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    #61
    [QUOTE=joe yap]Not surprising at all. I have even seen a 2 bladed fan design. You can also see that the fan blades are much broader to absorb the power of the motor, unlike the skinny GWS fans.

    Thank you Joe for your feedback.

    I have been toying with the two bladed EDF fan concept for quite a while using broad blade and a wide range of pitch as you have described. I did get some good result at low power setup. Unfortunately at higher power(higher rpm setup) I ran into severe vibration and resonance situation so I drop the idea for the time being.
    May go back to the two blade EDF concept once I figure out how to eleminate the vibration issues.

    On cutting down or reduce blade setup ....
    I don't just remove and reduce the blade count, to match the motor but also explore other type of 3 blade (very soon some other 4 bladed propeller) with different pitch, broadness and thickness cut and balance to fit the EDF shroud.

    However, I did get pretty good result interms of efficient and reasonable thrust with some of this modification when they correctly match the motor.


    Cheers

    Comment


      #62
      [QUOTE=Babylon5]
      Originally posted by joe yap
      I have been toying with the two bladed EDF fan concept for quite a while using broad blade and a wide range of pitch as you have described. I did get some good result at low power setup. Unfortunately at higher power(higher rpm setup) I ran into severe vibration and resonance situation so I drop the idea for the time being.
      May go back to the two blade EDF concept once I figure out how to eleminate the vibration issues.


      Cheers
      Hi Babylon,
      Since you have toying with 2 bladed EDF concept for years with broad blade and a wide range of pitch as Joe had described. I believe that you should be using those GWS fan, if that is the case may I ask where do you get those blades / rotor from to fit into the GWS fan?
      I am Keen to try out too.


      cheers

      Comment


        #63
        Hi Alwin, I use mostly GWS 9-7 3 blade available at most hobby shop.
        ....and 8-6 SL 3 blade from Sky hobby.


        I seldom use GWS EDF blade because mounting problem . They use special forcer fit prop pin so acessing the two grub screw is a pain in the neck.

        Other 4 blade got directly from USA.

        For two blade I use Taipan 8-6 blade ...use to get in S Hobby but not sure they carry this brand.

        I only started the experiment on the two blade last year.


        cheers

        Comment


          #64
          Thanks for your reply, but is'nt it cheaper to buy a suitable BL motor for the fan rather than buying different kinds of blades to cut off some blades and try until it works?

          Comment


            #65
            Originally posted by Alvin Roger
            Thanks for your reply, but is'nt it cheaper to buy a suitable BL motor for the fan rather than buying different kinds of blades to cut off some blades and try until it works?
            Well Alvin, .....


            Even if the EDF manufacturer recommend the type of motor for their EDF unit, will you trust their recommendation? Some people have already experience EDF meltdown or short flight through such recommenadation that was advertised in the website.

            See link http://www.daddyhobby.com/forum/showthread.php?t=24700


            It does not mean that you don't trust any recommendation but you have to exercise sound judgement.

            Reading about motor KV and good matching practices between EDF and motor can help save you your hard earn money and time.

            Your question a "suitable motor" ... is kind of very wide.

            Unless you buy a high end EDF that comes with a well proven and recommended motors .In this case the motor suits the fan. However, this setup comes with a price.

            However, some people like to try other fan and other motors and other experiment. They like to find out if they can push the unit to the limit or try to save cost...and other reasons...just like why some people wants to over clock a PC and push performance to the extreme. It the andrenalin rush.....

            ...and not about cost factor alone as you have mentioned.


            Cheers and all the best

            Comment


              #66
              Originally posted by Babylon5
              Well Alvin, .....


              Even if the EDF manufacturer recommend the type of motor for their EDF unit, will you trust their recommendation? Some people have already experience EDF meltdown or short flight through such recommenadation that was advertised in the website.

              See link http://www.daddyhobby.com/forum/showthread.php?t=24700


              It does not mean that you don't trust any recommendation but you have to exercise sound judgement.

              Reading about motor KV and good matching practices between EDF and motor can help save you your hard earn money and time.

              Your question a "suitable motor" ... is kind of very wide.

              Unless you buy a high end EDF that comes with a well proven and recommended motors .In this case the motor suits the fan. However, this setup comes with a price.

              However, some people like to try other fan and other motors and other experiment. They like to find out if they can push the unit to the limit or try to save cost...and other reasons...just like why some people wants to over clock a PC and push performance to the extreme. It the andrenalin rush.....

              ...and not about cost factor alone as you have mentioned.


              Cheers and all the best
              Hi Alvin ,Sorry I think I miss your real question. After going through your post I realised you are refering the motor match with the high performance EDf like Wemotec.
              For Wemotec or other high end EDf ,there is no need to experiment ,cut or change to other propeller and motors. The EDF and motor are already well matched.

