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Dust collection - what did I do wrong or right or what else can I try?

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Forum topic by WorksInTheory posted 01-17-2018 12:53 AM 3872 views 0 times favorited 28 replies Add to Favorites Watch
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WorksInTheory

143 posts in 1748 days


01-17-2018 12:53 AM

Hello – I have finally executed on a dust collection solution after all this time. Took forever to get to it but I did. Now I don’t know if I just misapplied all the hodge podge of stuff I read up on so looking for commentary and suggestions.

I have a Harbor Freight DC (the 2hp one). I put it together like April Wilkerson or Jay Bates, using the middle part as a Thien Baffle.

I know I should run a straight section for 6ft out of the machine but I don’t have that sort of set up or room, so I opted for a short run to make up for having to curve down. It literally just goes right into a router/saw/bandsaw line up right next to it.

The inlet is 5” but I opened it up to 6” w/ a sloping adapter. Then it’s 6” HVAC run until I have to branch off, so 4” to router w/ 2” branch from there to go to fence port. Also 4” to table saw and after.

Total run is probably under 7 to 10 feet long.

Any issues, any improvements. Should I have gone up to 6” where I could or should I have kept it 4”. Already had stuff for either but not 5”. Running one machine at a time and will shut off not used machines w/ blast gates.

Is venting it right out a door reduce suction performance or increase? Or would putting a bag over th eoutlet make it work better.

Thanks for your POV.


28 replies so far

View jimintx's profile

jimintx

834 posts in 1730 days


#1 posted 01-17-2018 01:06 AM

It seems to me that you have it just fine. Your design makes sense, and the blast gates are a must – which you have in the system.

I run a straight from the store, Powermatic system, and think it does great. Some of my runs are simply flexible 4” hoses, with no issues I detect. I cannot give any experience-based input on the HF based collection, but many, many others can speak from their experience there.

I am fairly certain that dust collecting might be the most over-worked problem in internet woodworking forums. Personally, I don’t think you can get it to 100% perfect. I say, don’t spend too much time thinking you are going to make your workshop living room clean. That’s ok, because you aren’t doing this work in the living room. Go with what you can reasonably assemble, and start making saw dust.

-- Jim, Houston, TX

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WorksInTheory

143 posts in 1748 days


#2 posted 01-17-2018 01:48 AM

jimintx – thanks for the response. I think you are so right and advice is sound.

My main 2 wonderings were 1) did I break a rule of some sort taking the HF and going up to 6” when it’s a 5’er, esp just to then go to 4” to the tools.

2) is there some guidance on performance if you just run it out the door vs into a Wynn filter, etc. I have the original 5 micron bag that I can sew so that it goes over the outlet as well if it needs ” resistance” etc.

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jimintx

834 posts in 1730 days


#3 posted 01-17-2018 02:11 AM

The 6” run going to 4” drops to tools is fine, and oft done. The 5” opening of the HF device should not imply that the main run to it should also be the same. Your scheme should give you good flow results. Similarly, smooth pipes will improve flow and produce a more efficient system than will the “corrugated” flexible tubes.

There is a definite pressure differential across any type of filter. Running the outflow out a door, or otherwise to the outside, has the effect of reducing “back pressure” on the system. It should directionally improve the operation of the system, not worsen it. Of course it might spray some dust into some area where it is not desired. That depends on your own location and criteria.

-- Jim, Houston, TX

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Rayne

1058 posts in 1685 days


#4 posted 01-17-2018 03:08 AM

When I was doing my research on duct size, increasing it was a bad move due to the DC not designed for a full 6” run. With yours though being only up to 11’, I can’t imagine it hurting it too much.

2) If you vent outside, you need to be able to bring air in as well. It was something about negative air pressure inside the shop from my memory. Someone with more knowledge will be able to explain it better or just search the forums and I’m sure you’ll run across that same question. Going through Wynn Filter is perfect in a closed garage.

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WorksInTheory

143 posts in 1748 days


#5 posted 01-17-2018 02:55 PM

Thanks Rayne and jimintx

Rayne – my garage has more leaks in it than… uh a gossip column? a leek garden? I don’t have a good joke right there, should have thought that through. Anyhoo so I think the air will be replaced.

For clarity I am not using a Wynn filter. Trying to avoid the cost and the space. It’s just going out the back door (also another source of air replacement?).

jimintx – I have a thien baffle in there so hopefully hardly anything is coming out the door but I haven’t
“pressure” tested this theory yet. I have used it and nothing is coming out but I haven’t cut a lot of stuff yet or done the router, etc. But your words encouraging and validating so far.

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Carl10

109 posts in 603 days


#6 posted 01-17-2018 03:35 PM

Everything looks good with your setup, except the 6” pipe. DC optimization is all about restrictions, both on the input and output. Since you vent outside you have eliminated the bag restriction (good thing). It appears you have kept the 5” exhaust hose but increased the inlet to 6”. So you are trying to take in more air through a 6” opening than you can exhaust through the smaller 5” outlet. Making the exhaust 6” will help that balance.

