J. Phil Thien's Projects

Interesting concept.  Would you do this on both ends of the slot or just the end farthest from the direction of rotation?

Quote from: retired2 on February 19, 2018, 06:40:02 AM
Your outlet neck is pretty long so it might need some stabilization, but I can't recall anyone mentioning vibration of the outlet.  The turbulance and noise I was getting until I added the air straighteners was coming from the blower housing.  I'm sure it was the effect of the turbulent air on the blades of the impeller.  I never noticed any vibration or noise from the outlet pipe, but mine is very short compared to yours.  And mine is connected to the blower with a few inches of flex hose, so that should isolate the blower from the separator from the blower or vica versa.

It's possible that your stiffener could act on the spinning air and cause some turbulance that would not be beneficial.  I think I would try to avoid it, but build your separator in a way that allows you to add it later if needed.  Another potential problem is long shavings getting hung up on the stiffener.  My outlet neck has a pretty good layer of fines stuck to it from use over time, so waste does get attached to even a smooth pipe.

Good points, thanks!

At this time, I plan to have my separator connected with hard pipe, not flex hose.  I don't have any 6" flex, and it doesn't seem feasible to buy some just for a few inches for this connection.  I plan to have slots for the motor housing attachment to the frame that the system will be mounted on.

This will allow for height adjustment of the outlet pipe in the separator and also for disassembly for any needed maintenance or upgrades, such as possibly upgrading the impeller to the rokon 60-200 that many have done to the HF units like I have.

I will build it without that stabilizers to begin with and see how it runs.   I think one thing that might help mine is that the spin in both the impeller and the separator are both in the same direction. 

I read in retired2's thread that the reason for the air straighteners was to reduce turbulence in the outlet pipe.  I plan to do the straighteners and have purchased 2 light tubes 1 for T12 and 1 for T8 to use for this part of the project.  However, since my top-hat will be 24" internal with a 10" inlet, making it more that double height, I though that vibration of the outlet pipe especially if only supported at the top could be an issue. This would be affected by it's connection to the impeller housing as well as the long length inside the separator.

To reduce this, I have an idea of stabilizer rings extending down from the top.  The inner surface of the rings would be lined with foam tape to support the outlet tube, which would reduce vibrations and harmonics of the pipe and negate any rattling caused by wood on metal.

This would also still allow removal of the outlet pipe for inspection and cleaning, as well as it would not be permanently attached to these rings so that while I experiment with height of the bell-mouth above the baffle I wouldn't need to completely open up the separator.  Here are some pictures:

This is the whole separator as I have it drawn in SketchUp.  I will be using metal for the tube, but I've made the external part of the metal a blue-glass color so it can be seen through. There will also be vertical supports around the outside, I just haven't drawn them in yet.

Please forgive my crudely drawn inlet.  ::)


Here it is without the metal tube..


This is just with the Top to show how the stabilizer rings will be attached.  As you can see, there is no bell-mouth, as I didn't see the need to take the time to draw that in SketchUp.



This one shows you a different view, with my inlet rings in place, and how I plan to mount the top-hat in the stand that I'm building for the full DC system.  I will also be changing the orientation of the vertical braces so that there isn't one in line with the inlet.


So, what are your thoughts on stabilizing the outlet pipe in this fashion to reduce vibration and noise from harmonics?

Thanks for the advice @retired2.

I'll go with the larger Rubbermaid can, but I think I'll only go buy the Brute if the one I have looks like it's going to give me issues. 

The dimensions you show in your thread seem to be about the same, so I'll build mine to work on the bigger diameter.  BTW, yes I do have a bellmouth.

I have plenty of casters around in the shop, so I'll build a platform that the can will sit on and self center, and then a cam-lift to raise it to the separator housing.

Just for consideration, you may regret only going with 4" piping.  Based on my research it may not give you enough CFM.  The HF Collector is 5" at the impeller body, but many threads recommend enlarging that to 6" for better volume.

