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Old Feb 18, 2013, 09:07 AM
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What is happening to all the comeratry around here?
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Old Feb 18, 2013, 09:11 AM
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Too much horsing-around............
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Old Feb 18, 2013, 11:17 AM
Life begins at transition
Australia, VIC, Sale
Joined May 2007
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Quote:
Originally Posted by PeterVRC View Post
Odysis, you must have missed the gist of getting a highly accurate fan balance....
You can NOT do it in "4 goes".
To do so you would have to have the perfect rotor imbalance to offset the rest of imbalances (motor/shaft) from that very first "4 go" attempt.

Seeing it is impossible to measure the exact imbalance difference without a sensor you will need X amount of guess attempts..
Here you go Pete. It's a 'how to do it in 4 goes' I wrote a couple of years ago.
http://www.rcgroups.com/forums/showp...&postcount=148
Here's a video of the same method, but using an iPad rather than a notepad.
Rotor Balancing with Single Plane 4-Runs Method (5 min 1 sec)


Google "no phase balancing" and plenty of references come up, including a paper explaining how to extend it to true dynamic balancing (two-plane):
http://2020engineer.iss.utep.edu/Eve...aneBalance.pdf
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Old Feb 18, 2013, 11:39 AM
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Uh Oh.............................
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Old Feb 18, 2013, 11:42 AM
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I read your technique once before when I was first learning how to balance with cell phone method. I didn't get it then, but this time it clicked for me.

I love it! Too bad I have to go out of town soon. I'll have to balance a fan soon for my Habu build.
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Old Feb 18, 2013, 01:35 PM
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O you know he's not going to approve that method. The Tri weighted method even mechanically has been around for a very long time.
There are many things you just can't tac a device around... large drive shafts, in which case they use the exact same 120* weighted method with a laser reading the vibration. They also have the tri weight sensors method set at 120*. Spin and it records the force exerted and averages for what degree.

It was already said. The real issue is how poorly manufactured is what you are trying to balance. Guys like TAM or ERC are, I assume sending back stuff that's just too far out of spec. We on the other hand are hearing what others did, adding this or that motor getting this number, not realizing we may be fighting the battle with something grossly out of balance. And at some point, higher rpms, it becomes the cheap out of balance motor that becomes the issue. Its then much harder to detect and remedy because we're trying to balance at the fan amplifying a Bi-planar out of balance. I suspect its why we get so varied a result with the same stuff.
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Old Feb 18, 2013, 04:06 PM
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G-force 5000 40c Warning

G-force owners you might want to check your connectors if you fly with the stock bullets-- I was swapping out for XT150s, and gently pulled the heat shrink to see if I could pull it back and the whole plug came off in my hand!! Terrible soldering job
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Old Feb 18, 2013, 04:57 PM
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Looks like another irrelevant comparison to me....
A 'perfect' machine.. shaft, drive etc... used to balance an item (one) in question.
Versus our imperfect motor, shaft, hub mouldings etc.
So our task is completely different to accomplish the best end result.

And for a reference of 'overly perfect balance', check some Tams ones, or the all alloy Mercury fans...
They sound like you are revving up a sewing machine, nothing like some jet. They can still sound somewhat ok in the air, the whoosh aspect, but are lacking 'depth' that a not quite perfect setup gives. And the detriment of it is minimal.
You only need 'sewing machine smooth' at very high end powers. Not down at the lower levels 90% of EDFs are used at. (eg even 1200w to 1500w in a 70mm). So I much prefer to be just '98% perfect' so it has some real engine character in.... plus you could never get stock stuff to be 100% perfect anyway, so even thinking you will is a dream.
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Old Feb 18, 2013, 04:58 PM
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Thanks for the tip!!!

I'll be sure to cut off all of the shrink tubing from my batteries, and re-solder as required................
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Old Feb 18, 2013, 05:02 PM
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Quote:
Originally Posted by PeterVRC View Post
Looks like another irrelevant comparison to me....
A 'perfect' machine.. shaft. drive etc... used to balance an item (one) in question.
Versus our imperfect motor, haft, hub mouldings etc.
So our task is completely different to accomplish the best end result.

And for a reference of 'overly perfect balance', check some Tams ones, or the all alloy Mercury fans...
They sound like you are revving up a sewing machine, nothing like some jet. They can still sound somewhat ok in the air, the whoosh aspect, but are lacking 'depth' that a not quire perfect setup gives. And the detriment of it is minimal.
You only need sewing machine smooth' at very high end powers. Not down at the lower levels 90% of EDFs are used at. (eg even 1200w in a 70mm)
Naturally, we already knew that would be your response.................

(I still HATE sewing machine sounds, so FORGET about perfect balance........ )
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Old Feb 18, 2013, 05:07 PM
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Yeah, Odysis will balance up his perfect rotor... just to end up with even worse imperfection outcome than not being done at all, thanks to the motor, adaptor shaft etc
This is why static balancing - which is 'very good' but never perfect - is actually more useful in the typical EDF.

IF you go and buy Tam''s adaptor.... spinner.... a high quality expensive motor.... THEN a perfect rotor is of use.
But then you have spent more on the EDF unit than the plane!! For no great real end use anyway! "Sewing machine smooth", versus "more than adequately smooth" for just a fraction of the cost..... go and buy two more planes for 'free' then!!
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Old Feb 18, 2013, 05:53 PM
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Who cares about perfect balance, certainly NOT you!!!
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Old Feb 18, 2013, 06:01 PM
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USA, CA, Aromas
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Quote:
IF you go and buy Tam''s adaptor.... spinner.... a high quality expensive motor.... THEN a perfect rotor is of use.
But then you have spent more on the EDF unit than the plane!! For no great real end use anyway! "Sewing machine smooth", versus "more than adequately smooth" for just a fraction of the cost..... go and buy two more planes for 'free' then!!
my 35yr RC path has led me this opinion
the plane should be the least expensive part of the package. airframes come and go. my power plant and electronics stay with me they go from airframe to airframe so I generaly buy the good stuff if I can. I would rather have two or three nicely configured beautiful models than 10 pos!! but this is just me.
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Old Feb 18, 2013, 06:05 PM
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"Let's please be civil and avoid ad hominem criticisms and insults. Try taking a break, stepping away from the computer, and cooling down before replying to something you feel strongly about - sometimes the best thing is to agree to disagree."
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Old Feb 18, 2013, 07:06 PM
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United States, NV, Fernley
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Quote:
Originally Posted by jcdfrd View Post
my 35yr RC path has led me this opinion
the plane should be the least expensive part of the package. airframes come and go. my power plant and electronics stay with me they go from airframe to airframe so I generaly buy the good stuff if I can. I would rather have two or three nicely configured beautiful models than 10 pos!! but this is just me.

I agree with this statement. I have also been at it thirty years and in the last year have started to retrofit all my nice models with upgraded internals. I'm going mid range on my Composite Typhoon and it still looks to be around $700 per side plus Battery costs. The way I look at it is I will own the molds and can fabricate quite a few whenever I need them so the high internals cost is justified.

The Chinese foam ARF,s are getting worse in regards to quality. I have just had to order two more sets of upgraded LG for my Trojan due to them wearing out with only about fifty cycles on the LG. I'm getting aluminum with bearings from now on even at three to four times the price. When the airframe bites the dust just move everything into the replacement. The biggest pity is many of them fly so good. I think it would be better to charge more and get better internals.
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