J. Phil Thien's Projects

In case you haven't seen this thread, others have used the blower inside the 735 to drive a separator, without the use of a vacuum.  See:
http://www.jpthien.com/smf/index.php?topic=809.0
or search the forum for dewalt 735 and you may find others.

Sounds like you plan to run the vacuum with the planer since the separator also will serve an auxiliary vacuum hose. 
With proper design, chips shouldn't accumulate in the separator and
the intake and outlet need to be above the baffle.

I like the idea.  Will there also be a blastgate on the planer discharge, to be closed with the aux. hose is in use?
-Dan

Could be the hose itself.  Some hoses that look like vacuum hoses but are intended for water (swimming pool filters, sump pump discharge, etc.) really scream when attached to a vacuum cleaner.

Yes.
Would it work on lint?  not sure.
The bigger question is do you really want to dump the water vapor from drying your laundry into your garage?  Generally you want that moisture to be dumped outdoors, not into the garage, basement, or the attic.  I would vent the dryer to the exterior.

Quote from: R.True on April 26, 2015, 12:10:02 AM
Don, take a look here for a pretty small yet very effective 5gallon separator.

And at the bottom of that page, Look here for a CFD simulation of the 5-gallon bucket separator:
http://www.symscape.com/blog/cfd-analysis-of-homemade-cyclone

The images for "Clipped Internal Pressure Iso-Surfaces" and "Clipped Internal Velocity Iso-Surfaces" show a section of the outlet without a bell-mouth that are interesting.  You can also see the turbulent flow through the short radius 90° elbow in the outlet airstream in a many of the images. 

Perhaps the author could be persuaded to do other simulations.... ;)

Quote from: ducky911 on July 21, 2014, 06:05:29 PM
It seems to me that the bell mouth is encouraging the air in a bigger diameter that may be dusty.

Good point.  We have been using the bell mouth shapes that are available in the marketplace, but they may not be the best shapes for our application.

3" outlet pipes sound a bit on the small side, even though you will have two.  This will reduce your airflow.  I saw a significant increase in airflow when I changed from a 6" to an 8" outlet pipe in an application similar to yours (except for the 1.5 HP blower)

I think raising the outlet & bellmouth should be your next move.  The velocity at the outlet is high, so you don't want that so close to the baffle where dust has slowed down. 
What do you have to lose?  Nice work, BTW.

You'll have to remove the spiral ramp, since it will force both air and dust underneath the baffle.  The spiral design may have made sense if you had filters above and below the ring, which is the way my Penn State collector was originally.  With a Thien baffle and a sealed container below the ring, all air exits above the ring, so the ring just increases turbulence. 

Be careful removing the ramp.  When you break the spot welds between the ramp and the ring, it is possible to create small holes in the ring.  There may be a photo of my rig in a recent thread....

"I would have thought the entry at the top would be most effective as the velocity of air entering the chamber would keep the particles against the wall. If there were 'dead' air above the inlet, would this not cause more turbulence with more chance of particles being held in the chamber longer than necessary? "

The CFD model showed particles were slowed down by the top when the inlet was tight to the top.  Slower particles are more likely to be pulled into the outlet airstream.  Air is probably better (more slippery) than a hard surface.  Less friction means higher velocity. 

I don't think there is any "dead" air in a top hat - it is all spinning around.  The slowest spinning air is that which is up against a surface.  At the side walls and the baffle, this helps dust to drop. 

Possibly the most beautiful top hat renderings ever!

The design represents the current thinking for a 1 1/2 H top hat. The recent thread on CFD raised some interesting ideas, however, and Phil's follow-up questions/thoughts pointed the way to what may prove to be a better design.

The first idea is that there is a benefit to moving the inlet away from the top of the top hat.  CFD modeling showed that particles were slowed when the inlet was tight to the top, and that separation improved when the inlet was lowered slightly from the top.  Phil speculated that it may be best to have the inlet closer to, but not tight to, the baffle rather than at the top.  Since we want the particles to end up at the bottom, why not introduce them closer to the bottom?  Air is more agile and will find its way out. 

The second idea is that the outlet may perform better if it is flush with the top of the top hat.  CFD modeling (with a high inlet) showed there was less pressure drop with a flush outlet.  The modeling held airflow constant, but in our systems, less pressure drop means higher airflow rates and higher velocity, so separation should improve.  Would lowering the inlet diminish the benefit of a flush outlet? I doubt it, but CFD could answer that question.  (hint, hint)

Combining these two ideas could be the foundation for the next generation of top hats.

I believe Phil raised the issue of a curved entry and the benefits it would offer in encouraging particles to move towards the side before entering the central ring.  Makes sense to me.  Seems you would get some of the benefit of a scroll inlet without the complicated construction.  This is also related to the issue of an off-center outlet that both Retired2 and Phil have mentioned.  In the CFD thread, replies #16 and 17 show why an off-center outlet should improve separation - you are moving the outlet away from the region where particle-laden air is entering the ring and has yet to be forced to the side.  Perhaps a curved inlet transition from round to rectangular, combined with an off-center outlet, would be a good combination. 

Regarding the OP question of dimensions, I'm not sure about the the radius of the curve, but I would think the piece needs to mate with a 20" diameter top hat.  The 32 gallon Brute has an inner diameter of 20" and is commonly used. 

The image below shows a curved inlet on the left and a typical straight inlet on the right.   Might as well curve it!

Quote from: phil (admin) on April 28, 2014, 07:26:17 AM
Did you measure with the baffle but without the chimney?  The baffle alone shouldn't cause a tremendous hit to CFM on a SS ring adaptation.  The chimney will, though.

However, the chimney will help with separation quite a bit.

No, but I will, maybe with the plywood opening rounded over to ease the exiting airflow.  Given the plywood ceiling, my rig is more like a top hat than a typical ring adaptation.  But you're right - it's all about the ceiling/chimney.

This table shows some of the motor measurements, and the relationship between watts amps and power factor is worth reviewing.  As AC motors become unloaded, the power factor drops, so if all you can measure is amps, be aware that the change in airflow is greater than the change of amps indicates.

First I measured the airflow with a 10' section of 5" steel duct, using a 6" to 5" reducer.  All subsequent measurements were made with a 10' section of 6" steel duct. Measurements were made 54" from the open end of the duct with a pitot tube and a digital manometer.  Motor measurements were made with a kW meter. 

Changing from a 5" to a 6" duct did not increase the airflow.  Next I removed the filter and the airflow increased slightly.  The filter is oversized and un-seasoned, so this made sense.  Next, I removed the baffle and ceiling altogether, installed a new bag, the filter and tested the airflow, which almost doubled. 

My baffle was causing a 50% drop in airflow, so before I put it back together, I decided to increase the chimney diameter to 8".  This improved airflow quite a bit lowering the impact of the baffle to a 33% drop versus the dust collector without a baffle. 

Last month I made some airflow measurements when I changed the bag under my dust collector.  It is a 1994 vintage Penn State DC-2 with a 1.5 HP motor; the blower has a 10.5" impeller, 6" inlet and 5" outlet.  I removed the original spiral ramp when I installed the Thien baffle last summer.  The baffle is ¼" masonite, sold for use as a whiteboard.  Since there is no cone in the ring, I added a ¾" plywood ceiling with a large coffee can chimney.  The can is 6" diameter and extended about halfway from the ceiling to the baffle.