View Full Version : CP Pro 2 Bouncing

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05-23-2009, 04:45 PM
For lack of a better term my CP Pro 2 has started "bouncing" up and down with no movement on the throttle stick while in hover. I just finished rebuilding after a crash and obviously put something together wrong. I replaced the main shaft, spindle, feathering shaft, blades, flybar and a servo. I know I read somewhere that a bent feathering shaft can cause this behavior but since I just replaced it this can't be the problem. Anything else that can cause this other than a faulty ESC?


05-23-2009, 06:41 PM
Solved the problem. Installed retaining collar upside down on main shaft. I'm thinking that this was causing too much friction between the retaining collar and frame. If this happens to you make sure to install the retaining collar with the tapered side down towards the frame.


05-23-2009, 11:51 PM
Glad you solved it. Any excess friction can definitely cause all sorts of shakes and wobbles. My Pro 2 is doing the Hula after I rebuilt it today. The whole thing sort wobbles like a warped hub cap as it flies. Looks like I get to take the head back apart and figure out what I did wrong. Maybe I'll post a video of it if I can get my neighbor to hold the camera.

cold duck
05-24-2009, 02:32 PM
Solved the problem. Installed retaining collar upside down on main shaft. I'm thinking that this was causing too much friction between the retaining collar and frame. If this happens to you make sure to install the retaining collar with the tapered side down towards the frame.

After reading your post I looked at my birds and yes, I have the retaining collar installed upside down also. However, I've had it that way for many months with no problems. I'll flip it right side up to see if there is any difference. Somehow I missed this during my many rebuilds. D'oh! :arggg:

05-26-2009, 12:51 PM
I've always wondered about that collar.....

BTW..... if you use one of those ribbed washers under it, you can use it upside down with no issues!

05-26-2009, 03:11 PM
WickedDragon: Great tip! I ended up doing that when I stripped the stock collar -- ended up using the stepped washer and one of the collars off a broken flybar holder...

05-26-2009, 03:18 PM
My collar hid from me on the bench..... couldn't find that little sucker to save my life.

I did the exact same thing....which is how I determined that you need the washer. Of course as I was putting on the 2nd main blade, I found the collar!

BTW...... I also use one of those washer on the bottom side of the mainshaft. I never like the plastic hub on the main gear against the bearing, Still use it with the auto gear too!

05-26-2009, 03:36 PM
Someone is always saying things like...... if it wasn't for the bad times, you wouldn't treasure the good times..... or some variation of the theme. It works here too.


Improve blood circulation
Increase body temperature
Build character
Allow you to spend time with the family
Justify the cost of the Sim to the other half :thumbup:
Give you opportunities to try those new blades you been eyeballing
Improve your mechanical abilities
decide on which new upgrade
ensure that the parts aren't going to just wear out
try that new paint scheme
pick up that new 30C LiPo you've been thinking about. After all, you'll need a new taco target :YeaBaby:
ensure that your tail boom is never dull and dingy
try out a new combination of 4 letter words
Fly a plank
Learn where your heli is deficient (Blade forum, right..... this would be the tail!!!)
Find out just how many pieces parts there are in this thing
Prove one or more of Newton's laws Esp. for every action there is an equal and opposite reaction..... like the heli crashed down and I blew up)
Increase spending to help improve the economy :banana

After a while, it's just amazing...... newbie crashes are nothing. Wait until you're running 85-100% throttle with some aggressive pitch curves and you loose a tail at 30 feet inverted..... the sound of breaking carbon fiber is disturbing!

And every time you crash a BladeCPx, just be thankful it wasn't a Rappy90 or the like; given the same crash...... you could at least completely replace your Blade with what it would cost to repair the Raptor!

Hang in there, guys...... if you ain't crashin', you ain't flyin'!

05-26-2009, 07:25 PM
Nicely put!

I feel like crashing my bird right now.....Oh wait, I still have a rebuild to do.


05-27-2009, 10:17 AM
Just wish ours had that little red reset button on the bottom of the Tx!

05-27-2009, 10:05 PM
LOL! Great stuff WickedDragon. I've been thinking about those high altitude crashes lately and cringing at the thought of them. I will soon be entering the higher altitude, faster flight arena and I know there will be some crunching carbon in my future! :shock:


05-28-2009, 07:09 PM
Hi Guys,

I've got the same up and down problem on my brand new CP Pro2. Have 4 hover flights on it now and has done this since first flight. Seemed to almost be related to minor changes in cyclic while hovering. Originally had throttle curve at 0-40-50-75-100 and pitch at 40-45-50-75-100. Made some changes to throttle curve...now at 0-50-85-85-85 and while better, still have the up and down without throttle/collective change. Will look at the collar but I think it must be something else. Almost like a negative mix of cyclic into collective. Don't have the slightest what could cause something like that. Any other ideas???

