American Woodworker Dust Article??

[Bill Pentz]

With six emails and four telephone calls from some of the senior air engineers in the country who also are woodworkers, I'm wondering if anyone else had a reaction to the new May 2003 issue of American Woodworker Central Dust Collection article by Dave Munkittrick?

Anyone else see the glaring error?

Below is a graph of real values using my cyclone design that is about 2" of water resistance more efficient than the proposed system.

http://cnets.net/%7Eeclectic/woodworking/cyclone/BlowerComparisonGraph.gif

bill

[Dave Hammelef]

Whats wrong?

[Glen Smith]

I'm no expert, and I'm still using a shop vac to suck the dust off the floor, but I'll take a guess.

Horsepower don't make a differnce, the important number is impeller diameter. In other words, putting a 5 horse motor on a 9 inch impeller does not make a better dust collector.:confused:

I think.

Glen

[Paul Geer]

"Shop size" is a little ambiguous...

[Bill Pentz]

Stepping up on my soapbox.

The article wrongly says 500 CFM is ample to collect the dust. Air engineers long ago upgraded that old 500 CFM standard to 800 CFM to assure getting not only the same sawdust that we could get with a broom, but also the really fine most unhealthy dust. This article's use of that old standard ends up recommending too small of a a blower, cyclone, and ducting that will not amply collect the fine, most unhealthy dust.

Most hobbyists vendors are not getting the message. To each I offer a challenge to either put up or shut up. Meet me at my local gym and we will have it out. The rules are simple. We each get identical straws and by personally sucking and blowing have to move a balloon without touching via lung power across the others goal line to score. I'll even give a huge handicap. I have no choice since more than half of my lung function is gone thanks to hobbyist vendors who sold me dust collection equipment that severely harmed my health. Regardless, my only condition is they have to suck and I get to blow. I'll put a $100 bill in the pocket of any one who can beat me.

The bottom line is that 500 CFM standard is pure uninformed garbage just like trying to use the self starting screws in that heavier ducting recommended in the article. To move that balloon, you need to enough CFM to take in a big enough sphere of incoming air around the inlet of that straw. The same is true of the fine dust. You have to have enough CFM at your larger machines, 800 CFM according to my engineer friends and leading experts in the field. Without that airflow, the much more powerful directed small streams of air from our machine belts, blades, cutters, motor fans, etc. will blow any that under 30 micron sized stuff all over our shops that does not get aimed right into the hood.

This is why anything less than a 2 hp motor driving at least a 12" diameter impeller that will move at least a real 800 CFM at our machines is the bare minimum for a small shop. Most of us with medium to larger shops (1 to 2 car garages) need a real 3 hp driving a 14" diameter impeller to get ample CFM. We then need good hoods, well designed machines, and at least 6" ducting to support the collection and airflow needed.

Unlike others, I chose to do something about this. I did not sue any vendors in spite of three having threatened to do that to me. Instead, I put in thousands of hours building informative web sites and designed a cyclone that beats the pants off of all of them. I'm most pleased that Terry Hatfield with his DustEliminator Cyclone (http://www.dusteliminator.com ) had the gumption and energy to make a kit cyclone from my design that others with minimum skill can build. I wish I had the health and energy left to join his venture and don't have a clue why fellow woodworkers are not mobbing Terry with orders. Regardless, the graph I posted is real using real airflow from three of the most popular units (including the two recommended in that article) were each measured using identical equipment, conditions, and test procedures. Only that unit I designed and recommend provides ample airflow to do the job.

Finally, The National Institute of Health is clear this fine dust over time like smoking causes everything from runny noses, to asthma, to cancer. The Australian government health organization says that respiratory problems disable one in fourteen professional woodworkers.

Stepping down off my soapbox.

bill

[Bill Pentz]

I own a Oneida 1.5 Cyclone system. I am currently running down a 20' flex hose that I move from machine to machine. Do I need to go through the pain of getting a more powerful system or going to PVC or metal pipe.

I've enjoyed reading your posts on the subject.
Thanks - Peter Gregory


Peter,

If you look at the graph I provided and check out the blue line, the Oneida Air with a 1.5 hp motor is too light weight to get the really fine dust amply at our larger machines. It does get most of it when used as you are and about the best you can do is run it with that 20' length of 5" hose. Most of my friends who bought these units had to upgrade to external filters using either one of the larger Farr or two Torit 0.5 micron cartridges. Those who bought this unit expecting it to run the kind of ducting shown in the American Woodworker article will get good performance on the same dust that we get with a broom, but still not get the job done on the finer stuff that is so unhealthy.

