Advice for new Heli Pilots - BALANCE EVERYTHING! - RCCanada - Canada Radio Controlled Hobby Forum
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Old 04-12-2007, 10:46 PM   #1
David McMillan
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Advice for new Heli Pilots - BALANCE EVERYTHING!

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I'm a new Cp pro Heli pilot, After 6 sets of blades I decided to go plastic.
In the process I decided to update the main shaft (Just incase) My suspicions were correct, a very slight bend.

Since I had the whole Heli apart in pieces, I decided to check balance on everything as I put it together.

I unplugged the main rotor and ran up the tail.
"Holy cow! brand new tail rotor and it was out of balance. The vibration had the tail hopping on the table. (I thought that was the main rotor doing that)

It took a piece of hockey tape 3/4 the length of one tail blade to balance it! Dont trust the parts right out of the box!

Next I set up the flybar and weights. Unplugged the tail and ran up the flybar. AGAIN! properly positioned, measured to the 1/2mm and wobble wobble wobble. I finally had to move one of the flybar weights in 3/4" to smooth it all out.

Luckilly the Plastic blades are of a uniform density and balance wasn't a problem, though I did debur the leading edge and gave it a slight radius, polished with emery cloth.

WOW! Even brand new this helicopter did not fly this smoothly!
What a Joy! It's even easier to control, less twitchy and more responsive.

I can't stress balencing everything enough!

Now, it just hummmmms happily 2 feet off my livingroom floor, staring our bay window, pining for the better weather.

Helicopters AKA- Flying Fatigue Machines!
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Old 04-13-2007, 06:52 PM   #2
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Blade CP vibration

Hi David

I have a Blade CP myself and it vibrates all the time quite violently. I was wondering how you balanced everything? Did you just keep adjusting things until you had the least amount of vibration? Thanks for the help.

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Old 04-13-2007, 07:12 PM   #3
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Dynamic balancing each rotating component in isolation via trial and error as you did requires patience but is a good way to go. It is the only way I have found to really smooth out a vibrating tail, for example.

Sometimes static balancing does little because it doesn't take into account small eccentricities and the like that creep into the mechanical assembly.

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Old 04-13-2007, 09:25 PM   #4
David McMillan
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In a nut shell .... YES
but you have to isolate one system at a time.
Tail rotor
Flybar with weights and paddles (this one takes a fair amount of time.)
Install the rotors and set the tracking.
Then balance with tape. (electrical or clear hockey tape works well)

After each adjustment, run it up and make a note of how it vibrates.

Harmonics will quickly vibrate then disappear as the rpm increases and decreases. (only so much you can do about that)

Out of balance conditions should be noticable at lower rpm's and should be more persistent. Don't just observe the helicopter. hold the tail boom in your hand so you can feel the difference. You'll be amazed at how discriminating your fingers can be.

One thing you should know about balancing is that at higher rpm's an out of balance object wil stop rotating about it's geometric center, and begin rotating about it's center of mass. It accomplishes this by deflecting or warping to compensate, and in effect the out of balance condition "goes away", but it also streses the material leading to fatigue and possible breakage.

Don't think that just because the blades stop vibrating at a Higer RPM that they"re in balance. look at the rotor head. if the shaft is moving, it's out of balance or the shaft is bent.

If you've had crashes (what new pilot hasn't) check the rotor shaft, blade grip shaft and flybar shafts all for damage. take them out and roll them on a countertop or flat hard surface. If they don't roll smoothly, replace them. This would be a good time to buy some extra bearings as well. If you have any trouble removing the bearings, the shaft is definately bent. You might not actually be able to get a beaing off even a slightly bent shaft.

Hope this helps.
good luck and let me kow how it works out.

(They really should have put a chapter about this in the manual.)
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