) with two sets of windows cut into the trashcan to indicate fill level. If I were to need to bag my trash now, I would opt for the vacuum line solution since that is a heck of a lot more convenient -- just insert the bag, fold top of bag over top of canister, and then simply lift bag back out for disposal.
The vacuum can either be externally generated (such as a simple diagphram vacuum pump -- think in terms of a reversed aquarium pump) or it can be drawn from the cyclone itself with a vacuum line installed at a point of restriction prior to the impeller (i.e. a venturi) -- the actual difference in pressure needed is quite small. If you attempt to create such a vacuum line yourself, verify that a differential vacuum actually exists by connecting a diffential manometer to your vacuum source AND the waste canister (without an installed bag). You will want a fairly sensitive differential manometer since you are likely to generate less than 1" of differntial vacuum (if going the internal venturi route). The CFM requirements for this vacuum are quite small unless you have significant leakage into the void between bag and canister, in which case the CFM of vacuum must exceed the CFM of leakage by a safe margin.
If you do opt for the "frame within bag" solution, make certain you take the canister outdoors before you try to lift the frame out -- and wear a dust mask or respirator -- because you will likely disturb a lot of fine dust in the course of removing the frame. BTDT
Whichever way you go, ordinary trash bags are too weak for the abuse they receive under vacuum. Only heavy-duty, heavy mil, trash bags should be used. Make certainthe bag is sufficiently larger than the canister, or frame, -- you want the bag to be able to thoroughly hug the canister or frame without stretching and enough height to spare to allow you to fold the top edge over the exterior of the canister, or frame, and lock the bag in place with a suitable ring clamp.
HTH
1) An insert drum or frame set within the bag. These models may or may not ship with an external drum. The frame or drum insert remains IN THE BAG and must be removed before the bag can be discarded. My JDS Cyclone-II shipped with such a frame and it was just a pain in the butt -- and a mess -- to remove from a bag full of sawdust and wood chips!
2) A bag lined canister (think your household trashcan) with a vacuum line that draws a greater vacuum between the bag and canister. The vacuum is designed to be greater than the vacuum within the bag region, this prevents the bag from becomming inverted and -- along with it's contents -- from being sucked into the impeller and clogging the exhaust filter(s).
The reason the vacuum line is needed is due to the fact that it is almost inevitable that some air will, over time, find its way into the voids between bag and canister (just the act of inserting a new bag will leave behind trapped air). Over time this opens an avenue for even more air to find its way in both during the cyclone's run as well as each time the unit is cycled. Without an internal frame set within the bag itself, the air trapped between the bag and canister will lead to the bag becoming increasingly inverted during cyclone operation due to the vacuum within the bag, eventually drawing the bag and its contents into the impeller and contaminating your cyclone's exhaust filter(s).
I can speak from experience that frames inserted within the bag are a royal pain in the butt. Since I don't need to bag my waste (I recycle it into flower beds) I replaced my original JDS (Cyclone-II) 40-gallon frame with a reinforced Rubbermaid Brute trashcan (33-gallon) with two sets of windows cut into the trashcan to indicate fill level. If I were to need to bag my trash now, I would opt for the vacuum line solution since that is a heck of a lot more convenient -- just insert the bag, fold top of bag over top of canister, and then simply lift bag back out for disposal.
The vacuum can either be externally generated (such as a simple diagphram vacuum pump -- think in terms of a reversed aquarium pump) or it can be drawn from the cyclone itself with a vacuum line installed at a point of restriction prior to the impeller (i.e. a venturi) -- the actual difference in pressure needed is quite small. If you attempt to create such a vacuum line yourself, verify that a differential vacuum actually exists by connecting a diffential manometer to your vacuum source AND the waste canister (without an installed bag). You will want a fairly sensitive differential manometer since you are likely to generate less than 1" of differntial vacuum (if going the internal venturi route). The CFM requirements for this vacuum are quite small unless you have significant leakage into the void between bag and canister, in which case the CFM of vacuum must exceed the CFM of leakage by a safe margin.
