TopHat questions

[jgt1942]

OK I think I'm slowly coming around but I'm surprised as to how long this is taking me and the mental mistakes I've made. Now I'm on a new track. I happen to have a 3' square piece of cabinet plywood that is comprised of two 1/2" pieces that were glued together for a project that never happened thus I'm thinking of using it for the bottom of my TopHat but have a few questions and would appreciate any feedback. 

• The total thickness is 15/16"
• Current plan is to use it for the bottom of the TopHat only, the top will be 3/4" MDF
• This TopHat will be used with my Ridgid shopvac
• I'm going to cut a 22" x 22" for the bottom
• I'm using a 20 gal Brute which has an OD of 19 1/2", ID of 18"

Questions:

• On the very bottom of the plywood which is the cap for the Brute I'm considering routing a 3/8" deep grove where the OD = 20 1/2". ID = 17" thus the 3/4" lip of the Brute has 1.75" track to fit in. Comments?
• Now if I flip the board over I make two circles  where the DIA is 16.75" & 16.25. This is a .25" track that will be routed out .25" deep for my .25" plastic. The inside circle will also serve as the outside circle of the baffle cut. Any problems here?
• The input and output for the TopHat will be 4" but in that it is being connected to my shopvac which has slightly larger than 2" hoses should I just use the same size on the TopHat? Until I get my bigger TopHat built I will be using this unit for all of my tools. At the rate I'm moving this might be quite a while.
• When I start the cutout for the baffle how close to the input should it start:
• Some of the baffle cutouts I've seen has a cutout of 240 degrees, is this correct? What determines how far it raps around the bottom?
• With respect to the input to the TopHat I've seen several different design with shoots of different lengths? What determines how long the shoot is? My current thought is to make it as short as possible. Suggestions?
• How wide should the opening for the baffle be? I've seen designs ranging from 1" to 1.5".

I've been working on this in SketchUp and can post my current model and or pictures to help with the above wording. I'm open for any suggestion.

[Dougp28704]

1. You want to have one of the diameters be a snug fit on the can. Like a Tupperware lid. Some designs fit the OD., Some ID, and I think some fit on both.
2. I don?t think you will be able to bend .25? plastic very easily. I have .125 thick and its plenty strong. I think .094 thick would be fine too.
3. No idea
4. Hard to explain in words. There are many pics of the correct orientation. That is one thing that is very important. Everyone I?ve seen has it the same way.
5. Ditto
6. Not sure what you are calling the shoot.
7. Varies, Phil recommends starting out at 1.125.

One thing I think you are missing is a thin baffle. You are planning on having the bottom be the baffle? Others have done this. But it is recommended to use a thin baffle. Like .125 thick  hardboard. Take another look at my design. Like others, I have .125 hard board supported by the bottom. The drop slot is like an inch or more wider than the baffle drop slot.

[RonS]

1) Make a tight fit to the inside of the can. You should be able to pick up the can & TH using the TH only.
2) ok
3) If your only going to use it with your "ShopVac" just make the inlet/outlet the same size as the SV.
I built my first Thien Baffle, using Phil's original design, on a Ridge SV and have used it with all my tools for over 4 years. I used a 10 Gal can that sits on a small shelf on top of the Ridge SV. It is held in place with a bungee cord. It rolls around on the SV wheels. It works great See First picture.

4) Here is a drawing that shows the orientation of the baffle with respect to the input.  Second picture

5) see no. 4 drawing.

6) If your are referring to the length of the inlet, it doesn't matter.

7) 1 1/8 inch

[jgt1942]

Big thanks Doug

• Ok I can easily adjust the fit for the lid, I'll go for both and test as I make the cut.  I just saw Ron's post and will start with a fit to the inside and give the outside just a small amount (about 1/8") unless I hear otherwise. This is just to make it easy. The Brute came with a lid which I will NOT be using and it is a very snug fit. I can lift the Brute with the lid handle and the lid will not come off.
• Bending the plastic "should be easy" by using a heat gun or Butane Torch to first heat the plastic. This will be new for me but from what I've see a Butane Torch works much faster than a heat gun mainly because the heat is more concentrated and is much hotter. This will be a learning experience for me!
• My current thought is to use 4" and use Kanaduct  which you can twist and reduce the size of on end thus giving you a smooth tapper reduction. For more info see http://www.kanaflexcorp.com/hose_product_detail.php?id=39 I just saw Ron's post and will just use pipe the size of the SV.
• I've added a picture below (not my unit I'm just using it because it shows the area of my concern). OK I just saw Ron's suggestion and will use input and output the size of the SV.
• Ron, your PDF makes it very clear for the starting position of the baffle cut out.
• Ron, your PDF confirms the 120 degrees between the baffle cutout start and end.
• Ron, the inlet length is what I was calling the shoot and I now understand.
• OK 1.125 it is.

