A puzzling T-rex 600 issue!
 

Hello all!

I'm having a strange problem with my T-rex 600 EPRO. I can't seem to figure out what's wrong with it.:confused: Basically, when I throttle up very quickly, I hear a terrible noise. It sounds to me like it's nylon slipping/grinding but I do not want to eliminate other possibilities!



Here's what I've done to assess the problem:

1. Noticed some bad wear on main gear and tail gears, replaced all nylon gears in the central portion of the heli. Took the heli outside and accelerated rapidly. TERRIBLE noise.

2. Isolated motor and reproduced the rapid acceleration on the bench. NO strange noise.

3. Removed blades and allowed motor to turn main gears and tail. NO strange noise!




So, it would seem to me that there are only two possible theories

1. The motor is making awful noises when under high load. It is an align stock... yuck!

2. Up force generated by the blades is forcing the nylon gears (or something else) to bind. There is very VERY little slop in my main gears, so I'm unsure of this theory...



Has anyone else had this problem? Any help would be greatly appreciated!! :D

Gear Mesh between Motor and Main Gear is what could cause the noise.

That, and be sure to run soft start on your ESC

+1 gear mesh

Did you notice if your tail blades are turning?

I recently had a tail drive gear strip on the shaft (not the teeth of the gear itself, but the gear is pressed onto the shaft, that came "unpressed" for lack of a better word) which actually caused me an unexpected landing on my 500. It made a "weird" noise when it let go in mid air...then again, could be like others have already said...gear mesh.

Yes, tail rotor works just fine. It is flyable, I only hear the noise when I accelerate quickly mid air.

The ESC is on soft start. That is a possibility- I admit I know basically nothing about pinion gears. What would cause it to not mesh properly? I bought it used with a 14T in there and haven't touched it.

To check gear mesh...take a standard piece of notebook paper and cut a long strip...say 5 or 6 inches in length by say an inch wide. Double this paper over "lengthwise" so you end up with a 5 or 6 inch by 1/2 inch strip (folded).

Run this paper through your main gear and pinion. It should come out looking nice and straight with no left or right curve to it and also "accordion" like in appearance with NO HOLES or TEARS. If it is barely ruffled (like the potato chip) then your mesh is too lose. If it is severely ruffled and pulls to the left or right with actual tears in the paper...your mesh is too tight. Given your symptom, I think the later is not the case here.

Back to another possible issue. Have you checked the motor timing on your ESC? Sometimes when the motor timing is not set correctly or the ESC doesnt have an automatic timing...this can cause a loud "shrill" sound which could be confused as a "grinding" sound. If you check your gear mesh and it looks to be okay...this would be my next step in the troubleshooting process.

goodluck

Thank you for the advice ATV! I learn something new every day. My mesh seems to be ok, if anything a little bit on the loose side. I got it as tight as I could.

I have a CC Phoenix HV 85. Went through the manual and it is factory set to have auto timing on. Went through all the settings and reset everything to the way it should be just to make sure. Went outside and flew, the problem persists.

I can describe it in a little bit more detail though- normal "scale" operation with smooth increases and decreases of throttle causes no problem at all. If I increase the throttle more rapidly, I hear a noise that sounds like severe binding and the motor slows to approximately 20% output. The heli will drop quickly unless I IMMEDIATELY reduce throttle. If throttle is reduced in time, the motor spools back up quickly and flight is maintained. If I'm unable to save it in time, the heli will go to the ground no matter the throttle movement. Once on the ground, it will stay there with the blades still being spun by the motor and the whole contraption sounding like it's having an awful time provided that throttle is not reduced below about 40%. If I increase throttle while it's on the ground, there is no change in motor speed (not sure about pitch). If I decrease motor speed, once passing ~40% it will decrease gradually and stop at zero, then let me spool it back up again sounding much better. Rapidly decreasing throttle in flight does not have the same affect (thankfully!). After a few minutes of testing, I took the heli inside and found no signs of damage to any gears.


I'm beginning to suspect my motor. It's an old Align BL650L 1220K and I've heard nothing but bad things about them! I will remove it tonight and see if I can get the case off and find anything suspicious. Thanks for the help so far guys, hopefully with your help I'll be able to fix this and get my bird in the air again!

Hmm Mechanicalfailures and fly_inverted are both me. I was in the process of an account change and I seemed to have mixed them up! My apologies.

I dont really know what else to offer you as far as advice goes. Maybe someone else will chime in on something else I havent experienced yet and give you something else to look at.

One more thing though, since you said you had the Castle ESC. Did you set your throttle end points? If not, search on how to do that and try that. I dont think that would cause your issues, but one more thing that should be looked at.

Im thinking you may be right about it being the motor. Perhaps a magnet has come unglued inside the motor and that is whats causing your issues.

A few questions:

Is this noise a new problem? Did your helicopter use to sound normal? How many flights on the machine before the noise appeared? Did the noise appear after a crash, incident, rough landing? As to the gear mesh other have mentioned, this part of the setup is critical. You should just barely be able to feel any play between the pinion and main gear - paper width as others have mentioned. If your machine has hundreds of flight, you need to also be suspicious of all ball bearings and even the motor. Best of luck!

You said you have the Pro, but running a 1220 kv motor. So I suspect you are actually flying an CF or ESP. One thing to look at is make sure your main gear and tail gear are not touching. I had a bad one-way bearing and allowed the two to touch with very bad results. Do you have a belt drive or TT?