So I've been working on this and looking around in my shop and have driven myself to another impasse.

I have a Fiber Barrel that I feel will be sufficient enough in capacity for the amount of woodworking I will be doing, however it is rather narrow in circumference.  It's only 17.5" in diameter.  With this, I've been considering stepping up the diameter of the Thein separator to about 18.75" and using the rings that attach to the barrel lid, to step up in diameter to get to the separator size.  The lid is metal and would be cut to act as the baffle.

My other option is a Rubbermaid Roughneck trash can that would allow me a separator diameter of about 20.5".  My hesitation on this is that I don't want to implode the plastic trash can.  I know it's not likely, but the concern is there, especially if I am careless and forget to open a blast gate before starting the DC system.

Is there a rule of thumb on diameter of the separator to the inlet/outlet sizes?  Both will be 6" on mine.

Any help and opinions are greatly appreciated.

Quote from: retired2 on January 26, 2018, 12:36:36 PM

Quote from: alan m on January 26, 2018, 08:40:54 AM
not really a hard and fast rule. but it make sense.
as the separator height increases the outlet has to get longer to get the benefit .
so keeping to half the inlet height above the baffle makes sense

It may indeed work just fine, I had just never heard that rule of thumb.  It does seem to produce reasonable locations for all but extreme cases.  In fact, as my tests show the performance is not terribly sensitive to position.  And ironically the best airflow was achieved when the bellmouth was closest to the baffle. It might be that in that position the air flow into the bellmouth was smoothed by the baffle.

Interesting points made here, I may try this as wel.l.. I'm contemplating making the outlet pipe long enough to experiment with flow, thank you for discussing this in my  thread as it has given me additional food for thought as I proceed with my build.

Thanks all for the feedback and I'll try to keep this thread updated with my progress on the placement.

Quote from: retired2 on January 25, 2018, 07:14:47 AM
There is test data in a table in the thread for my build, just below this post.  It shows slight air flow differences between positions, but not much.  As I recall separation did not change very much.  I think there might be a photo in that thread showing the attachment of the bellmouth to a straight section of pipe.

Ordinarily, I would recomment putting your bellmouth flange at or slightly below the bottom of the inlet.  However, you have a pretty tall inlet so I don't know if that is reasonable.  Is your double high 20" tall?  If so, my advice would be ok.

I think I may have seen your chart.. I also seem to recall seeing something about putting it below the inlet.  That seems to make sense to reduce by-pass.

I have metal that I'll be using for the sidewalls. It's 24" x 36" and I have 2 to make sure I have enough to make the top-hat.  I can do up to 24" with this arrangement, and probably will so I don't have to worry about an uneven cut.  I have the room as well, so height is not an issue.

I guess I should have mentioned that I'll be using the HF 2 HP collector and increasing the inlet size to 6" to match the ducting.  I may do the impeller upgrade later, but I'm going to try it as-is to begin with.

I know the rule of placement for a standard outlet in a single height tophat is 1/2 the height of the inlet centered on the inlet.  How does this change with;

(1) Using a bellmouth
(2) a double height, or higher top-hat separator?

My inlet is a 6" metal duct that transitions to a 4"x10" rectangle.  My outlet is a spun bellmouth that I'm going to have to attach to the outlet pipe, as the bellmouth is only about 4" high anyhow.  The circumference will be about 22" as that's the dimension on the fiber-barrel that I have for my collection bucket.

Let me know if you need any additional information.

Quote from: kmerkle on June 08, 2017, 01:17:32 PM
Where did you get the bellmouth?

I'll second that request.

Hi, I'm Alan.   ;)

I have been looking to step up my DC setup.  I recently bought the HF 2HP separator,  but haven't set it up yet.  I have the small Dust Deputy hooked up to my shopvac and it works OK, but I want a more permanent solution for the several machines I use with DC.  Especially as I'm building a router based CNC and that will create lots of sawdust.

I want to build a Thein separator and will probably have a few questions, so here I am!