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Old Dec 10, 2011, 12:08 PM
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USA, CA, Aromas
Joined Sep 2010
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maybe....technically, but it was so minimal as to be very difficult to capture in the logs.
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Old Dec 10, 2011, 12:31 PM
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United States, NV, Reno
Joined Mar 2000
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Fans normally do not... do not... unload. People do in fact hear increase in RPM for EDF's in flight - but that is a result of the doppler effect. The perceived pitch did in fact go up as the model flew toward the observer but they were just "hearing" the compressed sound waves showing increased pitch as the model approached at a faster speed than, say, the relative closure rate when flying parallel to the observer on downwind (or more noticeably yet with the negative closure value as it flies away).

There have been some anecdotal reports of the higher blade count fans unloading but I suspect that is a result of overloaded motors and their inability to reach their KV rating in a static thrust run case, and thus running their motors in an over amped state on the ground. I doubt this is an optimized setup though, the motor will sooner than later die/demag/etc this way. In flight they may be able to increase to their natural kv speed. But they will not "unload" beyond that, as in the same way an ICDF will. Of course, I will admit there may be a lot of factors at play I'm not familiar with but that's how I've understood the peculiarities of ducted rotor dynamics.
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Old Dec 10, 2011, 12:35 PM
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yep thats what I was hearing, I completely agree with your loading assement
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Old Dec 10, 2011, 02:02 PM
edf flyer
Mannyman535's Avatar
United States, CA, Marina
Joined Feb 2009
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balance

Quote:
Originally Posted by jcdfrd View Post
yep thats what I was hearing, I completely agree with your loading assement
Hey John, i might need you to balance my fan with the tacon motor,
the cs 90 5 blade is balanced pretty good,
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Old Dec 10, 2011, 02:54 PM
3DHOG
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USA, CA, Aromas
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Quote:
Originally Posted by Mannyman535 View Post
Hey John, i might need you to balance my fan with the tacon motor,
the cs 90 5 blade is balanced pretty good,
no problem Manny give me a call when you want to drop if off, did you get a fan ordered yet? which one?
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Old Dec 10, 2011, 02:56 PM
Bypass Ratio = Infinity
scatsob's Avatar
United States, NC, Jacksonville
Joined Apr 2006
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Just a thought on balancing. Has anyone tried weighing each blade with a relatively accurate scale and then simply pairing like weighted blade across from one another? I can’t imagine the blade portion being most of the weight discrepancy. Thoughts?
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Old Dec 10, 2011, 02:59 PM
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USA, CA, Aromas
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Quote:
Originally Posted by scatsob View Post
Just a thought on balancing. Has anyone tried weighing each blade with a relatively accurate scale and then simply pairing like weighted blade across from one another? I canít imagine the blade portion being most of the weight discrepancy. Thoughts?
thats how they do it with fans that have seperate blades that interlock to the hub, I think dynamax are this way
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Old Dec 10, 2011, 03:06 PM
Bypass Ratio = Infinity
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United States, NC, Jacksonville
Joined Apr 2006
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Quote:
Originally Posted by jcdfrd View Post
thats how they do it with fans that have seperate blades that interlock to the hub, I think dynamax are this way
Wonder if they do that with these fans from the factory.
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Old Dec 10, 2011, 03:35 PM
Hey Ya'll!! Watch THIS!!
Michael Paxton's Avatar
Nashville TN.
Joined Mar 2006
2,555 Posts
Myself and some others take advantage of this by choking intake and exhaust and setting KV higher than would be good for static.
I end up with very effecient, fast and quiet jets.
PAX
Quote:
Originally Posted by Eddie P View Post
Fans normally do not... do not... unload. People do in fact hear increase in RPM for EDF's in flight - but that is a result of the doppler effect. The perceived pitch did in fact go up as the model flew toward the observer but they were just "hearing" the compressed sound waves showing increased pitch as the model approached at a faster speed than, say, the relative closure rate when flying parallel to the observer on downwind (or more noticeably yet with the negative closure value as it flies away).

There have been some anecdotal reports of the higher blade count fans unloading but I suspect that is a result of overloaded motors and their inability to reach their KV rating in a static thrust run case, and thus running their motors in an over amped state on the ground. I doubt this is an optimized setup though, the motor will sooner than later die/demag/etc this way. In flight they may be able to increase to their natural kv speed. But they will not "unload" beyond that, as in the same way an ICDF will. Of course, I will admit there may be a lot of factors at play I'm not familiar with but that's how I've understood the peculiarities of ducted rotor dynamics.
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Old Dec 10, 2011, 06:26 PM
Extreme CNC Alloy EDF
Extreme_RC's Avatar
Australia
Joined Mar 2006
11,354 Posts
Ramtec weigh and adjust the blades to I believe 0.01g of each other, they use a hi tech scale and the rotors run beautifully. I have never had an issue when building dynamax either, I clean and check the blade weight and the rotors run really smooth.
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Old Dec 10, 2011, 06:32 PM
Fly it like you stole it !
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Australia, QLD, Coolum Beach
Joined Oct 2011
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Quote:
Originally Posted by scatsob View Post
Just a thought on balancing. Has anyone tried weighing each blade with a relatively accurate scale and then simply pairing like weighted blade across from one another? I canít imagine the blade portion being most of the weight discrepancy. Thoughts?
Yip, thats how they do it on turbines, but...but the hole in the hub needs to be precisely in the middle. Not sure that can be guaranteed on these.
B
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Old Dec 10, 2011, 08:16 PM
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Originally Posted by turbonut View Post
Hi Bob,
I was with Steve when his fan let go...after looking at the data logger it showed it went at about 42k rpm and it was at 4.2k watts
I think it was the 1900KV not the 1700
Scott it was the 1700kv on the 12 blade. We blew up the 1900kv at the field and not this 12 blade fan.

Can't keep track of all the dead motors we have pushed too far!

Steve
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Old Dec 10, 2011, 11:15 PM
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Originally Posted by therealhiphop View Post
SC, Bobbit, Turbo,

This is the exact same combo I plan on using. Very interested in seeing your final numbers once you do get it up to full throttle. I've got the motor and just missed the mailman this afternoon with my fan . I am not so interested in all-out speed, but would be happy with scale speed and awesome sound. This is going in my CMP T-45.

I am setting up my own test stand but might be a while before I get it all ready.

Any problems with fitting the rotor tightly on the shaft?
I just ordered this fan for my CMP T-45 as well... haven't decided on the motor or ESC yet... so I am very curious to hear about your results.
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Old Dec 12, 2011, 07:31 AM
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South Africa, GP, Pretoria
Joined Mar 2011
415 Posts
Received mine too. Quality looks good but seems fairly heavy.
Will be trying a Suxfly 3674 1620KV on 6S to start off with. The motor has got the big holes in the front and back.
Will advise on numbers.

Any handy tips on balancing this fan?
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Old Dec 12, 2011, 07:43 AM
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Κύπρος, Λευκωσία, Πέρα Χωριό
Joined Jan 2010
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Quote:
Originally Posted by Graham d View Post
Received mine too. Quality looks good but seems fairly heavy.
Will be trying a Suxfly 3674 1620KV on 6S to start off with. The motor has got the big holes in the front and back.
Will advise on numbers.

Any handy tips on balancing this fan?
haven't done anybalancing since mine is still in transit..
buw an accurate scale and having the opposing blades weighted and drill them with a 2 or 1.5mm drill underneath to match the weight.. at least that's what I intent to do
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