So I mention the 6” inlet as a possible issue because of velocity. The larger the pipe the higher velocity that is needed to keep things airborne. The HF DC uses an undersized impeller greatly reducing the available CFMs (that’s why people upgrade the impeller). To keep things airborne in a 6” duct you want your velocity to be~3500FPM. To get that you need 686 CFMs in a 6” pipe. The stock HF DC with a 5” inlet can’t produce 600CFM. Now you have removed the filter restriction and opened the inlet so it is unknown what your unit can produce. You also do not have a planer which really needs a higher velocity to keep the chips from clogging.

Most would think (myself included) that with such a short run it wouldn’t matter. I actually had 6” duct running 8’ from my small cyclone. When I hooked up my Pitot tube and measured velocity I was surprised that it was less than 2800FPM. So I reduced my duct to 5” and tried again and my velocity was up above 3300FPM. Not as much as I wanted but much better and this is only a temporary setup until my shop is done. So bigger is not always better.

Also, removing too many restriction from your DC can also be bad. If you opened the inlet and exhausted outside without connecting your separator or ductwork you could burn up the motor. By letting the motor run too freely you draw more current and it can burn up. In your situation, the Thein separator adds about 3” of SP add your ducting and hoses and you have enough resistance not to worry.

Bottom line, check your horizontal ducting occasionally for any dust building up due to lower velocity. Usually with that size of DC 5” ducts are usually best. 6” is too big and 4” is too restrictive. Plenty of people run miles of 4” pipe and claim it “works great”, “no problem”, “plenty of suction” but I have yet to see anyone measure that kind of setup with a Pitot tube and provide real data points (Handheld meters are far too inaccurate). Will it move air? Sure. Is it enough? Probably a little better than a shop vac.

Hope that helps. Let us know how it works.

Carl

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Mainiac Matt

8427 posts in 2474 days


#7 posted 01-17-2018 03:58 PM

If it works, it works… but there are a couple of principles that may have been misapplied.

Necking up from 5” to 6” didn’t really gain you anything, as it actually slows the air flow down in the 6” lines, and then accelerates it at the DC. As long as you still have enough velocity to keep the debris entrained in the air flow, you’re alright. But if you find debris accumulating in your 6” pipe, you’ll know why.

Running the 2” line to the router fence will likely not provide the collection you desire there, as the static pressure on most DCs won’t be sufficient to suck hard on small diameter pipe. (DCs are meant to move a lot of air quickly with little resistance). I have a 4” line to my router table cabinet, but use my shop vac at the fence, As shop vacs have a much, much greater static pressure and can pull sufficient velocity through the small diameter pipe (but they just don’t move as much total air).

Consider relocating your saw blast gate to the downstream side of the ‘Y’ so the line to the band saw has one less blast gate to go through. Each gate causes an increase in head loss in that leg of pipe. It may be a small loss, but every bit adds up.

-- I yam what I yam and that's all what I yam

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jimintx

834 posts in 1730 days


#8 posted 01-17-2018 04:02 PM

Carl, first – thanks for the thoughtful input and guidance. Then, I’d like to discuss a little more, if you will.

Reducing the line diameter will increase velocity, and also decrease the flow rate – the cubic feet per minute. When you dropped from the 6” line to the 5” line and used your pitot tube, you measured a predictable velocity increase. I’d like to know the corresponding CFM flow rates in the two line sizes.

Back to the basis for my comments to the OP:
My underlying approach regarding dust collection embodies that I do understand fluid flow dynamics, and thus have thought about what I was assembling and how it would impact overall collection results. And then, overall, I prefer practical versus theoretical. So I prefer to test actual systems to see what they accomplish versus what I want to have them do, and balance that actual, observed data and performance against the cost and hassle to assemble something else.

In my case, once I determined that the 4” hose-based system worked well enough or better than i had hoped, I have so far left it alone. I know that i could improve the theoretical characteristics with different lines and hoses, but i don’t need to because it already does what i wanted it to.

I will rework parts of it some day, however, because there are components of it that sometime get in my way, or frankly don’t look as cool as i would like, so I will change some things. In the meantime, i am happily making sawdust and carrying on with my shop work activities.
.

-- Jim, Houston, TX

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Ripper70

1135 posts in 1055 days


#9 posted 01-17-2018 04:43 PM

These two videos might be worth checking out:

Dust Collector Upgrade - Pt 1 - Upgrading to HEPA Cartridge Filter

Dust Collector Upgrade - Pt 2

-- "You know, I'm such a great driver, it's incomprehensible that they took my license away." --Vince Ricardo

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Carl10

109 posts in 603 days


#10 posted 01-17-2018 05:29 PM

Jim,

I got a hold of a free 1.5HP cyclone and did quite a few different modifications/ tests to monitor my ~70% performance improvement, so I had a lot of notes and tests to draw from. Unfortunately I can’t find the final compilation in the midst of my renovation chaos. I did find a rough note and my memory was a little off. 6” duct & hose ~2900FPM or ~570CFM, 5” duct & hose ~3800 FPM or ~ 520 CFM. I can accept the small CFM hit for better velocity.