If you do opt for the "frame within bag" solution, make certain you take the canister outdoors before you try to lift the frame out -- and wear a dust mask or respirator -- because you will likely disturb a lot of fine dust in the course of removing the frame. BTDT
Whichever way you go, ordinary trash bags are too weak for the abuse they receive under vacuum. Only heavy-duty, heavy mil, trash bags should be used. Make certainthe bag is sufficiently larger than the canister, or frame, -- you want the bag to be able to thoroughly hug the canister or frame without stretching and enough height to spare to allow you to fold the top edge over the exterior of the canister, or frame, and lock the bag in place with a suitable ring clamp.
HTH
The Shop Fox cyclone I have has an aluminum insert that fits inside the drum.
Grizzly sells one, but it's not cheap.
I looked at the one Grizzly sells, but $89.95 is a little more than I want to spend on this project.
Thanks for that detailed explanation, Ethan. Not sure I understand all of it.
Let's see if this would create a vacuum between the barrel and the bag. Drill a small hole in the 8" inlet to the cyclone and insert a piece of metal pipe, say, 1/4". Do the same near the bottom of the barrel. Run a piece of 1/4" plastic tubing from the inlet pipe to the barrel pipe. Would that work?
What about just weighing down the liner. Put the trash bag in the barrel and throw in a few pieces of scrap wood. Just enough weight to keep the bag down until it starts to fill with chips.
Let's see if this would create a vacuum between the barrel and the bag. Drill a small hole in the 8" inlet to the cyclone and insert a piece of metal pipe, say, 1/4". Do the same near the bottom of the barrel. Run a piece of 1/4" plastic tubing from the inlet pipe to the barrel pipe. Would that work?
What about just weighing down the liner. Put the trash bag in the barrel and throw in a few pieces of scrap wood. Just enough weight to keep the bag down until it starts to fill with chips.
What I did was to buy a sheet of 1/8" plexiglass and cut it to size. The size for one dimension was the inside height of my drum and the size for the other dimension was the circumference of the inside of the drum. Install the bag, roll up the plexiglass and insert it inside the plastic bag. Slowly let it expand. To remove, sort of wiggle the insert while lifting it up. Once it's out, empty the cyclone drum.
Be sure to sand all the edges and round the corners so you don't rip the bag.
Be sure to sand all the edges and round the corners so you don't rip the bag.
If your cyclone is like mine, there will be a roughly 12" (or thereabouts) inlet tube befor the impeller, I believe (but can not promise) that you will get an adequate vacuum if you secure your tube an inch or two down from the impeller inside this tube. You will need to securely seal the openining in this inlet tube as well as the opening in the outer wall of your cyclone if you go this route. I suspect you will have enough of a vacuum differential this way, I just can not guarantee it. You don't need much differential, you just want a hair more vacuum between the canister wall and bag then there is within the bag itself. The tubing can be plastic (even simple vinyl tubing) so you don't have to limit yourself to metal piping unless you prefer such.
In the bag housing, you will want to cut some MDF (or plywood) roughly the same diameter as your canister and cut narrow (say tablesaw blade wide) grooves over the area and secure the end of the tube so that it draws a vacuum within this space. The grooved bottom will ensure that the bag does not get sucked into the tube plugging off the vacuum (think of the MDF bottom as being similar to a vacuum press platen). The MDF might not be necessary, but it is good insurance. The MDF would be placed within the canister, not the bag.
You can probably get away with placing weights in the bag, but you will probably find that you need atleast a few pounds of weight to achieve the desired result -- and if there are sharp edges on your weights they could punch holes in your bag as the bag is pulled tight around them until it become sufficiently full with waste.
I like the plexiglass (acrylic) idea, though I would prefer lexan (polycarbonate) because polycarbonate does not shatter explosively if bent too much. This said, it still means having to pull something out of your bag of waste and I really hated doing that with my original cyclone waste bin -- but then again, like I said, I did not really need to bag my waste since I recycle it in flower beds so the extra effort of removing a frame had no positive payback for me!
It seems like the vacuum pipe idea would be a lot more effort and expense than I am looking for at this point. Setting it up would be a guess for me, since I don't have the proper tools to make the needed measurements.
