FBL Gyro AR7200BX Tail Issues

Tony

Staff member
Okay guys, I'm stumped. And when I can't figure it out, something has to be wrong.

Lets just start off saying that I"m not happy at all. I put two helicopters in today, thankfully this one, is just a front tail gear.

Since I crashed the crap out of my SE V2, I decided to go ahead and get the 450 Pro V2 in the air since it had not been flown in a very long time. This helicopter has the AR7200BX on it with the latest firmware. And it flew fine the last time I flew it.

Here is what happened.

I took it outside to do another shake down flight while the mobius charged up, then I was going to shoot some video that I have been needing to shoot for, oh, about 4 years lmao. So I take it outside and I plug it in and let it do it's thing. Once the gyro was happy, I picked it up, checked ALL directions and everything was perfect.

I spooled it up after centering the tail blades (then returning to HH mode) and put it in the air. Pretty much, I was getting back to basics (did I ever leave?) and I was doing some side in hovering. But I was doing it as I have in the flight school. First, go to a 45º angle each way, then go full side in.

I did the 45º then I did the full left side in and was holding it over the pad, then I rotated around and was in a full right side hover. That is when, WITHOUT ANY STICK INPUT AT ALL, this thing, after a complete stop in right side hovering, goes right rudder to a perfect nose in orientation. I TOUCHED NOTHING! It's like the gyro just moved it there like I told it to do so. I'm talking a perfect 90º rotation to the right.

Fine, I held it there for about 5 seconds and rotated it around (to the right, if it matters) to a tail in to start all over again. Then, I landed but the tail was twitching and I decided to go ahead and hit throttle hold and land it in the grass.

I know, TT tail and grass. But I have the black gears, I checked them at this time and everything was PERFECT!

So I spooled it up again and thought, maybe the head speed is too low (I was only running 65% head speed, which is great for this helicopter). So I put it back in the air, and just in case something happened, I went up about 40' into the air and hit IU1. All hell broke loose when I did that. A complete, out of control piro that I could not stop with any kind of input.

At this time, I had no choice but to hit throttle hold and try to save as many parts as I could This time, I was in a little taller grass though (just mowed parts of the yard).

When it landed, I heard the sound that no one wants to hear, grinding gears. I thought the cones stripped, but NO. The .06 gear that meshes with the auto gear stripped!

So I have checked every single setting on this gyro and the transmitter. I have watched the monitor menu for quite a long time and the rudder never moves, so this is not a transmitter issue. I have checked the gain (again, programmed into the gyro as set in Tx) and I'm showing a G on the gyro, and that is about right seeing as I have +45% on the gyro gain, so that is working.

The only thing left is the tail servo, but nothing has changed. I have not crashed it, it has not gotten wet. In fact, this is the ONLY helicopter aside from the 130x RB that has ALWAYS been in a case.

It just makes no sense to me that this thing would just wig out on me like that without any reason. I'm starting to think I should just stop flying, and stick to how to videos... I seem to be good at videos, but I seem to suck big time on flying anything...

so what are your thoughts on this?
 

Tony

Staff member
Well you know me, I just can't wait around for an answer so I started digging into this thing. I checked and double checked the settings and everything was fine. So it was then time to look at the gyro, it was the only thing left.

First thing I noticed was the signal wire had a little bit of insulation missing from where it goes into the plastic connector by the gyro. Common for these to strip because they are out in then open. I stripped it back completely, and it still had a good connection, so that was not the issue.

I tried moving the stick to make it do what it did again, still nothing. I tried moving the helicopter nose right/left to get it to do it, again, nothing.

After about an hour of testing, I decided to just put it on the floor and spool it up. There is no tail spinning so it should be fine. I held it down by the skids and spooled it up very slowly. Then, I grabbed the tail and moved it ever so slightly. Servo was working fine, until it stopped. I'm talking nothing. It just died.

So I shut the motor off and picked it up, still dead. I unplugged it from the gyro and plugged it back in, still dead. I wiggled the wires at the gyro and the servo, still dead. So I slightly touched the servo arm and it came back to life.

I then moved the helicopter very slowly nose right/left, and again it stopped. one light touch, alive again.

The friggin DS520 has a bad pot in it. There is dirt in it causing it to stop working. I have seen this before and don't know why I didn't think of it when this problem started. Probably because THIS THING WAS WORKING PERFECTLY WHEN i PUT IT AWAY!!!

