Very old Oneida cyclone and duct sizing

[Bruce Darrow]

I'm in the process (slow) of installing a CL find: 3hp Oneida cyclone - about 15 years old, 7" round inlet, 7" square outlet.

I've been planning out the duct runs in a 20 x 30 shop, branches and drops to 6" jointer, lunchbox planer (w/ 4" branches to DP and CMS) 10" cabinet saw w/ integral router table, and 17" band saw. Unfortunately, the TS and BS are at the end of the run.

Per recommendations, I've got 2' of 7" pipe running straight into the cyclone. It will then elbow up to ceiling height (10'), elbow and run straight for a bit, and elbow again to run down the center of the shop. Again, per recommendations, I will reduce to 6" on the main run within 5 - 10 feet.

I've been planning based on 6" branches and drops, but I'm having second thoughts about reducing further to 5". Any thoughts, one way or the other?

I've been to Pentz's site. I'm not planning on modifying the machines to allow 6" all the way - I'll be using 4" flex to connect to the machines, keeping it as short as is practical.

Additionally: the CL deal included a goodly number of fittings (yay!) and 6" pipe (one reason I've had 6" on the brain). The square to round adapter for the outlet goes to 6" round - would it be better to have a 7" outlet? BTW, this will be direct to the outside - no filters.

And the opening at the bottom of the cyclone (9") has a shop made adapter reducing it to 6" into the bin. It seems to me to be wise to make my own, increasing this to 8". Thoughts here?

Thanks in advance.

[David Kumm]

With no filters and mainly 6" on the inlet side, the 6" on the outlet side won't add restriction. Would go 7 with bags. If you use 6" drops you can reduce down to whatever makes sense and still have the flexibility to change machines in the future. You want more velocity on the vertical so some downsizing may be necessary depending how your system works in the real world. If your impeller is engineered for a 7" inlet, don't be afraid to stay at 7 until one or two drops. The leakage at the drops will still allow for pretty good velocity when you size down to 6. The end of a six inch run will be more effective if you don't have a bunch of runs branching off it so some 7 helps. I can't give you scientific advice on the cyclone drop, but can say my 5hp torit came with a seven inch bottom which is what my bin lid from Oneida has. I haven't seen the bottom larger than the inlet. Dave

[Aaron Rowland]

Can you tell me the diameter of the impeller and the HP of the motor? That effects duct size.

[Bruce Darrow]

3 HP motor. Impeller is not as large as most modern 3 HP cyclones. Nor is it non sparking aluminum - it's steel. I don't remember exactly, but I think I remember 12".
It's now buried in a rather complex stand I built - original configuration was floor mounted blower, 8" vertical and 90 deg turn into the top of the cone. I thought this was very inconvenient, and probably inefficient as well, so I designed a stand that allowed me to move the blower atop the cone, ala more modern designs. All will be well until I have to service motor or impeller - that'll be a bitch. It was a bitch getting it up there!

[Aaron Rowland]

The following are popular sizes for various cyclones, not my numbers but theirs. - 1.5HP = 12-12.5" diameter impeller., 2 HP = 14-14.5 ", 3 HP =15"- 15.5", 5 HP = 15.5"-16" . A 12" impeller in a cyclone would fit a 1HP- Harbor Freight so called 2HP dust collectors. Under no condition try this.

The impeller in a pull though cyclone operates in a partial vacuum because of duct work and cyclone restriction ahead of it.. The duct work subtracts a bit of pressure and the cyclone, especially the older one, have large pressure drops. For that reason much larger impellers are used in cyclones compare to single stage two bag systems. The two bag systems are not intended for use with duct work or cyclones. So if you put a 14.5" impeller on a 2 HP motor in a single stage system good bye motor. However if you put long or 4" duct work on a 2 HP blower it may will work just fine with a 14.5" impeller. Putting a 12" impeller on a cyclone is a waste of time. There is a way to beat the system however if you have a big motor and smaller then optimum impeller.. If the blower is placed in front of the cyclone in place of its normal position it will get more air and load better. Still not much gain if you have a big gap between HP and diameter. The only place small diameter impellers are used are if you stack two blowers in series. You double the Vacuum(SP) but you also have 4 HP doing it using 2 HP motors etc.. This makes a great high pressure system.

