Cyclone Collection Real World Measurements

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Forum topic by BlankMan posted 10-18-2009 12:27 AM 2928 views 2 times favorited 16 replies Add to Favorites Watch
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1488 posts in 2924 days

10-18-2009 12:27 AM

I did some testing yesterday on my Oneida 1.5 HP Cyclone after I removed the internal filter and added an external filter. Below is the table containing that data. Although I feel the CFM is good for the various machines the Air Velocity isn’t according to a lot I read. Maybe I shouldn’t have listened to the Oneida engineer that told me to use 5” ducting back in 2001 when I installed it and gone with 6” main ducting instead of 5”. Too late now, I’m not about to redo that.

But take note of the Static Pressure, Calculated verses Measured. I never put much faith in going through the motions and calculating that and this shows why. Unless it’s not close due to the Air Velocity being lower then 3500 ft/min but that was the lowest I could find for designing purposes.

I’m also starting to believe that 3 HP or more may be really be necessary.

-- -Curt, Milwaukee, WI

16 replies so far

View radfrac's profile


12 posts in 2727 days

#1 posted 10-18-2009 12:33 AM

How are you measuring your velocity?

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1488 posts in 2924 days

#2 posted 10-18-2009 12:42 AM

Air Velocity is calculated using Velocity Pressure measured with a Dwyer 475-0-FM Manometer and a 167-6 Pitot Tube and Air Density which is calculated using Barometric Pressure (from my Davis Vantage Pro weather station) and temperature (from my Oregon Scientific thermometer in my workshop). That’s why Temperature and Barometric Pressure are included in the table.

CFM is then calculated using Air Velocity and duct area in square feet.

-- -Curt, Milwaukee, WI

View jimofsanston's profile


36 posts in 2716 days

#3 posted 10-18-2009 12:59 AM

What did you say? That’s way over ny head as long as i have good suction at the port of the machine it works for me.

-- Jim LaCourse

View ondablade's profile


105 posts in 2769 days

#4 posted 10-18-2009 01:11 AM

Pardon my tabling this rather than answering directly BM. I don’t have the practical experience to get into your figures and methods. You may already be familiar with his material, but Bill Pentz discusses dust system design better than i can.

He suggests that something approaching 3500 fpm is necessary for effective vertical chip transportation. More to the point – while something approaching 350 cfm delivers decent coarse chip collection at most common woodworking machines, he suggests you need something more like 1,000cfm plus at most to get medically effective fine dust collection to Euro standards.

Here’s some of what he has to say on the topic, and on the various standards:

He’s pretty sceptical regarding the claimed filtration and cfm capability of most commercial units too – he reckons that test conditions are usually jigged by the makers to deliver highly unrealistic numbers, and that you need around a 5hp motor on typical materials handling type impellers of 15 to 16 in dia, and 5 to 6 inch dia ductwork depending on system layout to shift the required amount of air AND give sufficient velocity.

One of the unfortunate aspects of fans is that they are a bit counter intuitive. If the ductwork is restricted by smaller duct sizes, restrictive valves, corrugated hose, too many bends and the like then rather than drawing more power as a result of ‘straining’ against this, they actually draw less because they don’t shift enough air to fully load the fan and hence the motor. Yet despite reducing the CFM delivered by a specific fan set up, undersized ducting speeds up the air velocity/fpm, and makes it possible for undersized fans and ducts to avoid the blockage problems that would result from the air velocity dropping below the previously mentioned 3,500cfm.

This means that you don’t get the classic ‘underpowered’ signs from underspecified dust systems as you do from most sorts of machines – overloaded motors, blockages etc.

There’s actually a risk of running into blockage problems due to chips dropping out if you fit large say 6in ductwork, but due to too small/too inefficient a fan don’t get the cfm required to avoid chip deposition. (as a result of dropping below 3500fpm) Care is needed not to overdo the duct size, and to ensure that it is matched to the fan and the design of the whole system for this reason.

There’s in a sense a non-virtuous circle that kicks in – where skimping on specification is not found out. The system appears to be working fine because the larger particulates are handled (though not the invisible fine sub micron stuff that is the real health risk), and there are no apparent mechanical problems.

I’m no expert, but so many (all i’ve seen) seem to report such positive outcomes from systems based on his findings that it’s hard to dismiss. I’m currently in the process of ordering fan hardware to his spec. from Clear Vue …

-- Late awakener....

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1488 posts in 2924 days

#5 posted 10-18-2009 01:14 AM

Jim, LOL Yeah but I wanted to know.

After reading a bunch of stuff at Bill Pentz’s site I wanted to know. I was concerned about Air Velocity and it looks like it don’t hit the mark. A good Chip Collector but maybe not a good Dust Collector.

