Dust Collector Pipe Reduction

[SpiderDave]

I'd like to buy a cyclone for my shop Fox W1687, 3HP, 3450 rpm, 2800 cfm with an 8" inlet/outlet. I'm looking at the Oneida Super Duty XL with a 6" connection. Would this work well with a reducer? I'm looking to vent outside with the 8" and was told not to change the pipe size on the inlet. But it's going to change at some point anyway, so why not with this? Any ideas or advice out there? Thanks for your time!

[daddo]

8 to 6 will increase air velocity in relation to the static pressure available. Possibly increase or reduce motor amp draw- depends on the type of blower.
8" is about 25 square inches and 6" about 18.8 square inches- that can be a lot of difference.

That's all I can tell you. You would have to record the differences if they don't give you a specs blower chart.

Personally, I would take the advice of the manufacturer- they know best.

[SpiderDave]

8 to 6 will increase air velocity in relation to the static pressure available.  Possibly increase or reduce motor amp draw- depends on the type of blower.
8" is about 25 square inches and 6" about 18.8 square inches- that can be a lot of difference.

That's all I can tell you. You would have to record the differences if they don't give you a specs blower chart.

Personally, I would take the advice of the manufacturer- they know best.

The manufacturer hasn't answered back yet, still waiting on that one. My advice so far has just been from reading and people in general. I just figure since they come with a 4-way multi inlet adapter and two end caps, maybe it wouldn't hurt? If I ran the same inlet pipe from the machine, I'd eventually reduce the size to hook up to my tools down the line. But that might be some flawed attempt at logic there on my part as that run of pipe could be what gives me needed flow? As always, thanks for your help.

[fredhargis]

Dust collection questions are always the toughest when gathering opinions. So I'll just share some experiences. My previous cyclone DC had a 14 1/4" impeller (almost all DCs spin these at 3600 +/- RPM). I ran 7" ducting the first 5' off the DC, then reduced to 6" for the rest of the system. It pulled over 1000 CFM (measured) at the the duct hoods. There was one duct that was reduced to 4" (the TS overblade) and by itself I moved just short of 600 CFM. My current DC has a 16" impeller, and I run 6" through the entire system. I haven't measured the air flow yet but it's considerably more than the previous set up. Your Shop Fox has a 13" impeller so I'll predict the reducing will not be harmful.....but you will still experience some air flow loss due to the separator. Cyclones introduce considerable drag on the system, that's why most of the factory units come with bigger impellers/motors than their single stage counterpart. Even so, I'm predicting what you have will work fairly well; don't get caught into the numbers game for DCs, it will drive you crazy.

[TDKPE]

Not sure what the question is, but reducing the duct size won't hurt the motor or any other part, if that's what you're asking.  Choking down the air flow only reduces the load on the motor.  That's why your vacuum cleaner's universal motor speeds up when you block the inlet air.  You won't hear a motor speed change if you block the inlet because induction motors only change speed a little over 4% from no-load to full-load, but you can watch the current go down if you put an ammeter on the circuit.

Conversely, you may overload the motor if you don't have enough restriction on the blower (inlet or outlet), but that's not going to happen with a production stand-alone DC, especially with a reduced inlet duct and cyclone separator in the line.

As to reducing the duct diameter below 8", well, you're going to do that somewhere along the line anyway.  I would look for a long tapered reducer, or make my own, so air entering the blower isn't a turbulent mess, though I don't know how much difference it will make in the real world.  Oneida sells them, and I'm sure you can find them locally, too.  https://www.oneida-air.com/ductwork/stan...ct-reducer

   

[SpiderDave]

Reading my post, I really could've worded that better. I was trying to keep it short, but you all got what I was asking anyway, thank you! I was worried about the flow still being adequate if I used reducer earlier on. I was concerned what the proper size piping was and also the cyclones that say they're for 3HP 2800 cfm's have a 6' inlet so that reduction and drag of a cyclone worried me. I don't understand why they have such small connections if it's going to hurt performance? I wont have a large system. Just a few hooked up and a flex hose for tools on casters to connect to. The rest I'll do outside. Such a nice DC unit, that I didn't want to get caught up in those 'numbers', as said, and end up disappointed with how it performed in the end, only to try and change it later. That reducer makes complete sense - that never even occurred to me. I will either be making or getting one of those for sure. Really appreciated all the help and experience given. Thank you all!

[SpiderDave]

I should've asked if the reduction of the Shop Fox 8" pipe to the Cyclone's 6 1/4" connector was going to be okay for my DC unit? All other numbers match up, but I wasn't sure about reducing the pipe of my DC to fit that cyclone. I didn't see any that had an 8" connection, so I wondered if maybe that was intentional?

[jteneyck]

I should've asked if the reduction of the Shop Fox 8" pipe to the Cyclone's 6 1/4" connector was going to be okay for my DC unit? All other numbers match up, but I wasn't sure about reducing the pipe of my DC to fit that cyclone. I didn't see any that had an 8" connection, so I wondered if maybe that was intentional?
 

It's pretty common to use 6" ducting in a hobby shop set up, and that should work well for your system, too.  You won't get 2800 cfm in the real world with a 13" impeller, especially after you hook it to a cyclone.  I lost about 4" of static pressure with my admittedly non-optimum cyclone but all of them have losses.  Larger diameter ductwork has lower static pressure losses but you need velocity to keep large dust and chips suspended in the air.  6" is a good balance for higher flow hobby systems.  
John

[fredhargis]

I should've asked if the reduction of the Shop Fox 8" pipe to the Cyclone's 6 1/4" connector was going to be okay for my DC unit? 

Tom mentioned this above: reducing the pipe will reduce the air flow, which reduces (not increase) the load on the motor. Your DC will be just fine.

[R Clark]

I've been watching this with interest. 

I converted my HF conventional DC to a cyclone last month.  It uses an Oneida Super Dust Deputy with 5 inch inlet.  I went with the 5" inlet because the inlet on the impeller unit on the HF DC is 5".

I ran 5" ducting across the shop, reducing to 4" at the machines themselves since that's what they accommodate.

My system works, but certainly not perfectly.

I looked at a number of sites and read a lot of stuff.  I have to admit that I'm as bewildered now on some of that stuff as I was before I started.  Eliminating leaks and making smooth transitions around corners and junctions are more important, in my opinion.