Tail wag

[denis747]

Originally Posted by dva

I moved my ball link on the servo arm to the inside hole, was in the middle hole as suggested in the instructions. Had to mill off some of the servo arm near the spline connection to make the lock nut fit due to the servo arm geometry. Do not get full deflection anymore on the tail but the majority of the tail wag is gone. Have also noticed that there is a lot of slop in the tail blade grip to tail pitch assembly.

As for head speed, I'm running the same 85-80-85 and 95-85-95 throttle curve as before. With less mechanical servo slop the tail wag is about 10 percent of wat it was before. Thinking a better servo may be needed as well as better tolerances on the tail pitch assembly parts.

I have the 470LP version and it has absolutely no play in the tail pitch mechanism. Which version of the 470 have you got?

[dva]

I've got the 470LP version.

[dva]

After about 15 flights my tail started to wag and the waging started to increase so I landed. Decided to change packs as it was low. After changing packs the tail servo had no response. Think the tail servo has been bad from day one and it gave up the ghost this evening. Good thing this all happened while in a hover.

[perrypoint]

Lucky you - I had the same story but ended up in an uncontrolled spin and a crash. The tail servos apparently have some issues

[dva]

Any suggestions for a tail servo replacement?

[dva]

Any suggestions for a tail servo replacement?

[Memphis3]

Originally Posted by dva

Any suggestions for a tail servo replacement?

Yes
DS525M Digital Servo HSD52501 $19.99

Retail Price:$41.99
Your Savings:$22.00(52%)
In Stock
Part Number:HSD52501

I have these on one the other has KST tail servo. KST will run 2 to 3x the money but are reliable fast accurate tail servo.

[perrypoint]

I got the HV 93i, which is very expensive, but it works well. The stock one worked well too though, for a while.

[Yves128]

Hello friends,
I own a Trex 470 LM and this weekend to solve a similar problem to your, I found that the plate that supports the flybarless system had side play. I applied Shoe Goo glue part Interior and had a very good improvement.
Please see attached images

Please visit your local Hardware store to find the Shoe Goo

Yves

[perrypoint]

Interesting, mine is super tight. I wonder if it acts as a vibe reducer somehow. I am going to try it just for kicks even though mine doesn't have any lateral movement.

[dva]

Finally got the tail wag worked out. Just flew with a new BK-5005 and it is steady as a rock with no bonus tail blow out as with the original servo. Thinking the stock tail servo was faulty from day one. Still got some work to do for the final set up but ready to get some flying in this week.

[dva]

So my BK 5005 tail servo holds the tail steady during a hover and normal flight. Sometimes after hard collective or hard tail inputs the tail starts shake like a gyro with the gain cranked up too high. Following the new tail shaking, I noticed that the tail servo was hot. Been out of belies for 7 years but never had a hot tail servo before. Is the heat normal due to the power required for a servo with thes specs like a BK5005?

Running the Beastx at 32 on the gain. Tail servo is set at 760us dead band and at 333hz.


Not sure if the stock servo died fighting a problem that is not fixed on my 470. Any ideas what would cause this vibration? Belt slipping, blades too lose, sticking bearing? The heli has never been in a crash and all the bearings have no binding. Their is no noticeable vibrations other than the tail wag now after some hard inputs.

There is one tail blade that is looser holding the tail pitch due to more play in the bushing to tail blade grip connection.

Looking for some troubleshooting ideas.

[perrypoint]

Be sure the tail blades are balanced. A lot of the 74 blades I have gotten were not balanced well at all, which gives you a vibe that really screws with the fbl, causing constant fast twitch of the tail servo.

Remove ALL blades, and spool it up while you hold it by the tail boom. Get a feel for the amount of vibration. Then add the tail blades, and you should not get any additional vibration.

Also, the tail blades should be tight enough that they don't flop around or move side to side when you slowly rotate the tail.

[dva]

The 74 mm blades were out of balance with quite a vibration. Will see how the tail holds now and watch the servo temp after balancing the tail blades.