SP and CFM are tied together. Quoted separately the numbers means nothing. Similar to the HP and the impeller diameter. They must work together. A 3HP motor and a 12" impeller is a no no.

It took a long time for the suppliers to figure all this out unfortunately and some still don't get it. Check the impeller diameter of any system before you buy!!. . They are still doing some bad things but progress is being made. If you have a real 3HP motor and I say that because the off brands are sometimes only 2HP, try to find a 15.5" diameter impeller. You can make your own housing from Bill Pentz plans on his site. If the HP is in question drop back to 14.5-15".

[Bruce Darrow]

Thank you Aaron. The cyclone assembly is in place and undersized impeller or not, will operate as is, with whatever efficiency it is capable of in this configuration. I'll do whatever it takes with the duct work to maximize whatever efficiency I have.

This is very early Oneida - the original paperwork that came with it is dated '94. It is probable that this was designed before they learned some important lessons - like impeller sizing.

I realized this a while back - I was a bit low on the learning curve when I bought it, and although I saved money over a new system, it became evident this deal wasn't gloat worthy.......I'm not really the gloating type anyways :-)

I figure it'll be a hell of a lot better than the shop vac that is my only current collector. If it just don't work worth tinker's dam, I'll look into some of the alternatives you have suggested.......some day.......

[Bruce Darrow]

Thank you, David.

Good info.

[Anthony Whitesell]

The HP vs fan size numbers are what size impeller a particular HP motor can support. Obviously there's not much point to pointing a small impeller on a large motor or vice-versa. That would be like putting a lawnmower motor in Ford Mustang or a V12 in a pinto.

I too have an older Oneida cyclone with a 2HP motor and a 12.5" impeller. I believe it is newer than Bruce's but still before they learned what they needed to know.

[Jim Becker]

I have both 6" and 5" drops for primary machinery on my system with the main at 7" into my 2hp Oneida system. I stay at 7" until the first branch. (I do have a few smaller 4" drops for specific purposes) My J/P gets a 6" drop to it's 120mm inlets and absolutely benefits from the increased air flow. My slider also has an 120mm inlet, so a 5" drop works well with it.

On the bin, I'd suggest you try and stay larger, rather than smaller. My unit has (I believe) a 9" drop to the barrel which matches the cone.

[Jim Foster]

On the cyclone exit or bottom, I would suggest keeping it as big as possible and have the top of the bin a few feet below the bottom of the cyclone if possible. I would think 5" drops to the tools may be good to increase velocity at that point, but I have not run any calcs or properly set mine up yet. I can say that the flex hose can really add a lot of friction and bog things down if you use long runs of it, and try and use the wide metal 90 deg or 45 deg turns as opposed to short turns.

[Norman Hitt]

Since Bruce asked about exit duct sizing, I had a "Brain Gas Passing Moment", that might or might NOT have any theoretic validity, so for my own understanding, I would like to pose the question to those of you with more knowledge of this subject than me.

I realize there are differences that would have to be taken into consideration in the set up, inlet/outlet sizing variations to accomodate the cyclone's SPR, etc. between pull through and push through systems, so for this question, let's ONLY consider a push through system with NO filter on the outlet duct.

As I understand it, the design of a cyclone is to allow dust laden air to enter at a velocity sufficient to keep the dust suspended in the air, and then slow the velocity enough for as much dust as possible to drop out of the airflow and down into the dust collection bin at the same time the airflow continues out the exit duct.

With that in mind, "IF", in a push through system, you increase the size of the outlet duct by x amount, (assuming the Original outlet duct was sized correctly for max effeciency CFM airflow), would this increase in outlet size not further reduce the velocity while maintaining roughly the same CFM airflow, and IF so, possibly allow even more and smaller/lighter particles to separate and fall into the dust bin?

What say ye, Oh Mighty DC Gurus 'n Engineers, any validity to my musings or NO??

[Norman Hitt]

Just a bump to see if anyone has any thoughts to my question.