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Old Mar 08, 2013, 07:08 AM
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United States, FL, Sebring
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I don't know where one gets the idea that EDF people don't talk about blade pitch. It is a huge factor in efficiency.
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Old Mar 08, 2013, 07:45 AM
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Greece, Attica, Athens
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Originally Posted by Joe 1320 View Post
I don't know where one gets the idea that EDF people don't talk about blade pitch. It is a huge factor in efficiency.
I think that what mopetista was trying to say is that blade pitch by itself is not indicative of efficiency. Overall rotor and blade design is however.

For example, some rotors with higher pitch can achieve similar thrust levels at a lower rpm.
This does not mean that they are inefficient. Some higher pitch rotors may have proved to be inefficient.

The Changesun 70mm 10 and 12 blade rotors for example are not largely inefficient when compared to a wemo 5blade rotor for example. When the right motor is chosen, their thrust to watts numbers are similar to within a few %.

These new 10blade 50mm rotors seem to be pretty good. They don't offer extra performance.

They provide similar performance levels as 5 or 6 blade rotors at a lower rpm with much less rotor whine.

This however needs to be substantiated by several people in order to arrive to a common baseline of what's needed to run these rotors.

I am running some tests to show what's possible.
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Last edited by anlucas; Mar 08, 2013 at 07:51 AM.
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Old Mar 08, 2013, 07:56 AM
222 km/hr Parkjet flyer
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Latvia, Ventspils pilsēta, Ventspils
Joined Jan 2010
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Quote:
Originally Posted by Joe 1320 View Post
I don't know where one gets the idea that EDF people don't talk about blade pitch. It is a huge factor in efficiency.
Of course it's a huge factor ........ but it's rarely posted about. Number of blades ... kv of motors - yes - mills of posts ... but pitch ?

Compare to a prop discussion ............ pitch is so common a part of the chat - and also we all buy props with pitch in mind ... it's a basic automatic factor to consider ... diameter x pitch. But EDF's ? who actually quotes pitch of the blades ? Who asks ?

I for one would like a more visible pitch factor when deciding on rotor, allowing me to buy various and test to get best result ...... same as when I buy and test props ..........

Nigel
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Old Mar 08, 2013, 09:28 AM
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Vienna, Austria
Joined Apr 2007
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the sensitive multi-bladers...

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Originally Posted by Joe 1320 View Post
I don't know where one gets the idea that EDF people don't talk about blade pitch. It is a huge factor in efficiency.
Sorry, that was a bit cheap IMO - instead of quoting me out of context, maybe next time YOU might take on the effort to explain the differences between props and EDFs in as simple as possible a fashion - and since you will want to do other things in your life, too, you will try to be short. If you read what rcfisherman's post was about: efflux speed. So the context was: would blade pitch be an indicator of high efflux speed, and can you have, as is the case with props, e.g., high efflux speed with low thrust. Answer is no, not in an EDF with the same exit diameter. You will need lower RPM on a high-pitch high blade-count fan. But efflux is pretty much determined by the thrust and exit diameter (provided there is a bit of a thrust tube so that the speed of the accelerated air evens out).
I was not talking about designing a fan, but what are the differences when running it. And in use, you can all but forget about high or low pitch in general as far as efflux is concerned, that will be determined by the exit diameter. However, whereas the exit diameter just determines the ratio of static thrust vs efflux speed in a standard 5-blader, and you have to think about the tradeoffs between topspeed and good vertical, things are not so easy with the newer multi blade fans.
Blade pitch, or rather blade pitch distribution surely must be ONE of many factors in designing a good rotor. It is no accident that WeMoTec, Stumax, Ejets and others are still not producing smaller high blade-count fans. 80mm is minimum at the Jetfan, others stop at 90mm. Seems that things get very tricky, and it can be seen in the problems of the Change Sun 70mm with small inlets and exhausts that the devil is in the detail, the Change Sun performs - as anlucas has said - almost at the level of a Wemo Minifan on the test stand (there it has an open outlet, and gets air easily and smoothly via an inlet lip). In the airframes the results are often not so great, so that one has to be thinking of getting enough air in, and not going below 58mm at the exhaust. What the parameters are for the small 50mm 10-blade we will see, it might be that the slightly smaller exit on the AMX is less-than-perfect for the 10-blader, and the other, bigger ones at most Sky Angel models will help with static thrust using the 10-blader...
Thanks anlucas for getting ready for some testing on the 50mm Lander unit. I really appreciate it, and you did a lot for getting to grips with the 10-blade 70mm using different outrunners etc.
cheers
Clemens
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Old Mar 08, 2013, 09:49 AM
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Sunnyvale
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Originally Posted by chas650r View Post
unless you guys have overloaded motors u will find little difference between in and out runners, sorry no magic pill
There is a huge difference! Not only in performance but in price as well. What I have been doing is trying to find a happy medium between price and efficiency. My most recent motor is an outrunner for 64mm fans but is only cost $13. It may not be the most efficient but it was on the pocket book! Although the numbers and amount of thrust it produced were pretty good! I wil keep everyone posted on the test flight this sunday...

