FishRider

Ok, I have read every post here and on other boards I could find on this topic, but I cannot seem to find an answer to my problem. I have a Blade CX that started to get a shake. I have torn the thing down several times and replaced the inner and outer shafts. I have made sure the fly bar is balanced. I have CNC top and bottom plus grips and aluminum top bearing. It has always flown well until a couple days ago. I have gone through every step I can think of from starting with nothing and then adding each additional component. I think the problem might be in the top, but I can't confirm this. When I spin the shafts at low speed everything looks fine. When I hold it and spin it at top speed everything seems fine, but when I try and get it in the air it develops this back and forth shake. I have worked on this for two days straight. Any other suggestion? TIA

rchotrodz

I had this problem with my cx2 it was a small chip on the upper blade it drove me nuts because you could barley see the chip in it

FishRider

I am thinking it may be something that simple that I am missing, but as of yet I have not found the issue. BTW, I did replace all of the blades as a possibility. I even replaced the inner gear. The only thing I have not replaced are bearings and the aluminum parts. Unfortunately, I have none of the old plastic parts as I broke those long ago. I refuse to buy all new parts just to figure this out.

pikester

try a pair of new blades.

Doahh

strutz52

have you checked to see if the swash plate is connected

JPEE

Hello Rider,

I have read all of this thread and don't see any remarks as to whether you crashed and this shaking then occurred or not? It makes a difference as to what your issues could possibly be. With that said I am going make some suggestions for you.
Pull down the entire gears and main shafts and remove your blades. Take your main shaft and chuck it up in a cordless drill about a quarter inch and slowly bring it up to high speed (wearing safety glasses). This will determine new or not if that shaft is bent or if the bottom gear is warped. Next, put the inner shaft in the main shaft without the blades and leave off the top blade gear at the bottom and there will be enough center shaft to hook your drill to. This will again allow you the ability to spin the inner shaft through the main shaft checking all bearings and collars. If that all test shows good then re-install all to the chassis. Again while leaving the blades off run the motors up spinning both shafts withoutthe fly bar in place. Next, take your fly bar and pop loose the linkage that connects to the upper blades, just leave it loose floating on the metal. Once this is completed you will now be able to roll the fly bar on the table and look for any humping in the bar as it rolls. If those steps still show no issues then install the fly bar and just the upper blades and do a test spin again. Your last two things to check are your swash plate and lower blades. I have had happen to me my swash plate come apart under power but when looking at on the bench it looked fine. If yours is plastic look underneath and you will see a cone type affair that comes through the top and spreads under the plate. That flare has worn out on me twice and then under the power of flight is comes apart and the Heli is all over the palce. If your running an aluminum swash plate you need to spin that inner bearing and see if there is a rough spot or possible dirt got in. You mention you have changed blades but you make no mention to the fact that you are checking them for balance or for being warped? The story goes if you take them from the same pack they are matched, bull pucky, I have had them where their individual weights were grossly different. I also have to assume that you are testing your blades for their flatness and true form. If not, go to YouTube and plug in "CX2 blades" and it will come up.
And lastly I am giving you a web site that was helpful to me in the beginning and they speak to your issue too.
http://www.heli-wiki.com/mediawiki/i...et_it_straight

Good Luck and let me know what you find.

JPee

FishRider

Thank you for all of the pointers. The drill trick was a great tip. Unfortunately, I still have not tracked down the cause. I am off to the LHS to get a couple different items so I can try a slightly different set up. When I put the inner shaft on the drill it was bent slightly, but I do not think it was when I bought it. I straightened it out best I could, but that did not solve the problem. My current theory is that the top aluminum rotor head might have a very slight bend in it which is hard to see when I spin on its own but gets exacerbated when the fly bar and blades are attached to it. I think the out of whack rotation is what bent the inner shaft. Seems ridiculous that a small crash could wreck that small piece of metal. That's why I bought it in the first place. I was tired of buying new upper heads.

I did crash the heli before this started, but it was very minor. I have had a lot worse wrecks and never had this kind of an issue. There were no broken blades or other discernible damage. I guess it is possible it was worse than I thought.

The shake is very bad making the helicopter un-flyable. In the past this heli was amazingly stable when I had it dialed in correctly. Even with a slightly bent fly bar or a chipped blade the heli would perform admirably which is why this problem really has me vexed. Its tough because when I spin the motors up on the bench whatever wobble or vibration gets dampened through me when I hold it down making any variation in the spinning hard to see. Of course, once I let it go on its own I assume all of the vibration gets translated directly to the body causing the drastic back and forth wag.

FYI: This is a blade CX with CNC top and bottom rotor heads, CNC blade grips, metal upper bearing holder, and CNC swash plate, with stock fly bar and I use Axe EZ blades.
Blades are balanced, flybar is nice and straight and moves freely, swash plate is good, outer shaft is straight, gears are fine.

Pretty much leaves me with upper head, upper bearing holder, inner or outer bearings (although I think the bearings are fine). Did I miss anything? I am going to track this down.

evdreamer

Do you still have the plastic parts? If so, just replace one part at a time with the plastic ones if the vibration goes away you found the culprit. If you replaced all the aluminum parts and it still vibrates then you know it's not the aluminum parts. I have been in a couple of crashes with aluminum and it hasn't caused me a problem after the fix. Since the aluminum is a little heavier it could be amplifying something else that's wrong.

Nick

FishRider

I have been able to replace either with new parts or old plastic parts: Top rotor, inner shaft, outer shaft, swash plate, fly bar, blades, inner gear, top and bottom blades.