I'm going to experiment a little with weight in the bottom of the bag and see if I can get that to work. If not, I will start looking for sheets of polycarbonate or Plexiglas to use on the inside of the bag.
So, where does one buy large sheets of polycarbonate/Plexiglas, etc.? Looks like i will need a piece approximately. 33" x 72+-".
I'm going to experiment a little with weight in the bottom of the bag and see if I can get that to work. If not, I will start looking for sheets of polycarbonate or Plexiglas to use on the inside of the bag.
So, where does one buy large sheets of polycarbonate/Plexiglas, etc.? Looks like i will need a piece approximately. 33" x 72+-".
I know that Lowes and HD sell up to about 2'x4' (or threabouts) and you will want a sheet on the order of 0.1" to 1/16" (0.0625") thick so that it bends easily. If you go with lexan (polycarbonate) for safety, you could rivet two sheets together quite easily (just use backup washers) -- locate the backside of the rivet towards the interior so that only the smooth side (the rivet head) comes in contact with the bag. Rivets have considerbly more holding power than threaded screws. If you do not have a riveter (and they are handy) then short bolts with backup washers and locknuts (nylon insert type) can be substituted. Locate a rivet/bolt every 3-4" along the seam. Afterwards, check the rivets or bolts for any burrs and smooth them as needed.
For that matter, to make lifting out a bit easier you can make a piece a bit longer than the circumferance and rivet/bolt the two ends together so that you can pull it out as a simple cylinder/tube without the spring action of a loose sheet.
Don't foget to secure the loose top of the bag to either the insert, or the exterior of the outer canister, with either suitable tape or a band clamp. If the top of the bag is left to flap around loosely within the cyclone it will disrupt the cyclonic action a bit which could negatively affect performance.
Best of luck, let us know how your experimentation goes.
PS - For an inexpensive differential manometer, lookup U-tube water differential manometers. They consist of nothing more than inexpensive clear tubing bent into a vertical U shape with a column of water trapped within the U (add dye for greater visibility if you wish), the two ends are then attached to the two pressure zones you wish to test. It is easier to maintain the U-shape with the two sides kept close to one another (for simple comparison) if the U-shaped portion of the tubing is securely fastened to a board. The end with the lower water column is under pressure relative to the end with the higher water colum, which is under vacuum relative to the other. The inches of differential can be converted into more absolute measurements, though for your purpose all that matters is that a difference can be detected.
If you decide to go with Ethan's method, I wouldn't try to put the tube in the outlet leading towards the impeller; inserting it into the inlet to the cyclone should be fine. But, I would use a 6" piece of copper or aluminum tubing gently bent to 90 deg. so the part inside the inlet is parallel to the air flow and the opening is facing the cyclone body. That will get you a little more suction than just inserting the pipe into the wall of the inlet. You will be getting both static vacuum and a bit better (venturi) vacuum created by the velocity of the air rushing by. Properly shaped it will be even better, but without research, I can't say what the shape should be.
Also, you can line the inside of the drum with a porous material to ensure good distribution of the vacuum around the bag- open weave mat, fabric, etc.
In a perfect world there should be no differential between the vacuum in the cyclone and the drum, and a vacuum line should not be needed, but as Ethan said that rarely happens. Even with a vacuum line you will want to ensure the drum is perfectly air tight- if you have a standard fiber drum, all metal-to-fiber seams should get a coat of sealant and the lid needs to seal perfectly- that will result it better cyclone performance also.*
It sounds like you are not up for major tweaking, and I don't know what kind of cyclone you have, but if it is a DIY unit, the other thing you can do is convert it to a push- through configuration. That will allow you to eliminate the drum entirely so all you need are standard plastic trash bags mounted to the bottom of the cyclone (in a push-through cyclone everything is under positive pressure instead of negative pressure).
* I would completely seal a fiber drum with a coat or two of poly. MDF is often used as a vacuum platen for machining because it is porous!! If thicker sheet of MDF allows air to pass, a fiber drum might too.
