Hi Everyone,
I've been having alot of fun with my Exi450Pro until last week it started doing something weird. Please look at the video on youtube for a better explanation:
http://www.youtube.com/watch?v=H6Lu4Xo1uKQ&feature=plcp

After around 1/4 of the way into the video (1:00 mark), you can see that the tail jerked quickly and it sound as though the motor lost power for a split second there. It will keep doing this through the flight.
Do you guys have any ideas?

I'm having a similar problem with my Honeybee King 4 with DX6i TX and AR6115e Rx. The heli kicks ccw 90 def. for no reason. So far I've changed the rudder servo with no luck. I have a new gyro on order to see if that's the problem. Checked the belt and its tight, doesn't appear to be anything mechanical.

The tail is "jerky" when the motor looses power for that short millisecond or so. I think this is normal as your gyro is holding the tail by keeping the tail rotor blades at a certain degree angle. When the power is lost in that millisecond...the gyro has to put more pitch into the tail to keep a relative heading. So that would to me look to be normal...I may be wrong though.

I would guess that its either the motor itself, or your ESC. Do you have spares of both to try swapping out to see if it cures your issue? Id say change the ESC out first since its the easiest of the two.

I would guess that the reason it takes a minute or so to start happening is because its a heat related issue with either the motor or ESC. Doesnt do it till it gets hot enough, makes a bunch of sense to me.

i agree its either a servo or gyro glitching, have you sprayed the belt and inner boom with silicone spray?  its a must as you may be showing signs of a brown out there too. if it was a belt it would be much more severe.

I'm not sure if it's heat related because it starts doing it immediately. I stripped out the motor on it's own and it seems like the motor is the jerky victim so i'm ruling out my Gyro and because I don't have a spare motor or ESC, I can't test any of the two.

The only reason I didnt think it was a gyro/servo issue is because you can literally hear the motor power cut for a millisecond when it happens.

When the heli is under power...the gyro is constantly trying to keep the tail held.  When power is lost to the motor, even for a millisecond, the headspeed will decrease a bit...and the gyro will have to compensate for this.  Even though it is almost instant...the tail will have no other choice but to show some type of wag/reaction to the loss of headspeed (which directly effects the speed of the tail rotor).

At least that is what I got from the video anway.

I didnt really notice it till I got a few seconds into the video...dont know if it was exactly a "minute in"...but just thought that if the problem came in after about a minute of spooling up...that would be ample time to heat up motor/exc/batteries to generate enough heat, for heat to be a factor in the symptom shown.

I really dont think its a battery issue...although I guess a poor solder job on a connector "could" cause an issue.  But I would think a bad cell or connection would give low/no power at all times...not just intermittent.

At this point...I really dont know.  But I still think looking at the ESC/motor is a good place to start.

Exceed Alpha 400 and Pentium/Hobbywing 40amp ESC are very cheap at HobbyPartz.Com.  Could buy both for probably 40 bucks or less.  And if its not those items...not a bad idea to have a spare motor/esc in the parts box anyway.

goodluck

19 seconds in it twitches the longer he goes the worse it gets, to bad he doesnt have eagle tree to see what the voltages are doing.  what kind of esc and motor ,gyro and servos, battery? how hot are things when they come in after 30 seconds (motor,esc,batt,connections) it could be a bad esc, stuttering /power loss sounds more like the tail blades loosing power then catching back up. this will be a toughy unless someone else had this happen and can pinpoint it. im glad i have full replacement parts for the blade 400 and exi250 (can relace anything to find out whats failing if needed.</p>

I watched the video again...actually 2 more times and now Im not quite certain.  Thanks morgan for making me doubt myself!  LOL

It does sound like the motor is losing power for a millisecond and recovering.  But maybe the sound I am basing that off of is just the less resistance on the tail rotor when this "glitch" happens...thus making it sound like the motor.

Mabye it is a bad servo/gyro.  Do you have another servo to change out and check?

Unlike morgan...I only have a nice cache' of spare parts for my 450.  I really have hardly ANY spares for any of my other helis.  I need to work on that!  But, I have enough 450 spare parts to rebuild from a crash several times.  Probably have TOO many parts for the 450 and not nearly enough(none) for the others in my fleet! 

i wonder how many flights he has on this, i seem to recall the 1 way bearing in the exi 250 going bad in like 4 to 5 hovers and in the exi 450 it was within 20 i replaced both with align and have yet to have problems but i dont recall the tail twitching before failure. however technically the thwap i hear seems to be the tail catching back up lol and if the 1 way is starting to go it could cause this to happen, to hard to determine.

Could be.  Ive not had any OWB issues out of my EXI helis...the 450 or 500.  Both are fine stil.  But you could be onto something.

I noticed the OWB on my CX250SE was cruddy and I had to take the 250 apart and clean it when I was lubing up the bearing and loctiteing everything.

Its definitely gonna be one of those things that the OP will just have to start swapping out things one at a time till he figures out which part is the culprit.  It doesnt appear to be a "settings" or "gain" issue to me.  But like Ive stated, gyro setup is my "weak point".</p>