J. Phil Thien's Projects

Does someone have a quick/cheap way to measure air-flow, like in feet per second or feet per minute?  Preferably something that doesn't have to be calibrated.

In a perfect world, I would love to have a cheap 'attachment' I could hook onto or put in-line to a duct that would measure the flow rate.

Years ago (high school, back when dinosaurs roamed...) I built a wind tunnel.  And my Dad got the specs to build a pitot/static tube that I used in a science project.  It measured in inches of water the pressure differential.  I just don't remember the specs to re-build it.

TIA ... Jack

Has anyone tried an electric leaf blower as a vacuum?

I have one that has a 3" blowing hose, but a 6" vacuum hose (used to vacuum up leaves) and 'blow' into a bag.

Since I already have it, using that as the vacuum might be useful.

Thoughts?

I was reading on quieting a generic shop vac.  One set of folks made a muffler using PVC pipe and some open cell foam.  The best I have seen is a insulated closet, basically sending the dust collector to another room.  If you don't need to recycle conditioned air, sending the exhaust air out of your shop is not a bad thing.

Actually just the blower needs to be 'outside', putting a muffler on the exhaust of the blower can help.  I saw another article that did this before sending the air with fine particles to filters, it was basically large holes in the ducting sides, and wrapping that with backed fiberglass (or enclose it in a larger duct).  Think of a 6" duct, with many 6" holes cut in it, wrapped by lots of fiberglass, and that put inside a 12" wrap/duct.

This second one I think I saw on the forums at the ClearVue site.  The first one may have been in ShopNotes, but my memory could be off.

Does that help?

I saw a similar thing where someone had two smaller DC (bag systems, but same size), and basically cut some holes in the sides of a metal storage cabinet, One large input (like 6" and two 'exhaust' where the DC systems were attached).  It was like a 6' tal cabinet.

But my origional question was related to 'fine filters' and not the particle separation like the Thien Lid does nicely.

Sounds like a good design. ... Below the baffle I don't think the shape makes much difference, your box containing your barrel just must be 'sealed' so as to not leak vacuum. 

I have thought about making a similar setup, and either need to make the baffle a little smaller than the diameter of the barrel, or put a short 'funnel' below the baffle to help ensure all the chips fall into the barrel rather than 'around' it.

Quote...
some questions:

what is the ideal height of the spin chamber? most of the pictures seem to show the distance between the baffle and the lid at about 1-1/2 to 2 times the diameter of the inlet pipe. has any work been done with taller spin chambers? I have plenty of height to work with.

From my understanding the ideal height of the spin chamber is just enough to allow the fittings between the 'top' and the baffle.

Quote
is coupling the spin chamber directly to the blower a bad idea? I see pictures of blower over spin chamber generally coupled with a foot or 3 of pipe.

Coupling the spin chamber top directly to the blower is not bad (good in my thought... for the most part reducing the friction by reducing the length of the ducting).  But you might consider extending the blower inlet down into the chamber to about half way to the baffle.  Extend it by enough to make the cross section (in sq inches) of the duct close to the area of the diameter of the ducting times the length between the duct and the baffle.  A little more open area is OK, but probably not having it open all the way from the top to the baffle.

The 3 ft or so of 'extra' pipe seems to be overkill to keep from cutting the pipe.  Hopefully someone else could chime in on that part.

Quote
any thoughts as to whether to have the spin chamber rotation the same as or counter to it, and what a longer pipe between might play on that relationship?

Making them in the same direction would seem to keep the efficiency higher.  Whenever air changes direction, any energy in it must be dissipated before it can start swirling in the other direction.  (If you want to be 'retentive' about it, look at the way the toilet swirls in your hemisphere and make it go the same way.  Countering that will work, but it adds yet another 'little bit' of friction counteracting the 'natural' swirl motion educed by the earths rotation.).

Also having the area of the input ducting to be similar to the area of the exhaust (to the fan) ducting should help ... This part is a guess, but it seems to make sense to me.

