DC at 2 1/2 inch

[David Mueller]

What's your experience using your DC with 2 1/2 inch devices. I find it doesn't suck very well. Case in point, my DP has a loc-line DC and my shop vac seems to have better air flow then when I hook it up to my DC which is mostly 6" with some 4" lines. I find i'll most likely stick with shop vac for this type of use.

[Jim Becker]

Dust collection systems are designed to move a lot of air at low static pressure. Small ports allow for very little air and generate higher static pressure...which is why a shop vac actually works better on them. Nature of the beast. You might try opening another gate while hooked to the small port and see if that helps things a little, but the small vac is still likely to give you better performance.

[Ken Deckelman]

David,
I use the LocLine on my DP also (my local Woodcraft had all the LocLine stuff at 50% off one day when I just happened to stop in there ).
Anyway, I do what Jim suggested, I open a 4" gate thats on the same trunk as the DP, and the suction is fairly acceptable.

[Allan Johanson]

Hi David,

Stick with a shopvac for small ports for the reason Jim suggested.

Using your big DC and opening another branch somewhere else is going to do two things, one good and one bad:

- Bad thing: reduce the airflow through the tiny port you wanted in the first place.

- Good thing: increase the airflow in the main duct to help reduce potential clogging issues.

Cheers,

Allan

[David Mueller]

Thanks everyone, your conclusions support the data. Maybe I'll use this excuse to get another vac, Fein maybe?

[glenn bradley]

I have also experienced what others have put forward. Small port devices seem to work better with the vac than with the DC throttled down to fit. You don't move as much air but it is more focused. The exception is my jointer where I was able to adapt the rectangular hole to a 4" port. The factory 2 1/2" adapter didn't appeal to me for a jointer but the 'area' of the rectangular port was about 12 square inches. A little hardboard and a 4" coupler and I was in business.

[Mike Cutler]

David.

A few tricks that you might want to try that sort of combine everyones ideas.

Process flow( wood dust in a DC system) is equal to the square root of D/P (differential pressure) across an orifice. If the orifice restrictions becomes smaller, the flow rate across the nozzle decreases, even though the actual D/P at the nozzle, in H2O is increasing. The system CFM is decreasing, and the dynamic pressure in the pipe is decreasing. Opening another orifice, or blast gate allows the the dynamic flow of the process medium in the pipe to increase. The closer the other orifice is to the 2 1/2" orifice will aid in acting as an process eductor. If you were to put the 2 1/2" connection on a "Y", and put a blast gate on the other leg of the "Y", open to ambient pressure conditions, you could "throttle" the blast gate to enhance the dust collection capabilities at the 2 1/2" opening. Essentially what's happening is that the flow rates at the back of the "Y" are increasing, and the D/P across the 2 1/2" opening is increasing, but the overall net pressure D/P is decreasing, and or remaining constant at the "Y", and system CFM is increasing. There is also a larger negative pressure behind the 2 1/2" opening, due to the effects of vacum eduction.

So..... You could place a "Y", and blast gate close to the Loc line on your Drill Press, or.... you could get a Fein Turbo Vac. I have one and they're great. Very handy to have around the shop.

Me personally. I'd go for the Fein, and forget the jury rig setup that I outlined above


PS. I'm a little bored today. Could ya' tell Chased the horse around the pasture this morning, so now I'm kickin' back in the AC and staying away from the heat and humidity outside.

[Allan Johanson]

Interesting brain food, Mike.

I wish I had instruments that could measure airflow without requiring Dwyer's "10 diameters" of straight duct length for accurate readings.

Adding a "Y" should reduce the overall entry loss of the system, increasing the overall cfm, but a chunk of that cfm will now be coming through the open "Y" branch. Where would the balance be between the two branches even considering the eductor influence of a higher negative pressure area at the "Y" to help the desired branch?

I have a feeling the primary benefactor of the increased airflow would be at the open "Y" branch. Therefore I'd simply run a second hose to the tool so I had two hoods instead of one. Then all the increased airflow due to the lower entry loss would be helping me breathe easier.

Or I'd use my shop vac.

Cheers,

Allan

[Frank Fusco]

Some good experience out there. On this subject I'm a newbie. I just adapted my new Shop Vac (12 gal, 5.5hp, 2 1/2" hose) to the 4" port on my bandsaw. Seems to work real well. Prior to that dust was everywhere now sawing is a clean operation and keeps dust off of stuff in shop. I plan to make a collector for the lathe next.

[Mike Cutler]

Allan.

Yeah, it may not have been as effective as simply running two branches of 2 1/2", but...... dang that horse was fast

Note to all. No matter what stage of recovery an X-Thoroughbred racehorse is at. He's still way faster than a human. Glad it was only a 2 acre pasture I had to chase him around in.

I'd still use the inefficiency of the setup to justify the purchase of a Fein, or Festool vac.

[David Mueller]

Thanks for all oyur comments, a Festool CT-33 on order as wee speak.