R/C helicopter troubleshooting

[Wolfala]

This is a Coaxial Lama taken apart.

List of problems:

* The lower drive motor is binding and not spooling up to operational speed.
* There is 0.5 inch per second vibration which cannot be dampened and is affecting the gyro operation.
* Because of the vibration, the gyro calls for power changes which cause the helicopter to be uncontrollable in any axis. It cannot get off the ground without risk of flipping on its side from these erratic power changes.
* Also appears the wiring to the 4 in 1 mixer is incorrect, as right cyclic input causes the nose to pitch down as if forward cyclic was called for.
* Top rotor has a severe out of balance condition. Possibly a bent inner shaft.

Things the video shows:

* Trouble during startup with vibration problems. Look at the 4 in 1 mixer in particular and how much it moves.
* Look at my hands and how the helicopter wants to randomly jump out of my hand with no input on my side. This is a steady throttle state.
* Shaft binding - lower rotor does not turn freely and be the first to start before the top rotor. Lower rotor should spool up before the top under all conditions of flight.
* Helicopter cannot be controlled in any axis.
* Controls in use.

[Curlew]

you need to throw more money at it

[avionix]

How long have you had it, and did it do that out of the box? 

I would suggest taking it to the local hobby shop and have their heli guy look into it.  Unfortunately, helis are the hardest R/C aircraft to fly.  Even the co-axial kind can have issues if the rotors are out of balance or the pitch is incorrect.  You probably will be spending some money on it.  For parts for that, it could be a $10 part or $50 depending on the issue.

Not to discourage you, but any of the Eflight or Esky helis I have had, gave more issues and took the fun out of it.     Would recommend a little bit more and getting a gas heli.  Alot more work, but really cool to see a heli with a 3-4 foot diameter rotor hovering about 4 feet away from you.   

[Wolfala]

How long have you had it, and did it do that out of the box? 

I would suggest taking it to the local hobby shop and have their heli guy look into it.  Unfortunately, helis are the hardest R/C aircraft to fly.  Even the co-axial kind can have issues if the rotors are out of balance or the pitch is incorrect.  You probably will be spending some money on it.  For parts for that, it could be a $10 part or $50 depending on the issue.

Not to discourage you, but any of the Eflight or Esky helis I have had, gave more issues and took the fun out of it.     Would recommend a little bit more and getting a gas heli.  Alot more work, but really cool to see a heli with a 3-4 foot diameter rotor hovering about 4 feet away from you.   

It was straight out of the box and doing that. It is an Lama V6 - trying to get in touch with the RMA dept. Meantime, I have my Air Hogs havoc terrorizing my dog with impunity.

[ramzey]

Alex , cant you just take it back to store?

[Chalenge]

It looks like a bent shaft have you tried a runout gauge on it?

[DYNAMITE]

It looks like a bent shaft have you tried a runout gauge on it?

Possible...but I'm not sure if i agree with that.  Though it's worth exploring.  Regardless though... if that's out of the box, you've got a legit RMA.  Send it home and get a fresh one 

[Chalenge]

Easy enough to check. Runout gauges are standard equipment for helicopter fliers... serious ones anyway.

[SirLoin]

The shaft is bent at the lower rotor..That would explain the vibration and the stiction of the lower rotor.

[Wolfala]

The shaft is bent at the lower rotor..That would explain the vibration and the stiction of the lower rotor.

I put it up on the bench today with an accelerometer. I had a 4 Hz vibration now measured at 0.75 inches per second. When I took the main and inner shaft apart, sure enough the main drive shaft was bent. Side to that, full power could not be maintained as at full throttle the main rotor was surging and commanding a roll. Aside from that, the motors weren't putting out enough power to maintain a hover - probably because of the shaft scuffing. The vibration did some damage as it turns out - the motor mounts cracked, the fuselage showed stress risers at their attach points and the landing skids - their mounts cracked clear off the supporting truss.

Had it RMA'd out with the video - should get a replacement which was flight tested by end of the week.