It blows away the 1-1/2 HP 1200 CFM (manufacturer inflated, I know) Delta Dust Collector that I used to have and the Taiwanese 1 HP before that, but I wish it was better.

Good suction is subjective. :) This cyclone sucks good to, better then before, but the measurements show it doesn’t suck good enough.

-- -Curt, Milwaukee, WI

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1488 posts in 2924 days

#6 posted 10-18-2009 01:24 AM

ondablade, yeah that’s why I said 3 HP or more. Bill’s site is what got me going.

I’d consider a 3-5 HP cyclone but I don’t really have the room and I’d have to redo (enlarge) all the mains. That be too much.

I’m destined to suffer with it. It’s good, just wish it would have been better.

Back in 2001 when I bought it there wasn’t as much information as there is now and Oneida seem to have the leading edge. They may still. They started using neutral vane inlets back around 2003-4 that I can tell, maybe earlier, that’s one thing Bill harps on. My barrel didn’t have it (1999 or maybe ealier design I believe), luckily I do metal working too, so now it does.

-- -Curt, Milwaukee, WI

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36 posts in 2716 days

#7 posted 10-18-2009 04:00 AM

I think I am going to have to go back to school to make sure I have enough of a DC in my little shop to be safe. I thought i was doing good. Oh well back to the drawing board and i just bought my Delta DC.

-- Jim LaCourse

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115606 posts in 3148 days

#8 posted 10-18-2009 04:09 AM

Curt your the detail guy way over my head. But thanks for sharing.

-- Custom furniture

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11807 posts in 3259 days

#9 posted 10-18-2009 04:03 PM

what were your measurements before you changed the filters ? how big is your shop and what do you make in it ?

-- I'm absolutely positive that I couldn't be more uncertain!

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979 posts in 2865 days

#10 posted 10-18-2009 04:36 PM

I searched for a WC vacuum gage for a while and couldn’t find one that seemed in the range for this kind of information.

What kind are you using and where did you get it. Hopefully it isn’t too expensive.

Would love to get one that had range of 0-10 inches water to check my system. Best I found was a fuel pressure checking gage, but it only went from 0-10 in very short degree span.

My last idea is to just make a water column with tubing, but that isn’t too easy to move around.


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Bob #2

3809 posts in 3592 days

#11 posted 10-18-2009 04:56 PM

Those are interesting figures.
They definitely set the standard from which we can measure our own systems.
I too have read Bill Pentz data and it is very convincing.
On the other hand, a 3 Hp 3500 CFM wind tunnel is quite and investment for the average home workshop.
I can see it in commercial applications but the runs are much shorter in most home shops and rarely if ever is theremore thn one machine running.
Surely a 2 hp 14-1500 CFM system should be adequate for most of us.
What are your thoughts from a practical perspective?

-- A mind, like a home, is furnished by its owner

View khop's profile


134 posts in 3247 days

#12 posted 10-18-2009 05:21 PM

When I look at some of the installations of the DC systems on the Oneida site, I cringe. I am amazed at how many fittings some people use to get to a termination point. Most systems do not run at thier most effecient due to poor or wrong installations. Using the least amount of fittings to get to a machine is best. The kinds of fittings are also important. Long sweep ells and wye connections are the best. Even when someone uses pvc for their system, it is very important to avoid restricting flow, ie. reversing the hub to spigot connections. Remember, male into female. that has been the right way for years. Reversing the flow will create small turbulant eddys in the connection which will add to the reduction of flow.
Just the opinion of an old plumber.

-- How am I doing? Better than I deserve. Dave Ramsey

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105 posts in 2769 days

#13 posted 10-18-2009 06:26 PM

It’s unfortunate, but i guess it’s always the same Curt – no matter what once we design/buy something we figure how we could improve it. It’s a in a sense the nature of life – you don’t know what you have until you have tried it for some time, and by then it’s too late.

To your point Dusty – BP’s numbers are pitched towards the typical 2 car garage and a bit home shop, although these are determined more by machine extraction requirements and duct run distances than by shop volume.

If i have it right the key is not to so much to gather up and filter the air in your shop, but rather to prevent everything including the dodgy sub-micron particles escaping into circulation. If you think of particles being spat out by a fast moving blade, Bill suggests that well proven data indicates that they become much more likely to escape once they get beyond a point where the air is being drawn to the extraction point at 50fpm. (this is known as face velocity in the design of laboratory fume cupboards and other types of extraction hood)

As you move out in a sphere from the point of suction, area of the sphere very quickly gets larger – so that the suction has to maintain at least 50cfm over an ever increasing surface/face area. When the basic math is done on this it seems that 350cfm can maintain at least 50fpm over the surface of a sphere of only up to 12 in diameter, while even 900cfm can maintain it up to over only a bit less than 30in.

