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  • What are your DC CFM's

    Today I borrowed a friends anemometer to test out my cyclone airspeed which I have yet to test for the last two years. My friend which as well is a forum member let me borrow this little instrument and gave me a few hints how to use it more accurately. Initially I brought it up to where the opening of the 6 inch main intake is, and it overran the top speed of this instrument. So like I was advised build a bigger intake to slow down the air intake. I cut a hole in the bottom of a 5 gallon bucket and attach the bucket to the 6 inch opening which has 11 1/4 " ID at the other end. I retested the airflow at the opening of the bucket in numerous places to try to come up with an average. I decided to use bucket, as I calculated the opening was darn close to 100 in.² (or 0.7 ft.²) and I figured that would be an easy math calculation. The opening of the bucket was almost exactly 3 1/2 times my main. After testing this around six or seven times in different locations throughout the opening of the bucket, I came to an average of 2800 ft./m. Basically I think my homemade cyclone is getting around 1925 ft.³/m. Basically from my calculations the airspeed is 180 km/h. If I'm off with any of my math please inform me.


    I'm not actually sure if this would be considered extremely high or middle range. What are others CFM's?
    Last edited by Matt Matt; 12-07-2014, 09:49 PM.
    For every action there is an equal and opposite reaction.
    Sir Isaac Newton.
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  • #2

    Re: What are your DC CFM's

    Re: What are your DC CFM's

    Oneida told me you can't expect more than 250-300 cfm per HP when connected to a piping system.
    Add some resistance to the intake and you will see what I mean. Kind of like saying a Honda has 900 hp with twin turbos turning at 8,000 rpm on a test bench but has very little real torque at the wheels. Keep an eye on your FLA while you are at it.

    What are your impeller size and rpm Matt?
    Mike

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    • #3

      Re: What are your DC CFM's

      Re: What are your DC CFM's

      That sounds about right from my reading. Here are some links...

      http://www.wwgoa.com/stepping-up-to-...st-collection/

      I think the key is what you see at the end of the pipe going into your machines. The above link us showing 1000 to 1400 cfm with a 5hp Clearvue cv1800 cyclone.

      http://billpentz.com/woodworking/cyc...onereviews.cfm

      -Darryl

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      • #4

        Re: What are your DC CFM's

        Re: What are your DC CFM's

        Last winter I had an opportunity to due some airspeed and CFM readings with a fan type anemometer on my Clearvue CV1800. If you want I'll send you the Excel spreadsheet. It was all done with the 6" line in place and taken at each machine. I recently upgraded to a Felder RL160 and found an increase in flow but won't have an opportunity to test it until the new year.

        John

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        • #5

          Re: What are your DC CFM's

          Re: What are your DC CFM's

          Originally posted by M.McKenna View Post
          Oneida told me you can't expect more than 250-300 cfm per HP when connected to a piping system.
          Add some resistance to the intake and you will see what I mean. Kind of like saying a Honda has 900 hp with twin turbos turning at 8,000 rpm on a test bench but has very little real torque at the wheels. Keep an eye on your FLA while you are at it.

          What are your impeller size and rpm Matt?
          Mike my FLA is 19.5A. I did not check at the time but I can as I am going to do more checks. My fan is a 17 1/4 fan OMM, so there isn't an other out there which is the same. The rest of the cyclone is a pentz build. It is interesting that I am getting 100cfm per amp draw.
          For every action there is an equal and opposite reaction.
          Sir Isaac Newton.

          Comment


          • #6

            Re: What are your DC CFM's

            Re: What are your DC CFM's

            Matt, your bucket is too short, you should use maybe a 5 foot long piece of cardboard pipe.

            My system is at 750CFM which handles the machines I have.........Rod.
            Work is the curse of the riding class.

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            • #7

              Re: What are your DC CFM's

              Re: What are your DC CFM's

              Matt, your cfm will drop significantly once you add resistance piping, elbows etc.

              Used this book by Sandor as my guide when setting things up here.

              http://books.google.ca/books?id=-rkv...page&q&f=false
              Mike

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              • #8

                Re: What are your DC CFM's

                Re: What are your DC CFM's

                Originally posted by M.McKenna View Post
                Matt, your cfm will drop significantly once you add resistance piping, elbows etc.
                Yeah I haven't gotten that far yet. Now Rod suggests that I increase the length of the tube.

                Rod do you think a square tubing over around tubing would make much of a difference?

                Originally posted by Rod Sheridan View Post
                Matt, your bucket is too short, you should use maybe a 5 foot long piece of cardboard pipe.
                For every action there is an equal and opposite reaction.
                Sir Isaac Newton.

                Comment


                • #9

                  Re: What are your DC CFM's

                  What are your DC CFM's

                  Some companies list their test procedure - I know Grizzly does - use to be in their manual.
                  Bill Pentz has a page dedicated to Measurement. Follow the procedures and you will have a pretty good idea of where you are at.

                  Don
                  Last edited by Don Burch; 12-09-2014, 01:35 PM.