05-28-2009, 07:42 PM
Two things it could be:
1. sticking (anywhere), things to check:
--> step washer installed backwards
--> cracked center hub (EFLH1145)
--> dampener misinstalled (tough to do)
--> canopy riding on a servo linkage
--> paddle control frame (EFLH1148) tightened too hard (squeezed) onto the rotor head set (EFLH46)
--> Bell Mixer Arm (EFLH1172) tightened too far onto the blade grip
--> a ball link that is too tight (not likely)
--> the flybar not moving freely in the center hub (some poorly molded center hub slots out there)
--> a ball link that is over-installed, past the ball
--> the main shaft retaining collar installed upside down (pointed side down is correct)
--> bent spindle (feathering shaft)

Remove the linkages to your servos, at the swash plate, and make sure everything moves freely. Everything should feel "sloppy".

2. something electrical. Take the blades off and play with the throttle a little. Does it seem to be surging? Keep in mind that this may not be definitive, since the motor is not loaded up the same.

Let us know if you need additional info on the items listed above -- and definitely let us know your progress. Additional help is available...

And of course, let us know what it ends up being! We will probably learn from your experience.

Happy Flying!

05-29-2009, 10:38 AM
Sorry, guys..... just catching up.....you mean it's yoyo-ing.......

Don't know if this will help or not... the orig CP's were notorious for motor glitches. Since we're still talking about brushed motors this may still be the case. An auto main gear will smooth out a lot of these and a brushless motor will take care of the rest! LOL.

05-29-2009, 01:14 PM
I really don't think it is the motor. I have changed the throttle curve a few times to see if that would improve the situation and have been careful to observe the motor sound. At no headspeed did I detect any change in tone of the motor/blades. I am just now sitting down to tear the machine apart and check for some bind somewhere. I'm sure the wife will want to go to dinner cause it is Friday so that will set me back a little in time. I'll post whatever I find.

Thanks Fellas

05-29-2009, 06:27 PM
Well, I thought for sure I had found the problem. Found a very tight ball/link at the flybar control frame. The link was just fine, apparently the ball was a bit big. Some careful sanding with 320 grit got things freed up nice. Check rest of head for smooth non-binding operation, everything is nice and free now. Checked everything on your list without taking apart the blade grips and all is as it should be. I'm getting right at 7 minutes just hovering at 85% power so I don't think I have any kind of a bind in the power system.

The test flight showed no change from before - the Pro is still yo-yoing all on its own. Thanks for your help so far....if anyone has any other ideas, I'm listening!

05-29-2009, 08:48 PM
Unfortunately, you probably need to take off the blade grips and check the step washers...

Review the picture for correct orientation:
http://bladecprepair.com/images/thumbs/blade_grip_screws_and_washers_thumb.gif (http://bladecprepair.com/images/full/blade_grip_screws_and_washers_full.gif)

cold duck
05-29-2009, 10:44 PM
Yup, might just be the sticky collective syndrome. Also make sure the spindle is not too tight but just tight enough.

06-02-2009, 11:11 AM
Update to my yo-yo situation.....tried loosening blade grips just a touch - if any difference it was really minor. Went through head again and this time left servos connected to check and see where the slop might lie. Well, if I lightly grab the leading and trailing edges of the blades, I can rotate them (I'm guessing amount) 3 to 4 degrees just by gently twisting. The slop appears to be around center on the servos as the arms are clearly moving while the servos are not.

Anybody else seen this??? Any fix short of replacing the servos? What is the recommended servo should I decide to replace them?

Thanks - Joe

06-02-2009, 11:24 AM
Servo linkage? I'm still on a quest for microservo arms that don't flex, but sounds like you've got servo problems..... try gear sets.

06-05-2009, 06:45 PM
Mine did the yo-yo..Turned out to be the cheap stock e-flite servos. It works okay on the bench, but under load it started bouncing. When I'm in a stable hover, it works okay, but as soon as I touch the cyclic to correct, it bounces all over the place. I swapped them out with Hitec servos.


06-06-2009, 09:11 AM
Wow. Never heard of that, and I have been using the cheap stock servos for the past 2 years (same ones).

Are you sure you didn't have stripped gears?

06-06-2009, 09:29 AM
I am tending to believe it is the servos also. I can't find anything else wrong. I will say that I did find a few things that I fixed that have helped with the way it flys in general, but have been unable to stop the yo-yo.

If I switch servos to Hitec, what is the suggestion.....HS55's??

BTW, now up to 9 minutes in hover - guess she is getting broken in!

06-06-2009, 09:34 AM
You are doing great!

Don't overdischarge your batteries - fastest way to shortening their life.

Happy Flying!

06-08-2009, 09:00 AM
Wow. Never heard of that, and I have been using the cheap stock servos for the past 2 years (same ones).

Are you sure you didn't have stripped gears?

I'm tellin' you Tut, You should bronze those servos..... that's amazing. I seriously must have a dozen dead ones hanging on a nail! That doesn't count the ones HH replaced.