In that I'm using a 15/16" thick bottom I was thinking of NOT using the 1/8" thin baffle, e.g. no baffle just the cutout in the bottom board. Should I default back to two 3/4" and use the 1/8" baffle?
Super thanks for the input.

[Dougp28704]

If you decide not to use a thin baffle, Some have added a chamfer around the slot (can side) to kind of achieve the thin baffle benefit.

You can use a heat gun to bend .250 thick plastic I guess, but .125 is plenty thick if you use polycarbonate. You dont need heat to bend it. And you can reposition it. If I build a second one, I will use .094.

Like Ron?s design and mine, the distance to the opening is just a development of the 120? that is symmetrical.

The ?shoot? length. Again, this is a development. The length is determined by how wide your input is. Take a look at Ron?s drawing (middle bottom). His ?shoot length? is a development of the width he chose of 3- 7/8. The length of the sheet metal transition gives the air a chance to be pushed against the outside of separator.

[RonS]

If you look at my bottom panel (lower left), which is 1/2 inch thick, I cut a baffle slot that is about 1 inch larger that the slot in the Thien Baffle. This supports the 1/8 inch thick Thien Baffle and maintains the "Thin" baffle that Phil recommends.

[jgt1942]

OK I missed something in my research, what is the thin baffle benefit?

[Dougp28704]

The main reason I went with thin is because Phil says its better. It?s his design and he has done so much testing. To me it makes sense that debris can fall past a 1/8 wall easier than a 15/16 wall.

[jgt1942]

Doug - OK then I'm back to a design that is much closer to your design.

Most likely I'll not make any additional progress until Tuesday because I need to prepare for a class I'm teaching Monday.

Ron/Doug - again big thanks!

[retired2]

Separator Seal Comments:

When I built my separator, I used the friction fit design employed by a number of other builds.  However, I have since modified that design to solve a number of problems.  The modification is shown in the sketch below.  You may remember the sketch from the long thread on my "rectangular inlet, bellmouth outlet" build.

Here are some of the problems that a simple friction fit can produce:

1) Even a good friction fit is probably not air tight.  In a smoke test, you will likely see that it leaks.  The tops of drums are far from smooth and concentric.  I used a mill file on the top flange of my Brute to make it smoother and flatter.
2) Because plastic and metal cans are not perfectly concentric, they can be a pain to get them to engage the receiving dado.
3) Cutting the dado for a good friction fit can be tricky because it must be cut in two passes.  And unfortunately, you can't test the fit until both cuts are done, and at that point it is very easy to have one or both passes just a little too large or a little too small.  Nevertheless, it can be done if you are very careful.

Hopefully, my modification solves all three of the above problems:

1) It adds a foam rubber seal that presses on the top flange of the Brute or similar can.  If the flange is not perfectly smooth, the foam will take care of sealing the imperfectons.
2) I've added chamfers at the mouth of the receiving dado to guide the top rim of the drum into the slot.
3) I still recommend cutting the dado for a friction fit, but if you miss it by a little bit, the seal will still be air tight.

In my setup the drum is pushed against the foam seal by spring loading.  But if you plan to only use friction to hold the separator and drum together, then a further modification you should consider is to make the bottom flange thicker, possible one inch.

[pitbull]

retired2-

the foam is a very good modification. I had originally thought about it in my design but decided against it because it would have meant a thicker wall in the mdf. However, I would consider it for sure going the rout you did with the plexi.

If I get bored enough I may redo it all again just for fun...got a little better idea in my head that would make building even easier even if the results were just the same.

[retired2]

retired2-

the foam is a very good modification. I had originally thought about it in my design but decided against it because it would have meant a thicker wall in the mdf. However, I would consider it for sure going the rout you did with the plexi.

If I get bored enough I may redo it all again just for fun...got a little better idea in my head that would make building even easier even if the results were just the same.

Well, if you are going to go to the trouble of redoing it, then see if you can find a chamfer bit with a steeper angle.  I used what I had which was the common 45 degrees, but 60 degrees would work better if you could find such a bit.  The 45 degrees is a little blunt.

Let me know how you make out.