J. Phil Thien's Projects

You all can mock me if you have already figured this one out, but it has taken me a number of times trying to get a good measurement of something round, like a barrel or trashcan, to come up with it. I would normally lay a tape measure across the top in a number of places, trying to be on the diameter as best as I could, and then average the results. The other night, I was measuring the Brute trashcan I'm building my system around, and was getting diameter measurements that varied by as much as an inch. So I decided to measure the circumference of the can, and then used math to determine the diameter of a circle with that circumference. I haven't built the part that needs to fit the can, but I have high hopes for the accuracy of this method.

Do any of you have any tips like that that you might take for granted, that you wold want to add?

I have searched the site for information on this, to no avail, so I'll ask the members -

Has anyone done research on whether or not the relative smoothness of the interior of the baffle chamber affects fine dust separation? So many of the top-hats we see are made with clear plastic sides, which are very slick. If you were to use another surface that had some texture, do you think it might create a zone of slower moving air against it, or perhaps some sort of beneficial turbulence that might help with the fine stuff?

An extreme example would be lining the chamber with something like carpet - you could imagine that grabbing a lot of dust, but it would likely add too much resistance to the set-up. I am considering using bending plywood to make the circular part of my top hat; I could leave it as it comes, or cross sand it with coarse paper to make it rougher. I could try to paint it "slick", or even line it with thin sheet metal, to make it behave more like the plastic sides.

So do we have anyone who has tried this sort of thing, or who can model it on a computer, or has a strong intuition, or even just a strong opinion?

Thanks, Dusty

Hi, everyone - I hope this is of interest. I decided to try to modify my Ridgid Shop Vac, bought a few years ago from the local Home Despot, to include a Thien separator. I didn't want to go with a separate trash can model, because floor space is at a premium in my shop, and I move the vac around a lot. So, in the posts below, I'll show you what I have done. But first, a few things -

I tried my best to do this project "quick and dirty-" since I wasn't eve sure if it would work. And that rarely works for me, because halfway through I start liking the project, and wanting to do it "right." But I managed to keep this one pretty quick. And, of course, I now know how I would do it, if I decided to do it again.

In terms of quantifying my results, I did two things. First, I used a wind speed meter to measure the baseline performance of the vac. I found that it was drawing air in at a speed of 31 MPH, and blowing it out at a speed of 46 MPH. I attribute the difference to the lack of a really good seal between the top lid, and bottom bucket of the vac. Secondly, in terms of static pressure, I used the very scientific method of sticking my hand over the opening, and feeling how hard it sucked. I'd quantify it as "pretty hard."

Below, see pictures of the very common vac I started with.

Hi, everyone, it has been a pleasure reading all of the great information on this board, over the last few weeks. Honestly, I still have plenty to read. But not only is the information good, the tone of the board is nice also.

On to the question - I have an old Jet dust collector, rated at 2-1/2 hp, 1200 cfm. It has a 12" impeller with a 6" input fitting. I had it set up for a while years ago, and it worked well despite what I now know were some pretty inefficient home-made junctions and fittings. But of course, it was spewing fine dust throughout the shop.

Due to space and other considerations in my current shop, which is in the basement of a 110 year old house, now is not the time for me to do a full-on, perfect system. I am leaning strongly toward the kind of modifications shown in this thread - http://www.jpthien.com/smf/index.php?topic=145.0
(maybe without the cool paint job, though.) So, a Thien baffle in the bottom of existing "cyclone," cartridge filter above. One of the features of this particular DC is that it has a spiral ramp inside the "cyclone" part, and I am wondering how that might effect the working of the baffle, and if there are any design changes I should make. See picture, below, if it posts.

A specific question I'd have is, would it be worth me making an output tube with a bellmouth on it to feed up into the filter? I'm going to have to make the "donut" to support the filter,so I'd be halfway there, already. And if so, would it make sense to have a bellmouth on both ends of that tube? I don't think that air straighteners in the tube would be worth the time, since I wouldn't be feeding the impeller directly, but you could talk me into them. The "hole" through the inside circumference of the "ramp" is 9", so I could use a 6" pipe in there and have 1-1/2" of clearance on all sides of the tube.
So, thanks, I look forward to any and all replies - Dusty