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Sep 14, 2019, 09:37 AM
Big gov never Works
St. Martin's Avatar
And sometimes it increases efficiency, with a higher load. I noticed the high blade count CS types have a much less aggressive stator curve/angle, than the WeMo. Probably because it could cause a pressure increase or even more turbulence straitening the flow. Another example of how the WeMo is designed for higher efflux flow.

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Still waiting for a counter balanced single blade EDF with supersonic blade tip speeds. So the fuel guys can’t hear if their engines are even on
Hi Scott, I forgot this:

Many people, in this day and age, do not know that the most efficient prop is one blade. Even full scale racing boats use them. As far as the whine noise in the HET or WeMo 5b, it is due to the frequency sound made by one blade passing a stator at one time. Our ears pick this up easily. But, it's very efficient. The reason why the best fan designers use an odd/even rotor blade to stator count. If more than one blade passes passes a stator at the same time, the frequency is changed, where our ears do not hear it. Each passing still has the whine, but the combination of the two or more passing changes the overall frequency.

And, if the multiple passings are not distributed equally in the arc, then the fan will not dynamically balance. If you do not believe this, then try a WeMo 5b rotor in a 3 stator HET shroud. Not workable, and even more horrible sound.

The quietest fan I ever owned, was the old WeMo non glass filled 480. I used it with a Kontronic 400-23 and 5s-1800, in an RBC A4. You could only hear the air in the intakes. And only on a fly-by. A lot of the hard whine heard from these fans is balance, often caused by the motor. The difference in the motors rotor balance differs greatly, even between the same makes. The Kontronic is perfect two pole balance. Not segmented as with those requiring kevlar wrap. So, before blaming the awful noise on the fan alone, think not being able to clock the noise out of the motor.

Fuzz
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Sep 14, 2019, 11:17 AM
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What if they flipped the motor around, attached it to the intake ducting, and put the stators near the middle or back of the exhaust ducting. Could not the frequency be all but eliminated?

Scott
Last edited by Scottfpv; Sep 14, 2019 at 04:52 PM. Reason: I didn’t edit it
Sep 14, 2019, 11:20 AM
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turbonut's Avatar
The Wm fan was a pusher and make more noise than any fan I have ever ran
Latest blog entry: In flight
Sep 14, 2019, 04:17 PM
Big gov never Works
St. Martin's Avatar
Ditto, I had two in a Cutlass. Took for ever to get smooth. The WM-400 is an IGV (inlet guide vanes) fan, as was the early Stu Max fans. The rotor is 3b with huge wide chord blades. It has 4 IGV's. Still one blade/stator passing @ one time. Quite an efficient fan. I'll try to locate the video, as they did not sound that bad in a twin set-up. Most likely the combination of the two cancelled some of the high whine.

Fuzz
Sep 14, 2019, 04:46 PM
Big gov never Works
St. Martin's Avatar

WM-400 MkII


Some pics of an IGV "pusher" fan.
Steves Large Cutlass Full Power.wmv (2 min 5 sec)
Sep 14, 2019, 04:50 PM
Registered User
Quote:
Originally Posted by Scottfpv
What if they flipped the motor around, attached it to the intake ducting, and put the stators near the middle or back of the exhaust ducting. Could not the frequency be all but eliminated?

Scott
“and put the stators near the middle or back of the exhaust ducting.”

I believe that is the part that would reduce the noise per air to stator “strike”. But, what I am describing is theoretical, as I don’t believe it has been done. Not saying it should be either.

Scott
Sep 14, 2019, 06:37 PM
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putput's Avatar
Thread OP
I'm just theoretically you trying to get this plane to go 125 to 130.. I appreciate all the input.
I'm hoping that the eight blade fan unit makes something happen. If not I'm happy to go to an 80s setup and start adjusting fans etc to accommodate that.
Sep 14, 2019, 08:06 PM
Registered User
Quote:
Originally Posted by putput
I'm just theoretically you trying to get this plane to go 125 to 130.. I appreciate all the input.
I'm hoping that the eight blade fan unit makes something happen. If not I'm happy to go to an 80s setup and start adjusting fans etc to accommodate that.
If you want a bad idea, I can give you one. Just go up a cell and use throttle management so you don’t cook your motor. Make sure your ESC and airframe can handle it. A better idea, if you want speed. Put your effort into that Habu 32 I see that you bought. Now that airframe can be made to move. Over 200mph, but that is crazy fast. Getting 150+mph is easy.

