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Imbalance

Old 03-03-2007, 05:04 PM
  #1  
BubbaJoeLouis
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Default Imbalance

Greetings all,

I built a Century Hawk Pro for Christmas. Once it was built, the head was imbalanced, big wobble in certain RPM ranges. I checked the blades cg and total weight, the paddles weight, and centered the flybar very closely using my vernier calipers. There was still a wobble. I ran the motor with the blades off to try to isolate the blades. Same thing, still wobbled albeit less. I took the flybar off and left only the head with blade grips. Still wobbled! (very slight but it was there).

<VENT>Century said the shaft might be bent, go roll it on a piece of glass. Great, they preinstall the shaft without checking it? I just put the thing together, I dont want to tear the complete heli apart to double check their work!</VENT>

Then I disassebled the head and weighed each part and tried to balance the head/grips. It all measured perfect and seemed great.

So I finally ran the motor with just the washouts and swashplate. The shaft looked perfect! Now I didnt try to mount a dial caliper in and rotate the shaft to check for 0.001" of play, but cmon, a major wobble from one friggin thousanths?

But while running in "shaft only" mode, I *DID* notice the Counter Gear #HI3040 is warped something awful. I'm talking 1/16" see-saw as it rotates!! Nasty.

My question is, would the warp in the Counter Gear actually throw the whole head off balance?

Thanks!!!
Bubba


<OPINION>
I was really looking forward to building this thing from total scratch, piece by piece. But it came mostly assembled in the box. I was a bit dissappointed, but now that its done I really dont want to tear it down and start from scratch to fix their mistakes!

Also the start shaft is total junk and stripped out horribly causing all kinds of metal shavings to sprinkle the start shaft sleeves and who knows what else. Century's fix? UPGRADE to the new cooling fan/one-way bearing! $50 :/ I refuse to upgrade to fix a low quality design. Solution? JB Weld that hex adapter on the start shaft! Hey it wont strip now!! yeah i might have to grind it off later, but why grind it off if it never strips?! HAHAH
</OPINION>
Old 03-04-2007, 09:53 PM
  #2  
syclic
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Default RE: Imbalance

Have you tried to fly it?

If the rotor speed is too low on any heli, you will get a wobble.

A warped primary gear will NOT cause a wobble. Damping resonances, related to rotor speed are usually the cause.
Old 03-05-2007, 02:33 PM
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BubbaJoeLouis
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Default RE: Imbalance

No i didnt try to fly it yet. I had the skids pinned to the ground just for a "run up".

It didnt seem like the gear should cause the wobble, but its all I found so far. I will rebuild the head and run it and try to post some video.

Thanks for your input!

Old 03-06-2007, 04:56 PM
  #4  
syclic
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Default RE: Imbalance

You should not run-up a heli with it's skids tied to the ground as the ground resonances can cause all sorts of different wobbles and vibrations. That is why I asked if you had tried to fly it - that would mean that it would have not been "tied-down".

Also please note my post to you in another thread about your securing of your gyro with epoxy - this will also do a lot of undesireable things.

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