[Dave Paine]

If you just want to empty a bag, why not put the Thien baffle inside the dust collector.

I did this. Very simple installation. I only get small amount of dust in the cannister. Much easier to clean out, and less often.

http://www.woodworkingtalk.com/f32/making-dust-collector-cone-separator-44695/

 

[Dave Paine]

so i'm looking at your pictures dave, and i only see a bottom plate, is that correct?

Yes, if your plate reference is the baffle, it is simply installed in the bottom of the steel middle section of the dust collector. Just 3 screws.

Being on the discharge of the blower should result in less losses of pressure drop.

It does mean I am not using my baffle to as a pre-separator. I do not suck up large chunks of wood, but the blower impeller is very beefy and can withstand quite an impact.

From your photo shop it looked like you also were not looking for the Thien baffle to be a pre-separator.

This view is of the underside. This will be facing down when installed.

 

[Dave Paine]

I'm not terribly worried about what I suck up, like you it's only sawdust and chips and the occasional small chunk which have always clanked right through. So did you leave the cone you put in in place? Or nothing between the baffle and the top hole up to the filter?

Sorry to confuse. I started with the intent to make a cone similar to the Jet design, but then changed to just the Thien plywood baffle. In hindsight this was so much simpler and I feel more effective.

 

[Dave Paine]

So what keeps dust from coming in and going straight up the hole to the filter?

A very good question, seriously, not trying to be funny.

The air coming into the central collar is spun around at a high velocity.

The velocity creates a lot of centrifugal force. The bigger the particle, the more the centrifugal force will act upon the particle, forcing it to the outside of the central collar.

The baffle essentially acts as a one way stop. The air and the particles on the outside are pushed down into the lower bag. There is no twisting vortex in the lower bag to drag the particles up into the cannister.

This may sound like magic, but it really works.

When I remove my cannister there is no dust on the central collar. The flutes of the cannister have only the smallest particles, which are too light for the centrifugal force to trap.

 

[Dave Paine]

Ok.....so I pulled out the pan and built a thien baffle in the dust collector. Every time I pulled the bag to replace it, the filter was full......so here is my attempt....anyone see anything wrong with it?

Looks alright to me.

This is what mine looks like.

The baffle as it would be during use. I was using 1/4in thick plywood, and intending to screw through the drum, so I glued on three pieces of scrap to increase the thickness so I did not split the wood. I was aiming for the screws to be above the channel of the ring which holds the plastic bag in place.

The view from the underside of the drum. My baffle has narrower spacing than yours. I looked at Phil Thien's site, then made my guess at how much of a slot to cut.

I expect both of ours will work. Ideally I would have tried various slot widths, but that would have taken more time and effort than I wanted.

The main objective of the baffle is to prevent the normal "whirlwind" in the bottom bag which carries debris into the upper cannister. With the baffle you will see the debris swirling in the bottom, but in a downward direction. It does not come back up.

I did not need two ports at my dust collector, so I removed the "Y" and cut out a plywood donut to fit in the collector with a hole which is a tight fit for my fitting.

 

[Dave Paine]

I’m a little confused as to what the width of the slot is. I saw a video where the guy said he read it was supposed to be 1 ¼”, but yours looks wider. Does it matter?

You can always go back to the fellow who started this, Phil Thien.

http://www.jpthien.com/cy.htm

"The bottom view of the baffle. The baffle is cut such that its large diameter is the same as the inner diameter of the can measured at approx. 3" down from the rim. 120-degrees of the baffle is left at this larger diameter, while 240-degrees of the baffle is reduced in diameter by 2.25" (forming a 1.125" "drop slot"

My slot may have been 1 1/4 - 1 1/2in. I recall I was constrained by the piece of plywood I was using. It was not big enough to get to the slot size Phil Thien used.

I think if the slot is too large, more of the debris will escape up into the cannister. If the slot is too small, it will get choked and not allow the debris to fall into the bottom bag.

 

[Dave Paine]

I’ve been thinking about the support for the center of the slot and I think I’m going the use a steel rod all the way through the housing keep the slot as unobstructed as I can.

The baffle needs to be place below the inlet. I think the collar you show in the sketch would block all airflow to the slot causing all the debris to go upward.

You do not want to impede the airflow under the cone and between the cone and the baffle.

I am only using 1/4in thick plywood, and have this attached at only 3 locations. You mention using 1/2in plywood, even stiffer. It will only need a few points of attachment to the outside of the DC middle section. I glued on scrap blocks to span the slot gap, then screw in from the outside. Very simple.

 

[Dave Paine]

You just need the baffle, no cone or bucket in the hole, which would block the airflow to the upper cannister.

The air rotates at high speed in the middle section of the collector. The baffle keeps the heavier particles in the lower bag by preventing a swirling action in the lower bag.

If the lower bag is plastic, like my dust collector, all of the air needs to flow out of the top through the cannister. The air has to flow through the "funnel" in the middle. If you block the funnel then you will not get any airflow through the collector.

 

[Dave Paine]

Thanks for the clarification. I am not sure if such a modification would help or hinder.

I would be very interested in a with and without such a modification comparison of performance at the tool port and at the machine, although I am not expecting you to spend the time. More than a bit of a hassle.

 

[Dave Paine]

You seem to have more than your fair share of bad luck.

Sorry to hear about the MDF breaking. I appreciate the frustration of the time you spent on it. You may be able to salvage by gluing a piece of plywood across the break. I do not expect glue on the break without reinforcement would help.

Running the unit without the bottom bag should work, especially if you are trying not to use the top cannister. Without the bottom bag there will be no air pressure to push air into the cannister. You should feel more suction at the tool port though.