Modding your 1-stage DC for cleaner filters (Workshops)

[Phil Thien]

So a while ago I posted my separator design that uses a special baffle to optimize separation and reduce scrubbing. I noted that it could be used for 1-stage DC's, too.

David Romano modified his Jet DC1200 with the baffle and is reporting his results. He gave me permission to quote him and place a pic or two here:

To test the effectiveness of the baffle, I did something that I thhought would normally clog the canister. Having previously milled alot of Ipe and then cleaned the pleats of the canister the best I could, the inside of the canister was clean and yellow in color. So I took a 1x6 pine board, 5 feet long and milled on the jointer from a thickness of 3/4" to only 3/16". It made alot of white shavings that should be very easy to see.

After milling the board, I carefully took off the canister expecting it to dump a bunch of sawdust on my shoes, but I was amazed that there was hardly a spec of pine sawdust in it!

I told David I'd be posting here so hopefully if anyone has any questions he can help answer them.

More information about the separator baffle design can be seen at:

[Mike Goetzke]

Phil - this is excellent! It's exactly what I asked about in you original thread on this subject:

Quote:
Originally Posted by Mike Goetzke
Phil - great design and persistence!

I have a Jet DC with a canister on the top and bag on the bottom. I swear that if I clean the fine dust particles from the filter pleats and they fall into the bottom bag that they almost immediately find their way to the top again. Maybe a baffle like yours could be added to help reduce the lower bag turbulence which causes the small debris to always find it's way to the top while still having enough turbulence above the baffle to separate the dust from the air.

Mike

Mike, you need two: (1) Above the input that has a 7 or 8" hole centered in it. (2) Below the input, shaped as in the baffle on my page.

Of course, the input would have to be designed so it puts the debris into a circular motion already. I'm not an expert on single-stage collectors, but most of the ones I've seen and played with seem to do this.

Give it a shot, it substantially reduces the fines going into the filter.



I still don't understand what you mean in #1 above. Also, I would like to have more details on orientation, how it's mounted, what height is it mounted...

Thanks for sharing,

Mike

[Phil Thien]

#1 is the funnel that is normally part of the ring. I only called attention to it because I once ran into a very old, cheap DC that didn't have this donut/funnel. It is possible, I think, that the unit was shop made.

99.99% of single-stage DC owners will only need to add my baffle. It should be spaced approx. an inch or so under the bottom of the inlet. The larger radius should be underneath the inlet.

I've included a third picture from David's implementation that shows another angle.

BTW, David used 3/4" MDF, and screwed through the sides to attach his baffle. An alternative is to use dowel nuts with normal 1/4" machine screws (Phillips head):

http://www.woodcraft.com/family.aspx?familyid=1045

My local hardware store carries the dowel nuts.

To prevent the ring from distorting when you tighten the machine screws in the area where the baffle is held back from the inside edge (in the drop zone), you can make a spacer using plastic tubing with a 1/4" I.D.

[Bob Aquino]

Interesting. I have a PS dc250 that I retrofitted with a Wynn filter about 6 months ago. I find that it does build up some dust in the pleats. On this design, if I get it right, its got a 1.5" gap, 240 degrees around, and the 120 degree part is flush to the side of the metal. Is that where you are securing it or is it being secured all 360 degrees. (Where its catching shavings?) Does it reduce flow to the collector at all? Any issues using plywood over mdf?

[David Romano]

Interesting. I have a PS dc250 that I retrofitted with a Wynn filter about 6 months ago. I find that it does build up some dust in the pleats. On this design, if I get it right, its got a 1.5" gap, 240 degrees around, and the 120 degree part is flush to the side of the metal. Is that where you are securing it or is it being secured all 360 degrees. (Where its catching shavings?) Does it reduce flow to the collector at all? Any issues using plywood over mdf?

Bob,
It has about a 1.25" gap, but this is not exact. A good test would be to try different gaps. I am securing it with 3 screws along the flush part and just as a precaution, with 1 more in the center of the open part using a longer screw. Tighten the screw only until the gap is even otherwise you'll distort the metal. I don't know if this last screw is even needed. Obviously it will catch shavings, but the flow restriction and impact on separation is negligible. As far as the impact the the baffle has on airflow, I'm sure it is significant for a DC. For a shop vac, it doesn't matter because they can absorb the static pressure loss.

More testing has to be done to fine tune the separation. Of course there will be a limit to it's separation efficiency. MDF's dust is finer than plywood's, so you can test and draw your own conclusion. It's not a cyclone, but it's good enough for most people.

As I mentioned in my original post, it occured to me that there is a wedge shaped gap between the DC ring and the bottom of the canister. Before the baffle, when I took the canister off, there would always be dust left on the the DC ring. Do you see the same thing? We need to make a smoother path for the air going into the canister.

David

[Phil Thien]

Interesting. I have a PS dc250 that I retrofitted with a Wynn filter about 6 months ago. I find that it does build up some dust in the pleats. On this design, if I get it right, its got a 1.5" gap, 240 degrees around, and the 120 degree part is flush to the side of the metal. Is that where you are securing it or is it being secured all 360 degrees. (Where its catching shavings?) Does it reduce flow to the collector at all? Any issues using plywood over mdf?

The gap is 1-1/8" for 240-degrees of the baffle. The baffle is flush to the edge of the ring for 120-degrees. The 120-degree section should be placed under the input, as is designed to prevent the incoming airstream from causing too much turbulence in the bag.

The baffle is secured in at least three places. One on the 120-degree section, and two on the 240-degree section. I used some 1-1/8" long spacers between the ring and the baffle in the 240-degree section to accomodate the gap.