As a practical solution, you can keep using it, but should wear a good cartridge dust mask when working with any wood that is either toxic or when you are doing work that produces a lot of fine dust such as routing, sawing, and sanding.

bill

[Dale Sherman]

Hi, Bill.

The graph is confusing in several ways to me. From it I deduce that a small shop should have 1500 cfm @ 4.5" SP. A large shop doesn't need more than 1000 cfm, but lots more SP. Huh?!? Perhaps a better way to represent it would be to have a diagonal representation with biggest and best at the top right.

Stating 500 or 800 cfm as a minimum is really too generalized in my opinion. It really comes down to the hood design for an individual machine. I think a small bandsaw with a well-designed 4"-5" pickup adjacent to the blade below the table functions well at 500 cfm. However, most other machines come with undersized dust ports and can't pull the necessary air unless the duct is oversized or the SP is really high. Even then, good hood design is crucial to effective pickup of source-point ambient dust.

However, I do agree with you that in general, the more airflow, the better the pickup of those floating ultra-fine particulates. And your average shop tool would be better served with higher cfm dust pickup. And If I could get 2.35 million FPM through a soda straw, I'd have that 800 cfm needed to suck a ballon across the gym.
:D

Keep up the good work, though. I like what you're doing.:)

Dale

[Bill Pentz]

Originally posted by Dale Sherman
Hi, Bill.

The graph is confusing in several ways to me. From it I deduce that a small shop should have 1500 cfm @ 4.5" SP. A large shop doesn't need more than 1000 cfm, but lots more SP. Huh?!? Perhaps a better way to represent it would be to have a diagonal representation with biggest and best at the top right.

Stating 500 or 800 cfm as a minimum is really too generalized in my opinion. It really comes down to the hood design for an individual machine. I think a small bandsaw with a well-designed 4"-5" pickup adjacent to the blade below the table functions well at 500 cfm. However, most other machines come with undersized dust ports and can't pull the necessary air unless the duct is oversized or the SP is really high. Even then, good hood design is crucial to effective pickup of source-point ambient dust.

However, I do agree with you that in general, the more airflow, the better the pickup of those floating ultra-fine particulates. And your average shop tool would be better served with higher cfm dust pickup. And If I could get 2.35 million FPM through a soda straw, I'd have that 800 cfm needed to suck a ballon across the gym.
:D

Keep up the good work, though. I like what you're doing.:)

Dale

Thanks Dale!

The one thing you did not comment on, that I was wondering if you caught, was the result of testing my cyclone design and finding it only pulled 1.2" when being driven by a Grizzly 2 hp 1029 DC blower. The Wood and similar looking designs pull more than 4.5". Even with the so called "neutral vane" they barely drop to 3". Although I think 2 hp without at least a 13" impeller is a touch too small for a cyclone to work well, it does show that those who choose to use their existing blowers are going to get a lot more airflow and better separation then going with other units. I'm still pretty proud of the good work that fellow hobbyist Terry Hatfield has done turning my design into a nice kit.

I actually had to me a little easier to understand graph up initially, but after a handful of emails, I changed it around to match the same kind of graphs that the other dust collector and cyclone makers provide so people could compare apples and apples. I added the shop size information to show the relationship between longer ducting runs and increasing static pressure.

The 800 CFM minimum I share is not mine. It comes from the Department of the Navy, American Air Filter, Cal OSHA, Fed. OSH, and a number of other fan and engineering firms who developed the standards they use to layout shops. The 800 CFM figure comes from that table as the amount of air flow needed for most larger tools. A copy of that table is shared on my Dust Collection Basics (http://cnets.net/~eclectic/woodworking/cyclone/DC4Dummies.html) site.

At the same time I fully agree with you on how important the engineering is on hoods. I have a couple of Sweedish tools with really well designed hoods. I have an import twin to one of those same tools. I can't use the latter without filling my shop, yet both have exactly the same sized connection to my ducting system.

So with lung power you fully agree that there would be no contest with my blowing with about half my lungs left and someone else trying to suck. Lots of people just don't get it that you have to have a good hood and move a big block of air, or the other distractions and airflows will quickly escape the effective area around our machine hoods.

Thanks for input as always and keeping me honest! *smile*

bill

PS you are welcome to add to that my cyclone and dust collection pages any time you want. You are one of the most knowledgeable that visits here. I'm just a dumb frustrated engineer who decided to try to help others get a little better informed so they can take better care of themselves..