PilotLight

My Feedback: (1)

What is the deal here? For some reason, lately, my Axe has an unusual problem with suddenly changing collective. I'll be hovering and next thing I know is the Axe is dropping like a rock for about 3 feet. Either it recovers itself, or I've been able to catch it by adding lots of collective. Other times, it will suddenly climb straight up and then return to hover. All the servos seem to jump as I hear the motors and gears make sounds like they are moving. Strange it doesn't change direction as if only one servo moved or failed, or it there was a radio glitch.

I've tried cleaning off the shaft under and over the swashplate and adding some lubricant thinking its was getting hung up on some dirt. Hasn't prevented it yet. Could it be the potentiometer in the Transmitter? Other ideas as to why this happens?

Anyone else see this strange occurrence?

gibbonsbunch

My Blade CP Pro is doing the same thing and I can't figure it out either. I have changed the main drive gear and shaft and also made sure the tracking was correct but these things did not help.

ElectricHead

Will it drop after you make a cyclic input? Mine seems to drop if I add aft cyclic (back). I am rebuilding after a crash and I am putting in HS-55 servos. Will post how they work when I have heli going. I was looking at swashplate the other day with no rotor head on and was moving Tx sticks around and when I input cyclic the swash was moving up and down a little. Can you check this out on you heli and report what your swash is doing? Perhaps this may cause some of the up/down jump.

calcop

This should explain it:

[link=http://www.rcuniverse.com/forum/fb.asp?m=5325734]http://www.rcuniverse.com/forum/fb.asp?m=5325734[/link]

quickster47

Sort of sounds like a sticky collective issue where there is something binding ever so slightly in the head having to do with the feathering shaft. Sticky because when you input some cyclic nothing happens and nothing happens and then suddenly the binding stops or frees itself and the cyclic catches up and up your heli jumps.

If you rebuilt this part of your heli I would make sure everything is moving very, very freely and nothing is binding.

There are several threads about this subject regarding other helicopters on this forum and the one at RC Groups.

Carl

Blusaber

Hi

I had this problem until changing out the servos to 55s...... problem gone steady as a rock now. My last flight with the stock servos ended in a 15' straight drop out of the sky I don't know if the servo striped then or when earth met heli> the best upgrase you can make IMHO is the 55s. On another forum it was posted that the stock servos had to much travel and were binding the swash causing erratic behavior and eventual striping of the servo....Food for thought..... his solution was to move in one hole on the servo horn to reduce travel.

Gary

PilotLight

My Feedback: (1)

There is a slight vibration problem with the heli. I can't seem to locate where it is coming from. Everything looks like it is where its supposed to be. Perhaps the vibration is causing the "binding" problem by creating more friction.

I checked the blades to be sure there was no damage and no elongating of the mounting holes. Good and snug. Tightened all hex screws and nuts, nothing was loose. Besided taking it apart and checking the center hub for out of round, I don't know what else to check.

Guess I'll fly it 'till it breaks, then start looking for the vibration and replacing servos. Why fix it, if it still flies?

Heliko

Hey PilotLight,

If you haven't done it already I would remove the blades and spin it up. It will be easier to track down the vibration and if it goes away you know it's in the blades.

Good luck!

dfalcon

My Feedback: (76)

It'll fly much better without the vibration. The vibration will also cause premature wear and failure on a lot of different components. I got rid of 90% of the vibration I had by balancing the blades, then balancing the whole rotor head assembly with the blades on. I don't have any specialized tools for balancing the rotor head, so I took the spur gear off the main shaft, then put the shaft and head back onto the heli as they'd normally sit. I turned the heli so the shaft was parallel to the ground and found that one side was heavy, although the main blades were perfectly balanced. It was a little harder to check the balance in the direction of the flybar, but I did it.

Two little pieces of scotch tape, one on the C.G. of one of the main blades and one on a flybar paddle, worked wonders.

I've also noticed that having bumped a flybar paddle accidentally, changing it's angle, while installing the battery and canopy can impart significant vibration to the heli. This is obviously fixed by checking that the paddles are level everytime before you fly.

Ghost-Rider

I have the same problem. When my AXE is in a streight hover it will often loose altitude for no reason.

no hesitation

I had a speed control glitch in my first Axe. It would also drop suddenly. I thought it was my newb thumbs untill I let a pro fly it. Thank God for return policies and reciepts. My new one is much more stable.

ElectricHead

Here is something I was thinking about in regards to this altitude changing. I get my heli in a stable hover and if I add any tail rotor change I get an altitude change to some degree. So I was thinking that if you add power to tail rotor motor then you take away a little power from main motor causing RPM of main blades to sag a small amount. Then heli will drop some. If you take power from tail motor and let torque turn the heli then main motor gets a little more power and heli gains some altitude. If you hold the throttle stick at one spot then you have only so much power flowing thru system. If you make a correction to tail then the power is the the same but the distrubution of power is changed. I work my throttle quite a bit trying to get that dead on hover with no drift anywhere. Kind of a game for me. Some folks say it could be binding in system and I believe that will contribute to problem also. Gyroscopic precession may add its effect also. I think it is a combination of a few factors. Let me know what you think about this.

