J. Phil Thien's Projects

Rcox,

In my setup I have the blower directly above the top hat.  So really the longest pipe in the system during the testing was only about 6" long and I have similar result as yours.  I also looked at the Oneida super dust deputy.  I did get their mini dust deputy for my vacuum and there is a fairly significant amount of sucction loss with the deputy as well, although not as much as my DC setup. So I think it's just the nature of the beast; to get separation there must be a loss in suction/CFM.  I knew this going in, just didn't realize how much.

I was amazed how well it separated all the sawdust and junk I threw at it.  Nice work Phil!

Well I just finished my build and honestly I am a little disappointed.  The separation is simply amazing but there is too much loss of suction.  I might have messed up something in my build?
I would say the loss is almost 50% just by feeling the suction at the inlet.  It sounds like the air is too turbulent in there.  I also measured the amps of the unit to see what the loads were like.

Motor is rated at 17 amp (3hp 220v)
Just the blower nothing connected I got a reading of 17.8 amps
Connected with the baffle and no plumbing 11.3-11.5 amps

- Pipes are all 6"
- slot is in correct position
- top pipe is 3" down into top hat
- I took trash can off and duck taped the slot just to see if it was due to a leak down there, it wasn't

So what do you think is wrong?  ( or is it normal to have that much loss)

- the diameter is 19 1/2 but the height is 11" perhaps it would be better to make it shorter? Less turbulent ?
- I made the direction of spin for the separator the same as the direction of the impeller, correct?
- the inlet to the separator is square and at 4.75 x 4.75 is slightly smaller in area than the 6"
- I used the existing dust collector can to save time but I might have been better off custom building it

Thankfully my DC has its own little outside room so fine dust is not an issue.  If I cant find a solution I will just throw the dc in there and use it as it was intended.

Any ideas?  Havent givent up on the baffle yet, that separation is just amazing.

Thanks



Sorry no pic, can't figure out how to add them with my iPad

Hi Dave, nice shop!

I have the exact same dust collector as you and I just completed a top had for it.  Only problem is i find that there is too much loss of suction.  Did you notice a big difference in suction with and without the baffle?

Thanks

Thanks Phil, I had it backwards.  Glad I posted the question.

Hi, just finishing up my top hat build but I have a question.  What distance should the top pipe be from the surface of the baffle?

My can is roughly 19 1/2 diameter, 11" tall and the duct size is 6".  Motor is 3hp.

I thought I read someplace that it should be 2x the duct diameter from the surface of the baffle?  Is this right?  So in my case the tube would go down to 3" or the surface of the baffle.

Thanks

Quote from: retired2 on September 20, 2011, 07:35:12 AM
First, I would be hesitant about making modifications from which there is no return.  What happens if it doesn't work and then you have to build a top hat?

I bought this DC used cheap and I can't really use it the way it is, so either way it's going to be modified.  I bought it for the motor and blower.

Quote from: retired2 on September 20, 2011, 07:35:12 AM
Rectangular and square duct is not as efficient at moving air as round, so HVAC designs usually take that into account and upsize transitions from round to square or rectangular.  I don't remember the amount, but I think it is about 10%.  So, when I designed my rectangular inlet, I increased the total square inches by about 10% from the 5" round pipe.  Is this critical?  I suspect not even the least bit since the inlet is very short.  I just did it because I had the freedom to make my inlet size and shape anything I wanted it to be.

This is what I see as the main advantage of building my own.  I would think that a tall rectangular inlet would introduce the dust along the wall nicely.

Does the height of the top hat play a big role?

There are lots of successful builds with 2hp motors usually with a canister filter.  With a 3hp motor and no filter there would be more airflow.  So with the added airflow, do I need to adjust the dimensions of the typical 2hp top hat?  Or maybe the same size would work just fine and perhaps spin a little faster and in theory separate better.  I might even need the extra resistance to prevent the motor from drawing to many amps as a result of no bag.  I guess it will be trial and error. 

Have I missed a post with someone that built a 3hp top had direct vent?

I will start by building a very basic one using the collector can and see how it works.  Might be all I need

Thanks for the reply

Hi, Great forum!

I am getting ready to build a top hat/vent outside for my 3HP double bag.  Planning to build something similar to Retired2's build (nice job!).  But I was looking at one of the cans from my dust collector and it would be a heck of a lot easier to use that instead of building one.  I would flip it over so the ring is above or cut it out.  It even has a square inlet :)

Duct size 6" = 28 square inch area
square inlet 5"x5" = 25 square Inch area
ID 19 1/2"
Height: 11" but modifiable as per your suggestions

So what do you think build from scratch or try and adapt this one?  It would be easier to use the DC but if it's worth starting from scratch I will build it

Questions
- does the baffle have to be level with the entrance to the chamber?
- is 19 1/2 ID big enough for that 3HP
- I'm sure I'll have more....

Thanks for your help!