J. Phil Thien's Projects

Your scaling calculations appear correct for the assumptions you made, however other considerations may be needed.  Does the diameter need to change of the top hat? I haven't seen any info on 8" piping so you may need to experiment. The distance from the 8" pipe to the tangential inlet is narrower and could affect dust collection. Also, an 8" trunk line for a vacuum system requires a large amount of HP to keep the air moving at 45 mph to keep saw dust airborne.  Too slow and dust will collect in the 8" line. The advertised CFM on dust collectors is with no load and you can't trust them for your system design.  Scaling my HF 5" existing piping system would mean that I would need a 4-5 HP motor with an 8" line to keep dust from accumulating in the trunk line. The velocity of the air at the 4" intakes would be much higher than needed. The pressure losses of the diameter, length, number of elbows, and number of lines affect the HP requirements as well.  The top hat design is made for small DIYers with small systems.  The size of this system appears to be more of a commercial system.  Some DIYers with big shops will use a few portable smaller systems with a top hat rather than this large system with a lot of piping.  If you haven't already, look at all your needs and what designs can meet them before you go much farther. Also, small affordable cyclones are now available which were not available when Phil proposed this design.  If you need more information, there is a huge amount of info on the internet on any of these subjects with simple searches. 

Hello all, 

My plans to build a tophat seperator got stalled a few years ago.  Finally, I'm starting this project back up.  I have a homemade impeller blower based on a Pentz design with 8" inlet and outlet.  I have most likely overlooked it, but I could not find any other posts or examples of others making any tophats this big.  Anyway, at this stage in my planning I wanted to make sure my dimensions for the top hat are big enough to handle the volume of air moving thru that 8" pipe. I am going to use Retired2's build as a reference to compare sizes. Here are my numbers, Please let me know if my logic looks sound:

(for those pedantic math nerds I will be rounding number on occasion.)

Retired2's tophat:
5" ports with 22.5 diameter which is 6" tall
  5"diamiter= (2.5*2.5)*pi=20sq"
  22.5" diameter = (11.25*11.25)*pi=397.6sq"
  397.6*6=2386ci
  The ratio between the area of the port and the volume of the tophat is 119:1  (397.6/20=119.3).  (I know I am comparing area to volume, but I think it works for what I am trying to accomplish)

My tophat:
8" ports with 22.5" diameter with a height of ???
   8" diameter= (4*4)*pi=50sq"
   using the Ratio above 397.6*50 gives me a target volume of 5950ci
   I then take the Volume and divide it by the area of the tophat:  5950/397.6=15"
   Now I have my height at 15"
   the rectangular port size should be 50"/15"=3.3"

There for I think I am going to make my tophat 22.5" in diameter by 15" tall with a port transitioning from a round 8" pipe to a square that is 15" tall x 3.5" wide.  Does that sound good or do some of you see anywhere I really went astray? 

I know everyone here like the eye candy so here are some pics of the outlet pipe I created a few years ago when I started this whole thing.  It is an 8" thick-walled PVC pipe with a small bell mouth stretched into it.







The thick wall only let me stretch it a small amount, but I think it is enough to help.  Some of the whitepapers only showed the bell mouth curving about that far.

Thanks, Lance

Coming very late to this, and so may no longer be relevant. There is an enormous amount of IP (current and now in public domain) related to separation techniques that has come out of the pulp and paper industry. It would very much surprise me that any ideas discussed here would not be rejected due to prior art. However, a design patent (vs utility) could be pursued - that's like a recipe though, change one little element and there would not be infringement.

https://www.woodworkforums.com/f200/generic-2hp-dc-171247/2#post1659193

Woodworkforums.com>Hand tools & machinery>Dust extraction>The generic 2HP DC>post number 21

See if that works

I got a "page not found" on that link?

On the HF dust collector, the outlet of the impeller housing is about 6x4 inches, then gets choked down to a 5 inch round house. Not a huge choke, but a choke none the less. On an Australian woodwork forum I read about someone that replaced the round hose with a rigid adapter that matched the dimensions of the outlet on the impeller housing.

https://www.woodworkforums.com/f200/.../2#post1659193

Has anyone on here tried that, and if so, HOW, and what did you think of the end results?

In our experience the best location is up in front of the blade. This is because while the blade is starting the cut it is buried into the material, therefore any chips or dust are mostly confined within and mostly send downwards. This is also the reason of a second pickup under the blade. Once the cut blade starts its downward travel, the debris is shot forward (against the operator) and the pickup at the front is in the right place to catch them. We use an integral Thien baffle for dust collection.

Bear in mind that no dust collection system is a 100% efficient. In the case of table saws, you'll find that a rip cut so shave just 1 or 2 mm from its witdth will create a lot of dust that the pickup will not be able to collect. This is because the blade is just grazing the workpiece and dust flies everywhere.

You may find interesting a visit to our website www.aw-thinkbold.com. Coincidentally, the first article shown covers the same problem with our blade cover design and free plans to build it. If you're fitting this cover to an American style  of saw, you'll have to devise a suitable way of mounting it. American saws rarely have a riving knife and their blades usually raise following an arched path. Our design incorporates an original system that raises the blade vertically along with the riving knife. For more details it's interesting to have a look of the Reader's projects and, of course, to the videos and pics.

It it possible to add a riving knife to a blade that basculates on a fixed point. I know because I did it in my prototype. However, it's no mean task. If you're interested on how it was done, supply your mail address and I'll send you a white paper on the whole development of the saw with pics on its many parts and the riving knife installation.

Hope this helps!

Can anyone point me to research on the best location for the hose port on a blade guard.? I've seen some placed at the rear of the guard, others focused on the front of the blade. I'm trying to decide which way to go.

Anybody try the Wen impeller as an upgrade for the HF?
Thanks

Hello all

After seeing a video on you-tube, i am going to take a shot at building a dust collection system for my shop (i do almost exclusively metal work). Sanding and grinding make a hell of a mess and i would love to deal with it, but unless your willing to crank out thousands for one designed for metal your kind of screwed (most are for wood and using them for metal is a fire ball waiting to happen)

My plan is to use a Thien style collector power by a large metal blade blower (similar to the ones used in a house furnace) built inside a fully sheet metal housing. My issue before starting is trying to figure out the min airflow (CFM) i am going to need to make it work as the metal and stone dust is a lot heavier than wood dust. Love this site and have learned a bit so far but have yet to locate the info i need (doesn't mean its not here, i just joined and there is a LOT of info on this site). I'm hoping someone can help or point me in the right direction to be able to figure out what CFM i will need so I don't waste time and money using a blower not strong enough.

Thanks in advance, and now back to hunting the site