DC Branch Ducts Diameter

[Larry Frank]

Chris...not upsetting me but wanting to make certain you knew where to find the dust collector performance data that I have posted. Did you read the blogs that mentioned and did they answer your questions? Given that you ask so many questions and have advice, I expected that you had also done testing and would have some real world data to share with others.

There is so much second hand information and assumptions that it is difficult to find real data. For example, someone saying you can not get more than 400 cfm thru a 4" pipe. This is fine for some dust collectors but not all and not mine. We need to talk in more specifics and fewer generalities.

Unfortunately, it is not easy to provide good data and takes some effort.

[Chris Parks]

Chris...not upsetting me but wanting to make certain you knew where to find the dust collector performance data that I have posted. Did you read the blogs that mentioned and did they answer your questions? Given that you ask so many questions and have advice, I expected that you had also done testing and would have some real world data to share with others.

There is so much second hand information and assumptions that it is difficult to find real data. For example, someone saying you can not get more than 400 cfm thru a 4" pipe. This is fine for some dust collectors but not all and not mine. We need to talk in more specifics and fewer generalities.

Unfortunately, it is not easy to provide good data and takes some effort.

I will repeat what I asked, can you give me a link to the data you posted previously in this forum? People have had a shot at me for not providing links in the past but being external links I am not allowed to do that and I refused. Being obtuse and making it hard for all those who read this in six months time or even six years time does not help anyone. Like the PM saga I am outa here, I don't see what this sort of discussion gains anyone.

[Jim Becker]

Chris, there is no prohibition to "external links" outside of other forum sites and sites where the poster has a financial benefit.

Jim
Forum Moderator

[Larry Frank]

I have not provided links because the posts were edited by a moderator who decided it would make them easier to read but made a mess out of them.

The best place to read them is on Lumberjocks under RedOak49 blogs. I can not provide a link to an external forum site.

[Edward Weingarden]

Josh:
I have a similar situation whereby the main splits shortly after coming off of the inlet. With that in mind, I don't know if I would get much if any mileage from a short 7" main.

[Jim Andrew]

My experience is that machines that make large chips are easiest to collect, such as a planer or jointer. The smaller the chips the harder to collect, so your tablesaw and bandsaw are relatively difficult and need more cfm. The hardest to collect is sanding dust, so you need as large a connection as possible. I have a 4" connection to my planer, and can also have another gate open when planing lumber, and my jointer has a 5" connection, which works fine, My tablesaw I opened up to 6" and also have above the table 4", and it works fine, have 2-4" connections to my bandsaw, and my edge sander I opened up to 6", and it could use more, as well as my small widebelt sander, which I opened up as well, but it could use a 8" connection, and my system is 6".

[Peter Christensen]

Sorry Peter but where did you get your information about 400 cfm and what test did you run to confirm that.

For your information, I used a hot wire anemometer and ran many tests on my system to test various ports and create a performance curve. I published my data and methodology on this forum.

I am running a Oneida Dust Gorilla with a 15" impeller and 5 hp motor.

I have also published information concerning the poor accuracy when using a fan type anemometer.

Sorry Larry if I have implied that you are not telling the truth or incompetent. You have a decade of history of participating here over me and I haven't read your past threads and posts.

I don't at this time have all the testing tools (just a Dylos) and am still putting my own system together (a CV-Max). My information comes from what I have read elsewhere like the dust section of the forum down under that has to remain unlinked. (Shades of Harry Potter and he who must not be named .) At the top of this section of the forum is a Sticky with a chart with the same information. https://sawmillcreek.org/showthread....M-Helper-Chart .

I also did some additional searching to show what I said was widespread knowledge. None of them mention the static pressures.

This calculator, when you play with it, shows that you get a flow of 349CFM through a 4" pipe when the flow is 4000 feet per minute. In order to get 700 cfm through a 4" pipe the velocity has to be 7000 feet per minute. That is pretty high for most systems, almost double. http://www.1728.org/flowrate.htm

This company's chart shows expanded numbers to the sticky above but 350CFM at 4000FPM is the same and you get 615CFM with 7000FPM. http://www.1728.org/flowrate.htm

Most of Bill Pentz's site also says the 4" pipe having 350 - 400CFM air flows and that's what I remembered from reading the site many years ago but there was one sentence that I had forgotten where he stated "It takes a 5 hp motor turning a 16.5" diameter impeller to force a 4" duct to carry 800 CFM." That is in the size range your DC. http://billpentz.com/woodworking/cyclone/staticcalc_faqs.cfm#AirFlowRequirements It is in the paragraph D. 2. a. Main Duct.

So I learned it is possible to get more than 400CFM through a 4" pipe, most systems are not sized to produce 600 to 700CFM that you measured with yours. I hope that explains my skepticism and wanting to understand why.