PilotLight

My Feedback: (1)

Its not a gradual change in collective but a violent change. I mean WHAM its headed straight down, then Stop! Like it goes to full negetive collective for just a split second, then back to normal.

Or to full postive collective, then normal. I'll have to do more checking to find out what's happening. If I find out before it self-destructs, I'll post it here.[X(]

dfalcon

My Feedback: (76)

I think it was quickster that led me to the solution over on rcgroups. Check the washers on the spindle shaft, particularly the one between the retaining screw and the ball bearings inside the blade grip. The washer on mine was cupped slightly, and after reassembling the head, I had inadvertently put the washer on bacwards causing it to contact the outer ring of the ball bearing. After turning the washer around, the heli hasn't been 'jumping' on me anymore.

ElectricHead

Are your ball links free? I had to sand my balls[sm=regular_smile.gif] to remove some flash on them and ball links were much more smooth.

VBDave

TMI ElectricHead... T M I...

RCMDLR-RCU

My Feedback: (10)

A short story, followed by my OPINION based on MY experience, past and present.

I traded for an AXE CP from a fellow club member who had given up on it. Seems he thought he could not handle it or that it was too sensitive, had crashed it, and given up. After $30.00 worth of parts, I had it ready to go.

It was immediatly apparent something was wrong, this was not normal. Idle up produced the same results, only faster.
All the info above is good and worth concideration as possible causes, but this is extreme behaviour I am referring to.

I knew (i think) what was happening and a quick check proved that the servos are junk. They are in no way appropriate for the task at hand, they are way too sloppy and, I believe, are allowing the pitch to change at will.
They FUNCTION, OK, and I am sure they would work fine in a little foamy flyer or such, but IMO not to hold the swashplate on a heli.

I have HS-55 coming and will report back to any inquirery regarding my results.

My bottom line, check your servos, see what YOU think.

Sandy what? I thought that only happens at the beach...

Prontow

Same problem with the violent altitude change, straight up or straight down VIOLENTLY. I installed new HS-55 servos this weekend, and there is no binding on my main shaft, problem persists. Radio glitch?????? I am going to clamp my heli in a vise and run it up so I can watch everything under a load. Hope I can see something. Anyone consider a different radio? Futaba maybe?

dfalcon

My Feedback: (76)

I've even had the problem with HS-55's installed and using my Futaba 9CAP. I have to insist it's a problem that arises when rebuilding the head--just putting a tiny little washer on backwards against a ball bearing is causing a sticky collective.

Is anyone having this problem before they've taken the head apart to replace blade grips yet?

Prontow

Has this problem been seen with both the plastic and the CNC blade grips? Maybe binding between the head and blade grip at the washer between the two?

dfalcon

My Feedback: (76)

As I mentioned in post#14, my problems were caused by the washer between the screw that goes into the end of the spindle shaft and the ball bearing inside the blade grip. I haven't had any problems since turning the washer around.

EDIT: After changing the blade grips on my Axe, I noticed that if I tightened the screws fully into the spindle shaft, the blade grips were difficult to turn by hand. I loosened the screws a little so that the blade grips would turn freely, and accepted this as normal. After turning that one washer around, I could tighten the spindle shaft screws all the way, and the blade grips would still turn freely. There's a lot of info about this particular problem in the Blade CP threads also. They have a 'stepped' washer on the end of the spindle shaft, where the 'step' is placed agains the ball bearing's inner ring. I noticed that the washer on mine was slightly cupped, and when I put the convex side toward the ball bearings, my problems were fixed.

After getting this issue fixed and balancing the entire rotor head, the Axe has been a joy to fly. It was great last weekend to finally fly it without watching the antenna tube vibrate like all hell's breaking loose. It's been so great that yesterday I ruined one of my TP 1320's. I had expected it to happen sooner or later, though--it was an old pack without balancing leads--and one of the cells puffed on me.

RCMDLR-RCU

My Feedback: (10)

Good advice all around,

I will check the washers while waiting for the servos. I have not had the grips apart, but perhaps some else did.
Entirely unacceptable as is!

PilotLight

My Feedback: (1)

I haven't rebuilt my head yet. It's still the way it came from the factory, so it can't be an incorrectly installed washer. My last flight last week had only one occurrence of this "Glitch". I found, after removing the blades and running the heli, that the Side Block and Center Hub were wobbling at the top of the shaft. I tried to apply a little force to straighten everything out, and it helped a little. Not as much vibration and only one glitch after 4 batteries. Its still not perfect though.

It could be interferrence from the Flourescent lighting. (or from my fillings cause I'm grinding my teeth trying to hover nose-in)

dfalcon

My Feedback: (76)

I thought of radio interference for a while, but it seemed improbable that all three channels controlling the swash would experience a glitch in the same direction--without any apparent yaw or throttle glitching. Mechanical problems seemed much more likely.

RCMDLR-RCU

My Feedback: (10)

DITTO...