Weird wobble

[WickedDragon]

I'm getting a weird wobble in the main shaft of my CP.

On the bench, with the blades off, as I spool up everything seems to be fine but when the pitch gets to hover range the head bounces back and forth significantly. Then at full ptich it settles down again... at least most of the time. I replaced the main shaft and bearings. Everything seems to be balanced, flybar weights are evenly spaced, feathering shaft isn't bent, grips are okay. I using a FlightTech rotor head, E-flite aluminum swashplate and MicroHeli Aluminum grips... that all checks out. I would think that if the assembly was out of balance the wobble would continue at full pitch/throttle, but typically it doesn't.

Anybody got any ideas??

[rabidguineapig]

Check your tracking

[WickedDragon]

No blades

[txflyer]

main shaft or feathering shaft

[WickedDragon]

Both shafts appear to be straight, I get the same results with a number of main shafts, but I can try replacing both again. I'm going to replace the bearings again too and check it with just the swashplate, start adding parts and see when the wobble starts.

[rabidguineapig]

Maybe replace the bearing that hold the main shaft? only other thing I can think of... if those bearings are off than you'll get a lotta wobble

[WickedDragon]

That's what I'm thinking....I'll let you know.

[Mortificate]

If you still don't get results I put my money on your main gear. This weird wobble thing has happened to me several times and it seems to go away when I replace the main gear. If you haven't replaced it already I bet that is your problem.

[Smiley]

Check your flybar paddle tracking. In a crash they can come lose or turn slightly. Good luck.

[rabidguineapig]

I'm getting this ridiculous shaking when I get my pro into a hover, its so bad I can't even fly it, I almost crashed into a light pole actually... maybe I'll try replacing the main gear

[borocouncilman]

I'm getting this ridiculous shaking when I get my pro into a hover, its so bad I can't even fly it, I almost crashed into a light pole actually... maybe I'll try replacing the main gear

The Blade CP main shaft will bend if you look at wrong. It sounds like yours is bent.

[txflyer]

micro heli autorotation main gear with ejector pin main shaft mod..enough said..

[rabidguineapig]

what is the ejector pin main shaft mod, got a link? I love the T-Rex Jesus bolt instead of the stupid pin... thats what pissed me off on the blade

[cltmte]

If you cut a short length of a standard paper clip and use that as the pin (bend both ends to ensure it doesn't fall out) and it will sheer off quicker and easier in a crash than the stock pin, reducing damage to the heli head and main shaft.

[rabidguineapig]

cool

[WickedDragon]

I tore everything down and rebuilt it....again. Put it all back together and got even more wobble..... double checked everything and realized that the blade grips were reversed..... duh. That's what I get for staying up too late and R/Cing!!! Put the grips back on correctly this time, but still had the wobble. There was less, but still there. Everything was dead on and dialed in....... changed over to Hitec HS-55's, got rid of the ducted fan tail and went back to twin motors.... so I flew it anyway. It was the perverbial A rock on a string in the air, but just before lift-off it looked like a jumping bean. Hit a little too hard on a landing and the wobble's gone..... go figure!

Of course then it ballooned in the breeze hit a tree branch and came down in a "controlled crash". I only bent the main shaft and the boom...... easy enough to fix....... BTW the wobble is still gone, but get this....... when there's right rudder input (from me or the gyro) the pitch servo goes crazy in the negative direction. Collective seems to be is fine. I think I killed my RX.

[Skiddz]

Just because the paddles are the same distance from the flybar cage doesn't mean the flybar itself is centered. Pull the paddles off and measure the flybar from the cage to it's end on both sides. make sure they're identical. Screw the paddles back on and measure between the flybar cage and the paddle and make sure those measurments are identical.

I wouldn't discount the main gear either. Most of the "new" ones I got had bent shafts and needed to be straightened before I could use 'em.

[WickedDragon]

Thanks Skiddz!

I checked everything again and you were right about the wobble being the flybar. It was centered but was bent slightly inside the flybar cage. Must have hit harder than I thought. I'm using a FlightTech Aluminum frame so I knew it wasn't landing gear.

BTW all.... The possessed servo was due to the TR ESC going bad!

[jediwannabe]

After replacing the usual suspects:

Main and spindle shafts and possible the main bearings.

Make sure the frame is not CRACKED near the bearing housings! Somtimes these cracks are hard to see with no load, but as the head spins up the plastic allows the bearings and shaft to wobble.

Second possible problem could be the main rotor speed.
Is the head too stiff? If your head is packed to tight (too many dampners or washers) the stock motor does not turn enough RPM to run a real tight head. I replaced the rubber dampeners with bearing once to tighten mine and it developed a nasty wobble...

Sometimes the stock motors can wear out quickly and the lack of head speed will make the head wobble also. After returning to rubber dampners she was fine for a while but I saw the "wobble" come back.
A quick trip to the LHS for a $9 main motor she was good to go.


I fly a BCPP with stock motors cut down Pro wood 325's on a DX 7, no gyro, Stock 800mah lipo's. Great yard bird.

[WickedDragon]

No frame, motor or landing gear issues here. I'm using a FlightTech aluminum frame with an E-flite Park 370 BL main with a CC Phoenix-25 ESC, CC Pixie7a with a GY401 for the twin motor tail, A FlightTech head and hardened feathering shaft with MH aluminum blade grips turned by a Century Auto rotation setup, HS-55 servos and a Futaba R146iP RX, It's got a couple of other custom built parts too....... the Blade that thinks it's a TREX!

Here's a few pix.......
(The yellow and now blue one)