servo uncentering by itself
 

I have a boomerang XL - I am the origional owner and installed all new gear- 8411s throughout. This weekend when getting the thing assembled and plugged in, I noticed that the aileron servo on the right side was out of center. It has done this before - flight 40 something? Anyway, what would cause a servo to forget it's center point? I am using the smartfly EQ system. Maybe the smartfly adjusted it on its own? I am at a loss. I had to remove the control horn an re-adjust it to center. After that it was fine for 3 flights. If you do not turn the RX off before the TX will the Smartfly cause this?

Has anyone else here experienced this? My comfort level is reduced when these things happen without any explaination.

Andy

RE: servo uncentering by itself
 

Andy,

Are you sure that its not the plastic servo arm moving on the output shaft? I've had several of those strip (yes, the JR heavy-duty ones) and now I only use metal arms on my primary control surfaces in jets...

Bob

RE: servo uncentering by itself
 

Andy,
Bob is making a good point. I have had several of the DuBro heavy duty arms strip also.

Jon S.

RE: servo uncentering by itself
 

I am using the plastic arms that came with the servos. The teeth appear to be perfect. It even goes on real tight (no slop at all). I will look them all over again but closer this time.

RE: servo uncentering by itself
 

Andy,
Another thought. Are the aileron servos "Yed", or they plugged into a matchbox, or two separate channels on the receiver? If you are using two channels on the receiver and mixing them, make sure the slave channel has all switches and knobs programmed "off". If the knob is active it may be getting bumped when you handle the transmitter.

John S.

RE: servo uncentering by itself
 

I had a friend Don yockey that experienced the same thing a while back. Turned out it was the PCM10 transmitter that was the problem. He replaced to the 10x and no more problem.

Kevin

RE: servo uncentering by itself
 

Hi Andy

I had the same thing and it ended up being the horn, plastic heavy duty one that stripped. Looked OK though. It cost me my Eurosport!!!!!!!!!!!

Replace with aluminium ones ASAP.

Zane

RE: servo uncentering by itself
 

Interesting comments about the servo arms... I've bent an 8-32 bolt with an 8411 and a plastic arm........

RE: servo uncentering by itself
 

I have no doubt that is true, but I've been taxing out with my Eurosport and noticed one elevon was no longer centered. I went out and grabbed it and the arm was stripped out. Had I taken off, I would have lost it for sure. I later had one strip on a 50cc Yak and ever since, its been aluminum arms on all flight controls for me...

Bob

RE: servo uncentering by itself
 

man you are flying a jet don't mess around with it just replace the servo

RE: servo uncentering by itself
 

I sincerely doubt it is the servo. I sincerely doubt it is the servo horn also. I have seen the dubro horns strip as Bob has mentioned but never a JR horn.

I an wondering if you are using two spearate channels to control the aileron's? If so something is active as mentioned above. When using two channels to control aileron's you need to inhibit the slave channel under screen 17 on the 10X. Not sure which radio you are using, but my guess is the slave channel is not inhibited and a knob or something is getting bumped.

RE: servo uncentering by itself
 

Ah...I believe this might be the answer. I looked and under the F.MODE and D/R SW was set to AILE and not INH.

Andy

RE: servo uncentering by itself
 

John,

No doubt the JR HD nylon arms are very strong, but I have had two strip in "normal" use. Its difficult for me to see how those nylon arms are up to the task with a brute like the excellent JR 8711 (or 8611 for that matter). Luckly, Hanger 9 makes some excellent aluminum servo arms, that, along with good 4/40 ball links and Hanger 9 Titanium Pro-Links, makes a secure linkage that is worthy of those servos on a high $, high speed, jet aircraft.

I've never had a linkage setup that way fail, and for me, that's cheap piece of mind... [8D]

Bob

RE: servo uncentering by itself
 

Bob, how do you explain JR providing the heavy duty plastic with the 8711? IMO that's a broad statement from the manufacturer saying it's up to the task. I'm head scratching on this because a friend of mine had the heavy duty plastic do the same thing (spline problem) on a Euro last week. In his case, the airplane was landed safely.

In my case, I've been using them exclusive for years and thousand flights, no issue ever.

RE: servo uncentering by itself
 

Sean,

Ever see that show "Engineering Disasters?" Its all about how engineers (I am one, BTW), and in some cases, the manufacturerswho produced their designs, were ultimately wrong. I'm sure you can setup a test on the bench that shows that the HD plastic arms will take all that the 8711 can throw at it, but it CAN FAIL, even in a correct installation where it was not subject to unsusal loads or obuse. We've both seen it, and many others have too.

