Dust Collection Question

[Darren Vass]

I've been using my Harbor Freight 2hp DC through two 10' 4 inch flex hoses into a 32 gallon trash can with the Woodcraft cyclone top on it. I've noticed that the suction was not very strong. I cut the 4 inch hoses last night in half and noticed that the suction was stronger. In fact, I have a trash bag inside the can, sealed on the outside of the can with an elastic tie and a thin wire mesh cylinder inside the bag to keep it from being sucked up. The wire mesh folded inward from the pressure of the plastic bag after the modification of the hoses. Took out the plastic bag and the suction is stronger. I don't think the trash can is large enough because alot of the dust is making it to the plastic bag that swirls the collected dust around.

I wanted to do as the link below shows and wondered whether this was feasible with the HF machine. I looked in the blower and the impeller is only 10 inches across. My thought was to change out the outlet and inlet to 6 inch diameter with about a 6-8 foot run of 6 inch sewer pipe from the outlet. I want to mount the blower from the ceiling directly into the top of the trash cans that will sit on a table.

I'm not sure whether 1) I will burn the motor and/or 2) whether this motor coupled with the 10" impeller would be sufficient to suck through 6 inch pipe as stated above?

I truly appreciate your help.

http://www.woodcentral.com/shots/shot672.shtml

[Bill Lewis]

1. You will not burn up your motor. Contrary to what you would think, the motor is under no load if the inlet is blocked. Only when it is moving air is it doing any work.

As for number 2, well my gut instinct is that the 6" pvcis too big, and the 4" pvc is too small.

I used to have a JET 1200 DC, and I considered building a (Wood Mag) cyclone for it, but when I started thinking aobut all of the extra elbows and pipe that are needed I see a lot of lost energy, thereby reducing the efficiency greatly. Plus the amount of floor space that is taken up is almost double that of a cyclone unit.

I did have a drum separator for the Jet, but it was obvious to me that there was a big reduction in suction using it. BTW, Another killer for suction is flex hose.

[Tom Berninghausen]

The HF 2hp DC gets a lot of positive reviews all over the woodworking sites, so it must work OK. I've recommended it to my brother for his turning work.

From my experience the plastic garbage can top separators are best used in the garbage can and put on the street for collection. The can is "full" at the middle of the can and then the material goes to the DC and fills the bag. So much for saving wrestling with the DC's bag.

If you return to the Shop Shots page, you will notice that the first photo is a preseparator with four inch pvc piping. It worked OK, I changed to six inch pipe when I stepped up to a cabinet saw from a contractor saw---and just to see what the improvement might be. Works much better. Big difference in cost for the six inch fittings though, shop plumbing suppliers and shop several---I saw double the cost at different shops.

I'm don't think your plan would work, due to the garbage cans being after the blower, if I understand your description. Your DC needs the filter bags for exhaust\collection, even with a preseparator or a cyclone---air's got to go somewhere.

Bottom line: the HF DC should be fine with either 4 inch or 6 inch pvc (since five inch pvc doesn't exist), it will work much better with the pvc then it did with the flex, and if you shop plumbing suppliers (and soft drink companies) you won't spend a lot of money.

Give it a try. If it works you've improved your shop. If it doesn't, well, don't tell anyone and try some thing else. PM me if I can be of any help.

Tom

[Dave Harker]

To preserve a 6" diameter thru my separator, I made my own out of two metal trashcans, making the top one into a mini-cyclone, over the bottom one. The web link below has several pics, and much more info on how I made it.

It works well, the lower trash can is nearly full before any shavings start to show up in the clear lower-bag on my Grizzly G1029 DC.

http://webpages.charter.net/harkerho...separator.html

[Darren Vass]

Tom,

I did not make my layout plan clear:

Machine connected to short run of four inch flex hose, connected to short run of 6 inch flexhose to 6 inch sewer pipe 6-8 ft up to top of garbage cans, then air sucked up through 6 inch pipe through top cover of garbage cans directly through to blower housing to 1 micron poly air filter and plastic bag on the bottom.

[Jim Becker]

Darren, many folks that have tried to do the 6" duct/hose with a common trash can separator have reported that the air flow increase from using 6" duct/hose basically empties the pre-separator, rather than dropping the chips out. This is a damned-if-you-do, damned-if-you-don't situation...

[Darren Vass]

I wonder though whether they had used the combination of the 2x50 gallon barrels as in the intial link I had posted? It would seem that there would be a lot more volume of air to suck up in this setup than with a single 30 gallon can. The example of the duo 30 gallon metal cans seems to work in the posted example.

[Tom Berninghausen]

Hi Darren,

The main challenge I think you are building into your system is using the flex hose. I'd recommend using pvc, 4 or 6 inch, to as close to your machines as possible. As to the flow in the preseparator in the Shop Shots, the plastic bag on the DC doesn't recieve any shavings until the "window" in the barrels fills with material, then shavings pass just like the garbage can (single) setups. Flow through is good with either 4 or 6 inch pvc. And the up and down travel doesn't seem to be any major problem either. As with all ducting the elbows do cause some drop in air speed, but the "two-barrel" preseparator works great. As far as a bigger volume of air in the barrels, once flow starts, the blower only deals with resistance, not volume, it's just pumping air (and shavings, dust, etc). Seems that the increase in volume in the 55 gallon barrels might overcome the early fill habit of the single 32 gallon setup.

If your setup would be like Dave Harker's (nice metal work Dave!), with the "exhaust" from the preseparator going into your DC's intake, it should work fine.

Tom