I have not been able to replace: Top bearing hub, bottom inner bearing, both both outer bearings.

I have tried multiple configurations. I have even taken off the CNC blade grips and put on some new (balanced) E-flite blades. All with the same result.

Could it really be the bearings???

Could the motors be shot? I really have not flown this thing that much.

MY nearest LHS did not have the bearings. I might have to drive across town to find some. This is getting ridiculous. [&o]

evdreamer

Sorry you can't get it to stop shaking. Don't give up on it. Almost everyone in this hobby is going to run into something that frustrates them. But when all of that is over it is a lot of fun. I was just thinking did you check the servos? If you move the servo horn by hand does it make a bad noise or not move at all? Or do cyclic movements on the ground and see if a servo is twitching.

Nick

FishRider

OK...

So, I may have wasted a lot of time. I am not sure. I went across town to a LHS and spent an hour or so with a very nice guy there. He was nice enough to even let me try on a couple of parts without buying them. Nothing had any effect. Until... we were both lost and he said why don't you put the body on and try it out. My thought was that since this is a coaxial heli that the body is purely cosmetic, But when I put the body on it flew just fine. Did I mention I was trying to fly it without the body. Thing is, I had always done testing without the body, I just never tried to put it in the air. Plus, I have read somewhere else that this platform should fly without the body.

The $5 dollar question is: Will this heli fly without the body, or does the body offer some kind of support or dampening?

The reason I had torn it down and tried to fly it without a body was that I was planning on putting a boom on it, which I assumed was just cosmetic. I did try and fly it once with just the canopy and it seemed to jump a little at first and then calmed down. So maybe there is something to the design that requires some sort of shell or stabilization. Please educate me.

Really, I just want to fly. So if there is something wrong that is canceled out by the body then so be it. I'll be happy with what I have.

If in fact, I have wasted my time and an extra few bucks on parts I didn't yet need because I was ignorant, we'll I can accept that. Wouldn't be the first time. Actually, this would be preferable than finding out that I have an unsolvable issue. There is silver lining to this. I know more about this little model than ever before, and I could, probably, tear it down and build it back up with my eyes closed.

evdreamer

Good to hear you got your CX flyable. Now that you brought it up I think someone posted a similar problem a long time ago and had a video of it. And he put the body back on and it work just fine too.

Nick

ajpetty

Have a Blade CX 2 & 3 that were given to me from a friend (maybe not much longer if I can't get the problem fixed). My problem is only on the CX3. The other one flys great.On the CX 2lift off is good, and have plenty of power, and its flight is a controlled one.The problem I have only occurs when attempting toput it into a hover. It will startthe hover, but then its impossible to hold it there. Trimming has noeffectsstopping the problem.The chopper will begin to rotate in a circle clockwisemannor goingto the right and back and repeat the movement until it doing fullcircles, and unless I go intoforward flight the circlesget larger and larger until I finally force it into a landing. By rotate I do not mean like you are applying right rudderand have the nose turn. Its the whole thing. Any help would be nice. Jim.

FishRider

It's been awhile since I have messed with the old version of my CX2. My CX2 has been heavily modified and brushless for awhile. However, I would initially say that you have a tracking problem. When you hover the heli do the top (or bottom) blades look like they are spinning flat or do they look like they are coming apart. Of course on the CX3 I do not think you can adjust tracking on the bottom blades. Technically, they should track perfectly out of the box. I made a modification for that as well, but for a stock bird you can and should adjust the tracking of the top blades. You do this by lengthening or shortening the ball link between the blades and the shaft. Take the link off one ball and turn that link one turn left or right and see if the blades look better or worse. If better than you went in the correct direction. If the blades look further apart in hover then go then turn the other direction. Do this until the blades look flat as they spin in hover. GL.

-Fish

ajpetty

Hello Fish. I think I figured out the problem a few hours after posting this problem. My tracking is almost perfect, andwhen I add full power it still looks good. She flys good with some minor virbration, and a little whinning noise that I don't hear on my other ones. The real problem wastrying to hold itin a hover without it starting to fly in a circular motion. I found myself constantly fighting the controls to keep it in one spot, andthe nose stayed pointed in the right direction.Thewhole bird would start into circular motionsmall and then increased and kept getting wider and wider until I pulled it up and went into normal flight.I t was very hard to hold a hover. I have several CX 2's and 3's and have been flying them for years.I have never encountered this type of problem, and figured I would check out the site to see if other people has encountered the same problem,Well to make a long story short, I replace both drive gears wheels,inner and outer shaft assemblies as well as the balance bar and rotor head. The vibration stopped, and it does not sound like a coffee grinder any more. However,the hover problem is still there but not like it was before. Anyway I will putz around with it some more and see if I can't nail it down. Anyway thanks for your help. Have a Happy Holiday. Jim

FishRider

Sorry, I didn't get from your post that you were a veteran. I would have moved to other ideas as well. You would think changing all of that would have solved the issue. These little birds can be finicky though. I had times when I would, literally, tear the entire heli down into its component parts and then put it back together to see if I could find a problem. Sometimes it worked and other times not so much. Bent gears, shafts, unbalanced blades, flybar a little tweaked or somehow doesn't agree with the flight characteristics of a particular setup, goofy gyros, etc etc. Sometimes the bigger birds are easier to diagnose because the tolerances are not quite as strict as with smaller helis. Merry X-Mas.

-Fish