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Old Sep 20, 2011, 02:51 AM
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M120D01 flybarless - first 3d helicopter, main rotor seizing

Hi guys,

Just tried out my first 3d chopper today. The instructions were less than helpful with setting up the TX but I got it somewhat worked out. I've been having some issues though.

When I spool up the copter, there are certain parts of the throttle where the main rotor just seizes up and I don't know why.
Additionally, when in normal flight mode, the trims don't seem to do anything really.
Finally, I noticed that in 3d mode, the collective pitch is such that it produces plenty of thrust in negative pitch, but beyond 50% throttle, there is no positive pitch thrust, only neutral. the collective doesn't even change past 50%, no increase in RPM or pitch.

I'm a novice when it comes to complex helis but if someone could shed some light on what they did to set theirs up (especially if you've had experience with this one) I'd be grateful
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Old Sep 20, 2011, 08:02 AM
Hong Kong
Joined Jan 2010
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I would ask people in this thread whether they can help

http://www.rcgroups.com/forums/showthread.php?t=1363787

I have got a M120D01 and have found it very difficult to set up.

But at least I can answer one question: you don't need to use trims in a flybarless helicopter. The system makes the trims redundant.
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Old Sep 20, 2011, 10:31 AM
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Quote:
Originally Posted by komodomoe View Post
Hi guys,

Just tried out my first 3d chopper today. The instructions were less than helpful with setting up the TX but I got it somewhat worked out. I've been having some issues though.

When I spool up the copter, there are certain parts of the throttle where the main rotor just seizes up and I don't know why.
Additionally, when in normal flight mode, the trims don't seem to do anything really.
Finally, I noticed that in 3d mode, the collective pitch is such that it produces plenty of thrust in negative pitch, but beyond 50% throttle, there is no positive pitch thrust, only neutral. the collective doesn't even change past 50%, no increase in RPM or pitch.

I'm a novice when it comes to complex helis but if someone could shed some light on what they did to set theirs up (especially if you've had experience with this one) I'd be grateful
Can u tell us what you meant main rotor sieze up at certain parts of throttle. You mean rotor slow down or even stop spinning, making noise?

What tx u are using and what are settings for throttle curve and pitch curve. what s the pitch angle range for your M120.

For 3 axis gyro stablization, heli memorize the position leveling. To setup and level swashplate for 3 axis gyro fbl heli, I put the geli on flat ground, put throttle stick in mid position (pitch angle should be 0 deg in general, depend on your preference), adjust trims to level swashplate. This is how I level heli for 3 axis gyro. Then heli will memorize the leveling position for full range of throttle.
s.p. be careful and sure motor disconnect / idle when you adjust and level swaplate. Safety first.
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Old Sep 20, 2011, 08:30 PM
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I notice that on a completely fresh charge the motor rotates pretty well for a short time but anything below 3.9v is almost unusable. since the 1s battery is rated at 3.7v, it shouldn't have to be above this to function so I'm a bit confused. the video was taken after the battery was used only for a short time. additionally, at high rpm, I hear a sound that could almost be described as grinding...
this is a short video of what happens when I apply throttle. Sometimes this will happen in the middle of the rotor spooling up too, not just when I initially try to apply throttle. I can't tell if it's a brushless motor or speed controller problem..

Edit: it would seem that the blades spin after the copter has been left to cool regardless of charge. I believe the esc is heating up and malfunctioning to where it cannot supply adequate power to the motor but i don't know how to test this since i only get a few millivolts when testing the leads from the ESC. the motor spins nicely and doesn't heat up excessively in flight, however the ESC heats up considerably.

Big EDIT: it seems when I tap the esc while the blades are turning it makes the motor die and work again depending how i tap it...
http://www.youtube.com/watch?v=Wcs4wlYM8ug
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Last edited by komodomoe; Sep 21, 2011 at 02:02 AM. Reason: further analysis
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Old Sep 21, 2011, 04:12 AM
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1s lipo voltage should be 4.2v when it is fully charged. When lipid battery drain 80% capacity, voltage dropped to about 3.7v. Always use 80% rule, do not drain lipid more than 80% of capacity, ie below 3.7v.
As m120 is heavy, it is not uncommon helicopter take a lot of juice from lipo to fly.
for esc hot but motor cool. Can u tell us what is brand & model for the motor and esc. Are u using stock motor and esc. I suggest u check all motor & esc connections and make sure no loose wire, bad contact and soldering. If ESC too hot, some will cut off power but I don't know which esc you use.
I also suggest u disconnect motor plug, apply throttle full and see if esc still hot. If esc still hot /w motor unplug. ESC bad
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