Also, you can line the inside of the drum with a porous material to ensure good distribution of the vacuum around the bag- open weave mat, fabric, etc.
In a perfect world there should be no differential between the vacuum in the cyclone and the drum, and a vacuum line should not be needed, but as Ethan said that rarely happens. Even with a vacuum line you will want to ensure the drum is perfectly air tight- if you have a standard fiber drum, all metal-to-fiber seams should get a coat of sealant and the lid needs to seal perfectly- that will result it better cyclone performance also.*
It sounds like you are not up for major tweaking, and I don't know what kind of cyclone you have, but if it is a DIY unit, the other thing you can do is convert it to a push- through configuration. That will allow you to eliminate the drum entirely so all you need are standard plastic trash bags mounted to the bottom of the cyclone (in a push-through cyclone everything is under positive pressure instead of negative pressure).
* I would completely seal a fiber drum with a coat or two of poly. MDF is often used as a vacuum platen for machining because it is porous!! If thicker sheet of MDF allows air to pass, a fiber drum might too.
Thanks Ethan and Alan.
I do have a pop rivet tool and rivets and washers so attaching pieces of lexan together should be no problem. It seems to make sense to go ahead and rivet the ends together into a tube to avoid the spring action, too. I tend to empty the drum when it gets about half full, so that should make it easier to remove the lexan tube. Easier still if it has 'handles' cut into the top.
Alan, my cyclone is an Oneida Super Dust Gorilla, so converting it to a push through system would be impractical, if it is even possible. It has a 55 gallon fibre drum. I haven't done anything to the drum to seal it. I'm sure my DC system has lots of leaks, but it is getting the job done so I'm not to worried about it. One of these days, when I get some 'free time', I may seal up all the joints with something other than metal tape. And I may give the drum a couple of coats of poly. I'm actually glad I haven't done that yet, since I keep moving things around in the shop which means moving the DC duct around.
I do have a pop rivet tool and rivets and washers so attaching pieces of lexan together should be no problem. It seems to make sense to go ahead and rivet the ends together into a tube to avoid the spring action, too. I tend to empty the drum when it gets about half full, so that should make it easier to remove the lexan tube. Easier still if it has 'handles' cut into the top.
Alan, my cyclone is an Oneida Super Dust Gorilla, so converting it to a push through system would be impractical, if it is even possible. It has a 55 gallon fibre drum. I haven't done anything to the drum to seal it. I'm sure my DC system has lots of leaks, but it is getting the job done so I'm not to worried about it. One of these days, when I get some 'free time', I may seal up all the joints with something other than metal tape. And I may give the drum a couple of coats of poly. I'm actually glad I haven't done that yet, since I keep moving things around in the shop which means moving the DC duct around.
We were at Lowes the other day and checked out the acrylic sheets. They had 24" x 30" sheets for $19.95. I would need two of those, so a little over $40.00 plus my time, etc.
LOML tells me "Just get the kit from Grizzly", so I gave that some thought. I just didn't want to spend $90-$100 for that when I could spend it on something else. :tool:
In the meantime the 100 pack of 55 gallon drum liners got here. They are 3 mil garbage bags, so pretty heavy duty. I emptied the cyclone drum and dropped in one of the bags. Threw in a few pieces of scrap wood, maybe 4-5 lbs(?). Turned on the DC and checked to see if the bag got sucked up. Nope. Opened the barrel and checked the bag, no rips or punctures that I could find.
I'll check the bag when I pull it from the drum, obviously, but I think this is going to work out just fine.
LOML tells me "Just get the kit from Grizzly", so I gave that some thought. I just didn't want to spend $90-$100 for that when I could spend it on something else. :tool:
In the meantime the 100 pack of 55 gallon drum liners got here. They are 3 mil garbage bags, so pretty heavy duty. I emptied the cyclone drum and dropped in one of the bags. Threw in a few pieces of scrap wood, maybe 4-5 lbs(?). Turned on the DC and checked to see if the bag got sucked up. Nope. Opened the barrel and checked the bag, no rips or punctures that I could find.
I'll check the bag when I pull it from the drum, obviously, but I think this is going to work out just fine.
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