Gaui GS304HV tail servo inf-flight fail

[orozco-contreras]

Hi Guys!

About a week ago, doing some aileron tic-tocs about 30ft. high with the NX4, the tail simply began some crazy movements: kind of 90º banging to each side. I tried to get it down a bit, but as the issue was worst and worst I did a terrible auto.

The GS304 still turns on, but it doesn't moves properly - or only reacts at the extremes.

This heli has hardly 25 flights... running straight on 2S Lipo (hyperion 1600). My question is: I never got an Align servo with this short life... so for me, Gaui servos suck. At this point, I'm very concerned about the Cyclic servos too: loosing the tail was scary but ok... losing a cycling one would be a disaster.

Maybe, even with "HV stated" servos, I should go to straight 2sLiFe - but I'm not sure it was the cause of the failure. I'm thinking about changing all the servos by the 515/525s... not the most impressive ones, for sure... but quite reliable.

If anybody have any insights about, please let me know... I'm kind of stuck here... and I really like the way the NX flies...

[TVaillancourt]

After about a gallon my NX4 killed an Align tail servo and a lot of other things because of a wobbly clutch bell.

[orozco-contreras]

Originally Posted by TVaillancourt

After about a gallon my NX4 killed an Align tail servo and a lot of other things because of a wobbly clutch bell.

Wow... this sounds worst than my case... I'm not impressed with the parts quality on this machine.... but despite of that, it's really funny to fly!

[kiteman78]

I've had 3 align servos fail on my machine running of life pack direct. Two 525M and one 515M. All the same failure where the servo wouldn't move on its own from a standstill. Touch the horn and it would go.
Pulled them apart to diagnose, and it is a motor problem. Have now put a MKS on the tail and align every where else all regulated to 5V and seems fine since then. Time will tell, but they were getting pretty warm on 6.6V. Not on 5V.

I too still have a slightly wobbly clutch bell, and if I can get this sorted the machine will be perfect. It is so fun to fly!

Has anyone reworked a clutch to fix it? I'm going to order a spare and take it apart to see if I can remachine it to get it perfect. Or are the new replacements perfect out of the package?

[Rollin_3z]

Do you think its the bell? Mine was perfect when I first built the kit. I had a major dumb thumb and crashed. I inspected the whole heli and my bell wobbles now and feels gritty. I think the weakest point on this kit is the bearings in starter mount and the starter shaft itself. Once the clutch grabs the bell, it will stop it from wobbling. I just don't like the gritty feeling on the bearings. I think my starter shaft is bent or worn from the bearings.
Any opinions?

[kiteman78]

Maybe wobbling is the wrong word. I have no play in mine at all from bearings, just a lot of runout in the bell. Doesn't spin true at all. I had it out, and removed all the runout within a thousandth of an inch by bending it true, and after that it ran great for about 5 flights before it was showing runout again. I have a resonating type vibration that i can hear but not see and it was gone when the clutch was trued up. Hence my mission to get a true running clutch.
My next step is to remove the pinion from the bell and come up a way to mount them together with zero runout.

Does anyone have a clutch that runs perfectly true, new or modified?

[Rollin_3z]

I see what you're saying. Mine has that audible hum as well. My bell wobbles up and down compared to the bottom face of clutch. I am sure the run out on my bell and clutch is a lot too. I just ordered a new starter shaft,bell and mount. I am going to take everything apart and see what the run out is on my fan

[kiteman78]

Ok, so couldn't stop thinking on this one as this machine is so close to perfect. So, I pulled the motor and clutch and set about finding a solution for the clutch bell runout.
Unthreaded the pinion from the bell, and after a bit of analyzing found the source of the problem. The bell is meant to thread against the face of the teeth on the pinion. The way the threads are cut on the pinion doesn't allow this to happen as you can see in the picture the threads don't go all the way to the teeth. There is a bevel relief on the bell to accomodate this, but it isn't big enough. So in my case, the bell was jamming up on the last thread, and not the face of the pinion therefore leading to my runout issue.

The fix I came up with was to take a hobbyknife and enlarge the bevel in the bell. A couple of passes around and now the pinion seats correctly and I have 0.002" runout instead of 0.009". Put it together with red locktite on the threads and it looks perfect.

Will report back if the vibration is gone and if it stays running true after a few flights. Fingers crossed!

[Bigugly]

Good find

[Rollin_3z]

Right on, let us know how it goes

[kiteman78]

Well, flew 3 flights today beating on it as hard as I know how, and that clutch still spins perfectly true. So happy to finally have that sorted, and saved buying a new one that would probably wobble too.
The resonating sound is also gone.
Running smooth as glass now with gobs of power. Servos seem to be liking 5V, so time to burn some fuel.
I will add that I'm at 60 flights with no failures other than my Align servo issues.

[Rollin_3z]

Excellent news ..Btw how did you remove pinion from bell without distorting bell or damaging teeth?

[kiteman78]

I clamped the pinion in the vice between two blocks of wood.
Then I just turned the bell with my hands. It wasn't very tight.
Regular LH thread.
I think if you were to hit the bell with a bit of heat it would come
apart really easy due to the different expansion rates of the aluminum
bell and steel pinion.
Let me know how you make out.

[Rollin_3z]

Thanks for your help! I am going to try it this weekend

[tonyboy]

Originally Posted by kiteman78

Ok, so couldn't stop thinking on this one as this machine is so close to perfect. So, I pulled the motor and clutch and set about finding a solution for the clutch bell runout.
Unthreaded the pinion from the bell, and after a bit of analyzing found the source of the problem. The bell is meant to thread against the face of the teeth on the pinion. The way the threads are cut on the pinion doesn't allow this to happen as you can see in the picture the threads don't go all the way to the teeth. There is a bevel relief on the bell to accomodate this, but it isn't big enough. So in my case, the bell was jamming up on the last thread, and not the face of the pinion therefore leading to my runout issue.

The fix I came up with was to take a hobbyknife and enlarge the bevel in the bell. A couple of passes around and now the pinion seats correctly and I have 0.002" runout instead of 0.009". Put it together with red locktite on the threads and it looks perfect.

Will report back if the vibration is gone and if it stays running true after a few flights. Fingers crossed!

I was wondering if all went well with what you have done with the clutch bell bevel enlargement. I too have that wobble. Please advise. Thank you

[kiteman78]

Clutch has been working perfect and running true for 200 flights now.
No more issues at all.