6 inch drops vs 5 inch drops

[Rob Diz]

I finally picked up my new (to me) Woodsucker Cyclone II. It's 2hp and will be replacing a delta 50-760 I had plumbed with a 6 inch main and two 5 inch drops. I had decent collection of chips, but not great dust collection.

As part of my purchase of the cyclone, I picked up additional 6 inch ducting, wyes and blast gates. I have enought to go back to my system and replace the 5 inch drops with 6 inch drops and not get with any added costs - it would just take me a few hours to get it done.

I'm wondering if I will see any improved collection of dust if I increase the drops from 5 inch to 6 inch.

The entire system is on the inside of a single car garage with relatively short runs.

thoughts?

[Leo Graywacz]

The 5" drops will limit the max CFM to about 650. If your machines require more than that it would be a good idea to switch out. If not, there is no need.

I specifically used 5" drops to limit the CFM flow so I could use two machines at once. If I used 6" drops it would limit it to 800 CFM which is more than half of my 1440 CFM collector so I would have more duct than airflow.

[Roger Jensen]

Hi Leo,

Where do you get information like that? I have the 50-760 with four inch pipe everywhere (8 ft run, two 8 foot drops). I assume I should at least replace the 8 ft run with 6 inch pipe, but I'd like to know it is worth it with this dust collector.

Thanks,

Roger

[Leo Graywacz]

Can't really give you specifics on where I got the info. When I was installing my collector I found the info wherever it was and memorized it. 4" pipe has a max flow of 350 CFM, so it is really limiting.

[Leo Graywacz]

Look here at the Bill Pentz calculator

http://www.billpentz.com/woodworking...staticcalc.xls

[Paul Wunder]

Rob,
No one can really answer you because there is missing information:

What is the fan curve of your Woodsucker (cfm output at various static pressures)

What is the diameter and number of each port on your tools

The other poster was correct in sending you you to Bill Pentz'a website and his static pressure calculation Excel worksheet.

Pentz generally recommends 6" all the way from the cyclone to the machines port, but that assumes 6" inlet ports at each machine and a 5HP cyclone.

[Chris Livingston]

Leo, Great shop space....and I hate you for it

[Thomas Canfield]

Putting in larger drops than required for the service can result in a lower velocity in the drop than what is required to "lift" or "carry" larger wood chips. A cyclone is also designed to work with a minimum air flow to get proper dust separation and prevent carry out through fan to filter. I usually make sure that I have a second gate open on my 2HP Oneida as minimum to get air flow for the cyclone and still have good vacuum at the gate where tool is being used. I would recommend using larger horizontal duct and have the drops sized for the needed air flow of the equipment.

[Alan Schaffter]

Thomas, you are correct about not letting the velocity drop so the dust falls out of the moving air mass, but that is a function of the DC fan curve and the ducting and can be computed. Drops should never be larger, but in a single man shop should be the same size as the main and the machine port. Stepping down drops is only needed if you must balance a system when two or more drops are open. All other systems should be able to provide the required velocity with constant diameter pipe running all the way from the blower to the machine. If your DC can not maintain the needed minimum velocity, then your ducting is too big or your blower too small. Opening a second blast gate only serves to increase the amount of air available, but can drastically reduce the volume of air and dust collected at the primary source. The goal should be to collect as much dust as possible at the the source regardless of the CFM specs you often see quoted for certain machines. Cyclone separation efficiency is based on air velocity not CFM. If given the choice, I would give up some cyclone efficiency in favor of source collection. That is why Bill P. recommends discharging outside- in addition to reducing back pressure and improving flow, if the cyclone is not working efficiently you don't need to worry about clogging a filter.

[Rob Diz]

So I can't find the fan curve for the Woodsucker ii I just purchased and am still perplexed by whether I should put in 6 inch drops or stay with the 5 inch drops that I previously had. I will need to drop from 6 to at least 5 for my jointer and my planer and 4 for my TS,

[Alan Schaffter]

So I can't find the fan curve for the Woodsucker ii I just purchased and am still perplexed by whether I should put in 6 inch drops or stay with the 5 inch drops that I previously had. I will need to drop from 6 to at least 5 for my jointer and my planer and 4 for my TS,

Why will you drop to 4" at the tablesaw, that is one tool where you will want a 6" port. In most modest sized shops I think 6" to the tool will work fine with a Woodsucker.

If you search you may find the info you need. It might be on Bill Pentz's site too. When WS was still in business they had extensive fan curve data on their site. Bill said this:

In looking over the WoodSucker II design and airflow curves, this is the strongest available cyclone for its size motor. Those with larger shops and lots of ducting may find it not moving the air needed. The impeller design is a vertical bladed caged fan, which is far more efficient than normal dust collector material movement impellers and is the second most efficient unit that you can get today. The only thing more efficient is the same design where the impeller blades are airfoil shaped. The airfoil impellers though more efficient, can have problems with stalling that causes buffeting and bad vibrations, so this impeller choice is near ideal and the best engineering choice for those with smaller sized shops. Clearly this unit should be high on your list of considerations, but unfortunately the WoodSucker web pages have closed down and they no longer answer their phone. I'm afraid the absolutely terrible magazine testing that used inappropriate test ducts to make other units look better seriously hurt this top performer.

Here is the link to the offending article, so I suspect the actual fan curve is slightly better. Even this fan curve data should tell you what you need to know about CFM and velocity based on your duct work.

[Thomas Canfield]

In response to Alan's comments, I agree that it is more important to collect the dust at the source. The drop and duct size should provide for the maximum required for the tool/source. A good shop layout and plan will greatly improve a system installation and keep down cost. My 2 HP Oneida fan curve provides more than enough for 3 tools to be operating at the same time, but in my one person hobby shop there is usually only one and maximum of 2 operating and that is why I always make sure to have 2 ports open to provide enouh air flow for cyclone efficience. My shop is heated/cooled and the filtering of the air is very important and it is not practical to have the filter discharge outside and bring in that much fresh air to heat/cool. My heat is electric strip heaters in the air handler and maintaining 60F in winter costs more that cooling to 80F in Texas summer.

[Alan Schaffter]

In response to Alan's comments, I agree that it is more important to collect the dust at the source. The drop and duct size should provide for the maximum required for the tool/source. A good shop layout and plan will greatly improve a system installation and keep down cost. My 2 HP Oneida fan curve provides more than enough for 3 tools to be operating at the same time, but in my one person hobby shop there is usually only one and maximum of 2 operating and that is why I always make sure to have 2 ports open to provide enouh air flow for cyclone efficience. My shop is heated/cooled and the filtering of the air is very important and it is not practical to have the filter discharge outside and bring in that much fresh air to heat/cool. My heat is electric strip heaters in the air handler and maintaining 60F in winter costs more that cooling to 80F in Texas summer.

Tom, I understand. But still think you should just open the blast gate of the machine in use.

Something else to think about- your shop is like a refrigerator- the mass of the shop (walls, floors, ceiling, all machines, and contents) make a thermal mass that will retain heat and cool much better than most people believe. Air itself is a poor thermal mass. You can change the air out and the shop will quickly regain the previous temp, many times over, just like a refrigerator when the kids open and close the door all the time. However, if you leave the DC running all the time, the shop's thermal mass temp will eventually adjust to the temp of the air. TX summers and/or high humidity are something else again!