Personally, I think it might have something to do with vibration of large control surfaces. - like the Euro's elevons, that may be caused by things as simple as vibrations coming from the wheels on takeoff or landing. With a lesser servo, the motion may be partially absorbed by the servo, but the 8611/8711's are so rock hard that it gets transmitted all to the nylon splines, and eventually, they let go. Either way, in both cases, I was left with a surface that was not "centered" like normal, and a slight amount of pressure was enough to make it move with the servo stationary. Removing the nylon servo arm produced a white powder that was once the splines. I've *never* had that happen with a metal arm, so that's what I use on elevators (especially), ailerons, rudders, and sometime flaps, with 8611/8711 servos...

Bob

RE: servo uncentering by itself
 

Hey Guys,

It is really interesting the number of PM's I have received on this servo arm thing. We have never heard of one failing here at Horizon like you guys have talked about. In talking with a few of our hard, key flyers, they have never had this happen at all either. From what I am reading here it has happened more than anyone here at Horizon can believe. Now of course I am sure all of you are of the mind set "why don't they fix this problem". Well guys if we don't know about the problem we cannot fix it. Never has one of these arms been returned to Horizon for replacement (which would alert us something has failed). I am sure you have just replaced the arms and figured someone else had alerted us to the issue. I know I have doen the same thing over time.

So here is what I need from you guys to fix this. If any of you have any of these arms lying around that have the splines stripped, please send them to my attention at Horizon. I will get them sent back to JR for them to begin looking at the failed parts and see what they can do to fix it. So send them to me and lets see if we can fix this.

RE: servo uncentering by itself
 

Under flying conditions, the nylon ones will always be OK. Mine was stripped due to my own stupidity![:@][:@]

I decied to pull the Euro back to the pits from the flight line and accidently kicked the elevon. The plane was still switched on, and the horn had moved on the servo. Checked the servo out and it was fine, but the horn was stripped. Can't blame JR for that but have decided to go with aluminium horns since then. Suppose I will strip the gears now!

RE: servo uncentering by itself
 

Had a JR nylon arm strip that cost me my 100cc Yak couple of years back. Since then. I have always used SWB double loc metal arms or, more recently, the JR metal double loc arms.

Rgds,
Mark

RE: servo uncentering by itself
 

I believe that one of those companies that everyone ...well almost everyone, makes fun of ALWAYS supplies aluminum horns with their digital servos........:)

Tailwinds,

John

RE: servo uncentering by itself
 

Which insures that the surface will go hard over or lock in the neutral position when the servo its attached to does...:eek:

Bob

RE: servo uncentering by itself
 

John, I'll be sending in my plastic JR heavy duty servo arm as well as my 8611a servo tomorrow. I'm the dude that experienced servo re-centereing during my eurofighter flight sean mentioned. Lucky for me I was able to bring it back in for a somewhat decent landing. My caller said that I was mumbling explicitives uncontrolably, but hell, I dont remember, I was just happy to have it in one piece again.

Luis

damn the spell check on this thing!!

RE: servo uncentering by itself
 

Gee Bob, What do you want? EVERYTHING:D. Too bad the JR and Hitec splines don't match. Then you could use the "included" aluminum Hitec arms on the 86/711 servos and the JR plastic ones on the Hitec 5645's.

Marty

RE: servo uncentering by itself
 

OK guys, I have found out some information. Maybe helpfull, mayeb not, but it is here non the less.

The plastic arms can crystalize and become very brittle if you do the following: Trim off the un-used arms and then dremel or belt sand them donw to make then smooth.

Trimming the arms is perfectly fine, but the heat generated during "powered" sanding can cause the plastic to get hot and begin to crystalize which can then become very brittle and failures of parts breaking can occur. I normaly trim all of my horns down, but i hand sand them after that. Had never thought ofdremeling them, but I am guessing some people might have. If so could this be a common denominator as to the spline failures some of you have experienced?

This is all I have at the moment. I'm still wokring it guys.

RE: servo uncentering by itself
 

Interesting theory there. The amount of time it takes to round off the edges of the cut arm is about 2-3 seconds per side on a belt sander. I would have never thought that the heat could even build up in such a short time to the point where the spline area would deform/crystalize.

Marty

RE: servo uncentering by itself
 

The splines will not deform, but the plastic can become to crystalize. Probably would happen more when using a dremel. If you see the horn star to turn a milky white color, it has been compromised and needs to be tossed.