              The other lower cost fan like GWS are the one that need correct matching for brushless motor. Why ? Take GWS EDF. They were original design for brushed motor. GWS EDF with brushless motor only start to take root quite recently. This EDF are inexpensive and fertile ground for experiment.

              I hope I have answer your query.

              Comment


                #67
                Originally posted by Babylon5
                Well Alvin, .....


                Even if the EDF manufacturer recommend the type of motor for their EDF unit, will you trust their recommendation? Some people have already experience EDF meltdown or short flight through such recommenadation that was advertised in the website.

                See link http://www.daddyhobby.com/forum/showthread.php?t=24700


                It does not mean that you don't trust any recommendation but you have to exercise sound judgement.

                Reading about motor KV and good matching practices between EDF and motor can help save you your hard earn money and time.

                Your question a "suitable motor" ... is kind of very wide.

                Unless you buy a high end EDF that comes with a well proven and recommended motors .In this case the motor suits the fan. However, this setup comes with a price.

                However, some people like to try other fan and other motors and other experiment. They like to find out if they can push the unit to the limit or try to save cost...and other reasons...just like why some people wants to over clock a PC and push performance to the extreme. It the andrenalin rush.....

                ...and not about cost factor alone as you have mentioned.


                Cheers and all the best
                For someone like me who just started going into EDF, I will only trust those recommendation set up provided by proven EDF makers like Wemotec etc.. and not by those clone fans makers.

                What I am trying to mean is that why can't we just install a "suitable" motor to suit the fan, rather than get an "underpower" motor and cut off some blades to suit the motor.

                Btw, Babylon, may I know how long have you been into EDF set up plane?


                cheers

                Comment


                  #68
                  Originally posted by Alvin Roger
                  For someone like me who just started going into EDF, I will only trust those recommendation set up provided by proven EDF makers like Wemotec etc.. and not by those clone fans makers.

                  What I am trying to mean is that why can't we just install a "suitable" motor to suit the fan, rather than get an "underpower" motor and cut off some blades to suit the motor.

                  Btw, Babylon, may I know how long have you been into EDF set up plane?


                  cheers
                  Sometime, you must also consider the mounting and integrity of the fans. Using an overpowered motor and spinning at excessively high RPM can strip the fan attachments and possibily blow the fan. GWS fan probably will not state when will it happen, but Wemotec does tell you how much power you can input. They even recommend a RPM limit.

                  Comment


                    #69
                    Originally posted by Alvin Roger
                    For someone like me who just started going into EDF, I will only trust those recommendation set up provided by proven EDF makers like Wemotec etc.. and not by those clone fans makers.

                    What I am trying to mean is that why can't we just install a "suitable" motor to suit the fan, rather than get an "underpower" motor and cut off some blades to suit the motor.

                    Btw, Babylon, may I know how long have you been into EDF set up plane?


                    cheers

                    Hey mate, that is a good approach. Simply research, record what is the setup other used and you will get a pretty good picture

                    I usually dun recommend modifying the blades by cutting etc unless you know absolutely what you are doing and that you are not compromising the design integrity. Relating it to conventional propellors, I think it is ok to change between 2 and 3 bladed props etc and so on, But IMHO I think it is a bit crazy to cut a conventional 4 blade to 2 blade and think it is better. I would go the other route and find a suitable motor to mate that fan, otherwise I will find another EDF candidate.
                    Stop looking for a gyro in my plane, they are all in the head.

                    Comment


                      #70
                      From Edmond22
                      "But IMHO I think it is a bit crazy to cut a conventional 4 blade to 2 blade and think it is better. I would go the other route and find a suitable motor to mate that fan, otherwise I will find another EDF candidate.[/QUOTE]"


                      Hi Edmond22, if you look at some similar other thread, people have bought a complete RC jet model ,comes with the recommended brushless motor and fan unit and yet only to find out that the motor runs hot and even cause a melt down to the shroud.
                      Under this situation, they have a few option...return and ask for a refund(I doubt the can) , dump it into a dustbin (see your $$$ fly)or look at ways to make the system work....and other options.

                      People cut down or reduce the number of blade arrangement usually with good reasons.


                      Cheers

                      Comment


                        #71
                        Originally posted by Babylon5
                        Hi Edmond22, if you look at some similar other thread, people have bought a complete RC jet model ,comes with the recommended brushless motor and fan unit and yet only to find out that the motor runs hot and even cause a melt down to the shroud.
                        Under this situation, they have a few option...return and ask for a refund(I doubt the can) , dump it into a dustbin (see your $$$ fly)or look at ways to make the system work....and other options.

                        People cut down or reduce the number of blade arrangement usually with good reasons.


                        Cheers

                        So this "people" you are talking about is a minority or majority? IMO, I have been fooling around with EDF for a couple of years too and modifying blades is still a minority to me.

