Senior Contributor
Posts: 316
Registered: ‎10-22-2009

Making a DC flow more air

Howdy gang,


We have a number of new folks to the forum and the topic of how to get more airflow from a DC has come up.  About 4 years ago I really got the bug to try and get as much airflow out of a DC as possible so I figured I'd repost this old note as inspiration for some of you to help get more airflow from your DC without the expense of buying a new one.  A giant cyclone isn't in everyone's budget and there's always a way to get a DC to flow more air.  All it takes is a little effort....and a welder is nice at times.  Smiley Happy


Here's the old note:


Project Hotrod is what I've been calling a pet project in my shop. Taking a generic 2HP dust collector and pushing it to the limits, and beyond, in order to make it flow more air. The original "project hotrod" has been put on hold while waiting for the owner to finalize some shop details relevant to the final modifications, but what I'm going to show you now is a similar set of mods on another generic 2HP DC.

Base unit: "Trademaster" 2HP/12" fan dust collector. It has two key qualities going for it. 12" fan and a large, 12amp motor. Most 2HP DCs only have a 9amp motor.

Step one was replacing the small factory filter bag with an oversize aftermarket bag from Lee Valley.

Step two was replacing the stock 5" blower inlet with a homemade 6" one.

Step three, which was completed on Tuesday night, was replacing the stock 5" blower exhaust and 5" flex hose with a homemade metal transition to the filter stand and building a stand to relocate the blower to being 3" from the filter housing. Sort of like the construction you've seen on 1HP units for years.

Airflow performance numbers for you:

Bone stock unit with 5" inlet and caked factory bag......630 cfm

5" inlet and brand new, clean Lee Valley bag.........810 cfm

6" inlet and brand new, clean Lee Valley bag........930 cfm

6" inlet and typical caked Lee Valley bag...............860 cfm

Now for the fun part....bring out the welder and sheet metal and make a new blower outlet. When combined with the 6" inlet and typical caked Lee Valley bag......1180cfm!!! That was with 10' of 6" pipe on the machine and even a 45* elbow right at the inlet! The 45* elbow was an old config - it'll be change later to a straight shot into the DC.

1180cfm is a long way from the 630cfm max it could muster up before. The performance is outstanding for this unit and best of all, it's doing that while flowing around 9.6amps on the 12amp motor. It'll last for a very long time.

Doing similar mods to the unit in my shop isn't going so well due to the combination of the motor and difference in fan styles. The Trademaster seems to have a much more efficient fan style than the one in my shop so at times the one in my shop is drawing over 10 amps while flowing in the 900cfm range. Not good for a 9amp motor.

If any of you want to do modifications to your dust collectors, you really need to have an ammeter to check the motor load. Otherwise you may be prematurely ending the life of your motor. I'm still planning on working on the 9amp motor DC in my shop (getting it to flow around 1040cfm with a 6" inlet for example....but at 11amps!) and you may be wondering why? Why do this if I'm already exceeding 9amps?

I still see value in making a DC as free-breathing as I can get it because then I can tune each duct run for each tool individually. If the DC will burn up when running a 6" pipe wide open, all I need to do is put a limit on the blast gate for each tool that will stop it from opening up more than the max current I'll allow. I just need to be aware of potential sawdust buildups in the pipes though. No big deal. If a drop needs more resistance I can always use a 5" drop to that tool instead. But the end result will be a shop that has every duct run tuned to flow the max air the motor will allow and that's the best I can do given that DC.

So, here are some pics for you:

dc_filter_housing: rectangular area cut out. The 5" round inlet has been completely removed.



dc_sheet_metal_forming: Using angle iron to bend the long folds and welding pliers to bend the small areas



dc_transition_almost_done: New transition clamped in place, waiting for last piece to be formed prior to welding



dc_transition_welding: I'm welding the transition together and then I welded it to the filter housing. We're using the standard gasket and bolts to hold the blower to the new filter housing transition.



dc_metalwork_done: The stand is made and the blower housing is bolted to the filter housing. We're a little bit tired and it's starting to show.  Smiley Happy



dc_back_together: Motor and fan are now bolted in place, inlet cover back on and bags attached. Machine is running at this point for a last ammeter check.



dc_testing: Using a fancy digital gauge that Randy brought from his work, we measured the airflow and it fluctuated between 1180cfm and 1190cfm as you see in the pic. Just enough airflow to pull down a passing satellite. Smiley Happy



Once again this is an example of seeing higher airflow results when you let the DC breathe easier.  Look at the entire airflow pathway:


shop air -> tool cavities -> port on the tool -> ducting -> DC blower inlet -> DC blower exhaust -> filter -> shop air


Is this pathway as open, short and straight as it can be?  If you are using a 6" main duct, is anything in the entire pathway smaller than 6"?  Any restriction will reduce airflow.


There are always a couple things to be aware of when it comes to moving sawdust, but with a little planning and checking, you can maximize your current DC to flow as much air as it can.  Your lungs will appreciate it.


By the way, since that DC mod I've come up with another modification to the inside of the DC filter stand that will make it flow even more air.  When my house renos are done I'd like to try and combine my idea with Phil Thien's and make an even better version of his separator that doesn't have as much resistance.  One of these days.....  Smiley Happy



Allan Johanson
WOOD Online Forum Host
Specialty: Dust Collection