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Connecting tools to Dust Collection System

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Forum topic by JK0702 posted 03-24-2016 01:38 AM 680 views 0 times favorited 11 replies Add to Favorites Watch
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JK0702

131 posts in 1599 days


03-24-2016 01:38 AM

I could use some help/insight with dust collection. I have a Delta Unisaw without a motor cover or dust collection plate (it’s the small rectangular opening at the bottom type, under the motor). I can fabricate a dust port out of MDF and PVC pipe. Question #1, should I make the opening 4” or 6”? Question #2, does anyone know where I can get a motor cover? They have been discontinued by Delta. No one wants to sell just the cover on CL.

Next is connecting the table saw, jointer, band saw, planer (all 4”) and a disc/belt sander (2 1/2”) to the dust collector. Does hose length matter for good air flow? Each tool gets a blast gate, but should it be closer to the tool or dust collector? Any other insight would be appreciated. If it matters, I have a 1 1/2 HP, 1200 CFM dust collector with dual 4” intake ports.

Thanks in advance

-- John - Huntington Beach, CA --- Growth occurs when we get out of our comfort zone.


11 replies so far

View conifur's profile

conifur

955 posts in 619 days


#1 posted 03-24-2016 02:26 AM

I cant comment on the saw, other then I would go with 4” on that, the others, smooth hose/piping you have better air flow, and length and elbows reduce air flow, as far as where the gates are it makes no difference. Put them where it is convenient for you to open and close. Most likely if like in my shop, I only use one tool at a time and I have an 1100cfm 1 1/2HP Jet DC.

-- Knowledge and experience equals Wisdom, Michael Frankowski

View JAAune's profile

JAAune

1646 posts in 1784 days


#2 posted 03-24-2016 02:44 AM

For a table saw, 6” is preferable over 4” duct. If your collector can handle 6” duct then go for it.

Technically, blast gates located near the collector will result in less leakage. It’s way more convenient to locate them by the tools they service.

-- See my work at http://remmertstudios.com and http://altaredesign.com

View Fred Hargis's profile

Fred Hargis

3950 posts in 1961 days


#3 posted 03-24-2016 10:49 AM

I think that’s the saw I had and 6” is tough to do on that opening. I did that, but had to squash the pipe slightly into an oval to get it to fit under the shelf (thin wall PVC). The flange was a piece of plywood that I bolted to the cabinet, the PVC was screwed on the inside to the plywood. This works very well, but you do need to motor cover.With your DC it may be best to go 4”, and then plan on something over the blade.

-- Our village hasn't lost it's idiot, he was elected to congress.

View Redoak49's profile

Redoak49

1964 posts in 1456 days


#4 posted 03-24-2016 11:02 AM

Given your dust collector, 4” is likely the max size you can go to keep reasonable air speed in ducts. I have a similar collector and measured speed and cfm at the dust collector inlet. It was about 650 cfm and what is expected for that size motor and impeller. Companies over rate their collectors all the time and likely test them with no filter bag or canister.

View JK0702's profile

JK0702

131 posts in 1599 days


#5 posted 03-24-2016 12:17 PM

Thank you for the input so far. It looks like 4” for the saw port.

Fred, the picture you attached is the exact saw I have. Thanks for showing me how you did yours.

Anybody know where I can get a motor cover like the one shown in Fred’s picture?

-- John - Huntington Beach, CA --- Growth occurs when we get out of our comfort zone.

View brtech's profile

brtech

906 posts in 2390 days


#6 posted 03-24-2016 02:27 PM

I’ll betcha a local friendly HVAC contractor can make you one in an hour. Might have some tape on some edges, but it would work. Give him a picture, a couple key measurements, a beer and a few $20s and it will come out fine.

Another idea is build one yourself out of lexan, ply, or some other flat sheet (1/4”). Reinforce the edge joints with a hunk of 1×1 or even metal brackets.

View RonnW's profile

RonnW

2 posts in 261 days


#7 posted 03-24-2016 06:22 PM

You asked about length of ductwork. It is important. I did a fiar amount of research before buying my 1 3/4 HP Laganu DC. I urge you to google “Air Handling Systems” to find design info. I could roughtly summarize as follows. Your DC can effectively work with a max run of about 20” of straight 4” duct. But keep in mind that a 45 deg elbow is equivalent to 3” of straight duct, a 90 degree elbow is equal to 6” of straight pipe and one ft of flex pipe is eqaul to about 5” of straight pipe. This is assuming that you are running only one machine at a time and that the ducts to all other machines have closed blast gates.

I set my shop up so that the dc is one corner and I ran a 4” main along the wall to the right to my table saw, router table, drum sander and jointer and a 4” line to the left to my planar and band saw. I kept the 4” main mounted to the walls at a level that used the fewest elbows. No unnecessary vertical runs. I connected that DC to each main with the shortest piece of flex that would do the job and I came off the the main at each machine with a 45 deg wye and a short run of flex line. If your layout is simple like mine is, you really don’t have to worry about CFM and other calculations unless y our are really into the engineering end of it.

Another thing to keep in mind is that the fine, light dust from a sander can travel more easily than the chips from a planar.

I hope this helps.

View brtech's profile

brtech

906 posts in 2390 days


#8 posted 03-24-2016 06:35 PM

RonnW, I think you meant 20’ (feet) of straight duct. I was less sure if a 45 elbow is equivalent to 3” or 3’ of straight duct, probably is feet and the same with the equivalents for 90 elbows and flex.

View Redoak49's profile

Redoak49

1964 posts in 1456 days


#9 posted 03-24-2016 07:03 PM

If you use the Pentz spreadsheet calculator to estimate the static pressure of your duct system for 4” duct, you get the following in terms of losses.

Each 10 foot length of 4” duct provides 1.67” of static pressure (SP)

For a 90° elbow where the radius of the elbow® is the same as the duct diameter(D) – 1.12” SP or equivalent of 6.7 feet For elbows with longer radius, the such as a R/D of 2.0 you get 0.70” SP or equivalent of 4.2 feet. For elbows even longer radius, such as a R/D of 2.5 you get 0.63” SP or equivalent of 3.8 feet.

The standard PVC elbow that I have, the R/D is about 1 so it is equivalent to 6.7 feet of straight duct.

Pentz also suggests that it is easiest to just assume that a 45° elbow is half of a 90° elbow in terms of SP.

The Pentz spreadsheet is pretty useful in looking at the differences in various duct designs.

View JK0702's profile

JK0702

131 posts in 1599 days


#10 posted 03-24-2016 07:49 PM

Okay, that Pentz spreadsheet calculator gave me a head ache :-) The takeaway seems to me, to be as direct with your routes as possible, and have the fewest turns (90’s and 45’s) as possible. Straight pipe where possible, flex pipe where needed. Is that about right?

-- John - Huntington Beach, CA --- Growth occurs when we get out of our comfort zone.

View brtech's profile

brtech

906 posts in 2390 days


#11 posted 03-24-2016 07:51 PM

Sure, but no 90s. Either a wide sweep, or two 45s and a short straight section. Also use Wyes, not Ts for branching.

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