Blade CX2 yaw/hover issue

[ian928]

I recently replaced the outer shaft because my gear was missing a couple of teeth and now I have a hover issue that I can't figure out. I set up the proportional mixing so that the tail would have center trim.

It hovers okay for a little bit but then starts yawing to the right. Just a little at first which I can correct for with trim, but then it starts going faster to the right and I run out of trim and it's still going to the right. I now am having to hold some left rudder with the trim all the way to the left and then I start losing the ability to hover. The heli drops down at full throttle and lands or maintains a hover about an inch up at full throttle.

I replaced both main motors and the 4-in-1 and am still having the issue. I tried playing with the proportional mix and gyro gain. When I adjust the proportional to have some right yaw immediately and I let it yaw to the right I have full power available.

If I try to fight the yaw by adding left rudder it starts dropping a few seconds later. If I fly around in circles to the right or hover to the right I can stay aloft. Sorry for the long-winded post but I wanted to accurately describe the symptoms and what I had done to try and fix them.

Please help!:(

[carlo_the_wonder_frog]

this problem will be solved by a new battery, if you are flying the heli until it starts to lose power and no longer will hover, then you are ruining the LiPo battery, NEVER fly on a LiPo til it stops due to all the juice being gone, thats the #1 killer of LiPo. as soon as you first notice the power dropping off then you are done flying. Get a new better Flightpower or Thunderpower battery and all will be better again.


The reason it changes yaw trim so fast is because the battery starts losing its voltage really fast because it has been abused.

[ian928]

Thanks for replying but it's not the li-pos. I have two and I also tested it with a known good one at the LHS that hovered a different CX2 just fine immediately afterword without a recharge.

[carlo_the_wonder_frog]

Have you removed all your bearings and checked them out, any notchy or gritty feeling ones need to be replaced. Also when you adjust the proportional pot you are unplugging the heli everytime right?

[heyjack8]

you never said why you replaced the motors in the first place.... make sure flight bar is straight to....i know my cx2 does not stay straight all the time with out some stick input........even though its small adjustments it still has to be done i think you will see most cx2 owners have to make adjustments related to battery condition drops in voltage....you may alsi have a heat problem which will affect the 4 in one ability to mantain heading....im not a pro but these are some things that pop into my mind......also you may have a bearing problem which is causing you top blades to bind up and take you off your heading....also with stock body i have noticed the blade turbulance (prop wash) to be a problem so i have upgraded my tail assembly....seems to hold better...also are blades in good shape... i have installed heat sink and have holes cut in canopy to help remove excessive heat....the other thing that i might try is turn your pot adjustments all the way to the right and back off 1/2 turn and test.....thats what e-flite told me when i was having trouble with yaw......good luck.....

[ian928]

I am turning off the heli for changing proportional. I also have a heat sink installed on my motors. I replaced the motors because I was troubleshooting the problem. Same with the 4-in-1. My blades and flybar are in good shape. I think you guys may be on to something with the bearings. I haven't checked them yet. I figured it had to be something mechanical since I already replaced all the electronics except for the transmitter and servos.

[heyjack8]

hey buddy i just got to looking at my cx2 today if you grab the inner shaft at the top and hold the body firmly even put your fingers on the gear at the bottom i have found some play in the shaft its almost as if the bearings are moving in the housing or something...it doesnt fly to bad but i dont like the play that isnt condusive to good quailty flight......i really dont know if thats the way it should be or not i have experience with electric motors and bearings and play is not a good thing...makes your shaft whobble.....i cant believe they could be worn out already i havent got that many hours on this thing.....maybe there just cheap....i really dont know the jury is still out on this issue.....

[pittsjock]

I am a newbie with the CX2. I upgraded mine with a replacement aluminum lower head and swashplate. The heli is much more responsive than stock, but would not hover very well. I would describe it as oscillating randomly. It wasn't uncontrollable, but made it hard to hover steadily.

I have been flying a bunch lately and today decided that I wanted to stop the oscillation. I checked throughout the head for loose parts and found that there was play in the main shaft which allowed the main gears/top blade to move up and down a bit. I loosened the clamp on the lower gear, pushed the gear toward the main rotors while holding them tight and removed the slop. The heli hovers beautifully now.

[fdrotormedic]

I too have had this problem. It is a characteristic of the CX2 and it really has a lot to do with the battery and duration of flight. When newly charged you can trim the yaw perfectly. As the motors heat up and the battery looses power the CX2 will begin to yaw to the right which will require some more trimming. Towards the end of the battery, the CX2 will require a little rudder input to keep it straight. The heat sink helps. Vent holes in the canopy will also help to keep the motors cool. The porpotional pot mix can be adjusted but will quickly max out.

