Random veer

[Bikersurgeon]

Greetings, I've a similar issue as dpinvidic but don't want to hijack his thread. Apologies to the mods but I don't know whether to put this in the torq, beastx, or thunder tiger fora. I have an x50 with 7200bx and torq 9180 servos. Had a tipover many flights back but no problems since, till yesterday. During hover I noticed a random veering off to the LEFT quickly. It was correctable (was brief ). Did some pitch pumps and they veered to the left too. Put it on the bench and slowly went through full collective range and the swash stayed dead level. Twisted servos by hand and all smooth. Servos wires look good. Reset the 7200 bx and reprogrammed everything today and sure enough, same thing. When I sat it down from hover I was in throttle hold and pumped it through collective range and noticed one blade didn't move much. On closer look, the pitch servo (the one on the passenger side lol) was barely moving. I pumped it several more times and it slowly began to operate normally with the other ones. It was not hot. Servo issue or beast issue?? Other? Is there a way to test servos (with a multimeter or something). Thanks in advance.

Ps, wouldn't a slow/bad right/ pitch servo make the heli veer to the right??? Weird

[Steve Graham]

Sounds like a bad servo. Several possibilities. A gear train slowly losing teeth. Will work and occasionally miss a tooth or two till it strips completely. Test by slowly moving the servo up and down through it's entire range while holding the output arm and resisting the motion. Bad electronics in the servo circuitry that only fail once they start to heat up. The heat in your servo indicates to me that this is likely the issue. Bad potentiometer. These devices use a little metal arm that "wipes" along a carbon resistor as it rotates. The most common failure mode here is that the metal arm or the carbon resistor itself gets worn or contaminated in such a way that the resistance values become flaky. This is called a dirty pot. If you were to look at it on an ohmmeter and turn it through it's range you would see the resistance values jumping instead of smoothly increasing. I've cleaned these a couple times with contact cleaner and gotten a little more use out of them but replacing the pot is really the only fix. On a heli where servos are so critical I wouldn't mess with it.

There are servo testers that will cycle a servo up and down continuously through it's range. This is a good way to test a servo over an extended period of time and more easily identify intermittent faults. Some TX's also have a page that tests the channel outputs by moving all channels up and down. If you have this you can hook up just the suspect servo with a spare RX and battery and do an extended test.

[cudaboy_71]

i've seen two beastx do this. even flew one that did it. in both cases it was vibration induced.

you can try to mask it with thicker tape, or fix it by finding the vibe.

[Ah Clem]

"i've seen two beastx do this. even flew one that did it. in both cases it was vibration induced."

"you can try to mask it with thicker tape, or fix it by finding the vibe."

I have seen several do this.

In each case, the issue was the stock tape, which may actually be exacerbating the vibration. One or two layers of 3M tape, plus making sure no wires were getting pinched under the BeastX, of flapping/tapping near it, corrected the issue completely.

In those cases where I have seen this happen, the BeastX unit itself was perfectly fine. The tape was the culprit.

[cudaboy_71]

in the most recent one i saw, the tail shaft bearings were shot. fixing them fixed the issue. OP stated a recent crash, which is why i suspected new vibrations rather than the tape. but, like i said, it can probably be masked. but, not sure that is the best long term solution.

[Steve Graham]

But how do you account for the fact that the servo did this after it was on the ground with the blades stopped?

Maybe I missed something?

[Bikersurgeon]

Ah...ok...didnt realize this was an x50 specific problem

I do appreciate the input from you guys though. I will investigate each possibility.

[Vaeloron]

You could try swapping the pitch and aileron servo leads. If the issue moves to the other servo its a Beastx issue. If the same servo still has the issue then your servo is done. Just make sure to swap the leads back before flying it.

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[scottyay]

In the beastx setup, if you go into the function for adjusting cyclic limits it will let you have full pitch and cyclic movement without the gyros being active and possibly having an effect on the movement. This can give a clearer way of seeing how the servos are moving and as long as you don't push the rudder left or right, it won't change any of your settings.