If it ain't one thing, it's another... But at least I know I need a new DS525 servo now... So this helicopter goes back in it's case for another couple of years...
 

Tony

Staff member
Yup, took quite a while to find it, but it's the servo. I thought about just swapping out the one from the SE V2. I even found a new tail gear for the Pro. It's white, but whatever gets me in the air. That is until I found a tooth missing on it... It's always something.
 

Tony

Staff member
A tooth missing on the other tail gear, not the servo. I have not done any swapping other than putting the DFC tail block off the 450L Dom onto the Pro V2. A lot less play in teh tail now. Had to change out the grips though.
 

Tony

Staff member
So here is a picture of the two gears. The black one is the one I had installed and the white one is one that I found in a box to try and get it back in the air. How in the hell does a white gear strip a black gear. The black gears are supposed to be a lot stronger. And there is not a single mark on the white auto gear.

image.jpeg

image.jpeg
 

Smoggie

Well-Known Member
I was going to say 'bad pot on the servo'... good that you picked it up.

Those black gears are 'supposed' to be stronger but I've found that they strip pretty much as easy as the white ones. If they are stronger it's not by much. I'm not sure if it's possible to press off the tail gears from the shaft and make one good assembly from the two damaged ones? I've never tried it.
 

Tony

Staff member
I have tried it and didn't have much luck with it. If by some chance you can get it on the same splines, it's unlikely it's going to have the strength to actually be worth anything. Not worth the chance anyway IMO.
 

trainrider06

Active Member
They are on there pretty tight! Plus you wouldn't want em to move around anyway, because the gear is liable to slide up the shaft and either disengauge or be misaligned. They must use some sort of glue, or heat process to press these on where they stay on.
 
I've found that the align ds415m and ds416m servos will not take much abuse (i.e. crash). While they are "metal" gear servo's, there is one really bad weak point and that is where the main gear of the servo (largest gear) sits on the shaft, there is actually a nylon (plastic) area that lines up with the flat on the shaft. So, in my experience, what happens is that the metal gears won't strip, but the little piece of plastic does and renders the servo inoperative. The other thing that happens is that the shafts bend which can have two consequences: 1.) the gears don't mesh correctly and the servo will sort of skip, and, 2.) the servo motor is soldered to the circuit board and that connection can break resulting in either intermittent operation or none at all. I had a servo which had the latter problem. If I pushed the servo motor sideways, it'd work, it I let go it'd stop.
 

trainrider06

Active Member
I have the DS 430's and they don't do so well either, out of the 8 I have/still use, 2 had jitter problems 2 have stripped., due to hard landings.
 
I guess one has to weigh the cost of a new servo against the cost of many other parts if the questionable servo would fail in flight. I think if I saw any sign of inconsistency in the servo I'd replace it - the alternative is simply too costly.
 

trainrider06

Active Member
So far on my Align 450 Pro, these servo's have done well....after I replaced 1 in the beginning that was jittering on me.
I had again the very same issue of a brand new 430 being jittery upon initial build on my Align 450L, then 1 stripped on me from a hard landing a week or so ago. Luckily I had the jittery servo and just replaced the main gear of the servo that broke a tooth.
I had some EMax 09's, on another Align Pro flybar heli, these tough little boogers withstood an upside down drive into the ground, and never gave even the slightest hint of any failure or glitch on my 450 Pro FB heli! They still worked like a champ when I sold the heli. Had a V450D03 heli that I took all the electrics off, and ran some EMax 09's on it, crashed that one morning when I lost it in the sun, they survived without harm also!
Even though they were inexpensive servo's they sure were tough, and worked great!
 

Admiral

Well-Known Member
Hi Guys, I have been able to repair the main gear in a few DS415MG & DS416MG's that work as good as new.

1. Remove the main gear.
2. Place a piece of rod or small screw down through the top hole.
3. Support the outer gear on the edges. (I used a small shifting spanner or wrench)
4. Press or tap the rod or small screw the plastic inner may come out (About 1 in three it fails and the rod goes through the plastic center)
5 Turn the anti rotation lug on the plastic inner to the area with the missing teeth and re-insert the inner.
6. Re-assemble the servo and you right to go, be sure to remove the broken teeth from the servo.

[URL=http://s147.photobucket.com/user/ruby95/media/IMG_17331_zps7uwo4gt4.jpg.html] [/URL]

A repaired main gear, I don't have a damaged one to show you all the steps.

It saves me about $15 every time it works successfully.
 
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