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Old 08-18-2021, 01:22 PM   #1 (permalink)
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Default slow tail wag oxy4max

I have a newly built oxy 4 Max with tail wag.
I have been hunting the culprit for a while.
The machine had a lot of vibration as at came with bad main bearings. Replacing did not help. Tried all kinds of fbl tuning. Tried new tail servo. Tried changing fbl. Found some binding in the tail slider. Fixed that. Still wagging.
Turned off gov and even changed ESC. Still wag.
Today I'm testing for tail vibration. No vib with
blades off. Pretty bad vib blades on, 0 pitch.
No slop, no binding. Bearings feel good. Blades weigh the same on my trusty jewelers weight. Changed them for other stock blades that als weigh the same. Still vib.
Anyone got any ideas? I am at my wit's end here
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Old 08-18-2021, 02:17 PM   #2 (permalink)
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If you have tail vibes change your tail hub and shaft. One is bent. I've had brand new new ones that weren't bent.
Worst scenario you now have spares you don't have need yet.

You'll most likely not get rid of wag with vibs.
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Old 08-18-2021, 04:40 PM   #3 (permalink)
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I also have been attempting to get rid of a slow wag on my new built 4 max. Iím about at my wits end with it. I havenít started a thread yet, not sure I will because there are quite a few already. Hoping someone chimes in with an idea I havenít tried yet.
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Old 08-18-2021, 04:53 PM   #4 (permalink)
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First. Turn off any governors. An improper gain setting on the gov will cause wag.

Make sure the tail moves smoothly. It doesn't need to "fall on its own weight" like so many say here. Just smoothly and relatively friction free.

Make sure you're using the proper servo horn hole.

Make sure you have assembled the tail correctly. Take it apart. Don't just assume you did! I've done that only to find an improper assembly.
Are all thrust bearings in proper order? Bearings seated? All smooth in there? No loctite seepage into the assembly? Washers there if called for?

Never ever torque the tail pitch slider arm screw down too tight. This part needs to move very freely.

From here make sure your servo settings in the flybarless unit are correct for a tail servo! That means center pulse, frequency and proper travel left and right!

Make sure the roller bearing on the top of the belt at the tail side (if it has one) is not binding. I've bought used helis from here with this so torqued down that the belt slips on the roller instead of the roller spinning!

Be sure your belt is tensioned properly. Not silly loose. Not crazy tight.

Give it at least 10 flights. Things need to break in and settle.

After that and it wags, you have another issue.

Start looking for bent tail shaft and bent hub.
Look for bad bearings on the tail shaft also.

After all. This you should have a tail that works.

One last thing is to try at least 2 different servos. I've had helis that just will not stop wagging with certain servos. Nothing would stop it. Servo changed, and like magic, all is good.
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Old 08-18-2021, 08:20 PM   #5 (permalink)
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I have tried a second brand new servo (same MKS HV93i) with no change. I have not tried a different brand/model of servo yet. Everything on my tail is ultra smooth. One thing I have noticed is the plastic tail bell crank with the tail pin screw on top and bottom of the pitch slider ring causes slight binding at both right and left throw. If I take one of the tail pin screws out it will in fact fall under its own weight all the way beyond the travel limits I have set in my radio. I have read one person on here fixed his slow tail wag when he upgraded to the aluminum tail bell crank so I assume it corrected this binding the plastic one causes.

So I guess I have two things yet to try. A new servo (maybe a mini) and the aluminum bell crank.
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Old 08-19-2021, 05:33 AM   #6 (permalink)
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Quote:
Originally Posted by Ctimrun View Post
I have tried a second brand new servo (same MKS HV93i) with no change. I have not tried a different brand/model of servo yet. Everything on my tail is ultra smooth. One thing I have noticed is the plastic tail bell crank with the tail pin screw on top and bottom of the pitch slider ring causes slight binding at both right and left throw. If I take one of the tail pin screws out it will in fact fall under its own weight all the way beyond the travel limits I have set in my radio. I have read one person on here fixed his slow tail wag when he upgraded to the aluminum tail bell crank so I assume it corrected this binding the plastic one causes.

So I guess I have two things yet to try. A new servo (maybe a mini) and the aluminum bell crank.
Can't have a smooth tail and still have binding. The smooth has to be the entire motion. If your pitch lever is plastic, going to the metal one may help if the plastic one is out of tolerance. It may short cut you to correction. You have to figure out the exact tightness of the 2 screws need to be for the lever mount. Those screws don't need to be really tight. Let the loctite do its job.

Sent from my SM-G988U using Tapatalk
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Old 08-19-2021, 05:41 AM   #7 (permalink)
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Also - make sure your servo 90 for the tail servo has the tail bell crank at the correct position (I believe there is a tool same as with oxy 5 though its been awhile). You can easily change the servo 90 / tail position relationship by loosening the servo mount and sliding it on the boom.

I've heard of at least one tail wag that was solved by this (though was on a Goblin 380 + vbar NEO).
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Old 10-22-2021, 05:57 AM   #8 (permalink)
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Thank you all for your hjelp.
It turned out be binding between the tail bell and bell crank when the bell was rotated a certain way.
The crank was somewhat warped and also it's replacement. Bending was nessesary
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