Does all this make sense?

I am guessing you are right.  I can see that even if a 'regular' cyclone can take just about any amount of power (within reason), Phil Thein's design could be over powered if driven 'to hard'.

I would suggest use a larger design for your higher powered vacuum.

If you really want to know the CFM of your system at the dust ports, contact your friendly neighborhood HVAC person that has an air velocity gauge (or google to find how to DIY a pitot tube like used in airplanes to measure air speed). 

The air velocity gauge will tell you the speed of the air in feet per minute.  Here is the basic math: given you have the feet per minute (FPM) now multiply that times the cross sectional area you are pulling the air from (change it from square inches of cross section to square feet by dividing by 144).  So a 6" pipe is  29.27 sq inches or .196 sq feet.  So to get 1000 CFM you need an air velocity of 1000/0.196 = 5093 feet per minute in air velocity.  That is almost a mile a minute or 60 MPH (88 KPH).


So if you have a 6" duct, if you don't have 5093FPM, or about a 60MPH breeze, you don't have 1000CFM.

And for some popular ducts to give 1000CFM:

So the size of motor/impeller/duct(diameter, length, curves, and smoothness inside) combination you use still needs those air speeds applied at the tools to fulfill the air quality needs.  I think it is easy to see why a good system requires big motors!  And why using to much flex tubing will cause lots of friction in the air especially if there is much of it at lower sizes.

Now in defense of Bill... He is addressing what it takes to keep us healthy.  He has been effected by poor dust management in his own shop and this is what he has come up with to keep him healthy. ... If you are superman, well, this may not apply to you. ... All of us must make our own choices.

In short, more air removed from the work area, the fewer fine particles you will breath in.  If you must recycle the collected air back into the shop, you need to filter it.  A poor filter will let the 'bad stuff' on through, and to small a filter will clog a lot faster.   

In what I see in Bills documents, chip collection is a good thing (and helps keep the filters clean) but secondary to keeping the fine particles picked out of our breathing space. 

Bill has made his decision for him, and is just trying to let us know what he has found to be reasonable solutions in his eyes.

---

On duct work, not all HVAC type ducting will stand up to the vacuum pressure that a good dust collection system will generate.  If you close all the 'blast gates' it can starve the blower and the low pressure will cause the air to collapse the ducts.

---

If I am wrong, please correct me.  This discussion is to help us all.

Question on the plans: Exhaust air ducting...

Ok, the exhaust air leaves in the center of the 'top' of the baffle, that is the center of the 'lid'. 

How far down does the exhaust air duct extend below the top of the baffle or how much room is required above the bottom of the baffle to the duct to make sure it all works well?

In the pictures it looks like it is not even with the 'top' baffle and sticks in about half way between the 'top' and 'bottom' part of the baffle/lid.

TIA... Jack

If you can afford the space, how about one in front of each and powering different tools as needed?  Even possibly make one into a 'portable' collector.

I could see an issue with one collector if ducted together could just 'suck back through' the less powerful collector thus nullifying the benefit of having two.  Unlike computers (my day job), load balancing doesn't work well with disparate powered units with dust collectors.

If both were about the same power, I could see it as a benefit. 

I saw on the Woodwhisperer site he has a ClearVue cyclone, and the exhaust of the blower goes through an MDF built up duct directly into the top of a filter stack.  Using a solid duct that keeps down the friction should allow the air to blow smoother and dust not to collect in the creases in the hose.  Even a plastic hose or pipe would be OK here, and the smoother inside, the better.

I was thinking that using a 55gal drum or even a large metal trashcan would be nicely served as the chip collector.  But putting the fan and top 'on and off' could be a pain.  Making a 'short table' that the can or drum can sit on, with a simple lever to 'raise and latch' the empty drum or can in place while allowing it to be slightly lowered (half an inch or so?) for replacement might be a neat option.  That way the blower / chip separator could be stationary.

