"Top Hat" design?

[MunchyMonster]

Is there any advice about the height of the chamber in a "top hat" design?  I know Phil's rule of thumb about the outlet pipe extending by its radius into the chamber from the center of the chamber.  I also know the preferred air flow is parallel to the top and bottom plates of the chamber (with the bottom plate being the baffle of course).  Should I shoot for a chamber that is the height of my inlet pipe diameter?  Is taller better?

[juicegoose]

I'm curious for some direction on this as well. I'm currently designing my side inlet on a 55 gallon plastic barrel. Problem with the traditional drop in desig is that the top of my barrel tapers in slightly and i don't think i could get the lower baffle in the top of the barrel. I had thought of a top-hat baffle like the original poster and utilize the lid as my lower baffle.

eagerly waiting some inputs from the community.

[phil (admin)]

The taller the top hat, the lower the velocity of the debris you're spinning.  The lower the velocity, the lower the rate of separation.

I'd try to stay within the parameters of what you've seen here, with the size of the top hat sized slightly larger than the inlet pipe.  So for a 6" inlet (for example), you might want the overall height approx. 8", so you have enough material above and below the inlet pipe for strength.

[MunchyMonster]

Cool this is exactly the kind of info I was hoping for.  Since I'm still playing with a shop vac as my vacuum source I'm thinking I can make the interior of my "top hat" just a little bigger than the 2.5" hose that I'm using.  Using a standard garbage can I ought to have a very nice outer diameter and the relatively thin top hat chamber ought to keep the swirl spinning nicely.  I'm also going to experiment with using a subtle spiral as my interior wall in an attempt to make the air flow as uniform as possible with the new air being brought in through the inlet.  The idea is to introduce the new air into a stream of "cyclone" air such that they meld at the point where the two streams would be parallel.

Does anyone have any opinions about the slot portion of the design?  In the original design the bottom baffle was made out of 1/8" hardboard.  I assumed that was because a thin baffle allowed cleaner airflow into the bottom of the chamber while the baffle itself kept most of the material in the bottom chamber after it had passed through the slot.  I would assume a thicker board would cause more turbulence in the airflow.  But wouldn't it also help to isolate the aircurrents to above the baffle?  Taking the concept to the extreme, what would happen if I had a really thick baffle (like 12" thick)? 

Which leads to another question...

I can see how we would want air flow as smooth as possible in the upper portion to keep particles thrown to the outside edges until they get a chance to fall, but what about the bottom portion below the baffle?  Wouldn't it be a good idea to try and slow down/disturb the airflow below the baffle to give paticles a chance to fall out of the stream?  I'm thinking of an inverted cone so as you fall deeper the diameter is larger so the velocity is smaller so more particles fall out of the stream, or an angled guard that diverts air below the baffle away from the drop slot making it harder for air to recirculated back in to the incoming stream from below the baffle, or even just some vertical bars installed below the baffle to with the intent of to trying to disrupt and cancel air currents below the baffle.

Thanks for the advice and the great idea.

[phil (admin)]

Increasing baffle thickness will reduce separation.  I've never quantified going from 1/4 to 1/2 or 3/4", but as you continue on that path, you will reduce the rates.

[juicegoose]

Phil what about the use of the lid from a 55 gallon barrel? It's thin (thinner then 1/8" ply) but ridgid. My only concern is the lid I have has ridges in the the top. They might work to an advantage but needless to say the lid isn't flat like ply would be.

[bagger don]

Juicegoose

I just posted my setup with the blue can and I cut off 3" of the top. Mine has a taper and I only lost about 1: in the top diameter.

Don Z.

[phil (admin)]

Phil what about the use of the lid from a 55 gallon barrel? It's thin (thinner then 1/8" ply) but ridgid. My only concern is the lid I have has ridges in the the top. They might work to an advantage but needless to say the lid isn't flat like ply would be.

Depends on the size of the ridges.  You want the surfaces to be as smooth as possible.  Using the plastic top can be a problem in terms of getting fittings attached to it.  Some people have been able to do it.

[juicegoose]

I'll try and get a picture tonight but the ridges are in the same direction as airflow would be. Also I wouldn't be attaching any fitting to the lid. It would act as my lower baffle. Top hat design per say.

[c_irie]

did you ever make the top hat design with the lid ?