My blade CX2 has a forward and backward motion (swinging, stuttering, wobbly)when flying it in a particular direction. If I am flying it forward, it will go forward, but it seems to stutter forward because it goes backward a little. It is not a smooth forward movement. It is hard to explain. But, this motion makes it harder to fly. I started to notice this after a crash. But, I have replaced everything that broke in the crash. I replaced the inner shaft with the aluminum shaft. I check every thing and every thing looks fine. Does anyone have the same problem? What could be causing this?

I was playing with it a little more and it seems like a toilet bowl effect. It makes it hard to control because if I am going forward, it will thurst forward for a second and then go back and slow down a bit.....very hard to keep under control.

Things I have check:
1) I took off the fly bar and rolled it on a table. It is straight enough, I believe.
2) I made sure that there was no free play when I pull up on the outer shaft.
3) I made sure that there is no free play when I pull up on the inner shaft.
4) The inner shaft is new (Blue aluminum).
5) I checked and made sure all blades are balanced.
6) I checked the outer shaft by rolling it on a table.

I have taken it apart about six times. One thing that I noticed is with nothing else attached to the outer shaft, the outer shaft seems to wobble (vibrate) slightly. I just attached the outer shaft and watched it spin from the top. But, I removed the outer shaft and it looks straight. I also rolled the outer shaft on a flat table with the wheel hanging off the table and it seems straight. Could it be a bearing? What else can I check and test out? It just has to be a part....I know it. But, it's driving me crazy trying to figure it out

Two additional suggestions here. First, with the heli assembled, power up the upper blades (but don't hover), then look directly from the side and make sure they're tracking properly. If not, you may need to adjust the flybar linkage. Second, in spite of people swearing their flybars are absolutely straight, some folks have had luck fixing the "toilet bowl effect" by replacing it completely. Next, you may want to consider one of the shortened, lighter flybars. (See BP Hobbies webpage and look for the Dynam Vortex flybar. It'll work just dandy.) Or, you can shorten it yourself (there are threads here that describe the mods. Finally (ok, four suggestions), with the heli battery removed, rotate the flybar through its full range of motion, while attached to the upper blades. Make sure there is absolutely no resistance as the ball linkage moves. You can bend the linkage just a bit if you have any binding whatsoever. Another thing you may check is the overall balance (CG) of the model. If you pick it up by the flybar, it should be level, both left to right and front to back. I rubber band a long, light dowel to the skids, both left to right and then front to back, to help me check the balance (tilt) of the model. Beyond that, you may have to live with it. You didn't mention if you're using the training gear, but that could have an effect, too.

With no blades or hub attached to the outer shaft (and with inner shaft removed), I also get a very slight wobble in the upper shaft when I spin it up with the motor, but it's very, very minimal. That's normal, and I don't think that causes the toilet bowl effect, because I don't seem to have that problem with my heli. The shaft seems too close to the CG, and spinning too fast, to have a significant effect on the toilet bowl effect. More likely, it's a balance issue with the blades, flybar, upper blade tracking, or the whole vehicle balance.

You're getting lots of good stuff from these guys. Let me throw in another thought about the flybar. There are 3 things that I know will cause TBE. 1-Absolute freedom of movement of the flybar is critical. 2- bent shafts will cause problems. 3- blade balance will cause it. You've covered 2 and 3, so look at #1 again.
First, is the rotor / flybar linkage binding? You should be able to wiggle the link on the balls. Is the link sticky? Many of the new blades have just a bit of flash on the link balls on the blades. If you have the slightest plastic flash, scrape it off with a knife. Or use very fine sandpaper. DON'T rough up the surface of the balls. When you flick one end of the flybar, it should bounce back and forth before coming to rest.
Hmmm, Remove the link from the upper blade and ensure the flybar is free.
Check the shafts by moving your throttle stick fully right, then apply a little power and look at the hub from the top. Then move the throttle stick fully left and apply a little power. How does that top hub look when viewed from above? Oh, this test works best with the blades removed.
I had one of the plastic bearing holders go bad. It didn't stay seated square on the top of the outer shaft. A replacement with the aluminum bearing cup and new bearings fixed it.

Does the heli shake if you hold it in your hand and run up the RPM? If it shakes, it may be knocking the flybar out of balance as it spins, yet it will look fine when it stops.
Maybe something in here helps. Hope so.
Good luck
Soloboss

Thanks guys/gals for the information. I checked the movement of the ball joint on the flybar and that looks good. I also disconnected the linkage from the top blades and the fly bar has good movement. What I did notice is that some of the teeth on the outer shaft gear were chewed up a little. This caused a rough spot on that section of the gear. So, I think that might be what is causing the wobble in the outer shaft. I think if the outer shaft wobbles, it causes every thing else to get out of wack. The wobble affect is compounded once the inner shaft and blades are added. Do you guys think that might be it? Also, what is the purpose of a shorter fly bar? I am trying to come up with a list of replacement parts I might need. Thanks.

http://www.bphobbies.com/view.asp?id...=NDYN202&img=l