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Old Feb 14, 2013, 06:24 AM
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Joined Oct 2012
48 Posts
Hello, i have a problem with my 120SR and i would like your help please. This happened after i had one crash few days ago. I am using the stock tx, and the problem appears to be in rudder stick i think. While hovering, i noticed the tail makes very small left and right movements, without using rudder at all. After few minutes, the heli makes turn 180 degrees, like i am using rudder and face it nose in, again, without using rudder..I tried to keep it with my hand down, while i use throttle, to check the tail motor how reacts and it seems like its push the tail to the wright with wright rudder, and stop push to the left, but not instantly..I am confused..any help??
By the way, i check everything on heli and seems like everything is ok..
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Old Feb 14, 2013, 06:51 AM
Rockin' & Flyin'
Saxguy1000's Avatar
Virginia Beach
Joined Dec 2009
2,845 Posts
Quote:
Originally Posted by ikarous View Post
Hello, i have a problem with my 120SR and i would like your help please. This happened after i had one crash few days ago. I am using the stock tx, and the problem appears to be in rudder stick i think. While hovering, i noticed the tail makes very small left and right movements, without using rudder at all. After few minutes, the heli makes turn 180 degrees, like i am using rudder and face it nose in, again, without using rudder..I tried to keep it with my hand down, while i use throttle, to check the tail motor how reacts and it seems like its push the tail to the wright with wright rudder, and stop push to the left, but not instantly..I am confused..any help??
By the way, i check everything on heli and seems like everything is ok..
Most likely, your problem is in the signal to the tail motor. First check the connections at the motor and at the main board. If they are plugged in fine, then it's probably damage to the wire(s) at the motor--inside. A replacement tail motor will normally solve the whole problem. This is a common problem.
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Old Feb 14, 2013, 03:45 PM
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DGrant's Avatar
United States, CA, Clovis
Joined Mar 2004
3,249 Posts
Quote:
Originally Posted by ikarous View Post
Hello, i have a problem with my 120SR and i would like your help please. This happened after i had one crash few days ago. I am using the stock tx, and the problem appears to be in rudder stick i think. While hovering, i noticed the tail makes very small left and right movements, without using rudder at all. After few minutes, the heli makes turn 180 degrees, like i am using rudder and face it nose in, again, without using rudder..I tried to keep it with my hand down, while i use throttle, to check the tail motor how reacts and it seems like its push the tail to the wright with wright rudder, and stop push to the left, but not instantly..I am confused..any help??
By the way, i check everything on heli and seems like everything is ok..
Also, you might check the motor shaft for any debri that might have been picked up in the crash.. as well as make sure your tail rotor prop is not slipping on the shaft. Run it up while CAREFULLY holding the heli in your hand... not that any of this is an answer to the problem.. but food for thought... I've had debri/hair/stuff get caught up in the tail rotor motors on my smallish coax heli's.. its a pain.. I hope you get to the bottom of it.
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Old Feb 14, 2013, 03:52 PM
Against Helicopter Cruelty
Heli Pad's Avatar
Joined Aug 2011
6,621 Posts
Quote:
Originally Posted by ikarous View Post
Hello, i have a problem with my 120SR and i would like your help please. This happened after i had one crash few days ago. I am using the stock tx, and the problem appears to be in rudder stick i think. While hovering, i noticed the tail makes very small left and right movements, without using rudder at all. After few minutes, the heli makes turn 180 degrees, like i am using rudder and face it nose in, again, without using rudder..I tried to keep it with my hand down, while i use throttle, to check the tail motor how reacts and it seems like its push the tail to the wright with wright rudder, and stop push to the left, but not instantly..I am confused..any help??
By the way, i check everything on heli and seems like everything is ok..
Let me start with the last part there. If I understood you correctly, you were trying to see how the tail motor reacts to the rudder control by holding down the helicopter with you hand, so that it is not free flying. That, unfortunately, invalid the test. I've make that same mistake before.

You see, the whole purpose of the tail rotor is counter rotation. The main rotor asserts a rotational force on the body. The tail motor works to compensate and stabilize. It knows how hard to work by reading the signals and controls from the head holding gyro. But when you hold the helicopter down, the heading is not changing, and the gyro is saying, "I'm still, no need for anti-rotation". That's why everything is skewed once the helicopter is held down. You won't get a true reading or response from the tail this way.

I'm not saying that the tail doesn't have a problem. I'm just saying that benching the helicopter will not tell you much. Sax has offered you advice on the issue and he's most likely correct.