                        If 1 experiences a meltdown or for that matter a genuine issue with a recommended setup, it would be a disaster for the manufacturer and the recommendation should be revised etc etc.

                        When you say "people" cut down or reduce the number of blade arrangement with good reason, I honestly still think it is a minority and it is definitely not always for good reasons. More like desperate measures.

                        Like Joe Yap says, the underlying physics will still be there. So it really doesn't matter if a motor is recommended or not, it is still good to learn the basics of electronics and make sure you motor and EDF is not pushing beyond its intended usage.

                        I dun always trust manufacturer's recommendations but I TAKE their caution warning seriously, and that includes modifying the blades lol.

                        I am not saying you shouldn't experiment with what you are doing currently, but advocating it needs some care on your part.

                        So are we saying cutting down the blades is a good practice and that it increases EDF efficiency? Answering this will be quite a bold statement.
                        Stop looking for a gyro in my plane, they are all in the head.

                        Comment


                          #72
                          After reading so much on micro EDF threads posted by babylon.
                          I realised that Joe yap and edmond22 statements / advices make more sense to me.

                          Sorry to say that babylon, I really have doubt in you.
                          Good luck with your testing.

                          Cheers

                          Comment


                            #73
                            Originally posted by Alvin Roger
                            After reading so much on micro EDF threads posted by babylon.
                            I realised that Joe yap and edmond22 statements / advices make more sense to me.

                            Sorry to say that babylon, I really have doubt in you.
                            Good luck with your testing.

                            Cheers
                            Hi Alvin. No problem. I can handle that.

                            Comment


                              #74
                              Hi guys.

                              I think, I think this thread is getting hot for not the right reasons. I guess we have to understand that this hobby of ours is quite technical as such it can get complicated and open to intepretations. For the same reason, some input and findings might confuse new comers.

                              Over the years, in my over-spent social gathering in bars, pubs,parties,lectures and workshops, I have learnt that there are all sort of different characters. It take active effort to keep dicussion fun and interesting. For this I salute Tomcatflyer for his occasional one liners to cut the tension.

                              As for EDFs, it is reasonably new as such a lot of experiment are going on. However approaching a new subject, it is common to lean towards our trade to explore the subject. Unfortunately this biase sometime is not correct. For those of us who are lucky enough to have an Aviation engineering job, invariable the contribution is a little more elaborate and correct.

                              Having said that, theorist will go on and on explaining how an elephant can fly. Being a theorist myself, I am guilty of that all the time. However we have to understand there are aeromodellers who are flyers, not builders. Building is just a consequent. With this in mind it is of paramount importance to make things simple.

                              As for the Pragmatise, thinking outside the box is very important in Aviation otherwise the Wrights would never have invented the airplane. So keep up the good experiments and ...let us know. Might not immediately know what would work but knowing what would not work, helps as well.

                              With all the interest in mind and with the right attitude, I hope we will, together, resolves the mystery of EDF sooner than later. Also to get above the 10% mark

                              Just to contribute further, I will like to put forth the following challenge in the good interest of effective EDF set ups.

                              The Challenge'

                              Pls put together a set up that would run at full power for 3 minutes without exploding and able to power a reasonable size aircraft(no peanut size or 1/2 scale planes) and continue to work out the following numbers.

                              Pls calculate the amount of static thrust per unit watts. grms(static thrust)/watt(I*V). Eg. a set up that produces 500gms of static thrust at 3S drawing 30 amps would yeild, 500/11.1*30=1.5grm/watt. Thru my elementry maths, this would be a good indication of efficiency of the set up.

                              The prize.

                              Of course there is a prize. It is the recognition of coming up with a good set up and Mastering the black art of EDF. Also a life time supply of air for all your future EDFs.

                              Ps, the formula also work for brushed motor as some of us do like to use brush motor still.

                              So there you have it, time to walk your talk and talk your walk...

                              cheers

                              Comment


                                #75
                                I was thinking that this is just a discussion and didn't intend to heat it up. I believe that there are just some minor disagreements of something we know or believes and is perfectly normal in such discussion. If I ever raise any heat, which I never intend to, I apologise beforehand. Afterall, discussion doen't mean that we have to come to an agreement.

                                As of the mentioned so-called recommended setup which has experienced a meltdown, it seems that the motor is severely overloaded, and one alternative rectification, other than cutting the blades is to reduce the cell count.

                                Oh yes, I almost forgot. Even if you have the bestest setup in the world, all you need is to screw up the inlet and exhaust ducts, you'll screw up the entire system. Like what Vortices has mentioned, air intake is everthing. To add further, the exhaust duct also determines how much useful work you want to waste away.
                                Last edited by joe yap; 11-07-2007, 03:12 AM.

                                Comment

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