How do you spot stock Cx2 motor wear?

[AH-64-D]

After bumping into a downspout, denting the nose and breaking all 4 blades, my repaired Cx2 precessed counterclockwise in a circle. I checked new blade balance, warpage, and tip alignment. Bought a new 4-in-1. Works better, but still some precess. Rotorshafts and bearings seem OK, but motors do not sound like new - is the precession a symptom of motor wear? What are "tired motor" symptoms? I want to understand/solve this behavior before upgrading. Can you suggest other possible reasons for precession? Thanks in advance for your comments.

[Fly-guy]

The counter clockwise circles you descirbe (usually about 3 feet diameter?) in my experience with thse counter-rotaters is normally a slightly bent inner shaft.

I have seen it with old motors too but more often a bent shaft.

Roughly how many flights has the heli had, to get an idea of wear/use.

[BR289]

Not sure what that could be. I have fixed alot of those at our local hobby shop. One mistake I have seen made is using two of the same motor. The two motors in it are both different. None of any of the shafts are sipossed to be slighty bent. Thats usually where some noise comes from.....
Blair

[AH-64-D]

Good Suggestions. Thank you. A bent shaft is a possibility considering what happened. Shaft and motor upgrades ought to cover all bases in one swoop. Total flight time is between 6 and 10 hours with this being the first real crash. The diference in sound may be the bent shaft rather than a motor, but if I have to take that much apart, I am going to put in better motors and a heat sink at the same time.

[BR289]

I am not sure who sells aftermarket motors for these but I am sure someone does. They are an odd shaped motor. Usually whn someone brings one in for repair and its noisy, its a bent shaft, either inner or outer. I rarely see burnt out motors.
Blair

[Fly-guy]

	Quote: Originally Posted by AH-64-D
	Total flight time is between 6 and 10 hours with this being the first real crash.

	Quote: Originally Posted by BR289
	Usually whn someone brings one in for repair and its noisy, its a bent shaft, either inner or outer. I rarely see burnt out motors. Blair

6-10 hours shouldn't be a burnt out motor, like BR289 I've rarely seen burnt our motors. I have seen it on a few CX2s that are well over 1 year old and get used at least 4 times a week

[AH-64-D]

Mystery solved: Under bright lights and magnifiers, I found I had not properly re-tightened the screws of the gear retaining collar onto the flats of the inner shaft. The drive gear was slipping on the shaft at speed causing precession. I had messed with the gears before I crashed. Failed to notice precession on that flight because a sudden rise in wind seemed to be reason I was having control problems. Hovers well, now. Also have some shiny new spare parts in hand, 2 Extreme motors on the way, and a better understanding of my Cx2. Lesson learned.

[AH-64-D]

More flying showed my Cx2 still precessed even with the gear retaining collar correctly fastened. I decided to adjust the main rotor link arm away from its optimum setting where the rotor tips track in alignment. One full turn longer and the Cx2 stopped misbehaving even though the rotor tips no longer tracked. Just to be sure, I went back, induced precession, and then fixed it again by returning the linkarm to its new position. I uploaded "tip tracking=precession.wmv" to the video gallery to document what I learned.

[Fly-guy]

	Quote: Originally Posted by AH-64-D
	More flying showed my Cx2 still precessed even with the gear retaining collar correctly fastened. I decided to adjust the main rotor link arm away from its optimum setting where the rotor tips track in alignment. One full turn longer and the Cx2 stopped misbehaving even though the rotor tips no longer tracked. Just to be sure, I went back, induced precession, and then fixed it again by returning the linkarm to its new position. I uploaded "tip tracking=precession.wmv" to the video gallery to document what I learned.

Thats a different one for me. I've properly tracked a few co-axials before and the difference is amazing (balance your blades too if you can ) But I haven't seen a bad track cause this issue. I'll keep it in mind next time i see it.

[BR289]

	Quote: Originally Posted by AH-64-D
	Mystery solved: Under bright lights and magnifiers, I found I had not properly re-tightened the screws of the gear retaining collar onto the flats of the inner shaft. The drive gear was slipping on the shaft at speed causing precession. I had messed with the gears before I crashed. Failed to notice precession on that flight because a sudden rise in wind seemed to be reason I was having control problems. Hovers well, now. Also have some shiny new spare parts in hand, 2 Extreme motors on the way, and a better understanding of my Cx2. Lesson learned.

I should have mentioned that....If the screws arent tightened against the two "Flat spots" of the inner shaft, it will basically make noise and not hover well at all.
One other common mistake that people make that is critical to keeping the CX flying is the weights on the flybar...they must be in front of the leading edge of the upper blade...it will just fall over if not and I have seen that happen many times.
Blair

[AH-64-D]

Thanks for your comments and suggestions. By now, I understand that moving my tip tracking away from good alignment is just canceling one harmonic imbalance with another to achieve stable flight. But the "cure" wastes power. I plan to dig further to uncover what is really amiss. In the meantime, I bought Hanger 9's FS One simulator and was surprised to find that its Blade Cx simulation has the same drunken sailor circling movement in hover that my real Cx2 suffered until I messed with its tip tracking. Does this mean that there is a way to trim away this behavior in a real Cx2? Anyway, I contacted FS One to see if they can help me get their sim to sober up.

[AH-64-D]

Just to finish the thread - My video about adjusting tiptracking away from specs was a workaround to counter TBE. Flying that way cut flight time to 4 min because it wasted so much power. I eventually got my Cx2 flying like new by replacing the inner shaft gear, flybar, lower blades and polishing linkages with 8000 grit emery cloth to eliminate any binding. Life is good again...