[Mike Goetzke]

Alright, I need to make one of these this weekend. One (of several, I'm sure) question. I see David made his out of 3/4" material. Is there any advantage to fabricate it from thinner stock?

Mike

[Bob Aquino]

Bob,
It has about a 1.25" gap, but this is not exact. A good test would be to try different gaps. I am securing it with 3 screws along the flush part and just as a precaution, with 1 more in the center of the open part using a longer screw. Tighten the screw only until the gap is even otherwise you'll distort the metal. I don't know if this last screw is even needed. Obviously it will catch shavings, but the flow restriction and impact on separation is negligible. As far as the impact the the baffle has on airflow, I'm sure it is significant for a DC. For a shop vac, it doesn't matter because they can absorb the static pressure loss.

More testing has to be done to fine tune the separation. Of course there will be a limit to it's separation efficiency. MDF's dust is finer than plywood's, so you can test and draw your own conclusion. It's not a cyclone, but it's good enough for most people.

As I mentioned in my original post, it occured to me that there is a wedge shaped gap between the DC ring and the bottom of the canister. Before the baffle, when I took the canister off, there would always be dust left on the the DC ring. Do you see the same thing? We need to make a smoother path for the air going into the canister.

David

My cannister conversion was a bit different, I didn't have a 360 degree flush surface to mount the cannister so I made a donut that sits in the top of the metal base and the cannister sits on top of that. Consequently, I don't have any buildup of dust on the inside edge of the cannister. It has a mildly spiraled surface that pushes the airflow down to the lower bag. When its running, it looks like a tornado, but maybe they all do that.


My concern with this design would be how much if any flow could be lost. Not sure if you already answered the question, but do you have a feel for whether the flow is about the same or noticeably different with the baffle in the collector? Have you thought about something like a neutral vane, or some type of extension from the inlet into the housing that directs the air flow farther downward and possibly limits the turbulence in that area of the collector?

[Bas Pluim]

I made mine out of 5/8" particle board, same material I used for the lid for my trashcan. It doesn't need to be that thick, just make sure it doesn't flex too easily. 1/2" plywood, or even 1/4" MDF should do fine.
I have to remove the lid (and baffle) to empty the can, so any reduction in weight makes it easier to lift it. But, that's not much of an advantage - the can is heaver than the lid anyway. I suggest you use whatever material you have on hand, cheap is a real advantage!

[David Romano]

Alright, I need to make one of these this weekend. One (of several, I'm sure) question. I see David made his out of 3/4" material. Is there any advantage to fabricate it from thinner stock?

Mike

In theory, probably. In practice, doubtful.

[David Romano]

My concern with this design would be how much if any flow could be lost. Not sure if you already answered the question, but do you have a feel for whether the flow is about the same or noticeably different with the baffle in the collector? Have you thought about something like a neutral vane, or some type of extension from the inlet into the housing that directs the air flow farther downward and possibly limits the turbulence in that area of the collector?

There is no doubt that there is less airflow, but I have not measured it. I would like to very much, but I can't afford a pitot tube right now. In fact, I'm out of a job in one week. We're having massive lay-offs here.

This is very subjective, but there is not a "noticeable difference" in airflow. But, it could have dropped from 900 cfm to 700 and it still seems like "alot of air flow"

I did have a neutral vane. I took it out. It seemed to me that it may hurt separation by providing a hard surface for the dirty air to collide with and get deflected out and into the canister. Maybe with the baffle, the air is clean at that point anyway. But without the baffle I bet that it is still quite dirty. Maybe the vane was responsible for alot of my canister clogging problems.

All the talk about the neutral vane is that it help airflow, and I have no reason to disagree with that, but there is never a mention of separation efficiency. It would also depend on the design of the DC. An air ramp would be good match for the vane, as it seems your PS sort of has, but my Jet DC and most others have a simpler design.

I realize that questioning the neutral vane is tantamount to heresy at this point in any discussion about dust collection, but so what. I would like to see someone prove the effect of the vane on separation, with and without the baffle.

David

[joe milana]

I don't understand how the dust gets down below the baffle. Can someone explain?

Thanks!

[Phil Thien]

I don't understand how the dust gets down below the baffle. Can someone explain?

Thanks!

Gravity. Incoming airstream with suspended dust is spun in a circular motion. The contact with the outside edge of the can causes the dust to slow down, whereupon gravity can pull it down into the can.

BTW, in case you didn't notice, the baffle does have a "drop zone" in it where there is a gap between the baffle and the can for the dust to drop.

[joe milana]

I see, but what if there is a high volume of dust/chips? ie: planing or sweeping a large pile of dust/chips into a floor sweep? Is there a problem with clogging?
I am trying to decide between a single stage dust collector and a cyclone. I would like to save the $$'s if possible, but if a cyclone will pay for itself in the long run with filter cost savings, I will go that route.
Cyclones seem to have more effective filtering. ie: <1 micron as opposed to the oem canisters at about 2 microns, or do I need to invest in a filter upgrade?
Thanks for all the helpful input!

[Steve Sawyer]

I haven't tried Phil's baffle inside the DC unit, opting instead for a two-stage setup. That said, though I can contribute the following to the discussion:

• Thickness of the baffle - I cut two baffles from 1/8" particleboard, and glued them together to make a baffle about 1/4" thick.
• Clogging - the advantage of the two-stage is that the first stage gets all the large chips (especially those produced in high volume from operations like jointing and planing) into a more easily emptied drum, allowing the DC system to deal with the fines. I have had no problem whatsoever with clogging of the baffle from these kinds of high-volume chips.
• Baffle attachment - threaded rod extending vertically through the upper "donut" shaped baffle and into the lower baffle with the 240-degree slot work very well, and do not impede the airflow at it's most critical point, around the perimeter of the central drum.