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HomeAircraftHelicopterHelicopter Main Discussion › balancing the tail rotor assembly?
06-16-2013 02:46 PM  5 years agoPost 1


Yellow Springs Ohio USA

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I have a pretty bad tail vibration I am trying to work out. This is a century radikal with 95 fun key cf blades. I am using a align slider and grips. Anyone have any tips on balancing the assembly? I have a high point balancer and it shows one side of the center hub assembly usually dropping to the bottem with the blades in the grips. But I notice if the blades are not perfectly inline with the shaft it will throw off the balance with the highpoint. Any help would be appreciated.

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06-16-2013 03:09 PM  5 years agoPost 2


Richmond, VA, USA

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Balance the hub and grips first. Use a thin washer under the drag bolt for horizontal balance. On some models you can balance the vertical orientation with a longer bolt through the pivot bolt, an extra nut on the backside, etc. Remember to balance with no grease in the thrust races as it will affect balance. If the model has inherent endplay in the grips, you can keep them fully bottomed against the bearings with a short length of dental floss between the hub and the inner bearing.

Next add the blades and see how things shift. If you see a side fall low, the quick way to get it close is with a piece of tape on the lighter blade. The gold standard way to do it is to weigh each blade, find the light one and how much lighter it is, and apply a piece of tape of that same mass difference wherever it needs to be on the light blade to make the assembly balance.
Doing it this way actually zeroes in the spanwise CG as well. It's more work, so if you aren't game for it, the quicker method will get you close provided you already have the hub assembly right. Note that the crappier the tail blades in terms of things like chordwise cg, the fussier the overall tail will be for running smoothly because of the way the blades may lead excessively when the system is running. Radix and Rails run well, but assume nothing with balance; always check. Nothing is done at the factory but pairing for total weight to the vendor's specs. You can easily get a set with spanwise cg's a good deal off, which means they will not run smoothly even if the total weight is the same. Been there, seen that, have the T shirt......

Blades must be correctly feathered in the tail grips with matched lead lag or the results on the balancer will be erroneous. Do not skip this step.

Ben Minor

Peak Aircraft/Team Minicopter Team Futaba Team Kontronik USA

06-16-2013 04:34 PM  5 years agoPost 3
Girard Ibanez


Tucson, Arizona (formally from Guam)

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It's been a long time coming since I read of a detail rotor balancing on the forums.

The days of book reading (Ray Hostetler ) about the importance of a well balanced rotor assembly when the World Wide Web was just beginning to explode with numerous forums.

Thanks Doctor Ben for your contribution of a detail explanation. I find reading technical articles an inspiration of the "Good O'l Days".

Team Thunder Tiger
since 6/2005 to 12/2014

06-16-2013 07:14 PM  5 years agoPost 4

rrElite Veteran

Las Vegas , NV

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As usual you have the cure for what ails the r/c helicopter Dr, great info !

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