I'm not too concerned about the small movements, both left and right. Our helicopters do that, some more than others. But when it does an 180, I'm curious. Does it do a quick 180, or a slow 180. When it does that, does it always turn in the same direction, or one direction one time, another direction another time? If if always turn in one direction, is it Left?
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Old Feb 14, 2013, 06:38 PM
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St. Louis, Mo.
Joined Jun 2008
394 Posts
Quote:
Originally Posted by Saxguy1000 View Post
Most likely, your problem is in the signal to the tail motor. First check the connections at the motor and at the main board. If they are plugged in fine, then it's probably damage to the wire(s) at the motor--inside. A replacement tail motor will normally solve the whole problem. This is a common problem.
I agree with Saxyguy. These kinds of problems are usually the tail motor. I have had to replace the tail motor on mine twice with these types of problems and it always fixed the problem. A cheap and easy fix.
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Old Feb 14, 2013, 07:26 PM
USAF Retired - 1968-1988
Jake8131's Avatar
United States, IL, Mascoutah
Joined Dec 2010
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Is the tail rotor tight on the motor shaft?
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Old Feb 14, 2013, 08:29 PM
Heli's rule!
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Midvale, Utah, USA
Joined Mar 2005
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definatly sounds like a tail motor connection problem.... when it spins 180, which way does it spin? (nose right or nose left)
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Old Feb 15, 2013, 03:27 AM
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Joined Oct 2012
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-DGrant: everything is clear in the motor as i noticed, also the tail motor spins free and the tail prop also..i will check again

I'm not too concerned about the small movements, both left and right. Our helicopters do that, some more than others. But when it does an 180, I'm curious. Does it do a quick 180, or a slow 180. When it does that, does it always turn in the same direction, or one direction one time, another direction another time? If if always turn in one direction, is it Left?[/QUOTE]

it turns a fast 180 degrees, as it hovers nose out, to the left, And doing this only with this direction.

-Jake: yet it is tight, no problem there.

-dacaur: i check the motor connections to the board and to the motor, everything seems fine. I will check again. It spins nose left.

-One more point: one item from the motor seems to be lost, its the *tail motor protective sleeve*, i found it on the ground..but i dont know where to replace it again..maybe this cause the problem?
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Last edited by ikarous; Feb 15, 2013 at 03:49 AM.
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Old Feb 15, 2013, 09:48 AM
NotAnotherMomentLostToSei zures
Chap1012's Avatar
United States, MA, Malden
Joined Mar 2008
11,488 Posts
Don't worry about the protective sleeve just yet. That's not the problem. Look at your tail rotor from the rear. The tail rotor should be perfectly straight (up and down) and not curved in (or out). These tail rotors have a nasty habit of curling inward towards the boom and will look like this from the rear...")" This is actually one of my pre-flight checks, checking the tail rotor. If you find it's out of shape, simply work it back into shape using your thumb and forefinger paying particular attention to the rotor pitch.

The tail rotor can take on this shape right out of the box OR just sitting around for weeks. I know!!!!

Tail rotor straightness and pitch are one of the most over looked problems.

Mike.
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Old Feb 15, 2013, 10:32 AM
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Joined Oct 2012
48 Posts
Thank you Mike, and thank you ALL for your fast replies
The problem still exists, after all the checks i've done, so tomorrow i am going to get a new tail motor. Fortunately, i found at one of my local shops here, so the replacement its going to be fast..Thank you again!
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Old Feb 15, 2013, 10:34 AM
Safety : practice & promote!
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Joined Dec 2011
4,822 Posts
Random question. Has anybody used one of those great Harbor Freight suitcases with the pull-and-pluck foam inserts to make a carrying box for their 120SR? I was thinking about doing that with mine since I prefer carrying those suitcases to the field rather than the heli's own box.

Seems to me that you'd have to mount it sideways and then carefully support the flybar so it wouldn't be bent. I'm going to be finding a solution to this soon as spring is coming!
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Old Feb 15, 2013, 12:19 PM
Rockin' & Flyin'
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Virginia Beach
Joined Dec 2009
2,845 Posts
I always put my heli on the dashboard and let it warm up on the way.
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Old Feb 15, 2013, 02:27 PM
Wind you go around in circles
Wind Spirit's Avatar
United States, FL, Middleburg
Joined Jan 2012
1,366 Posts
Quote:
Originally Posted by RoboHeli View Post
Random question. Has anybody used one of those great Harbor Freight suitcases with the pull-and-pluck foam inserts to make a carrying box for their 120SR? I was thinking about doing that with mine since I prefer carrying those suitcases to the field rather than the heli's own box.

Seems to me that you'd have to mount it sideways and then carefully support the flybar so it wouldn't be bent. I'm going to be finding a solution to this soon as spring is coming!
Yes, I have one and it works great. I put my DX6i, my 120SR, chargers, and batteries in it. The one I have has a tool holder in the top that you can leave in or take out. I keep tools and spare parts in that. WS
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Old Feb 15, 2013, 03:25 PM
Wind you go around in circles
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United States, FL, Middleburg
Joined Jan 2012
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Originally Posted by Wind Spirit View Post
Yes, I have one and it works great. I put my DX6i, my 120SR, chargers, and batteries in it. The one I have has a tool holder in the top that you can leave in or take out. I keep tools and spare parts in that. WS
PIc.WS
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Old Feb 15, 2013, 03:28 PM
Wind you go around in circles
Wind Spirit's Avatar
United States, FL, Middleburg
Joined Jan 2012
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Quote:
Originally Posted by Saxguy1000 View Post
I always put my heli on the dashboard and let it warm up on the way.
I have no space on the dash, lunch is there warming up.WS
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