[Bikersurgeon]

thanks, guys....I tested each servo buy moving them through their range against the resistance of my grip and they seem fine-stronger than me and no clicks. tape and wiring is a good thought but they have not changed and it always flew beautifully...no loose flopping wires, and none that are tight to the BX. the tip over I had was months ago and it has flown perfectly many times since, so don't think I bent a shaft or anything.

spooled up the heli and heard a faint squeak. back on the bench I grabbed the head and rocked it back and forth. The upper bearing has a small amount of lateral play...maybe 0.1 or 0.2mm. I can even see a bit of grease push out between the inner and outer races when I rock it. I am guessing this could cause my beastx to act weird. I already have the aluminum bearing block upgrades in my box-was looking for a reason to install them....if it doesn't fix it, at least I'll still have improved bearing blocks lol.

[Bikersurgeon]

well, strike one....at least I have brand new bearings and the nice shiny aluminum bearing blocks now....but I guess I'll go to step 2 and get a new torq servo.

[Steve Graham]

Couple more thoughts here.

You mentioned at one point that your "bad" servo was really hot. To me this is a sign of an electronics issue internally with the servo. A servo frequency that is set too high can cause a servo to get hot. There is a setting in the BeastX for this. You might try lowering the servo frequency and see what happens. I still feel its a servo issue. Were you ever able to find a way to continuously cycle the servo for an extended period of time to see if it gets hot on the bench? When electronics go intermittent it can be VERY difficult to fault isolate.

I tried Torq servos recently and had two gear trains fail out of four new servos. One cyclic and one tail. Failures are one thing. The fact that the gears in the servo were not the helical gears I paid for bothered me. Until someone from Torq or Outrage can explain to me why or how this possibly happened I will not be using Torq servos. Too bad too because I've heard good things about them. Just not my experience.

I'm still not sure if you meant to state that the control issues happened even on the ground with the blades stopped. If that is the case this is NOT a vibration issue.

[Bikersurgeon]

Hi Steve, thanks for the reply! The servo in question did not get hot...the first thing I did after spool down was feel it because I figured it was hot, but no. about the ground episode: in one instance, the veer began in the air, as usual, so I landed, and yep, right after the blades had stopped spinning I went through the collective range and the the servo was barely moving....I kept cycling the collective and over about 5-6 seconds the servo slowly and steadily returned to it's normal function. I have not been able to repeat this on the bench. One thing I still find very curious: the servo that is acting up (barely moving at times) is the right sided one (at least that is the one that was slow during the ground episode) so the swash tilted RIGHT when pushing up the collective, however, the heli always veers LEFTWARD in the air when it malfunctions. gotta be a clue there lol.

[Steve Graham]

While it does seem odd a circuit going through intermittent periods could do just about anything. I suppose it is possible you still have a vibe or FBL unit problem.

Another possible troubleshooting technique might be to remove all the blades and have a friend spool the heli up while you hold it out in front of you. Have him go through the range of collective and cyclic inputs. Also with the heli level zero out the cyclic and pitch and roll the heli watching for correct swash compensation or more importantly malfunction. Be very careful if you do this not to get your body parts caught up in the mechanism

Even if you do this I'm not sure it really helps with the fault isolation.

[Bikersurgeon]

More clues:

I think it must be the 7200bx but I've no idea why...I tried a rebind today...I didn't seem to get the random occurrences of left veer when in hover but with pitch pumps it still veered left. Back on the bench, cycling through collective range and swash dead level. Then I thought " this is a nitro, flip the TH off". Then when I went through the collective the right servo was slow...after cycling through it several times worked normally...until I went to full neg collective and sat there a few seconds, then it goofed up again...I repeated this and sometimes the LEFT servo was slow instead of the right. With TH off I noticed the throttle servo was buzzing more than I was comfortable with...I adjusted the low throttle endpoint down until it stopped buzzing and then the right servo would barely move at all, and it would not resume normal function after cycling through collective range several times.

Now I have nice new main bearings, and I am going to buy a new beastx (unless you guys see a different issue). ....worst case scenario is a spare beast x

[Vaeloron]

Mispost

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