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                  • #10

                    Re: What are your DC CFM's

                    Re: What are your DC CFM's

                    The way companies juice their ratings is to measure using a bellmouth opening and sometimes omit filters. Matt, you don't want to increase the length of the bucket, but of the 6" pipe. How well your DC performs is a function of cfm under pressure. Some impellers will deliver huge cfm at low pressure but drop like a rock as SP increases. Key is to find a combination of efficiency and pressure within the working range of your specific system. Some cyclones have more pressure drop than others, same with filters, and the pipe resistance increases dramatically with velocity. That is why undersized pipe can be fatal to an impeller. System can only increase cfm until the velocity increases the resistance to the pressure limit of the impeller design. Your impeller is oversize for a 5 hp motor but the nature of curved blade fans is to drop off quickly. If you can hold your 1900 cfm over 20-30 ft of pipe and a couple of ells, you are really golden ( I would guess less). When I ran a 15" curved Oneida impeller I would max out at 1600-1800 cfm with all gates open but the amp draw was under 11 three phase amps so the impeller would not max out the motor. Speeding up the impeller helped only slightly due to the curved design. I swapped the impeller to a 15x3.5 straight blade and could increase cfm slightly at max but at a higher amp cost so it wasn't feasible with the 5 hp motor. It did outperform the curved at the end of a 50' line -8" reduced to 7" by a couple hundred cfm but again at higher amps. At low pressure it wasn't nearly as efficient as the curved. My final swap was to a 15.75x6.25 straight radial with a 7.5 hp motor. I can pull a max of 2200-2400 cfm with all gates open but also over 1600 50' away through a 7" pipe and 6" port. Amp draw is about 15 and I can speed up the blower to 70 amps and the cfm will continue to increase although the noise is a killer. I find I run at 55-60 hz unless using the edge sander at the end of the line. Then I ramp up to 65 hz. When I ran the 299 I needed all the 1600 cfm I could get at the machine because old machines have crappy hood design. My SAC 530 is way more efficient. I will be anxious to see your readings as the system is run. I would not ever use 6" as my main run. Like choking a sports car with a small filter and crimped exhaust pipe. Too much velocity and SP . I measure with a Velocitor so my readings are a range and I usually take the low end of the range. Not the proper way but good enough for me. Dave
                    Last edited by beckerkumm; 12-09-2014, 07:34 PM.

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                    • #11

                      Re: What are your DC CFM's

                      Re: What are your DC CFM's

                      Matt, are you measuring it without ductworK???

                      You need to measure at the tools you're using.

                      For example my highest flow is with 2 gates open for my saw, I have 600 at the cabinet and 148 on the overhead guard.

                      My J/P which is the longest run is 540.

                      You need to hook up your ductwork............Rod.
                      Work is the curse of the riding class.

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                      • #12

                        Re: What are your DC CFM's

                        Re: What are your DC CFM's

                        This is what I like reading!!! Thanks Dave !

                        I have read all that Pentz has written(maybe twice). it is nice to hear others experiences, tests and trials. The device I am using only has a 6000 feet/min max capacity. At three inches from a 5" port trough 12' of flex and 15' metal ducting hit 6000f/m. I want to get a end of pipe reading that is accurate and within the devices limits. I do need to enlarge the end intake and rid of any turbulences and have air stream uniform to measure. Based on the bucket test my 6" port off at 16' main(no hose) I would have almost (from the highest reading) 11000f/m calculated up. Well more to try.
                        For every action there is an equal and opposite reaction.
                        Sir Isaac Newton.

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                        • #13

                          Re: What are your DC CFM's

                          Re: What are your DC CFM's

                          Dave,
                          if I understand you are running a VFD on your 3 phase DC motor. Never thought of that. Curious to know,was you blower designed for increased speeds or did you have the impeller balanced for those higher rpms? Or did you wire it up and ramp up the hertz up till it was screaming?
                          Mike

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                          • #14

                            Re: What are your DC CFM's

                            Re: What are your DC CFM's

                            Matt, 800 cfm through a 5" and flex is in the ball park for your impeller. Flex is a killer but your extra diameter helps.

                            Mike, I run the vfd for two reasons. Speed control is nice when just using the dc to clear the air or when I'm using the far away old stuff. For that to really work you need the radial fan. Second, it saves the amps on my 10 hp phase perfect as the dc runs off a separate single phase line. Downside is the radial is loud- really loud. My Cincinnati RBE 9 is rated to 4500 rpm and sits up in the attic. Cartridges are wrapped with acoustic blankets and i have a muffler on the exhaust. I always wear hearing muffs when in the shop ( makes me feel safe from the world in the silence ) so not a big deal. Dave

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                            • #15

                              Re: What are your DC CFM's

                              Re: What are your DC CFM's

                              Rod, I really like hearing your views on dust collection, as I feel you spent a good amount of time trying to perfect it. Rod what is the horsepower of your cyclone?


                              Shortly after I built my cyclone and got rid of my 1.5 horsepower bag style, I had to micro just the 5 inch gate (as you know to go back and read the manual lol)to about little less than 1/3 open for my jointer/planer which the exact same as yours, but creates different chips.


                              When I went from my 1.5 hp DC to my homemade 5 hp Pentz I started building a system. Right now I have 16 feet of main 6" ducting, 2=>6" gates and 2=>5" gates and quick connect hoses. I still move hoses around a little bit. I no longer move the DC as I can't. If I can ever figure out how I want to leave my shop permanently maybe I will duct right up to each station. I have a somewhat small basement shop 12×23. Sometimes I need to rearrange the machines so I can utilize the doorway to be able to handle longer boards, so the DC will always have 10' & 12' hoses. My favorite hose is the 5 inch as I turn up quick connects for the standard 5 inch blast gate using PVC couplings. Anyway, when I perfect the testing I'll shoot a video for critiquing.
                              Last edited by Matt Matt; 12-09-2014, 09:50 PM.
                              For every action there is an equal and opposite reaction.
                              Sir Isaac Newton.

                              Comment

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