[ian928]

The problem I'm having isn't normal. The problem is that when I hold left rudder to compensate it will lose altitude after a few seconds and be unable to fly. If I wait a little bit and then take off again I can climb out fine as long as I don't try to prevent it from yawing to the right. It used to fly fine. This is a problem I started having in the last month or so. It might be a problem with the bearings. I haven't had a chance to tear it down and check yet.

[skigolfmike]

I've had something similar with mine. I think someone else suggested using a better TX. Since I have a DX6i for a Blade 400 I haven't flown yet, I setup my CX2 on that. Basically, it didn't make a difference. At about 2/3s flight duration the yaw trim goes South and it take more and more left rudder to hold heading. It's more of a nuisance than anything and it doesn't take much to get used to it.

My CX2 has the CNC lower head and swash plate. I also added a heat sink to the motors. Lastly, I moved the cyclic pushrods out a hole on the servos to get more response and upped all the throws to 120%. It's significanly more responsive than stock and is several times faster in forward flight.

[Blue Thunder]

Hey guys,
I'm new here and just got a CX2 for Xmas. I am now hooked hard on heli!
Any how, after flying my CX2 for a good 7-8 min. straight, I temped the stock
motors and one of them was 15F different. This may have something to do
with the yaw.

[Spahic]

I have been having the same issue... I pulled the left motor and found the internals to be very tight compared to that of the right motor... Anyone else find this... It would explain the power loss as the current draw on that crappy Li-Po battery would be way higher....
Also, Anyone find a longer lasting, faster charing battery for these things... 2hours - 15 minutes is starting to suck ..

Thanks
:arggg:

[TowPilot]

The problem I'm having isn't normal. The problem is that when I hold left rudder to compensate it will lose altitude after a few seconds and be unable to fly. If I wait a little bit and then take off again I can climb out fine as long as I don't try to prevent it from yawing to the right. It used to fly fine. This is a problem I started having in the last month or so. It might be a problem with the bearings. I haven't had a chance to tear it down and check yet.

You mean that when you apply left rudder and then add full throttle it still descends?

This happens to me but only on the one battery I have which has become very weak.
Do you have a second battery to test with to eliminate that as an issue?

[TowPilot]

I have been having the same issue... I pulled the left motor and found the internals to be very tight compared to that of the right motor... Anyone else find this... It would explain the power loss as the current draw on that crappy Li-Po battery would be way higher....
Also, Anyone find a longer lasting, faster charing battery for these things... 2hours - 15 minutes is starting to suck ..

Thanks
:arggg:

The motors are not expensive and under such duty, to have one fail is not too surprising. To replace a motor is about on par with having to replace blades or bent shafts.

Replace it though soon because if it is stiff, it is drawing a lot more current through the FET on the 3 in 1 for the entire flight and heating up the 3 in 1 more than normal which could shorten or end it's life soon.
A failed 3 in 1 is about $50.

The LiPo is a LiPo, as long as you keep the run times such that no more than 640 mAh's is drawn from the battery, the service life should be a good long time. The stock charger does not let you know how many mAh's are being put back in but I have a charger that does display how much was put back in. At 7 min, it is around 600 mAh, so I set a timer for 7 min and then the battery won't be run down more than the recommended 80% and shorten it's life. I used to run them until the power fell off and those 3 batteries are now weak compared to the replacement batteries which I've been better caring for. Don't need a fancy charger, just a timer to cut the flight off at least a minute before the loss of power is evident. Takes a little discipline to do so :)

The mAh rating determines how long the battery will last. The answer is more batteries. For faster charging, the answer is a more expensive charger. The cheap Lightening Power charger I have takes about an hour to charge.

Larger batteries equal more weight, more work for the motor, more current drawn to lift, more heat on the 3 in 1 and the motors and this extra current draw works against the extra battery capacity of the heavier battery.

Even the larger helis don't fly much longer when doing 3D.

[ChunkyMonkey]

hey guy, im new the cx2 aswell and i ran into a problem with the same symptoms as your problem. Try taking the heli all apart and rebuild it. Play close attention to the lower blade mount and use a sharpy to make sure you put the screw in the holes of the shaft. also make sure youre tightening the lower gear down onto the flat part of the inner shaft. either of those to mistakes could be giving you what youre experiencing. hope that helps. rebuilding seems to work well for me;)

[Nitromethane]

The sheer weight of the flybar is enough to heat the motor responsible for the upper blades, a bit more then the lowers, which are only turning blades.The 'upper' motor is likely getting hotter then the 'lower' motor due to strain...in turn causing a gradual loss of performance in that motor during flight..try to only be airborne for like 3 minutes at a time then set er down and let the motors cool for one minute then try it again. Constantly adjusting gyro pots in the receiver will only end up in headache for the guy who expects a 200$ electric heli to fly 'perfect' all the time.