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Modifying a dust collector...is the venturi effect considered?

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Forum topic by DocSavage45 posted 03-21-2017 12:06 AM 2789 views 0 times favorited 13 replies Add to Favorites Watch
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DocSavage45

8112 posts in 2505 days


03-21-2017 12:06 AM

Topic tags/keywords: question dust collector air movement improvement

Talking with a friend about modifying my Delta 1.5 hp dust collector. I was explaining that the intake has a 6 inch diameter nub where the 4 inch dual connection screws on. And I noticed that the hole that allows the air into the shroud was smaller tan 4 inches??? He mentioned the venturi effect. Is this smaller hole important in creating the suction?

I have been reading Pentze’s information and looking at YouTube and checking forum topics. I need to move so many cubic feet per minute. The ducting is most efficient if diameter is larger. 6” vs 4 ” and the often used flex tubing provides significant wind resistance.

My plan was to sell the Delta and buy a 2 hp dust collector like a Grizzly which has larger impeller and an actual 2 hp motor and run it at 220. Not much response on my Delta DC from Craig’s list or scammers and low ballers. It is in excellent condition.

So I’m investigating modifyig the impeller and wring the motor for 220. So far Delta service mechanic says too many unknowns and it could destroy the machine? My friend said take the low ball.

I am not jumping into this, but I actually have a HF dust collector sitting new in a box that I found has a very small impeller and sucks not as advertised.

Looking for informed technical and mechanical advice and suggestions here in the forum.

Thanks for your input!

-- Cau Haus Designs, Thomas J. Tieffenbacher


13 replies so far

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shipwright

7553 posts in 2461 days


#1 posted 03-21-2017 12:21 AM

I can’t speak to your other questions Tom, but for the air flow I can add an observation that I made in my system at home. http://lumberjocks.com/shipwright/blog/31966
I find that in a multiple branch system like mine that it sucks better when some air is let in at the extreme end. In the case of my system, the last thing at the end farthest from the DC is a downdraft sanding area in my primary bench.

Just out of the picture, at the top there are two ~1” finger holes for lifting the hinged lid.
If I block those holes it seems to create a vacuum behind the first branch entering the main (the table saw as it turns out). Strange as it may seem the table saw seems to get better suction if the holes are open.

Just an observation and admittedly not exactly on topic but as you are doing a pre-build analysis, I thought I would throw it out there.
Good luck with your system.

-- Paul M ..............If God wanted us to have fiberglass boats he would have given us fibreglass trees. http://thecanadianschooloffrenchmarquetry.com/

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DocSavage45

8112 posts in 2505 days


#2 posted 03-21-2017 01:17 AM

Thanks Paul, That is something I have run across as there needs to be air flow. How many HP in you DC?

-- Cau Haus Designs, Thomas J. Tieffenbacher

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pontic

338 posts in 271 days


#3 posted 03-21-2017 01:28 AM

When you decrease the diameter of a pressurized tub system you increase the air flow but decrease the pressure. Conversely if you decrease the diameter of your suction unit you will increase the air flow but decrease the mm. of Hg. or neg. pressure. This may reduce the ability to move large wads of sawdust all at once.

-- Illigitimii non carburundum sum

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DocSavage45

8112 posts in 2505 days


#4 posted 03-21-2017 01:38 AM

Pontiac Thanks,

Trying to increase the cfm at source. A number of unknow varibles? The size of the hole at the entry to the shroud is reduced. 1. Does that affect air flow? Would enlarging the impeller or changing the design of the impeller ( different manufactures) also increase air flow?

and then… is it all affected by that inlet port?

-- Cau Haus Designs, Thomas J. Tieffenbacher

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pontic

338 posts in 271 days


#5 posted 03-21-2017 02:20 AM

Increase the cfm at source. You can decrease the diameter of the inlet(not by too much). You also could increase the rpm of impeller. You also could increase the size of impeller. Usually Manufactures just increase the size of the impeller and its cage keep the rpm’s the same.
Some of the commercial units have two stage empeller systems or multi pully belt drive systems so they can increase the rpms. In short if you want more CFM in all your dust collection system get a bigger unit and a prestage collector or cyclonic collector for worry free operation.

