Allan Johanson
03-06-2005, 12:05 PM
Hey guys,
I had an interesting evening doing more airflow testing on my Delta 12.5" planer and Delta DJ20 jointer. My planer has the factory 4" hood and my jointer didn't come with a hood. So I made 6" hoods for my planer and jointer so I can get the most from my giant cyclone.
Before we start, I thought I'd mention that I got more airflow when my planer was actually running. So I can confidently pass on this great tip, turn your planer ON for better airflow. :p
On a duct run, I tried a variety of flex hose and port sizes at my planer and got the following results:
6" flex + 6" hood........779 cfm
6" flex + 4" hood........725 cfm
5" flex + 5" hood........718 cfm
4" flex + 4" hood........659 cfm
On my jointer I got the following:
6" flex + 6" hood........1029 cfm
6" flex + 4" hood........969 cfm
5" flex + 5" hood........1043 cfm
4" flex + 4" hood........811 cfm
Without any hookups to the tools, this duct flows well over 1400cfm.
With both machines hooked up at the same time with 5" flex and 5" hoods, the combined airflow is 1252 cfm.
Due to gauge reading errors, tolerance levels, etc, I expect the test results to vary by at least 20-40 cfm for each test. So don't get too picky. :D
When you look at those numbers, something to keep in mind is the brands of flex hose are different. The 6" hose is clear, very flexible (droopy) and has moderately heavy ribs. The 5" flex is really nice. It's grey and the ribs are very smooth on the inside. It's also not very flexible (can't bend it into a tight radius) so it isn't surprising just how well it can flow air. The 4" is your basic black 4" flex. I think this is why the jointer performed so well with the 5" flex because it's so smooth and the jointer airflow isn't being restricted much. Also, I found during testing if you lay out your flex hose in curves then you will reduce the airflow. If you straighten out the flex you'll increase the airflow. I didn't have space in my shop to be choosy so the flex curved and laid down where it wanted. Especially the 6" flex. But that's what it'll do at the tool so I wasn't too concerned.
To me, these numbers clearly indicate just how restrictive the planer is. That single 6" flex hose should be able to flow around 1150cfm in my configuration. This is an indication that you should really be paying attention to the tool itself to see if it can support the custom hood you're trying to install.
So, what does this tell you about 6" vs 4" drops and 6" vs 4" hoods? I'd say it confirms what you knew that a larger port and larger flex hose will flow more air. But now you have an indication of how much more it'll flow - at least with a large cyclone with a 7" main duct that's about 17' long and also has a few bends. :)
One set of tests doesn't scientifically prove anything, but would it be wrong to maybe use the following as a guideline if you want a ballpark number?
Going from 4" drop + 4" port to 6" drop + 6" port might give you a 20-30% increase in airflow at the tool.
Going from 4" drop + 4" port to 6" drop + 4" port might give you a 10-20% increase in airflow at the tool.
BTW, for this test my 5" and 6" hoses were about 10' long and the 4" was about 6' long.
I'm just trying to remove some of the mystery and unknowns from modifications like this so you all can make a more informed decision about what you'd like to do in your shop.
In the future I'll be duplicating a bunch of the tests I've been doing with a basic 1.5 - 2HP single stage DC unit. Something that more folks will have, rather than a large cyclone.
Cheers,
Allan
I had an interesting evening doing more airflow testing on my Delta 12.5" planer and Delta DJ20 jointer. My planer has the factory 4" hood and my jointer didn't come with a hood. So I made 6" hoods for my planer and jointer so I can get the most from my giant cyclone.
Before we start, I thought I'd mention that I got more airflow when my planer was actually running. So I can confidently pass on this great tip, turn your planer ON for better airflow. :p
On a duct run, I tried a variety of flex hose and port sizes at my planer and got the following results:
6" flex + 6" hood........779 cfm
6" flex + 4" hood........725 cfm
5" flex + 5" hood........718 cfm
4" flex + 4" hood........659 cfm
On my jointer I got the following:
6" flex + 6" hood........1029 cfm
6" flex + 4" hood........969 cfm
5" flex + 5" hood........1043 cfm
4" flex + 4" hood........811 cfm
Without any hookups to the tools, this duct flows well over 1400cfm.
With both machines hooked up at the same time with 5" flex and 5" hoods, the combined airflow is 1252 cfm.
Due to gauge reading errors, tolerance levels, etc, I expect the test results to vary by at least 20-40 cfm for each test. So don't get too picky. :D
When you look at those numbers, something to keep in mind is the brands of flex hose are different. The 6" hose is clear, very flexible (droopy) and has moderately heavy ribs. The 5" flex is really nice. It's grey and the ribs are very smooth on the inside. It's also not very flexible (can't bend it into a tight radius) so it isn't surprising just how well it can flow air. The 4" is your basic black 4" flex. I think this is why the jointer performed so well with the 5" flex because it's so smooth and the jointer airflow isn't being restricted much. Also, I found during testing if you lay out your flex hose in curves then you will reduce the airflow. If you straighten out the flex you'll increase the airflow. I didn't have space in my shop to be choosy so the flex curved and laid down where it wanted. Especially the 6" flex. But that's what it'll do at the tool so I wasn't too concerned.
To me, these numbers clearly indicate just how restrictive the planer is. That single 6" flex hose should be able to flow around 1150cfm in my configuration. This is an indication that you should really be paying attention to the tool itself to see if it can support the custom hood you're trying to install.
So, what does this tell you about 6" vs 4" drops and 6" vs 4" hoods? I'd say it confirms what you knew that a larger port and larger flex hose will flow more air. But now you have an indication of how much more it'll flow - at least with a large cyclone with a 7" main duct that's about 17' long and also has a few bends. :)
One set of tests doesn't scientifically prove anything, but would it be wrong to maybe use the following as a guideline if you want a ballpark number?
Going from 4" drop + 4" port to 6" drop + 6" port might give you a 20-30% increase in airflow at the tool.
Going from 4" drop + 4" port to 6" drop + 4" port might give you a 10-20% increase in airflow at the tool.
BTW, for this test my 5" and 6" hoses were about 10' long and the 4" was about 6' long.
I'm just trying to remove some of the mystery and unknowns from modifications like this so you all can make a more informed decision about what you'd like to do in your shop.
In the future I'll be duplicating a bunch of the tests I've been doing with a basic 1.5 - 2HP single stage DC unit. Something that more folks will have, rather than a large cyclone.
Cheers,
Allan