CX Wobbling shaft and severe untrimability  
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All Forums >> RC Helicopters >> Electric RC Helis >> E-Flite Helicopters >> CX Wobbling shaft and severe untrimability
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CX Wobbling shaft and severe untrimability - 2/10/2008 7:08:45 PM   
Ziff


 

Posts: 13
Joined: 1/7/2008
From: , CA, USA
Status: offline 		If untrimability is a word...I've had a number of good wrecks since I bought her, but now I can't seem to get it trimmed properly. I've replaced the blades a couple times (which usually works), pulled the whole thing apart and reassembled checking for breaks. I added the aluminum top head also (a while ago). On spool up, the shaft seems to wobble a bit and don't remember if it always did that a little or not. Could the freakin' aluminum shaft be bent already? That would suck. Could it be a bushing//bearing or something? Also, I noticed that the lower blades don't like to start spinning right away with the uppers, and I've unplugged and plugged the battery to start it over to no avail. Could the one motor be giving up the ghost? Thanks for the help guys.

-Steve
       Post #: 1

RE: CX Wobbling shaft and severe untrimability - 2/10/2008 7:46:46 PM   
evdreamer


 

Posts: 2376
Joined: 8/12/2007
From: Lincoln, NE, USA
Status: online 		It is normal for one blade to start up faster than the other. As long as it doesn't rotate in the air you are fine. Is a flybar bent? Get the rotors spinning slowly then go full rudder in one direction then the other direction. If one wobbles and the other doesn't your culprit is the assembly of the blade that wobbles. If the inner shaft is bent you should be able to take the head off and replace the shaft for around three bucks. I would try that and let us know what happens.

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Since I started this hobby money seems to keep disappearing. :)
T-Rex 450SEV2, Gaui 200 SD

(in reply to Ziff)
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RE: CX Wobbling shaft and severe untrimability - 2/10/2008 8:07:27 PM   
Ziff


 

Posts: 13
Joined: 1/7/2008
From: , CA, USA
Status: offline 		Thanks for the reply. The top assembly is wobbling after doing that test and the bottom is smooth. So, I can just replace the actual shaft and put the aluminum head on it, right? Does that explain the tendency for the heli to rotate nose-CW and aft/starboard or rear/right drift? I can't trim out the severe drift and wondered if eliminating the shaft wobble would take car of that? Thanks again.

-Steve

(in reply to evdreamer)
       Post #: 3

RE: CX Wobbling shaft and severe untrimability - 2/10/2008 8:17:17 PM   
mosiris


 

Posts: 74
Joined: 1/28/2008
From: Auburn, AL, USA
Status: offline 		Yes, you can just replace the shaft, but you are gonna need a 1.5 mm allen wrench if I recall the right size, then pop the head on it.

While apart you may wanna look at the flybar and try to bend it back to straightish. If bent it will lead to the 'toilet bowl effect'.



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RE: CX Wobbling shaft and severe untrimability - 2/10/2008 8:19:17 PM   
Ziff


 

Posts: 13
Joined: 1/7/2008
From: , CA, USA
Status: offline 		Good call...I've been in the 'toilet bowl' a bit lately. Thanks.

(in reply to mosiris)
       Post #: 5

RE: CX Wobbling shaft and severe untrimability - 2/10/2008 8:53:37 PM   
soloboss


 

Posts: 1637
Joined: 9/17/2006
From: Fort Wayne, IN, USA
Status: offline 		I'd try straightening the inner (longer / top) shaft first. Take the upper blades off, take the flybar off. Strip it to just the head sitting atop the shaft.
Get a sharp felt tip marker and run up the inner shaft so it's going as slowly as possible and touch the side of the head with the felt tip. It will leave a mark on one side where the head touches the marker.
Now you know which way the shaft is bent. You can straighten the shaft easily with your thumb by simply pushing the head on the side with the mark. I'll bet the first time you do this you'll push too hard and bend it the other way. Anyhow, mark the shaft and push the shaft and repeat until you get it straight. And it is amazing how easily the shaft is bent at the top.
You'll get it straight in about 5 tries. It's really no big deal.

You can also take the shaft out of the heli to work with it, but it's easier to just push it with your thumb.
If you don't mind a little surgery, remove the bottom drive gear and the inner shaft will turn freely so you can more easily see which way the head wobbles. When you put the bottom drive gear back on, be sure to align one set screw with the flat on the bottom end of the shaft or you'll have to endure a whole new set of oddities.