-- Illigitimii non carburundum sum

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DocSavage45

8112 posts in 2505 days


#6 posted 03-21-2017 04:01 AM

Sorry about previous misspelling of your avatar…. Pontic, Thanks again,

If I could see the bigger impeller characteristics I’d be more apt to go ahead. As long as vanes are in same direction and the width fits the cavaty of the current shroud.. At this point no pictures of any impeller I might buy.. If I had the funds and not two dust collectors I also would buy a larger dust collector ie, impeller and motor.

I have a 55 gallon Thein collector preceding the dust collector and measured cfm’s today and then at the end of a 50 foot flex hose which is currently in use.the drop in volume movement was down to half at the point where I’ve been connecting the hose to my machines. Sigh!

-- Cau Haus Designs, Thomas J. Tieffenbacher

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shipwright

7553 posts in 2461 days


#7 posted 03-21-2017 04:15 AM



Thanks Paul, That is something I have run across as there needs to be air flow. How many HP in you DC?

- DocSavage45

It’s a Craftex 3Hp but is handles my fairly large system well, especially with the Donaldson canisters.

-- Paul M ..............If God wanted us to have fiberglass boats he would have given us fibreglass trees. http://thecanadianschooloffrenchmarquetry.com/

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DocSavage45

8112 posts in 2505 days


#8 posted 03-21-2017 05:07 AM

Thanks Paul,

3 Hp is generally recommended and it also costs more to run. LOL! With your dust collector table and lathe which are open ended the extra volume in cfm is needed and with 3 hp the open blast gate at the end of system is warrented. I just ran a cfm check and I loose have my capacity before it gets to my 3 hp table saw or the 2 hp band saw which has two dust collection ports.

I’m at least going to improve the waste removal with some ductwork. ( previous forum topic LOL!)

-- Cau Haus Designs, Thomas J. Tieffenbacher

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pontic

338 posts in 271 days


#9 posted 03-21-2017 12:52 PM

If you have two dust collectors then Make a two stage system.

-- Illigitimii non carburundum sum

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pontic

338 posts in 271 days


#10 posted 03-21-2017 01:02 PM

Take one of your dust collectors and move it as close as possible to the problem source.

-- Illigitimii non carburundum sum

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DocSavage45

8112 posts in 2505 days


#11 posted 03-21-2017 06:05 PM

Pontic,

Again good suggestions. If the dust collectors pulled evenly a two stage might work. But they might work against themselves causing motor overload?

My main shop area is a room that is 12 ft by 26 ft which is @ equal to one side of a 2 car garage. I have other rooms that serve as storage and furnace room. Another room has my floor mount drill press , sander and I planed to make a paint booth some day.

Awhile back I build a garden shed next to my shop which holds the Dust collector and 55 gallon thein chip collector and the 50 ft hose was to be temporary. LOL! Trying to fix that now, but I was ignorant of dust collection details although I was understanding health risks.

I’ve since added a 3 hp cabinet saw, lathe and now a 17 inch 2hp bandsaw. In that workspace

As it is said “Hindsight is 20-20.”

-- Cau Haus Designs, Thomas J. Tieffenbacher

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pontic

338 posts in 271 days


#12 posted 03-22-2017 02:05 AM

Bingam’s effect says that when two Compressors or Vac’s. are hooked in series the distal devise requires less power to work. So they will not burn each other up.
You will just not get twice the suction that you would think you would.
I think your best bet would be to hook up one of your collectors to the machine that makes the most dust and just dedicate it to that tool.

-- Illigitimii non carburundum sum

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DocSavage45

8112 posts in 2505 days


#13 posted 03-22-2017 04:02 AM

You’re probably right and I would like to keep the Dust collector and Thein chip collector out of my work area. That said I have another solution in mind. I have 6 Inch galvanized pipe and flexible elbows that cannot be returned to my big box store because they’ve changed suppliers. Keeping bends to a minimum 45 degree angle I will put the pipe together and run a test. i also have 6 inch metal flex pipe that I can use with the DC.

The connecting in series might improve the two smaller machines enough for a total of 40 ft as a main with 4 inch legs at the machines with metal blast gates.

-- Cau Haus Designs, Thomas J. Tieffenbacher

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