Bob.R

My Feedback: (2)

I posted this in the JR forum, but I've not had any useful responses. I thought I'd check with the JR experts in this forum. I'd very much appreciate it if we could avoid another radio flame war.

I have an unstable travel adjust setting that nearly lead to the loss of my 1/6 F-16. 12X radio/1221 receiver/8611 servos (one on each stab, one channel per stab). The airframe and all components have flown for over a year and have about 100 flights on them.

I pulled elevator on a down-line and the plane rolled severely. I landed and did a thorough checkout. Both stabs were properly centered. However, the right stab had several degrees more up throw than the left stab, and several degrees less down throw than the left stab. The travel adjust settings in the transmitter had not changed. I checked the next day and the elevator throw was still screwed up. However, I checked this morning and elevator travel was correct, so the problem is intermittent. The only change is that I flew a different model yesterday, so I went through the model select procedure twice in the transmitter.

One of the servos would seem to be the likely culprit, but both hold center. Both servos operate smoothly with no jitter or jerkiness during actuation. However, the variable/unpredictable up and down travel is a serious problem. I was going to do some diagnostic work with different servos, but now that the system is working properly, I'm out of ideas.

Advice would be most appreciated. And again, please avoid a radio flame war.

Thanks,
Bob

basimpsn

My Feedback: (5)

Could be a switch still active. Next time check your radio servo monitor to see if both elev travel is linear.

Bob.R

My Feedback: (2)

Could you elaborate a bit? Switch settings are identical/unchanged when the problem arises. Servo travel on the servo monitor is the same for right/left elevator. However, travel is not "linear" as I have some expo programmed.

basimpsn

My Feedback: (5)

Ok thats what i was talking about. Did you put expo on both elev channel with identical percentage?. Try connecting both servo to one channel and measure the travel on both.

invertmast

My Feedback: (23)

I had a similar issue with another brand servo. It did the same thing a couple of times in flight, and was never able to reproduce it on the ground. Then one day the servo finally started doing it on the ground. I replaced the servo, and had no problems after that. I assumed the potentiometer had a corroded spot on it that gave a false position report to the board under certain conditions..

jayman618

My Feedback: (5)

I had a similar situation on my plane. I had a nose gear problem and after reinstalling the nose gear found it was off just a bit so I used sub trim to correct. After several flights I noticed the rudder would not center correctly. I tried everything I could with no success until I remembered I had used sub trim on the steering servo. I returned the sub trim on the steering servo to the same setting as the rudder servo and made a mechanical adjustment for the steering servo. Everything fixed works perfect every time. Hope you find the problem I believe it is in some of your settings.

Jay

racer8297

My Feedback: (13)

I would replace both elevator servos and any extensions. Also make sure that the servo leads/extensions are not running past or along side any wires from the motor since things like the RPM sensor wire can cause some anomalies.

I am assuming that there are no match boxes or other type of equalizer in the system.

Jim

GR7Racer

I think the first poster might be on to something....

Did you use the "mate" function to make your 2nd elevator channel, or did you write a program mix? If it is a mix, you might have different values for positions 0 and 1 and a switch on the transmitter could be toggling it back and forth. When you flew the other model you may have moved that switch to a different position.

I would methodically change the position of all of your switches and knobs one at a time while observing your elevator travel to see if one of them is making your rates asymetrical.

Using the "mate" function requires you to inhibit the aux channel that you want to follow the primary channel. That keeps you from having a switch or knob that is still active on that "slave" or "mated" channel which can foul up the servo position. It also matches the travel (assuming the travel adjust is the same), applies trim to both channels, and dual rates/expo to both channels. It also applies mixes to both channels when selected as a slave in a program mix. It even labels the channels LElev or RElev (Aileron, Flap, etc) in the different programming sections of the transmitter so that you can better keep track of which surface you are adjusting. It is a MUCH better way of setting up a channel to follow a primary surface channel.

If you can make it misbehave again, I would select the monitor function in the transmitter to see if the transmitter is telling the servos to travel differently. If the indicators are the same in the monitor function, and the surfaces are still not traveling the same, then it is most likely a servo problem.

KennyMac

rcand

you did not say how you programmed the 2 elevators. Did you do your own program, mate them or a match box? Need to know that before anyone can figure it out. Also, are both linkages exactly the same in position of the arms

Bob.R

My Feedback: (2)

Thanks for all the replies. There have been several questions regarding setup. A few comments/answers:

- This airframe with transmitter, receiver, and servos has been flown 100 times over the last year without incident. The intermittent failure began this weekend after 100 successful problem free flights.

- No matchbox.

- One channel per elevator servo. The channels are mated. The mated channel is inhibited.

- I have methodically activated every switch and knob to determine if there is some oddball setting or mix that could be giving me difficulty. I cannot reproduce the problem I had this weekend.

- The elevator linkages are nearly, but not exactly, the same. The programmed right and left servo travel to achieve proper elevator throw differs by 1 to 2%.

If I can't get the system to act up again, I'll replace the elevator servos and extensions and then hope for the best. My first thought was that one of the servos was at fault - what confuses me is that the servos hold center and operate smoothly even when the elevator travel has gone whacko.

turnnburn

My Feedback: (49)

Sounds like a servo issue to me. I say replace both of them, unless you are 100% sure of which stab has the problem.

GR7Racer

Ok, good info Bob.R.

Last thing that you might want to check is to see if the "eyebrow" trim switches on the upper outside corners of the gimbals are trimming your second elevator channel. If you used the flap (aux1) or the aux 2 channel as your 2nd elevator channel, it's possible to independently trim that channel with one of those trimmers. I like to deactivate the trimmer in the trim menu when I use one of those channels for mating purposes.

I kind of doubt that this is your problem though as your 2nd elevator surface would show a different center position when things are acting up.

Other than that, I'm running out of ideas. Could be a poor extension/connection, but that would probably show other signs too like jittery servo or slower speed. I guess it could be the servo, but I've never heard of that symptom from a servo.

Sure sounds like an errant mix in the transmitter somewhere, or something causing the transmitter to send the odd signal. You might take a look at the mix monitor and make sure nothing is listing the right or left elevator channel in a mix that could somehow affect the travel.

KennyMac

Moerig

If you had an accurate servo pulse display gizmo you could verify the channel if you could replicate the problem. You would need one capable of 1uS resolusion. It does sound like a dormant mix issue. A pot problem would manifest itself differently, but you cannot eliminate the servo entirely. Personaaly i think the mix setups can be confusing with many feeback possible.

Boomerang1

Yep, keep a Y lead handy & if it goes ape again Y the servos together to see if it's a servo or other problem. Of course they will not travel the exact amount as you said you put in a couple of % of different travel due to the linkages but you should see something amiss.

I have had issues with extension leads too, I think if they are not plugged/unplugged often they have a problem with the signal wire & even two servos on a Y lead (with the same signal) will do different things. This can happen after many trouble free flights & after unplugging & replugging the leads the problem disappears. I try to avoid extension leads & just extend the servo leads. - John.