When and if I find the official tabulation I’ll post an update.

Hope that helps

Carl

BTW: When I tried a 4” duct the CFMs dropped so much (below 400CFM) I didn’t even bother doing any official testing.

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WorksInTheory

143 posts in 1748 days


#11 posted 01-17-2018 05:31 PM

Wow such great information and really appreciative of everyone taking the time to impart their knowledge. Some of these responses required thought and effort to type out. Thank you so much.

Maniac Matt – on the 2” at the router fence. My concern is running a shop vac, dust collector and the router all at the same time – could blow a circuit though I need to still figure out what circuit is on what. Old house, garage was add on and I may be running all from nearest outlet which is a lot splitting out of it.

Would changing it to a 4” until it hits the fence port and go down to 2” help? I was worried about the weight of that tubing on it.

On 6” vs 5” vs 4”. I was given some HVAC as well as dust collection stuff in 4” and 6”so I was just using that to save cost. Plus has anyone tried to get 5” stuff – it’s almost impossible to find, especially in fittings like wye’s etc.

I will take a look again at my blast gate config and see if I can remove one or move.

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jimintx

834 posts in 1730 days


#12 posted 01-17-2018 05:58 PM

All interesting, Carl, thanks.

Also of general interest is that well-known DC makers sell products, often at not-cheap prices, with 4” duct lines anticipated and set up.

The unit I splurged on is the PM 1300-TX-CK, so that rounds off to a thousand dollar machine. The inlet port that is built into the impeller shroud is a 6” metal flange, however PM supplies it with a plastic Y that splits into two 4” ports. The 6” sheet metal flange is not very deep and not designed to make attachment of 6” lines easy, but it it is do-able.

As supplied, this plastic Y device is attached onto the machine with sheet metal screws, and comes with a cap so that you can readily use only one side of it. Each leg of the Y has a 4-spoke grid to stop larger chunks from going in to the impeller. This Y-component adds to their costs one way or the other, yet they do put it on there. This sure indicates that their product designers think it is ok to run that DC with 4” lines. I mean, I have to ask: If PM thought their unit was optimized and performed best with a 6” inlet, wouldn’t they just ship it with the 6” flange and not add the Y?

-- Jim, Houston, TX

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YesHaveSome

124 posts in 404 days


#13 posted 01-17-2018 06:09 PM

I have an Oneida Mini Gorilla with a 5” port. I asked Oneida if I could run 6” pipe from it and they said I would lose significant performance if I did. Just FYI.

-- But where does the meat go?

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WorksInTheory

143 posts in 1748 days


#14 posted 01-17-2018 07:02 PM

Not to throw a wrench in the conversation, but considering also replacing the impeller w/ the Rikon impeller everyone is talking about. Someone mentioned that you need a “puller” to pull the old one out. Does anyone know what that is called or have a picture of that tool?

I am sure this is going to generate a debate as it seems there are 2 camps when it comes to doing this hack (or not)

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Carl10

109 posts in 603 days


#15 posted 01-17-2018 07:04 PM

Jim,

The single stage DC market has been fairly stagnant for the last 15-20 years. There have been impeller improvements and better classes of motors but the basic design is unchanged. These machines where never intended to be attached to large duct runs. The Y’s are a convenience to attach multiple machines at one time. Two 4” hoses is just less than one 6” hose, area wise. So you could theoretically run 2 machines simultaneously. Also, most woodworking machines come with 4” ports (or smaller). Years ago the idea was to just pick up the big stuff so CFM expectations where pretty low. Connect any of these 1.5-2 HP units to a machine with a 4” hose and you have pretty good dust collection. When you have several machines it gets to be a spaghetti mess of hoses and gates, so people started running ductwork up in the air to clean up the shop floor. Nobody tested the airflow after running all the ducts but they put a had to an opening it felt like air was moving so it “works great”

The other reason for 6” port is to maximize performance. If you put a 5” port on your machine the maximum advertised airflow would have to drop. You can look at most DCs and cyclones that use the same impeller and change the size of the inlet, outlet or both to get performance differences. I have seen the same cyclone use the same impeller one had a 6” inlet the other a 7” and the larger had better performance. It is silly to see a 2HP cyclone with an 8” inlet. The Grizzly 1.5HP cyclone comes with a 6” inlet (to get a better performance curve), but they include a 5” reducer with the machine (knowing that is the ideal duct size for a 1.5HP unit).

The bottom line for me is how good the real airflow is at the machine, not that I can still feel airflow. Someone told me about running his DC with 50’ of 4” line to his planer. He measured less than 200cfm and was getting clogs. 200 is better than most vacuums and “feels great”, but is obviously too low for a dust collector.

I hope that helps. Let me know if you have any other questions.

Carl

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