Help needed

[broncoholic7]

I need help trying to figure out what problem I could be having with my heli. Any help would be appreciated.

My tail will not hold in HH when in high torque. Raja and some of his buddies were trying to help and they think it is the gyro servo and or my thrust bearings.

Here is what Raja was said at RR;

An hour later we were off to the field to try out the Bergen. The strangest thing was that the tail would go left (nose right) when I increased the rotor rpms to idle up 1 and 2 (worse in 2). It was weird and we spent alot of time trying to figure out if the tail rotor was losing rpms, if the gyro was bad, or the servo, or what was going on. We check and double checked and triple checked radio settings but did not fix it in that matter.

Finally we took the rotor blades off, spun it up to a pretty good rpm (not takeoff but fast enough), and started to move the rudder around. After a minute or so, the rudder servo would only go right and not left. I disconnected the link from the servo and looks like the pushrod to the tailrotor is pretty hard to operate (needs alot of torque) while the tailrotor is spinning. The servo is also weak (9254) and you can hold the horn and with a little force either stop it from moving or move it to one extreme or another with you hand while powered up and once you let go it recenters.

Any ideas as to what could cause this?

Thanks in advance

[broncoholic7]

Here is another post at RR that is having the same problem I am.

http://runryder.com/helicopter/t298288p1/

the tail on my bergen gasser upon entering hover, begins wagging and then it just swings left and wont stop. i have checked and rechecked everything, gyro settings and even servo direction. upon entering hover sometimes it will hold for a few seconds but it then swings to left and wont stop unless i land. any ideas? i was using the 401 and took it off, i replaced with the logictech 6100t/servo combo and does same thing.

So anyone have any ideas that could help us?

Thanks

[tigger28]

If you so a search for 9254 on various forums you will find a fair amount of information. There "may" be an issue with some late-model 9254 servos, it may be some components in this servo are prone to failure in a gasser environment. I had the exact problem you are having with two 9254's. One locked, causing a pirouette and crash, the other I managed to land safely. I was able to play with the second one with the engine idling and noticed behaviour like yours. I replaced it with a Hitech 6965 and it's now about 4 gallons later and I have had no problem with the tail servo. The 6965 is a little slower but it works for me, do some reading and you should find other alternatives. Try this link to get started:

http://www.runryder.com/helicopter/t286437p1/

[broncoholic7]

Thanks Tigger,
I thought it may be the servo, until another guy was having the same problem with a different gyro/servo combo.
So I do not believe it is totally a servo problem. I am thinking it is something in the thrust bearings. Although, I tried the little trick I read about to test the bearings and they seem to be working fine.
So I am still at a loss.
But thanks for the information on the servo.
I do plan on replacing it.

[Gyan]

Take the tail grips apart & look to see if the races have little notches in them. That locks up the tail pitch when up to RPM. It's the only thing I can think of except the 9254 issue.

[broncoholic7]

Thanks Gyan,
That is what I am going to do tomorrow. I read your post on this very thing and that is the only thing I can come up with.
If the other guy had not used a differnt servo I would think it was the 9254 also.
I will probaably replace the gyro and the thrust bearings just to eliminate those possiblities.

I keep looking for a 601 but cannot seem to be in the right place at the right time.

[Gary Travis]

I have seen this problem several times on gassers and have solved the problem for several people.
First make sure that your tail is set up so that it does not drift in non heading hold.
With the 401 9254 combo if the engine is to lean it will cause high frequency vibes at the gyro, this in turn will cause the servo to be constantly working causing it to heat up and stall.
In the cases I have seen the heli would actually lift and then within 1 min the nose would drift to the left, upon landing it appeared the servo was not working and then after a moment it would come alive only to do it again like clockwork. Try and richen both the high needle and the low needle and see if that corects the issue. Also if this is your problem I would replace the sservo as it won't be long before it fails completely. Give it a try and let me know how you make out. The engine can seem like it is running rich enough when actualy it is not especialy when running a govenor as it masks the lean condition.
Gary Travis

[broncoholic7]

Thanks Gary!
I was hoping you or Chris would pop in and let me know what and how to take care of this.

I will give it a try and let you know if that takes care of it.

I think I am going to replace the 401/9254 gyro with a 601 if I can find one, if not spring for the 611.

I really appreciate the information!

[Gary Travis]

Let me know how you make out, don't give up on the 401 most guys are running 401 combos on the gassers with no problem. Also I have seen the same thing happen on the 601/9251 combo as well.
Gary

[broncoholic7]

Also I have seen the same thing happen on the 601/9251 combo as well.


Wow, OK glad you told me about that. Saved me some money. :D

I will definately try it and let you know how it goes.

I will just replace the servo and keep the 401. The guys at the field said the gyro seemed fine.

I will try to get it tuned in as you suggested.

Thanks again Gary!

[rjflyer]

Mike, It has happened to me before, make sure the tail has no binding, and that it is silky smooth, then take out the thrust bearings and look real close, for any pitting or ridges. You can"t be positive until you take them out. Even one pit will cause the tail to lock up. If everthing looks good then check motor tuning and gyro. Take care of the easiest first, saves time and aggravation. :)

[broncoholic7]

Thanks Rick,
As a precaution and to rule out the bearings and just to see what they looked like I took out the bearings. The bearings and the races looked fine. I could not see any problems. I may order new ones just to have or compare.

I am going to do what Gary suggested when it stops raining and when my new collective servo arrives. Others have said they did what Gary suggested and it worked for them. Hopefully that is the problem as I cannot find any other reason for it.

As for the motor, I did see a lot of vibration, especially in the tail boom supports. They looked like a rubber band when stretched and pulled and let go Still not sure if/how that effects the tail not working.

Does anyone who does balancing of the motor?

Thanks again