In a sense you could probably say that all the palaver about system design is about (a) delivering enough cfm at the suction point to give 50fpm plus over the required dust collection area/volume at your machine (good hood design etc can reduce this), and (b) (in the case of a shop that can’t dump all it’s extracted air outside – for reasons of location, or because the replacement air being drawn in to replace it is cold so it would cost a fortune to heat it etc) the filtered air being returned to the shop is genuinely clean, and not full of the previously mentioned invisible sub micron particles

The physics are the physics. What frustrates me so much is the misinformation and OTT claims put out by most machine (not just dust system) makers – it’s downright dishonest, and makes it necessary to to do so much homework to even figure out what you are buying in terms of the price/performance mix. It’s not just passive either, it seems for example that Bill has been the subject of all sorts of legal threats from commercial dust system makers too.

I bought one of the typical 1 hp mobile filter and chip bag units from the maker of my combination machine, but realistically it flat didn’t work – it wasn’t even gathering the visible stuff properly once the filter got a little dust in it. I get a lot of sinus trouble, and using the saw for even a short time was ending up with a hay fever type response.

Luckily it’s only now that that i’m going full time that i’m looking to install a ducted system. I’m tight on space too, but have the option to place the cyclone in an adjacent store room and with ducts under the ceiling will be OK i think…

PS on motor HP. It seems that these BP systems draw something below 4hp in normal use. The 5hp requirement arises because (in keeping with the first post) if your fan is sized to deliver the required performance in normal use (with filters fitted, and the duct to one machine open) it will pull close to 5hp if it’s allowed to run with minimal restriction. e.g with several branches open or whatever.


-- Late awakener....

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1488 posts in 2924 days

#14 posted 10-18-2009 10:17 PM

a1jim, yeah that I am, a bit of a perfectionist, and have been called anal and have been accused of worrying about minutia, but I sweat the details. I don’t like doing things twice, yet this is my fourth go around at using collection. Believe me I did all the homework I could. I’ve probably got 6 books on the subject over the years. A set of three engineering level books that someone doing this full time as a day job would be using, lot of theory. My first DC was that 1 HP Taiwanese Dust Collector and 4” PVC plumbing and gates back in 1994 when I was getting serious about woodworking and there weren’t a lot of choices for the home shop.

Then I went to that Delta 1-1/2 HP 1200 CFM unit when it came out still using the 4” PVC, not much better, somewhat of a joke. That’s when I kept eying up the Oneida Cyclone, thought it would be the save all. It was definitely the best so far but it could be better, but it was at the top end of what I could afford at the time. I probably spent again as much for the all the 5” ducting as the cyclone cost. This is the fourth and probably last go at it. I removed the 8”x16” internal filter and it’s mounting assembly, replaced it with just the Oneida vertical tube, and attached a 13”x39” external filter with almost three times the surface area.

Dusty, unfortunately I didn’t take readings before the filter change. I didn’t have the manometer I used on Friday, just a fluid one whose accuracy is 3% of Full Scale which is 7”. That doesn’t sound like much but it’s +/-0.21” which again doesn’t sound like much. But when you’re dealing with measurements in the 0.5” to 1.0” range if it’s 0.75” it could be 0.54” or 0.96” that equates to 575 CFM at 2930 ft/min to 767 CFM at 3907 ft/min, not really of much value so I opted not to bother. Shop’s about 400 sq. ft. and I make anything I want. It’s fully outfitted with woodworking machines and metal working machines, although some of the metal working machines have spilled out into the garage, just didn’t have room for them all.

Steve, the vacuum gauge I have is a Marsh and I got it directly from Marsh Bellofram, you can order on their web site. But really be careful if you do, the catalog isn’t (well at least wasn’t) as informative as it could be. When I ordered my 3-1/2” (round) gauge I wanted a 0-10” vacuum gauge, I got a 0-10” pressure gauge. And to send it back I was charged a 25% restocking fee, the lady was a b**. You had to be a guru to understand their catalog at the time, nowhere did it clearly indicate vacuum or pressure in the line items on the catalog page you had to know their codes. But she was emphatic about the 25% because I ordered the wrong gauge, even though she couldn’t show me where it said pressure on the line item. That was my single worst experience dealing with any company, most will be accommodating, even if the customer may be wrong, not this lady. Still got her name someplace in email, hopefully she retired by now…

As for cost, a 2-1/2” gauge will run you around $50-55, a 3-1/2” around $96, I just ordered a 3-1/2” 0-10” pressure gauge last week (shoulda just kept that one…). I’ve got the 0-15” vacuum gauge on the inlet of the cyclone using a Static Tube and I’ll put the 0-10” pressure gauge on he outlet between the blower and the filter with a Static Tube. Now that I know what my static pressure is with a new clean filter for each machine, if I see the vacuum go down the filter needs to be cleaned, if I see the vacuum go up something is blocking the duct. Likewise for the pressure gauge, if I see it go up by an inch or two, time to clean the filter.