Reading the Pentz site for a 'long' time gives some insight as to why he chooses a 5HP blower and 14 to 16" steel impeller (like you get with ClearVue) similar to what Jet has on their larger units.  It is that a small shop full of tools requires it.  He has lots of information about calculating it all, and the size of 'vacuum bubble' needed around various tools.  The size of the 'bubble' and the speed of the air needed to collect the fine particles determines the number of CFM needed.  In addition to that, there are friction losses, leaky blast gates, etc that all need to be considered, plus you should never close all the blast gates (you will starve your blower of air)... anyway, Pentz helps you calculate it all and also has a 'short cut' rule of thumb.  A small one man shop with one or two major tools running at once will have around (or under) 200' of ducting, and to run the amount of air needed, typically needs 6" duct, and to keep that all moving fast enough it requires just under 5HP with a well designed blower.

Using Bill Pentz rules, 2HP blower is about right for some tools, but wouldn't cut the mustard to power even a small shop with his kind of desired specifications.

Would a 2HP unit work?  Obviously the answer is yes.  Bill Pentz would suggest it still needs the find dust collection filters on it.

Bill Pentz has major health problems caused by his long term wood working as a woodworking professional.  So his focus is NOT the large particles that his cyclone and the Thien Cyclon Separator Lid collects so well, but the fine particles.  And to Bill, you need to collect particles down to half a micron to keep the air 'healthy enough.  That is why he suggest filters like Wynn sells and that is why ClearVue (which uses the Bill Pentz design for their cyclone, just implements it in plastic) uses the big filters that are rated to the half micron level and has LOTS of filter material, partly so it doesn't need to be replaced so often and it allows enough air to come through without generating a lot of back pressure across the filter.

Sorry for being so long winded.

I know we all would like to have Wynn or similar filters, but for the budget minded of us, I saw where someone built a box that fit house type air filters.

Does someone have suggestions on building 'proper' fine particle exhaust filters for the fine particles (down to half a micron) that come out?
Any pans, pictures, drawings, etc would be appreciated, along with how it is working for you.  Do you need/have to clean or replace them often? (Yes, without knowing how you are using them it is difficult to truly compare.)

Would you mind posting a pic or two of your unit so I can understand what you did different from the standard build?

The long run of 2.5" hose I could see as being an issue, but you need to keep the speed of air throughout the tube to make sure all the particles are washed from the hose into your collector.

At the end of the day, do you have dust left over inside your hoses?  If so you may need more vacuum or put a 'booster' in there along the way somehow.  Hopefully someone could suggest how to do that.

If you have enough volume of air available (big enough blower), you might try a larger hose, as this will lower the friction in the hose with the air, but it requires a bigger blower to keep the volume going.   If it takes say 600 CFM to do an effective job with your sander, getting 600CFM through a 2.5" hose takes a LOT more power than from a 4" hose.  Also, some hoses have more 'air friction' than others, you want one that is as smooth as you can get away with to reduce the air friction.

Just some thoughts. ... There is quite a discussion on the Pentz site about air volumes and duct sizing, but it is a pretty intense read.

http://www.wynnenv.com/cartridge_filters.htm

You might consider these folks filters for fines.  It is the ones
Clear Vue uses (the clear plastic design of Bill Pentz collectors).

Quote from: RCP612 on May 21, 2008, 08:47:06 AM
Another question.
What would be wrong with venting this DC through the wall with no bag?  Do these units require a certain amount of back pressure to work correctly?
I'm thinking that this would increase the CFM and, any fine dust would just be blown away outdoors.
Is my thinking correct?
Thanks Phil,  keep up the good work!

The only issues I can think of is you will be loosing any heat/cooling that you
paid for.  If you don't have a conditioned space, make sure your exhaust is
on the leeward side of the building and air intake is on the normally windward
side so you don't re-circulate it.  Also if your family patio or back yard is
where you are planning to exhaust, you might want to put it elsewhere.
You don't want to get rid of the fine particles to give it to your family.

Just a few thoughts.