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Thread: What makes a 6ch heli wobble in hover?

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    What makes a 6ch heli wobble in hover?

    I brought one of those t-rex 450 clone rtf on ebay. The only parts i replaced is the 3 cyclic servos with the t-pro metal gear. The stock ones seem to twitches a lot. Anyways, when try hovering in no wind, the heli seem stable. But when there is a breeze, just a little, the heli would wobble around. up/down, left/right, ect. This makes it hard for me to fly. So what causes a heli to wobble? Does the esc, motor, gryo, servo, ect cause it to wobble? I did blade tracking, tighten all screws and locktite them, and i also balance the main blades. Does the tail blades need to be balance? They are a little chipped from hitting the ground.

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    Legendary Member Orb Weaver D's Avatar
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    Re: What makes a 6ch heli wobble in hover?

    Couldn't hurt to balance your tail blades, but you may also have a slight bend in your main shaft or feathering shaft.
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    Re: What makes a 6ch heli wobble in hover?

    Quote Originally Posted by Orb Weaver D
    Couldn't hurt to balance your tail blades, but you may also have a slight bend in your main shaft or feathering shaft.
    I dont think the main shaft is bent. When i spin up the heli, the rotor head looks fine, cant see any wobbles in the head. As for the feather shaft, i cant take it apart to check. When i unscrew the bolt, the whole shaft turns. I need 2 small hex screw to do it, but only have 1. I will try to balance the tail blade. I dont know, but i was thinking its probably the gyro that is making the heli wobble. Might replace it when I have the money.

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    Bronze Member fbc's Avatar
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    Re: What makes a 6ch heli wobble in hover?

    Quote Originally Posted by omegaweaponx
    I brought one of those t-rex 450 clone rtf on . The only parts i replaced is the 3 cyclic servos with the t-pro metal gear. The stock ones seem to twitches a lot. Anyways, when try hovering in no wind, the heli seem stable. But when there is a breeze, just a little, the heli would wobble around. up/down, left/right, ect. This makes it hard for me to fly. So what causes a heli to wobble? Does the esc, motor, gryo, servo, ect cause it to wobble? I did blade tracking, tighten all screws and locktite them, and i also balance the main blades. Does the tail blades need to be balance? They are a little chipped from hitting the ground.
    If your heli is completely true and properly adjusted. Then I think it can only be servos or gyro issues.
    Frank
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    Re: What makes a 6ch heli wobble in hover?

    Wobbling ... or bobbing front to back (aka tail up & down) can be attributed to a low head speed. Increase the throttle curve.
    Out of balance blades, bend shafts, bent links, and bent head will cause vibration (aka the shakes). At some RPM a harmonic can produce a wobble, but it is rare at those high head speeds.
    If the tail is rapidly swinging back and forth, that is called hunting or tail wag. The Gyro is too sensitive (too much gain), or the servo can't keep up with the gyro, or a linkage binding issue.
    If it is swinging the tail back and forth slowly, then the gyro gain is too low, and/or linkage binding issues. If all is correct, and the gain adjustment does not resolve it, you may have a cheapo gyro that slipped through ??QA?? with issues.

    Hope you find your wobble issue



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    Re: What makes a 6ch heli wobble in hover?

    Quote Originally Posted by JerryShaw
    Wobbling ... or bobbing front to back (aka tail up & down) can be attributed to a low head speed. Increase the throttle curve.
    Out of balance blades, bend shafts, bent links, and bent head will cause vibration (aka the shakes). At some RPM a harmonic can produce a wobble, but it is rare at those high head speeds.
    If the tail is rapidly swinging back and forth, that is called hunting or tail wag. The Gyro is too sensitive (too much gain), or the servo can't keep up with the gyro, or a linkage binding issue.
    If it is swinging the tail back and forth slowly, then the gyro gain is too low, and/or linkage binding issues. If all is correct, and the gain adjustment does not resolve it, you may have a cheapo gyro that slipped through ??QA?? with issues.

    Hope you find your wobble issue



    Just like you said, my trex 450 clone wobble front and back. (the tail/front goes up and down). The heli also wobbles left and right. I dont seen any tail wag, so probably not gyro or tail servo problem. I've only hover it in normal mode, since my backyard is too small i dont want to turn on 3d mode. My thro curve i set in 0, 25, 50, 75, 100 on normal. What is a good setting for thro curve in normal? It does seem/sound like motor in spinning low while mid stick on normal.

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    Re: What makes a 6ch heli wobble in hover?