Thank you for the feedback perrypoint. Will keep you all informed if balanced tail blades are the final fix.

[dva]

Flew with the balanced tail and the tail wag is still there. At the beginning of the flight the tail has little to no motion. About 2 min into the flight the wag in the hover starts to come back and after hard inputs the tail wags like a gyro with to much gain.

The tail servo after two back to back flights is hotter than the motor.

Lowered the tail gain from 29 to 25 and the tail started to get mushy. Have not tried any hard inputs with the lower tail gain yet but will try this evening.

Anyone know if changing the 760 us dead band to 1500 us will help any?

Trying some changes but do not want to release the smoke from the tail servo.

[dchekas]

Servos have a certain centering pulse width as apart of their design, you cannot switch centering pulses.

If the BK5005 is a 760us, then you must use that, or you will burn out the servo when it powers on and tries to turn to center at 1520us, which is outside of its operating pulse width.

I would not expect the servo to get super hot in flight, unless there is some vibration or something that is working the servo hard.

[soviet911]

Originally Posted by dva

Flew with the balanced tail and the tail wag is still there. At the beginning of the flight the tail has little to no motion. About 2 min into the flight the wag in the hover starts to come back and after hard inputs the tail wags like a gyro with to much gain.

The tail servo after two back to back flights is hotter than the motor.

Lowered the tail gain from 29 to 25 and the tail started to get mushy. Have not tried any hard inputs with the lower tail gain yet but will try this evening.

Anyone know if changing the 760 us dead band to 1500 us will help any?

Trying some changes but do not want to release the smoke from the tail servo.

hmm, I wounder if your tail bearings are locking up? It is pretty well known on Oxy3 that the tail can bind the bearings and lead to wag. I would check to see if after a flight your tail bearings are hot (maybe belt to tight or just crappy bearings...)

[cschmidt]

My lm Is a new build, during the build I spun up with no blades, it ran well so i added the 74mm tail blades and got terrible buzz/ flutter at 3/4 power. Same for the 69mm blades. Balanced tail blades with the hub, and it's still there, even changed tail shafts and it didn't help, ran belt loose and tight, no change. I managed to do some hovering test at @ 60% and hs of 2600, all went well but when I went to setup governor at 85%, the tail does the flutter still. The gov will have to wait till this is sorted out. So, I ordered some rt 71mm carbon blades to see if it helps.
Could this be the same problem causing other to have wag and hold issues? I think so!!!

[dva]

Originally Posted by soviet911

hmm, I wounder if your tail bearings are locking up? It is pretty well known on Oxy3 that the tail can bind the bearings and lead to wag. I would check to see if after a flight your tail bearings are hot (maybe belt to tight or just crappy bearings...)

Checked the bearings and they were not hot.

I dissasymboled the tail grips and control links from the pitch slider to the t-arm. One of the blade had much more slop than the others due to the fit of the colars on the control links. After swapping the collars around, the slop between tail blade grips is reduced by quite a bit.

Flew with the original settings including the governor still activated and only had the tail wag on hard collective inputs but it is reduced from before. I was able to do some rainbows with no tail wag but hard collective inputs is what still brings in a tail wag.

Also got 3 flights in after some major rain on a cool 80 degree Arizona morning. The tail servo was not hot at all. At 100 degrees ambient temp the tail servo is still hot but not as much as before.

Making some progress on this tail wag issue and hot tail servo, but not still have some work.

[dva]

Got some more flights in with no tail issue. Conclusion with my tail had the is following problems:
-stock tail servo had a ton of slop, replaced with BK5005HV
-tail control link slop was uneven, causing the loose blade to over work the tail servo. Fixed issue by moving bushings to different locations.
-unbalanced tail blades
-loose belt

With the tail wag issues worked and over worked tail servo issue fixed, the 470 is now flying great. This thing has tones of power. Think it is time to move the cyclic control links to the outer holes on the cyclic servo arms.