Argh! Dust Collectors

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Forum topic by Shamus posted 01-02-2011 05:12 PM 1281 views 0 times favorited 7 replies Add to Favorites Watch
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16 posts in 2535 days

01-02-2011 05:12 PM

Why is it that 90% of the dust collector systems end up looking like some version of a Rube Goldberg octopus? Not saying your system doesn’t work. It’s whether it’s working at an efficient level and mine did look like the above mentioned octopus.

With a bit of a break in the weather last week I decided to pull apart some of my DC ductwork and see what, if any, build-up of dust / debris I had sitting inside the pipes. Well I was in for a surprise. I could have used a chimney sweeps brush for a few hours. I cleaned out a 5 gal bucket of sawdust in just over 60’ of pipe.

What got me on this in the first place was I was talking with an Engineer over the holidays. I had asked him to help me design the most efficient DC system, with the cleanest looking install for my applications. It is now clear that I am undersized by half. My 5HP collector needs to be 10HP. My duct work is oversized by 30%. I should have bought 4” runs not 6”. I should keep my horizontal ductwork no more than 1’ above the cyclone and never try and lift the dust more than 1’into a horizontal run.

That’s the ideal application and he suggests putting the DC in the center of the shop regardless of what I use. His list goes on and on.

I pulled everything out and am starting over. Relocating most of my power tools and will attempt to do things better this time. I need to put as many power tools against a wall as I can. That way all the horizontal runs will be mounted on the wall and I can get close to the 1’ rise he suggested. That’s my first goal to improve efficiency. I’m not about the put the DC in the center of the shop but I am going to locate it midpoint between the two longest runs, instead of at the end. (with a 5’ pipe height) I know some of you have done exactalluy that and have a very efficient system.

The second part is the bigger issue. Nobody makes all the components you need that will actually fit together and will optimize all the different size component discharge dimensions. I’ve got 2 1/8, 2 3/8, 2 ½, 2 9/16, and a few metric ones thrown in and that’s not even half of them. Looks like I’ll have to use some foil tape again.

Lastly, why in the world would a company market a DC with inlet ports located the way they have them. Your basically forced to start with flex hose from the get-go.

Ok, I’ll admit it. The holidays have gotten to me and I need to just sit back and open a bottle of scotch. For me it’s too late to change though. I like to see things that look neat and organized. Small shop Dust Collectors are designed to look unorganized.

Thanks for listening. I feel better now.

7 replies so far

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16 posts in 2535 days

#1 posted 01-02-2011 05:40 PM

Charlie, I should have mentioned this in the post. It’s a working shop with usually 2 people running equipment at the same time and that does make a difference. But, we typically spend 2 days a week in the shop, the rest of the time we are out. System was installed 10 months ago.

Thanks for the heads-up on the Fernco. I’ll look for some today when I’m out.

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4821 posts in 2466 days

#2 posted 01-02-2011 05:47 PM

This is why I hesitate building mine.
Every system I saw so far look like hell on earth, with ducts all over the place and maze of elbows and 45 degrees.
I do not want something hanging from the ceiling or running all over the walls.
So far the best solution I imagine is to run everything on the floor and to build another floor on the top of it.
I do not have the money to do it now, this is why I wait.

-- Bert

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2393 posts in 2301 days

#3 posted 01-02-2011 07:04 PM

Shamus, you may want to take a detailed read of Bill Pentz’s site. A lot of the issues that you mention (eg. oversized ducting etc.) he goes into a lot of detail about. Suffice it to say that from his research; the majority of us woodworkers have improperly sized systems. The common advice you hear is to go with 6” ducting, but he has some very detailed graphs demonstrating that the majority of the small DC that are used do worse with the large ducting etc. Another apparent no-no is using 4” vertical take offs from 6” duct; the drop in air flow is too great to keep all of the wood dust mobile, it is better to drop to 5” or use 5” mains and drop to 4”. Anyways, I’d highly recommend a read of his site before your upgrades. Your 5hp DC may be sufficient just with a larger impeller rather than replacing the whole machine.

-- Sometimes the creative process requires foul language. -- Charles Neil

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95 posts in 2245 days

#4 posted 01-03-2011 02:07 AM


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1540 posts in 3179 days

#5 posted 01-03-2011 02:32 AM

There are just two basic rules for a dust collection system. The airstream velocity must be at least 3500 cu ft per minute in order to keep dust particles suspended in the flow. Next, The capacity, cubic ft per minute, must be enough to carry away dust and chips as fast as the machine generates them. A planer is a good test.

The common misconception is that a 6” pipe is “better” than a 4” pipe, when just the opposite is the case. The velocity falls off according to the square of the difference in diameter. This is why dust is accumulating in your pipes. Yes, you can make a 6” pipe work if you increase the HP enough. But isn’t this a lot of overkill.

I blame the magazines and their advertisers for leading woodworkers into oversized piping and excessive HP.

-- "Heaven is North of the Bridge"

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1540 posts in 3179 days

#6 posted 01-03-2011 05:22 AM

Correction to my comments above. The airstream velocity needs to be at least 3500 feet per minute.

-- "Heaven is North of the Bridge"

View Shamus's profile


16 posts in 2535 days

#7 posted 01-03-2011 01:19 PM

Biowa, your spot on.

I initially set-up my system with the DC at the end of a 60’ run instead of in the middle and was using 6” feeding from 2” and 2 1/2”. That was the main problem on my set-up. That’s why it was recommended I use more HP. The better solution was to relocate everything and re-size the pipe and move the equipment producing the greatest amount of dust/chips closer to the DC.

Thanks to all for your comments.

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