Scott
Sep 15, 2019, 02:51 AM
Big gov never Works
St. Martin's Avatar
Scott, regardless of where the stators are, the rotor still has to pass in front or behind. The original designer of the Offshore P-80(now RBC), used a tandem 66mm fan with brushed motors. THe stators were between the rotors. I have some pics, I'll find them.
Sep 15, 2019, 03:34 AM
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putput's Avatar
Thread OP
Quote:
Originally Posted by Scottfpv
If you want a bad idea, I can give you one. Just go up a cell and use throttle management so you donít cook your motor. Make sure your ESC and airframe can handle it. A better idea, if you want speed. Put your effort into that Habu 32 I see that you bought. Now that airframe can be made to move. Over 200mph, but that is crazy fast. Getting 150+mph is easy.

Scott
Yes, the habu is going to be a different animal. That one is going to be a jet fan 8s setup. Nothing crazy, but should be a 150 jet. Looking forward to that build.
This had become my experiment unit. It's already much better than stock, but looking for ways to improve. Hence the original??? About exhaust diameter vs FSA.
I never leave things alone for long lol. I like to tinker, and enjoy the reward and defeats.
Sep 15, 2019, 09:48 AM
Big gov never Works
St. Martin's Avatar
Here's some pics of Ralf Dvorak's Tandem fan. circa 1998. And the Force One IGV/EGV fan of the 80's. Ralf's fan was 66mm and designed to work in restrictive ducting of scale models. I think the Force One was a big failure. But, they both came from an age, when static thrust was not everything. We soon learned that some fans just can not take any reduction in duct area. So, your good to do experimenting with these areas on different fans, put put. Thats the best way to learn.

Fuzz
Sep 15, 2019, 02:15 PM
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turbonut's Avatar
Cool..I have one new in the box still...I will put it together some day just for fun..that and my RK fans
Latest blog entry: In flight
Sep 15, 2019, 02:43 PM
Big gov never Works
St. Martin's Avatar
Hi Scott, I wonder if brushless could be made to work? It was the offshore designs that brought about the 505 fan, which I like better than the 68 anyway. The 65Evo is a great fan. Easier to fine balance, and a real high efflux. Sounds better, Too! The Kress fans were a good learning experience. Would you believe I had the tandem rotor RK-049, that used a Kirn Kraft TD.09? Had it in a Walt Musciano F-84. Bob sold me one with no promises.

Fuzz
Sep 16, 2019, 11:07 AM
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turbonut's Avatar
One day when I am bored I will dig them out..I was thinking 2 mega might just work on RD fan. I have the RK 049 and 750? new..they will look good sitting on the display case..
Latest blog entry: In flight
Sep 16, 2019, 04:06 PM
Big gov never Works
St. Martin's Avatar
Bobs first fans were large diameter low efflux, as with the RK-.049, RK20 and RK-40. Later he came out with smaller diameter fans with more pitch for higher efflux. He took the RK-049 and made it into the RK-709(TD 09). The RK-720(K&B 3.5) was new diameter. And the RK-20 became the RK-740(K&B 7.5). In the early 90's I made the Ziroli Viggen, and F4. The Viggen used the 720, and the F4 the 740. THe Viggen was the better.

At the time, I was experimenting with glass ducting since the mid 80's, and noticed the old RK series did not like less than 90% FSA exhaust. While the later 7xx series could function much better under restricted areas. I think this time period was a transition of thinking that static thrust did not give speed. After seeing Bob Violett's BA Skyhawk II fly with just a Turbax, convinced me to learn the difference between the fan types.

I think Ralf used two SP-480BB in his. A couple of /3's on 4s should do he trick. Make a nice stand and intake bell/exhaust, and run it display. Were not the stators just supports? The actual flow stratening was done by the reverse rotation of the rotors to each other?

Fuzz


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