unstopable pirouette on startup

[whittm]

Ok, my 130x has been out of use for a few weeks due to waiting for parts from america, illness and bad weather. fitted new parts, tail grips, and metal a gear. before needing these parts it was working fine. Now it piro's uncontrolably to the right. I have been tirelously trying to fix this all evening and no joy! The servo even came apart! I tried cleaning the tail servo which was really dirty, also adjusting link rod and boom length. I have unplugged the servo and adjusted it, so that on startup there is zero tail movement. As soon as i plug in the servo all hell breaks loose! Here are the symptoms:

With throttle hold on, the servo moves very smoothly. When i then dissengage throttle hold(whilst holding the heli down, and watching the tail and servo) and throttle up, the aileron servos bank right and tail servo also pirouettes rightward. Looking more closely the servo seems to be binding and will stick in one position indefinately. As soon as i stop. the servos function perfectly. What on earth is going on here?

[trexamanic]

Have you tried freeing the servo by moving the cog until it moves the servo rod down a fair bit?
that works for me on my msr x with similar symptom

[tomatwalden]

unstopable pirouette on startup

Sounds like the C gear is stripped. Have you tried changing it? Note that the gear strips internally so visually you won't see anything.

Easy way to check - hold main gear still and try to turn the tail rotor. If you can turn the tail rotor with minimum pressure then you need to change the C gear

T

[maddog7]

Ok, my 130x has been out of use for a few weeks due to waiting for parts from america, illness and bad weather. fitted new parts, tail grips, and metal a gear. before needing these parts it was working fine. Now it piro's uncontrolably to the right. I have been tirelously trying to fix this all evening and no joy! The servo even came apart! I tried cleaning the tail servo which was really dirty, also adjusting link rod and boom length. I have unplugged the servo and adjusted it, so that on startup there is zero tail movement. As soon as i plug in the servo all hell breaks loose! Here are the symptoms:

With throttle hold on, the servo moves very smoothly. When i then dissengage throttle hold(whilst holding the heli down, and watching the tail and servo) and throttle up, the aileron servos bank right and tail servo also pirouettes rightward. Looking more closely the servo seems to be binding and will stick in one position indefinately. As soon as i stop. the servos function perfectly. What on earth is going on here?

Mine did exactly the same fella, in my case it was the tail end umbrellas. I couldn't see any signs of damage but had read up lots about it and it was the only thing left to try.

Replace them with new ones and epoxy the gear to the shaft (just a tiny dab so you can get it off again)

It has been faultless since.
Hope this helps.
D

[dillwhacker]

A drop of CA will often fill in the gap of the rounded out 'D' shape in the C gear.
Dont get it on the teeth.................

[whittm]

Sorry guys should have said, c gear is brand new and is not slipping. The tail case is a nearly new rakon heli one so loose bearings are not the problem. I have stripped the servo and cleaned it, I also wound it out by hand using the cog. There ids a new rakon pitch slider also. The other symptom is the servo gets jammed on. I've unplugged the servo and spooled up the heli which then doesn't pirouette. The servo only hajams when the rotor spins up, when in throttle hold or in min throttle position the tail servo moves smoothly. Once rotating the servo essentially judders and skips violently back and forth. I have a horrible feeling the gyro or the board is knackered.

[Mike00top]

Doesnt sound good, as you were waiting for parts, that sounds like it crashed, did it go in with power on, or anything get jammed in the rotors, cos if it has it is possible the main board has taken a hit, failing that if you have been replacing parts, you havent accidentilly put the tail and cyclic servos into the board in the wrong plugs ? ? ?

also now that you have fitted new parts does everything rotate freely ?

[whittm]

No, never with power, Always got a finger on throttle hold, I fly with a finger on it permanently and only over soft grass at three mistakes height. The A gear teeth were stripped and this was causing strange power loss and a few small crashes in a row, which caused a crack in the tail grip. These are the two parts i had to wait for. Also didn't have to strip the heli down much to get at the a gear and tail grips so the servo plugs stayed put. Everything is running free, I was concerned about the link arms being tight on the pitch slider so i popped them off and wiggled them back and forth until they were loose, But, as i said the whole system moves very freely until you spool up. The aileron servos are also jaming up I've noticed on spool up. It seems like the gyro is 'confused' some how.

[Mike00top]

well i have done a work around for this issue, and that is providing the board isn't U/S ( if it is, only a trip to HH will sort ) firstly the servos can get dirty and flick around badly, they can be stripped and cleaned or sprayed with contact cleaner/ lubricant, there could be a little hair or debris in there

after that spool it up and have someone on the radio in sub trim page, as soon as a servo starts to move dial in opposite subtrim, slow the motor to a stop and then spool up again , watch again it should move slower this time, continue to do this until all controls stay put, with out travelling to their end points, if you have to use loads stop there could be something wrong on the main board.

its worth checking the tail mesh and TT is correct now too, just undo the two rear most screws holding the boom, slide the boom in untill it binds the rotor from turning freely, now back the boom out a touch at a time until it all turns freely, now do up the two boom screws on the main frame, next undo the two cross screws that hold the tail servo on the boom and slide it until there is a 2mm gap between servo holder and main frame and then retighten

you should be good to go now

[enterpryse]

Re: unstopable pirouette on startup

Just read this and remembered mine threw a tail blade the other day and needs replacing- thanks!

[SamS]

If none of the above works, Loosen the tail blades. I once sent my 130X to HH because it kept spinning uncontrollably, they sent it back saying "we've loosened the tail blades"

[Mike00top]

also if it piros real quick while spooling up and taking off, just advance the throttle a little slower at the beginning, at low rpm's the tail doesnt stand a chance of holding the heli straight against the torque

[whittm]

Thanks guys, I am a former mcpx owner so know a lot of the usual things. So in the end called horizon hobby. They went through everything I could think of and all the things you guys came up with on top. The heli is now winging its way to hh as we speak. Thank you very much all!

[Nick B]

Tail grips on the right way round?

[whittm]

Very good question! Oh crap! Are they really handed?