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Originally Posted by Wrench66 View Post
Nice Delta Pool Noodle 50mm, Al!
I was gonna say the same thing! Love it when someone makes something from scratch!! One of the pix made me do a double take though.... it looked like a

Quote:
Originally Posted by rcfisherman View Post
everybody has to remember that thrust and amp numbers are not enough to tell the performance. you also have to know the efflux speed.
a 13x4 prop and a 6x6 prop may produce the same static thrust numbers but, they will propell a plane at very different speeds. the more blades you have, will act like a bigger prop. a 4 blade edf with the same thrust as a 10 blade will have higher efflux and thus more top speed
You are right about prop planes but things are a lil different with EDF's. Pitch does have something to do with it but in different ways. I just don't have the brains to say it in ways that make sense to everyone... But from what I have gathered in my experience is that ducting has a lot to do with how these things work. If you don't have enough air coming in and the proper amount of air going out then you won't get good results. I don't use graphs or flow charts to see what works best. I use a wattmeter, fresh battery and the plane pointed nose up in my hand. If the plane feels like it will leap out of my hands then I have done something right. But that is just the start...

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Originally Posted by solentlife View Post
Very true .... I've run both Out and In runners .... both up to 5000kv formats .... difference ? Haven't been able to detect significant benefit other than slimmer motor body allowing exhaust flow of fan to be cleaner / less obstructed with the inrunner.
Whatever you do ... it all still obeys Physics Laws ... you don't get anything for nothing. You may gain a little by increasing efficiency of motor by a few % points - but that's it.

In my view - the biggest gains are got by :

a) Better battery to provide the power needed
b) Clean efficient ducting.

Nigel
Inrunners may run hotter than most people are used to but they are some of the most efficient set ups out there.

Quote:
Originally Posted by anlucas View Post
I think that what mopetista was trying to say is that blade pitch by itself is not indicative of efficiency. Overall rotor and blade design is however.

For example, some rotors with higher pitch can achieve similar thrust levels at a lower rpm.
This does not mean that they are inefficient. Some higher pitch rotors may have proved to be inefficient.

The Changesun 70mm 10 and 12 blade rotors for example are not largely inefficient when compared to a wemo 5blade rotor for example. When the right motor is chosen, their thrust to watts numbers are similar to within a few %.

These new 10blade 50mm rotors seem to be pretty good. They don't offer extra performance.

They provide similar performance levels as 5 or 6 blade rotors at a lower rpm with much less rotor whine.

This however needs to be substantiated by several people in order to arrive to a common baseline of what's needed to run these rotors.

I am running some tests to show what's possible.
I think that you came the closest to what I would have said myself...

Quote:
Originally Posted by solentlife View Post
Of course it's a huge factor ........ but it's rarely posted about. Number of blades ... kv of motors - yes - mills of posts ... but pitch ?

Compare to a prop discussion ............ pitch is so common a part of the chat - and also we all buy props with pitch in mind ... it's a basic automatic factor to consider ... diameter x pitch. But EDF's ? who actually quotes pitch of the blades ? Who asks ?

I for one would like a more visible pitch factor when deciding on rotor, allowing me to buy various and test to get best result ...... same as when I buy and test props ..........

Nigel
My trial and error with all of these different blade types relates to what it is that you are saying here. But what I am looking for is the sound. Once I heard the CS 10 blade fan and then the other fans I was hooked on the sound. They sounded like actual jet engines! The 8 Blade AEO fan has come the closest to making that same sound in these little 50mm EDF units.

I think that discussions like this are good! Keep it going guys!
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Old Mar 08, 2013, 10:01 AM
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ok guys I got the Screamer done. It seems pretty promising! Take a look...

final fan fitting


I could have done just a little better cleaning up the front now that I look at it...


battery placement.


it looks like an alien space ship! Pretty cool looking little bird!


shot from the rear


this looks a little better. 8 blades sound very cool!


Ok here are the watt meter readings. What these don't show is how much thrust this plane actually has!! I could barely hold it with one hand! In the AMX it didn't make this much power so I am pretty surprised at how it felt! Can't wait to maiden it on Sunday...

This battery was a little cold since it had been outside. I know that the numbers would have been better with it warmed up a bit. The voltage drop is always much less on these higher C packs when warm.