If you would rather get a new shaft, go for it. Or get a new shaft and straighten the old one so you always have a spare. With the inner shaft out of the heli, just lay the shaft on a counter top or hard flat surface, lay a hard cover book or flat board or a piece of plexiglass or something on the shaft and roll it between the two hard surfaces. 10 seconds and it's straight.

It's more work to describe it than fix it.
And try to stay outa the toilet.
Soloboss

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Soloboss
If everyone''s thinking alike, then somebody isn''t thinking. George Patton

(in reply to Ziff)
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RE: CX Wobbling shaft and severe untrimability - 2/10/2008 9:00:38 PM   
mosiris


 

Posts: 74
Joined: 1/28/2008
From: Auburn, AL, USA
Status: offline
quote:


If you would rather get a new shaft, go for it. Or get a new shaft and straighten the old one so you always have a spare. With the inner shaft out of the heli, just lay the shaft on a counter top or hard flat surface, lay a hard cover book or flat board or a piece of plexiglass or something on the shaft and roll it between the two hard surfaces. 10 seconds and it's straight.




lol, I have never thought of that. would this 'between 2 hard things' method work on a pro main shaft and spindle ??



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RE: CX Wobbling shaft and severe untrimability - 2/10/2008 10:03:18 PM   
hollywood54



Posts: 181
Joined: 10/7/2005
From: Somerset, MA, USA
Status: offline 		When you replaced the main blades did you balance them?Unbalanced blades cause a lot of wobble and shaking.

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HBK2

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RE: CX Wobbling shaft and severe untrimability - 2/10/2008 10:39:20 PM   
evdreamer


 

Posts: 2376
Joined: 8/12/2007
From: Lincoln, NE, USA
Status: online
quote:

ORIGINAL: Ziff

Thanks for the reply. The top assembly is wobbling after doing that test and the bottom is smooth. So, I can just replace the actual shaft and put the aluminum head on it, right? Does that explain the tendency for the heli to rotate nose-CW and aft/starboard or rear/right drift? I can't trim out the severe drift and wondered if eliminating the shaft wobble would take car of that? Thanks again.

-Steve


Bent parts can lead to drifts, but check how level your swashplate is. Try to use the pushrods to level it out not the transmitter trims. Try turning the proportional potentiometer to the left to cancel out the CW turns. If it is not a bad turn that is fine because the helicopter will rotate a little with different voltages.

_____________________________

Since I started this hobby money seems to keep disappearing. :)
T-Rex 450SEV2, Gaui 200 SD

(in reply to Ziff)
       Post #: 9

RE: CX Wobbling shaft and severe untrimability - 2/11/2008 12:14:21 AM   
soloboss


 

Posts: 1637
Joined: 9/17/2006
From: Fort Wayne, IN, USA
Status: offline 		If I've told you boys once, I've told you a hundred times.
To set the proportional;
Number One- Charge the battery
Number Two - Run the helicopter for one minute to bleed off the high initial charge
Number Three - Now you can balance the proportional blade dokickey. But know in your own mind that as the voltage drops off, the motor controller will not balance the two motors exactly.

So to review, You can't get a good Number 3 if you don't have both a good Number One and a good Number Two.

Boys.
I swear.

Soloboss

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Soloboss
If everyone''s thinking alike, then somebody isn''t thinking. George Patton

(in reply to evdreamer)
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RE: CX Wobbling shaft and severe untrimability - 2/11/2008 12:15:54 AM   
soloboss


 

Posts: 1637
Joined: 9/17/2006
From: Fort Wayne, IN, USA
Status: offline 		Unless the shaft is hardened like piano wire or a drill rod it should work. It can't hurt to try.

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Soloboss
If everyone''s thinking alike, then somebody isn''t thinking. George Patton

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RE: CX Wobbling shaft and severe untrimability - 2/11/2008 12:17:16 AM   
soloboss


 

Posts: 1637
Joined: 9/17/2006
From: Fort Wayne, IN, USA
Status: offline 		A bent head will cause even a good flybar to deform at speed. That's a fooler. The shaft needs to run true if the flybar is to work properly.

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Soloboss
If everyone''s thinking alike, then somebody isn''t thinking. George Patton

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RE: CX Wobbling shaft and severe untrimability - 2/11/2008 6:31:34 AM   
Ziff


 

Posts: 13
Joined: 1/7/2008
From: , CA, USA
Status: offline 		Great stuff everybody. Appreciate the help. I took all the advice and got her flying pretty smooth.....still a little wobble, but not bad, as I can hover hands off in my apartment now.... Thanks again!

(in reply to soloboss)
       Post #: 13

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