finished my build

[wannabedivin]

I finally got around to finishing the build.  Not pretty, used what I had around the shop.  Any way I built it 8 inches tall, bucket size is 20 inches in diameter.  I am using 4 inch pipe that plugs into the  inlet box which is rectangle (8 inch tall  by 6 inch wide and about a foot long).  the four inch pipe plugs into the top of the inlet box.  The outlet tube is about 2 1/2 inches above the baffle.  I can tweek the outlet and the inlet if I need to.  So as far as performance goes I put about 15 gallons of sawdust (way faster than a tool could generate) through the unit and about one gallon made it to the dust bag.  not the 100% I was hoping for but much better than it was. Does anybody have any suggestions on where I could tweek it to get better collection?  I also want to thank everyone on this forum for the help. 

[galerdude]

Any pictures?

[retired2]

I finally got around to finishing the build.  Not pretty, used what I had around the shop.  Any way I built it 8 inches tall, bucket size is 20 inches in diameter.  I am using 4 inch pipe that plugs into the  inlet box which is rectangle (8 inch tall  by 6 inch wide and about a foot long).  the four inch pipe plugs into the top of the inlet box.  The outlet tube is about 2 1/2 inches above the baffle.  I can tweek the outlet and the inlet if I need to.  So as far as performance goes I put about 15 gallons of sawdust (way faster than a tool could generate) through the unit and about one gallon made it to the dust bag.  not the 100% I was hoping for but much better than it was. Does anybody have any suggestions on where I could tweek it to get better collection?  I also want to thank everyone on this forum for the help.

Your inlet box is four times the area of your 4" inlet pipe, and because it is 6" wide it allows the waste stream to get close to the outlet pipe.  So, I suspect you have a lot of bypass.  I would put a baffle in you inlet box that tapers the box from 8"x6" at the 4" pipe to 8"x 2" where it enters the separator.  You might need to experiment with this a little.  Make sure the baffle is placed eccentrically, i.e. so that it forces the air stream to the outermost wall.  All the taper should be on one side.  Let us know how that works out.

[tvman44]

No experience here but common sense tells me 8" x 2" would be a much better choice and is what I am planning to do whenever I get around to building a top hat.  :)

[wannabedivin]

I will give it a try tonight and post the results

[retired2]

I will give it a try tonight and post the results

You might want to take the inlet modification a step further.  You have essentially built a double high separator, i.e. the chamber is twice the height of the inlet pipe diameter.  To take better advantage of that you might want to put a floor in the inlet box so that it is only 4" or 5" high, not 8".  If you do that first, the the baffle that I suggested that you install to taper the width would have to be a little wider at the mouth.  The area at the mouth should be slightly larger than the area of the 4" pipe.  So, you should be shooting for something around 13-15 sq. in.

One other thing you should try to do is repair the separator wall so that it is smooth and concentric.   A 6"x8" opening is a pretty large gash.  When you reduce the inlet to 4.5"x3" or something near that, you should "skin" over the dead space.  Otherwise, you are going to have a lot  of performance robbing turbulence.  In fact, your current opening is so large it may also be causing excess turbulence.

Since you didn't provide any photos or description of the rest of your build, I'm assuming it follows normal guidelines, i.e. drop slot sized and placed correctly.

[wannabedivin]

I had to order another cable for my camera.  Anyway here is the pciture.  The inlet was 6W X 8H. I ran about 15 gallons of sawdust and about 1 gallon made it throught to the dust collector.  The tornado was perfect and almost all the dust went down at the 3/4 mark.  Based on comments I readjusted the inlet tube to be 2 1/2W by 8H.  Perfect seperation but the CFM was severely diminished.  Based on other comments I added false floor in the inlet tube angled correctly.  New measurement is 4 1/2W by 5H.  In this variation the dust does not hug the sides and it takes for ever for the dust to drop.  Since it takes so long the fines stay suspended and almost 100% of the fines went on to the dust collector,  Looking for any advice

[retired2]

I had to order another cable for my camera.  Anyway here is the pciture.  The inlet was 6W X 8H. I ran about 15 gallons of sawdust and about 1 gallon made it throught to the dust collector.  The tornado was perfect and almost all the dust went down at the 3/4 mark.  Based on comments I readjusted the inlet tube to be 2 1/2W by 8H.  Perfect seperation but the CFM was severely diminished.  Based on other comments I added false floor in the inlet tube angled correctly.  New measurement is 4 1/2W by 5H.  In this variation the dust does not hug the sides and it takes for ever for the dust to drop.  Since it takes so long the fines stay suspended and almost 100% of the fines went on to the dust collector,  Looking for any advice

Frankly, I'm a little surprised it is not working better, but I do have two thoughts:

First, I wonder if everything is air tight?  If you are getting air leaks, especially between the separator and the waste drum, you will have an updraft in the drop slot, and that is disaster.  As I recall you are using a shop vac.  Shop vac's typically have high static pressure compared to dust collectors.  That means they will suck air through a pinhole.  In fact, the high static pressure will suck open a joint you may think is sealed. 

Secondly, your baffle is very thick, it should be thinner.  In fact, the thinner the better.  What I would suggest as a possible fix, is undercut or chamfer the underside edge.

[wannabedivin]

I am using a 1500 CF dust collector and I did rabbet the underside of the baffle so it is about 1/4 thick along the edge.  I was wondering about the barrel to separator seal. I bought some foam weather stripping last night and will give it a try.  Looks like I am going to have to build another one with the inlet on the other side to work with current dust collection configuration.  Do I gain anything by using a double height?

[retired2]

Do I gain anything by using a double height?

Depends who you ask!   

I should probably add that it may also depend on the material you are separating.

[wannabedivin]

Mostly table saw and planer.  Very little fines

[wannabedivin]

Went out an took another look.  If you look at the photo the inlet tube is very large and it is heavy.  It was pulling the front down and lifting it off the barrel in the back.  I added weather stripping and repositioned till level and ran  the test again.  100% improvement.  Still tweaking the outlet tube.  Thanks for all the advce.  Now that I learned from my mistakes, the next build should be about perfect.

[retired2]

Went out an took another look.  If you look at the photo the inlet tube is very large and it is heavy.  It was pulling the front down and lifting it off the barrel in the back.  I added weather stripping and repositioned till level and ran  the test again.  100% improvement.  Still tweaking the outlet tube.  Thanks for all the advce.  Now that I learned from my mistakes, the next build should be about perfect.

Given your poor results, I would have bet money on a leak under the baffle.  However, you can't afford a leak anywhere in your system, no matter how small.  I can't emphasize that enough!

Given your waste material, you should get very good results with a single or double high separator.  I don't think the double high will hurt, and it might help, so if you have the vertical space go for it.