Modded single stage dust collectors/shop-vac

[Heizenberg]

On Tue, Jul 7, 2009 at 7:57 PM, Phil Thien <phil@cgallery.com> wrote:

Do me a favor and post this at the forum:

Phil Thien (phil@cgallery.com)
414/963-6336
414/963-6338 (Fax)

----- Original Message -----
From: Ananda Debnath
To: phil@cgallery.com
Sent: Tuesday, July 07, 2009 7:41 PM
Subject: [SkipSpamFilter] Modded single stage dust collectors

SkipSpamFilter


Hi Phil,

I've been trying to follow discussions on cyclones and lid-based separators for a while and my head's spinning a little now :)

Like many, I am a hobbyist WW'er and at the moment, just don't have the space in my two car garage to spend money on and install a serious Bill Pentz type big impeller type DC. I have a Ridgid 16 gallon wet/dry vac (WD1665) that I just bought a new HEPA filter for (and on the box it says that the filter is even washable). I also have a 3M darth-vader like respirator, that I just find too cumbersome to use all the time... especially in Texas summers.

There are a few things that confuse me and I'd love to read your opinions on:

   1. Both cyclone and lid based designs seem to rely on spinning dust laden air tangentially so that heavier dust is thrown out as if in a centrifuge and loses momentum and settles to the bottom. The confusion for me here is, what exactly does the conical shape of a cyclone do differently compared to the shape of a circular trash can, which at best has only a very slight slope to the side?
   2. In cyclone designs, there seems to be talk of a 'neutral vane'(?) which seemed quite intuitive to me... "encourage" the air stream to corkscrew down in a helical along the circumference so as to impart a downward momentum to the dust, and also minimize the turbulence caused by the entering air-stream by minimizing it's "collision" with the air-stream that's just traversed along the circumference of the cylindrical portion at the top of the cone. The confusing thing here to me is that in your baffle based design, you seem to have a "negative" neutral vane type structure... i.e. the vane portion is actually empty space (the cut-out along the circumference of the baffle), and the empty space, is actually a solid partition

In short I'm having trouble visualizing how exactly the baffle based solution works. I can completely understand how it prevents dust that's settled at the bottom, from being sucked back into the vac... but totally unsure how it helps in separating the dust.

A separate question on the baffle design: If I use a tangential intake (as opposed to a lid-based intake), with the intake pipe glued onto the outside tangentially and not sticking inside at all, would the cutout need to go all the way around (instead of the 60 degree uncut portion in your design)?


Lastly, this line in your design page caught my eye:

    "I have also modded single-stage dust collectors with my baffle (this allows units with cartridge filters on top to stay cleaner, longer)."


With a traditional 2-stage separator design, the shop-vac's chamber is such a huge waste of space! I'd love to see pictures or notes/ideas on modding a shop-vac so that it's collection chamber can actually be utilized to collect. The ClearVue mini-cyclone setup looks very attractive for the same reason as well - were it not for it's ridiculous price-tag. I'm almost tempted to build my own with oneida's cone and mdf, but I'd love to your ideas on using a baffle design with shop-vacs!

Many thanks again for putting together such an awesome design and notes page! I look forward to reading your reply.

Warn regards,
Ananda


No virus found in this incoming message.
Checked by AVG - www.avg.com
Version: 8.5.384 / Virus Database: 270.13.8/2223 - Release Date: 07/07/09 17:54:00

[phil (admin)]

Hi Phil,

I've been trying to follow discussions on cyclones and lid-based separators for a while and my head's spinning a little now :)

Like many, I am a hobbyist WW'er and at the moment, just don't have the space in my two car garage to spend money on and install a serious Bill Pentz type big impeller type DC. I have a Ridgid 16 gallon wet/dry vac (WD1665) that I just bought a new HEPA filter for (and on the box it says that the filter is even washable). I also have a 3M darth-vader like respirator, that I just find too cumbersome to use all the time... especially in Texas summers.

There are a few things that confuse me and I'd love to read your opinions on:

   1. Both cyclone and lid based designs seem to rely on spinning dust laden air tangentially so that heavier dust is thrown out as if in a centrifuge and loses momentum and settles to the bottom. The confusion for me here is, what exactly does the conical shape of a cyclone do differently compared to the shape of a circular trash can, which at best has only a very slight slope to the side?

On a cyclone, the direction of air changes as it exits the vortex finding tube.  The debris has already been slowed by surface resistance of the cone.  So the combination of slow debris and sudden change in air direction allows this debris to fall out of the airstream.

Separator lids (w/o baffle) simply work by spinning everything in bin, and counting on the fact that most of the debris will be at the outside of the container, that the air in the center of the container should be relatively debris-free.

   2. In cyclone designs, there seems to be talk of a 'neutral vane'(?) which seemed quite intuitive to me... "encourage" the air stream to corkscrew down in a helical along the circumference so as to impart a downward momentum to the dust, and also minimize the turbulence caused by the entering air-stream by minimizing it's "collision" with the air-stream that's just traversed along the circumference of the cylindrical portion at the top of the cone. The confusing thing here to me is that in your baffle based design, you seem to have a "negative" neutral vane type structure... i.e. the vane portion is actually empty space (the cut-out along the circumference of the baffle), and the empty space, is actually a solid partition

In short I'm having trouble visualizing how exactly the baffle based solution works. I can completely understand how it prevents dust that's settled at the bottom, from being sucked back into the vac... but totally unsure how it helps in separating the dust.

It helps to separate the dust by "focusing" the fast-moving air ABOVE the baffle.  The faster this airstream moves, the more dust which is separated.

A separate question on the baffle design: If I use a tangential intake (as opposed to a lid-based intake), with the intake pipe glued onto the outside tangentially and not sticking inside at all, would the cutout need to go all the way around (instead of the 60 degree uncut portion in your design)?

Nope, if you see some of the examples here, you want the baffle tight to the side of the container under the inlet.

Lastly, this line in your design page caught my eye:

    "I have also modded single-stage dust collectors with my baffle (this allows units with cartridge filters on top to stay cleaner, longer)."


With a traditional 2-stage separator design, the shop-vac's chamber is such a huge waste of space! I'd love to see pictures or notes/ideas on modding a shop-vac so that it's collection chamber can actually be utilized to collect. The ClearVue mini-cyclone setup looks very attractive for the same reason as well - were it not for it's ridiculous price-tag. I'm almost tempted to build my own with oneida's cone and mdf, but I'd love to your ideas on using a baffle design with shop-vacs!

Many thanks again for putting together such an awesome design and notes page! I look forward to reading your reply.

Warn regards,
Ananda

It wouldn't be difficult to mod a shop vac.  Many people probably done because of the limited capacity.  And man of them allow you to use bags, which do an excellent job of keeping the filter clean.  But it could be done.

[bennybmn]

Phil, I think I did exactly what he is talking about with inserting the baffle into a shop vac directly...



Most of the added height is because you need to allow room for the vac filter which normally takes up a considerable amount of the volume of the tub of the vacuum. So, it's a pretty large rig now, kinda tough to haul out of the basement, but it works GREAT so far. And I could probably actually suck up 12 gallons of junk now!

[Heizenberg]

Yep! I saw this post late last night while browsing through most of them. Thanks for adding it to this thread... this is exactly what I was looking for!