Thread: round DC help

Based on Bill's specification I would have gone with 13'-14" impeller had one been economically available when I was building my system. I did search long and hard for a solution at the time (seven years ago). The best I could do was get a 14"or 15" airfoil impeller that would have cost me many times more than I could justify at the time, and there was also additional issues to manage with an airfoil design.

Yeah I would stay away from airfoil designs for woodworking.

How long is the duct from the lathe to the cyclone?
The final flexible 6" ducting is just a few meters long. I need that flexibility for its manoeuvrability. Between that and the cyclone I have also a few meters of rectangular ducting (internal 9" x 4.5" providing 40.5 sq ins section compared to 6" diam which provides 28.3 sq ins). I discussed this design with Bill Pentz before using this and he advised that rectangular was more efficient for airflow than round. I should also mention that none of my bends from the cyclone to the inlet have less than a 500mm radius.

OK that will explain your good flow rates as your essentially you have very little back pressure from your ducting

Unfortunately at my current workshop location it has not been possible to vent outside, so any inefficiency in the system will result in an accumulated of micro-fine dust inside the workshop.

Is it because it is physically difficult to arrange an external vent or are your worried about dust affecting neighbors? If you only get a cup of dust every year on your filters no one will see that much dust as the lightest of breezes will take it away.

This is one of the reasons that I use a full head respirator for most of the time that I'm in the workshop in addition to running the cyclone and the ancillary HEPA air filter). I have plans to move to a new workshop where I will revisit the external venting option where it may be possible with a silencer (and favourable wind conditions).

I guess one can get used to it but find it very difficult to wear a full head respirator for more than about 20 minutes.

The new workshop doesn't have 3ph connected at this stage and I'm not sure I will go to the cost of having it connected just for the DC system. So I will be revisiting that component of my system to see what I can do with 240V. For example, the Clearview importers are running their largest cyclone with a " 3kw Teco motor. These 3Ph motors have ample power with a full load rating at 20.8 A at 230 V". My reading of that is that it runs off 240v single phase. I also understand that their impeller is 15"diam. Whether they will sell me just the motor and impeller unit is another matter.

If you have a 3 phase motor now you should check and see if it easily rewireable to delta mode and will run on 240 V 3 phase. Then all you need to buy is the VSD ($150 delivered) and that converts 240 v Single to 240 V 3 phase.

Bob, do you know of any other options for a single phase motor/impeller combo that would meet the Pentz specification here in Australia?

Unfortunately no but I have not tried looking too hard.

I'd like to be living closer as your system intrigues me and I'd like to be able to measure the flow rates on it.

Originally Posted by BobL

Is it because it is physically difficult to arrange an external vent or are your worried about dust affecting neighbors?

Not the dust, as you say, there's not enough of that to be an issue, but just very difficult to arrange an external vent. And, even with a silencer, there is likely be noise pollution issues in the house and for the neighbours.

Originally Posted by NeilS

Not the dust, as you say, there's not enough of that to be an issue, but just very difficult to arrange an external vent. And, even with a silencer, there is likely be noise pollution issues in the house and for the neighbours.

Thanks. I hope the new workshop setup works out for you.