This pack had been inside for a few hours so it was much warmer and the numbers show that. Normally the 40c packs are better than this one. Still impressive for a 25c pack none the less!!
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Old Mar 08, 2013, 10:02 AM
ICrashRCs
United States, TN, Memphis
Joined Jun 2011
1,196 Posts
Quote:
Originally Posted by Mike20 View Post
I found the mini concept x motor that i believe is the 5800kv motor that I have in my f18. It has the same size bullet connectors as the one I have had. So Im assuming its the right motor.

http://www.nitroplanes.com/69a501-09-motor.html
Does this have a 3mm threaded shaft?
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Old Mar 08, 2013, 10:15 AM
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Vienna, Austria
Joined Apr 2007
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Originally Posted by gooniac33 View Post
ok guys I got the Screamer done. It seems pretty promising! Take a look...
Really nice bird - like you I've got a MPX Microjet and love it, but the screamer is "cooler" I think.
Hope you'll video it soon, itching to hear the 8-blader. Ray, with this low-pitch 8-blader you can only hope that the EDF gurus are right insisting that blade pitch is irrelevant, only thrust counts :-) Looks like a short tube but this approximation will still work pretty well (uniform air speed). It gets air much easier than in the AMX with the large short inlet, but there is also the smaller exhaust on the AMX which accounts for the lower static thrust - for full speed potential you'd have to make a thrust tube on the Screamer, you know that anyway. Good luck on the maiden!
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Old Mar 08, 2013, 10:18 AM
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Bulgaria, Sofia-grad, Sofia
Joined Feb 2012
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Guys, I managed to pull off a 10 min 45 sec flight to day with my T-45 and a 45C 1000mAh 3S Nano-tech. So proud of myself. It was a tad nose heavy though, so I had to compensate throughout the whole flight. I bet it will go over 11 mins if I move the battery back a couple mm.
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Old Mar 08, 2013, 10:29 AM
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United States, ID, Boise
Joined Mar 2011
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How do you get 10+ minutes? I
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Old Mar 08, 2013, 10:32 AM
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Sunnyvale
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Originally Posted by mopetista View Post
Really nice bird - like you I've got a MPX Microjet and love it, but the screamer is "cooler" I think.
Hope you'll video it soon, itching to hear the 8-blader. Ray, with this low-pitch 8-blader you can only hope that the EDF gurus are right insisting that blade pitch is irrelevant, only thrust counts :-) Looks like a short tube but this approximation will still work pretty well (uniform air speed). It gets air much easier than in the AMX with the large short inlet, but there is also the smaller exhaust on the AMX which accounts for the lower static thrust - for full speed potential you'd have to make a thrust tube on the Screamer, you know that anyway. Good luck on the maiden!
I think that you are right about the AMX. The screamer has a lot more open intake in the front. It gets a lot more air and you can feel it! The plane wanted to launch vertical out of my hand when I was running it up! Way more power than the other planes it has been in. I have a feeling that this is going to be really good! The AMX was radared at a little under 90mph with this exact same fan.so this one which feels much stronger should be even better! Maybe not as fast as the 4s 6000kv missile that are already out there but still pretty good! I will for sure post result...hopefully someone will do a video for me...

By the way here is a pic of my MicroJet wattmeter reading on 4s...

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Old Mar 08, 2013, 10:39 AM
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Sunnyvale
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Quote:
Originally Posted by Arxangel View Post
Guys, I managed to pull off a 10 min 45 sec flight to day with my T-45 and a 45C 1000mAh 3S Nano-tech. So proud of myself. It was a tad nose heavy though, so I had to compensate throughout the whole flight. I bet it will go over 11 mins if I move the battery back a couple mm.
I for sure can be done with some throttle management. It doesn't take much to keep the little bird in the air on 4s. So I am not skeptical at all! I have gotten some 8 min flights on my T-33 and L-39 even with some full throttle blasts on occasion. I am positive that it can be done with no full throttle passes at all...
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Old Mar 08, 2013, 10:55 AM
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Vienna, Austria
Joined Apr 2007
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Screamer and multi blade fans...

I just remembered that Martin (who posted 2 videos of his Nano Vector aka Screamer w/ 10-blade 3300kV combo here) had told me that the thrust would be so good, the plane would already hover in his hand at just over half throttle (small 4s lipo) - I had trouble believing him...
I guess it's an ideal "work environment" with plenty of air in, and no restrictions out.
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Old Mar 08, 2013, 11:17 AM
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Originally Posted by mopetista View Post
I just remembered that Martin (who posted 2 videos of his Nano Vector aka Screamer w/ 10-blade 3300kV combo here) had told me that the thrust would be so good, the plane would already hover in his hand at just over half throttle (small 4s lipo) - I had trouble believing him...
I guess it's an ideal "work environment" with plenty of air in, and no restrictions out.
It is pretty amazing!! More power than I have ever felt from one of these little planes!
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Old Mar 08, 2013, 04:22 PM
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Joined Sep 2012
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Well I made myself a new edf unit test airframe today after a mishap on my last flight of the day. I had about 5 flights in today annoy last one I got disoriented and thought I was upright but really I was inverted and and it started to drop so I pulled back on the stick and you know the rest. So it was demolished so I cut the rest of the front off since the rear of the fuselage was fine and now I'm gonna use it as a test airframe. The ducting is all fine and I cut off from the ducting up.
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