J. Phil Thien's Projects

I am planning to put together a dust collection system for my bandsaw. (14" grizzly) I am planning on using the ever popular harbor freight 2 hp. I am planning a top hat build with the fan mounted directly on top of the top hat and the top hat inlet at the same level as the bandsaw dust port with all 5 inch duct work. I plan on keeping all duct work as short as possible.  I have a few questions.

1. I don't see too many designs where the fan is mounted directly on top of the separator is there a problem with this design?

2. I will wind up with a fairly short container below the separator. How short of a container causes problems?  Dust port on the band saw is ~ 30" of the floor at the center.

3. I want to also add a Wynn 35a filter and I see 2 options - one is a nano version($177) and the other is a 80/20 blend($115) both appear to be rated the same.  Any reason I should go for the more expensive one?

rough sketch of plan attached

Quote from: clydeone on February 02, 2014, 08:05:38 PM1. I don't see too many designs where the fan is mounted directly on top of the separator is there a problem with this design?

2. I will wind up with a fairly short container below the separator. How short of a container causes problems?  Dust port on the band saw is ~ 30" of the floor at the center.

3. I want to also add a Wynn 35a filter and I see 2 options - one is a nano version($177) and the other is a 80/20 blend($115) both appear to be rated the same.  Any reason I should go for the more expensive one?

rough sketch of plan attached

(1) The blowers are heavy, I think a lot of people try to avoid having to life the blower to empty the drum.  Also, you need something on which to set the blower while emptying the drum.

(2) A short container shouldn't matter too much, other than the obvious (lower capacity).

(3) I think the Nano has the highest MERV rating, but there are plenty of users of the spun-bond and paper filters out there, too.  To the best of my knowledge, the spun-bond is the only washable unit, though I wouldn't tend to wash any of these anyhow. 

If you search through the many posts on this forum, you will find many examples of blowers sitting directly over the separator.  However, every example I can recall has a short section of flex hose separating the two.

In some cases the flex hose allows the separator to be raised to free the waste drum.  In other cases, like mine, the drum is dropped down, but the flex hose allows just enough flexibility to insure the separator and drum are aligned and sealed properly.  As Phil points out blowers are heavy, and if you build a configuration that requires lifting both the blower and the separator, you better plan on using a car jack.

My only other comment is do a search on air straighteners.  Unfortunately, some of the discussions may be buried in threads on a different subject.  However, some of these discussions have been repeated recently. The short version of this discussion is that the performance of a close-coupled separator and blower will suffer if you do not use one.  And to use one, you will need some space between your separator and blower.

DC systems with short runs and very few bends are a good thing, but I think you may be overly concerned.  If you are using your planned build just for your band saw, and the blower is anywhere close by, even with some bends, it will provide all the cfm's and sp you need.  In fact, the bigger problem might be the band saw porting.  Often bandsaws have small ports which restrict the air flow so the DC can't do its job adequately.  I finally took the steel door of my Powermatic bandsaw, and took it to a metal fab shop where they burned a 4" hole in it so I could add a larger port to replace the worthless 2" port that came with it.

Sorry, my intention was to have the waste container drop down in some fashion - either by use of latches or toggle clamps - and have the blower and separator fixed in place.   

And I was also intending in using straightening vanes and a bell mouth in the separator to address those issues as my current design would have the "cyclone" turning in same direction as the fan. 

My bandsaw is a newer unit (circa 2004) and has a 4" port in it.  I was also going to modify it and put a hood directly below the table with a 2.5 duct to it

Glad to hear you have a 4" port on the bandsaw.  I don't know the exact configuration of the Grizzly, but you need to let enough air into the housing to feed that 4" outlet.  My old Powermatic is pretty tight, so to some degree I am starving my newly added 4" port.

An update - wish I had pictures but, I am traveling today and will post some when I get home.  I have cut the bottom and top ring have wrapped it in aluminum flashing.  I have also cut some stanchions and to support and space between top and bottom.  Mine will be a rectangular inlet 6 x 3.25.  Most of the ducting will be plywood.  My design is a bit different as the flashing wraps around the outside of the top piece and inside of the bottom

Pictures showing the trial arrangement of the can, separator and blower.  Still need to build the inlet duct, suction for the blower and the the cart (all in various stages of completion)

Following is my Grizzly 3 HP mounted on top of the TopHat. The intake on the impeller was slightly less than any 6" pipe and I could find a good fit. I took a 6" PVC, split one side, removed the amount I needed to fit the impeller intake, glued the seam and used a metal band to clamp it to the impeller intake. To help ensure an air-tight  fit on the impeller intake I put a couple of layers of Duck Tape on the impeller intake before sliding the pipe on.

Before I put the pipe on the impeller I used it to draw the circle for the cutout in the top of the TopHat.

I used a block and tackle to lift the motor and impeller and placed it on top of the TopHat. The motor and impeller was much to heavy for me to lift.

I used a 2x4 and 4x4 to support the motor/impeller on top of the Thien and on the left side of the motor/impeller you can see it bolted to 3/4" plywood which is bolted to 2" angle iron.