    Do you know the pinion size? best one (IMO) for the 450 is a 13T
    I would bump the throttle curve up to 0,50,60,80,100
    If your motor wants to spin up at bottom stick, then you can reduce that 50 to 40 or lower. What is important is what is at the half stick and above.
    Hovering is usually around 3/4 stick and +5 degrees of pitch so that curve is a starting point for you.

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    Re: What makes a 6ch heli wobble in hover?

    Quote Originally Posted by JerryShaw
    Do you know the pinion size? best one (IMO) for the 450 is a 13T
    I would bump the throttle curve up to 0,50,60,80,100
    If your motor wants to spin up at bottom stick, then you can reduce that 50 to 40 or lower. What is important is what is at the half stick and above.
    Hovering is usually around 3/4 stick and +5 degrees of pitch so that curve is a starting point for you.
    pinion size or number of tooth? It should be the same size use on the t-rex 450 se v2. I count the number of tooth, it has 13T. Motor is rated 4000 kv. I will put in those thro curve and see if that makes it more stable.

    edit. after changing the thro curve to 0,50,60,80,100. I plug the battery in and the motor twitches a bit, and makes a beeping sound. I thought something was wrong with the motor or change motor with one of my 450 size motor on my other heli. It still makes the sound and doesnt stop. I changed the setting back to 0,25,50,75,100. When i plug in the battery, it makes the beep starting sound and stop. I guess those setting wont work on this heli. I flew it, was pretty stable for the first few minutes, then the wind pick up a bit and tail started bounding around. Maybe gryo or tail servo, they are cheap anyway. Im sure a little wind doesnt make a 450 size heli bounds around like that.

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    Re: What makes a 6ch heli wobble in hover?

    The issue with the motor is because of two things.

    First you need to always (religiously) plug the battery in with the throttle hold on. It is beeping because it has jumped into fail safe mode. It detects throttle input on power up, and prevents itself from slicing you up (a safety feature of the ESC). Its a good idea to reset the throttle range in the ESC anytime you make serious throttle curve changes. If you don't know how to do that setting, let me know and me or someone will help you set that up.

    Second is the #2 point in the throttle curve is 50 (a recommendation by Chuck Bassani). Without resetting the ESC's throttle range, that will effect the #1 to something greater than 0. The curve is an assignment to the radio that will then interpret those values and adjust its internal ratio (smooth it out via its own calculation). That in turn puts a higher PPM signal value than zero at #1. Once you reset your ESC's throttle range setting, it will know that value to be the bottom stick, and no longer jump into fail safe. Basically you tell the ESC what your new throttle curve top and bottom are.
    You can choose 0,35,60,80,100 to let it spool up a little slower as well. Some pilots run a flat line curve, 0,90,90,90,100 in normal mode. But... you have to set the ESC throttle range so it knows about your throttle curve changes.
    13T is a good pinion size for that heli.
    What radio are you using?

  10. #10
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    Re: What makes a 6ch heli wobble in hover?

    Quote Originally Posted by JerryShaw
    The issue with the motor is because of two things.

    First you need to always (religiously) plug the battery in with the throttle hold on. It is beeping because it has jumped into fail safe mode. It detects throttle input on power up, and prevents itself from slicing you up (a safety feature of the ESC). Its a good idea to reset the throttle range in the ESC anytime you make serious throttle curve changes. If you don't know how to do that setting, let me know and me or someone will help you set that up.

    Second is the #2 point in the throttle curve is 50 (a recommendation by Chuck Bassani). Without resetting the ESC's throttle range, that will effect the #1 to something greater than 0. The curve is an assignment to the radio that will then interpret those values and adjust its internal ratio (smooth it out via its own calculation). That in turn puts a higher PPM signal value than zero at #1. Once you reset your ESC's throttle range setting, it will know that value to be the bottom stick, and no longer jump into fail safe. Basically you tell the ESC what your new throttle curve top and bottom are.
    You can choose 0,35,60,80,100 to let it spool up a little slower as well. Some pilots run a flat line curve, 0,90,90,90,100 in normal mode. But... you have to set the ESC throttle range so it knows about your throttle curve changes.
    13T is a good pinion size for that heli.
    What radio are you using?
    oh yea, i forgot about thro range. When i purchase my esc, the manual talks about it and how to set the thro range. No wonder the motor keep beeping nonstop. Thanks for reminding me. Ill change the thro curve and thro range. BTW the 450 heli im trying to flying is the titan 450, a trex 450 clone. It came with a rx/tx. It says titan on it, but it is the same one as the fly sky/exceed tx on xheli. I used t6 config to program the tx.

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