Since the system is marginal I want to monitor it closely so that I keep it running at its highest efficiency possible, ergo the gauges and not just gut feel.

You can get a 0-10” WC pressure gauge from Marsh but not a 0-10” WC vacuum gauge, 0-15” WC vacuum is the closest. I think there might be a 0-5” WC vacuum but if using that one there’s a chance you should wrap the needle around the stop post. The meters I have have about a 270 degree sweep, maybe a bit more. And these meters are a bit delicate.

You can buy a Dwyer Fluid Manometer that I’m pretty sure can also be used to measure static pressure. A 0-10” one will cost you around $76 and if you need more fluid for it that cost $40+ for a 3/4 ounce bottle. But again the accuracy is +/-3% of full scale. Marsh meters look more attractive…

The Dwyer Digital Manometer that I used Friday is +/-0.5% of full scale. It’s range is 0-10” WC so it’s accuracy is +/-0.05”. Sounds like overkill but not really when you’re taking reading in under the 1” range.

Bob, the data I posted was from a spreadsheet I made that has all the formulas in it, plug in the measurements and you’re good to go. I orginally wrote a Perl program to do it, just give it the numbers and it spit out the answers. But once I started the spreadsheet I thought heck, I’ll just put the formulas in the cells. If anyone is interested in it I’ll post a link to it that people can grab it.

khop, I used the minimum number of transitions to get from point A to Point B, I really read up on this stuff before plumbing it in metal because I did not want to have to do it again. If I get some time I’ll do a CAD drawing of my plumbing and post it. I used all Oneida ducting, tees, long radius elbows and such, again, because I didn’t want to do it over. It was pricey but I bit the bullet, I didn’t want to compromise just to save bucks, that would have probably lead to a worse system. And for where I had to reduce to 4” for 4”ports I kept those as short as possible, in the 1/2 foot to 1 foot range.

ondablade, I did the best I could at the time thinking it was going to be really good from what I knew. It’s not bad but it could be better. But I agree with what was said, I cringe at the cost too, there’s a point where it just becomes not affordable.

If I had to do it now with all the information that is now available at a minimum I’d go for the Oneida 3 HP Super Gorilla and maybe even the 5 HP.

I guess I can keep my two ceiling mounted air cleaners running more to hopefully pick up the stray fine dust.

-- -Curt, Milwaukee, WI

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105 posts in 2769 days

#15 posted 10-18-2009 11:42 PM

Cost sure is the problem Curt. The BP approach generally gets around the heavy cost by steering people to go DIY on the cyclone and the fan, or to buy from Ed M who seems out of goodwill to run a very low overhead operation.

I’m buying the impeller and fan kit from Ed, and sourcing the motor and the ductwork locally, and will fab the cyclone and install everything myself. I think i’ll get away at about $1,250 in total, albeit at the cost of a lot of my own labour.

It’s hard to see how the commercial producers can do a 5hp system with properly sized cyclone and ducts and get the sort of mark up demanded by most commercial concerns on home use systems. Which i guess explains a lot.

On cheap means of measuring low levels of pressure an vacuum. It may well be feasible to do this using a simple transparent u tube with water in the bottom – just cable tie it to a board, leaving one end open and at a level well above the inlet to minimise the chances of the water being blown out by some sort of transient condition. It’s certainly not unusual to see U tube type installations on HVAC systems.

With no air flow the water will be at the same level in both legs of the U tube. Suction or positive pressure will drive it in one direction or other. As i’m sure you all know the ins water gauge pressure or suction is the vertical difference in height between the water in the two legs of the U tube measured in inches.

I don’t know if in practice there might not be some issues with fluctuation and dust. If so the first can probably be solved by fitting a small nozzle between the U and the duct to act as a flow restrictor/damper. You could fit a small filter (most of the pneumatics kit suppliers do them) between it and the duct if needed, but i guess you would only need spot reading.

You could fit a valve in the duct connection, and if the worst came to the worst just hook the U tube up when you need a reading.

A drop of food colour in the water, and a drop of bleach to stop algae and you should be in business??

-- Late awakener....

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