Dust collection

rocke1 · Post by **rocke1** » Fri Jan 30, 2009 3:53 pm

A few years ago I bought a Jet 650 with the 1 micron filter canister to replace my faithfull DC3300. Cleaner air and the propect of much greater volume was my reasoning. Well to a degree that works. But after Nick Engler did a good session on a system I looked a bit closer at what you can get with the 2 1/2 inch ports on all my SS machinery and the practical results in a small shop with 2 1/2 flex hoses I use. Shopsmiths woodworking for every one stated that with 8 feet of hose on one outlet that 107 cuft was available with the DC330. At first I thought the 650 Jet would really boost the volume however a bit more study in wood magazines article of systems stated that the max cfm for a 2 1/2 port was 140 cfm max. So a non scientfic test of mine did show the gain with the Jet wasn't anything like doubled. Using a wind speed meter at the end of a short 2 1/2 inch hose came up at 80 mph. That's 7040 ft per min and calculates to 153 cfm. So with the errors of measurement probably comes up to the 140 cfm max. The 4 inch to 2 1/2 inch adapter means more loss and the velocity in the short 4 inch flex hose really drops the advetised 6750 fpm for the Jet way down so that the hose holds a bit of dust in the folds of the hose. So with the 1 hp Jet against the 1/2 hp DC3300 a lot less electrical power for the SS.

Had I known I'd have kept my DC3300.

Rock (300sq ft garage shop)

dusty · Post by **dusty** » Fri Jan 30, 2009 4:10 pm

rocke1 wrote:A few years ago I bought a Jet 650 with the 1 micron filter canister to replace my faithfull DC3300. Cleaner air and the propect of much greater volume was my reasoning. Well to a degree that works. But after Nick Engler did a good session on a system I looked a bit closer at what you can get with the 2 1/2 inch ports on all my SS machinery and the practical results in a small shop with 2 1/2 flex hoses I use. Shopsmiths woodworking for every one stated that with 8 feet of hose on one outlet that 107 cuft was available with the DC330. At first I thought the 650 Jet would really boost the volume however a bit more study in wood magazines article of systems stated that the max cfm for a 2 1/2 port was 140 cfm max. So a non scientfic test of mine did show the gain with the Jet wasn't anything like doubled. Using a wind speed meter at the end of a short 2 1/2 inch hose came up at 80 mph. That's 7040 ft per min and calculates to 153 cfm. So with the errors of measurement probably comes up to the 140 cfm max. The 4 inch to 2 1/2 inch adapter means more loss and the velocity in the short 4 inch flex hose really drops the advetised 6750 fpm for the Jet way down so that the hose holds a bit of dust in the folds of the hose. So with the 1 hp Jet against the 1/2 hp DC3300 a lot less electrical power for the SS.

Had I known I'd have kept my DC3300.

Rock (300sq ft garage shop)

I never go back and reevaluate past, irrevocable decisions. I always come up on the losing side so I quit checking.

:rolleyes:

beeg · Post by **beeg** » Fri Jan 30, 2009 4:11 pm

Thanks Rock. I've often wondered if I should have gotten a different dust collector.

And what Dusty said.

fjimp · Post by **fjimp** » Fri Jan 30, 2009 5:35 pm

Leave it to Dustry to esplain it to us in clear and understandable terms. fjimp

8iowa · Post by **8iowa** » Fri Jan 30, 2009 6:31 pm

It seems that a commonly held belief is that the larger the diameter of the piping/hose, the "better the flow". While the larger diameter may reduce friction somewhat, the air velocity falls off inversly to the increase in cross sectional area of the pipe. Once the velocity falls below 3500 fpm, dust starts to fall out of the airstream and collect in the hose and piping. You can get a 5HP dust collector with 8" pipes and still find that it doesn't work.

Other than the minimum velocity of 3500 fpm, the system needs to be able to have enough flow capacity to keep up with the production of dust and chips being produced by the machine. Once a dust collection system satisfies these two requirements everything is fine. If the 1/2 HP DC3300 can satisfy these requirements, then oversizing your dust collection system, both in HP and pipe diameter is nothing but money and space wasted, not to mention the increased electrical requirements. I think the real test of the DC3300's ability is when it is hooked up to the Pro-Planer. I find that virtually all the dust and chips off my planer's cutter head are promptly sucked up into the bag. Obviously the flow capacity is adequate.

A few months ago I criticized Wood Magazine's report on dust collection systems, titled "for the home workshop". They only tested one 1 1/2 HP unit and gave it poor marks. They convinced their readers that the 2 HP Grizzly was the best home workshop dust collector (also their top advertiser). I sent them an email telling them that a 2 HP unit with 4" piping was way "overkill" for the average garage and basement workshop. I even sent them a link to Nick's sawdust session on designing a dust collection system.

On the lumberjocks forum I've tried to explain how a lower HP system with 3" piping and a 2 1/2" hose will do the job, but I'm beating my head against a brick wall. The thought still prevails that you simply have to have at least 2 HP and 4" or 6" pipes.

rocke1 · Post by **rocke1** » Fri Jan 30, 2009 7:08 pm

dusty wrote:I never go back and reevaluate past, irrevocable decisions. I always come up on the losing side so I quit checking.:rolleyes:

Not so much a look backward as a help to others in regards the bigger is better advertisements imply.

rock

qtndas01 · Post by **qtndas01** » Fri Jan 30, 2009 7:21 pm

I use a permanent piping dust collection system in my shop using 4" thin walled PVC going into the Shopsmith Dust collection. The design came from Shopsmith many years ago. I have 45 degree branches off to 2 1/2" tubing to the equipment. I don't think Shopsmith even offers the 4" connector into the DC anymore. maybe that is why Nick had the system they recommended. I was looking to purchase another DC to the other side of my shop and could not find the 4" connector in the catalog anymore. I have been very pleased with the results of my system.

nuhobby · Post by **nuhobby** » Fri Jan 30, 2009 9:21 pm

Cool analysis, rocke1!

BTW, I keep noticing that Festool gadgets (which always get rated highly) seem to be designed for small dust-extraction tubing. Chances are they really have optimized the fluid (air) mechanics by design.

charlese · Post by **charlese** » Fri Jan 30, 2009 10:41 pm

Rock -As I read through your post (#1) I thought to myself - this guy must have a whole lot of respect for all the folks on this forum to thoroughly expose the performance of his Jet 650 DC. Especially, now that he has discovered his mistaken purchase!

Thank you very much for swallowing "pride-in purchase" and posting your effort to help enlighten us!:D

As 8iowa has also told us: The more power/new tool advertising has/is succeeding in developing a "more/newer tool" myth that is universally accepted.

iclark · Post by **iclark** » Sat Jan 31, 2009 1:53 am

8iowa wrote:Once the velocity falls below 3500 fpm, dust starts to fall out of the airstream and collect in the hose and piping.

hi, 8iowa,

can you point me somewhere to learn more about this? since it is independent of the flow diameter, it has to be based on something besides Reynold's number or making the flow laminar or turbulent.

thanks,
Ivan

Shopsmith Forums

Dust collection

Dust collection

Bigger not always better....

Thank You Rock!!!