Mechanical Adjustment of Servo Linkages for Stable Hover - RC Groups
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Nov 21, 2011, 12:46 AM
Team WarpSquad
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Mechanical Adjustment of Servo Linkages for Stable Hover

To adjust the servo arms mechanically, means you trim the heli by lengthening or shortening the servo linkages. Instead of using the trims on the remote controller. Doing it this way preserve the full servo throws. Both forward and backwards.

Perhaps others could chime in on better step by steps...but here is a summary of what I do when I first get a heli.

Remember to get the heli up in the air to accurately see which way it's drifting. Keep the heli away from the ground. Otherwise the downdraft from the rotor wash will affect your heli and cause your heli to drift, messing up your result. This issue is evident if you try to trim in too small a room as well. The rotor wash will affect the heli, nullifying your effort.

Step 1a: Reset the remote control's electronic trim back to neutral.

On the 9958 remote, it's about 15 clicks from the endpoints. You can tell when your remote's electronic trim is neutral when you hear a long beep. Note: Only the throttle, elevator and aileron has a neutral trim position. I don't think the rudder does.

Step 1b: Adjust rudder
Rudder trim is responsible for the heli spinning left or right.

Start by giving throttle to get your heli in the air. Ignore the forwards/backwards or any tendency of the heli to slide left/right. Use the rudder trims on the remote to get the heli to stop rotating. Once the nose of the heli is pointed in one direction, you are ready for mechanical trimming.

Mechanical trimming

Step 2: Trim out the forward or backwards movement of the heli.

Pop off the servo linkage responsible for forward and backwards flight. You can simply move the remote stick forward and backwards to so you can determine which servo linkage is responsible for the forwards and backwards movement of the heli.

If the helicopter moves forwards. Then you have to lengthen the linkage to give it some backwards trim. Simply turn it counter clockwise to lengthen the linkage. I find that on the 9958, you can do a complete full turn or half turn. How many turns clockwise depends on how much trim you need. Just roughly guess. I'll start with 5 complete turn if there's a lot of forward momentum.

Conversely, if you the helicopter moves backwards. You shorten the linkages by simply turn the linkage clockwise.

Step 3. Trim out the left or right movement of the heli.
The concept is the same as the above.

If your heli is moving too much to the left. Twist counter clockwise to lengthen the servo linkage.

Conversely, if your heli is moving too much to the right. Twist clockwise to shorten the servo linkage.


Eventually, you'll get proficient in doing this. It takes a few seconds for each step. And you'll be able to get your heli to hover in place, retaining the full, balanced throw of the linear servos.

From this point, you can use the electronic trims. Usually, very little is needed if at all. And you can electronically trim to compensate for battery voltage drop during your flight or for different battery types and sizes.

For outdoors flight, you can use the electronic trim to give more forward bias and still be able to go back to neutral position for indoor flight.

Anyways, the above is how I learn to do it. Not sure if it's correct. But it works for me. Hopefully others can add or give further insight into this.

Last edited by Daryoon; Jan 11, 2012 at 09:24 AM.
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Dec 08, 2011, 09:58 AM
Registered User
heli noob here. if you have the time sir, can you provide pictures or better yet a video on how to do this? thanks
Dec 09, 2011, 02:34 PM
Team WarpSquad
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Thanks...I have a bunch on my plate right now. But I'll put this request in the queue and see what I can come up with.
Jan 20, 2012, 08:56 AM
We can rebuild it!
djdavies83's Avatar
Hey thanks for the guide, mine is in serious need for mech trimming, I've maxes out the "click trim" and it's still playing up. I had a rough idea of what I should do but now I've read your guide I am confident I'll get a good result.

If I am lucky I will get to do it today, I see photos will be useful so I'll take a shed load of photos from all sorts of angles while I'm doing it and you can fit whichever ones work best into your guide.
Last edited by djdavies83; Jan 20, 2012 at 09:10 AM.
Jan 20, 2012, 09:29 AM
Team WarpSquad
Daryoon's Avatar
Thanks. And good luck.
Feb 21, 2012, 12:44 PM
Registered User
Thanks for the guide, has been perfect for a newbie!
Feb 26, 2012, 09:41 PM
Registered User
EdmundGerber's Avatar
What if the heli moves in an ellipse? As soon as I lift off it wants to start moving in an elliptical pattern, that slowly gets larger and faster. I'm dealing with 4 different directions and am unsure what to adjust.

Do these have a tendency to behave like this, or have I gotten a dud?
Feb 27, 2012, 12:25 AM
Team WarpSquad
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The condition you're describing is known as TBE (Toilet Bowl Effect).

All the micro heli will behave this way if the flybar is binding. I would take apart the head, linkages, flybar, blades. And then put it back together. Sometimes that's all it takes.

Check to ensure the linkages are on correctly and swing freely.

It should not be doing that if everything is working properly.
Feb 27, 2012, 04:36 AM
We can rebuild it!
djdavies83's Avatar
Morning Daryoon, anti quite had time to fully adjust mine yet, it's better but not quite there, I think I have excess play in my linkages, ant idea how to sort them out?

In the mean time here is an example image I made during my last attempt.
Mar 30, 2012, 11:09 PM
Crash and learn

Mechanical Trim and Battery Drain

Three V911's fly about the same after breakin. All hover fairly well. One I adjusted servo pushrods and arms to hover better outdoors. I hardly ever hover except to recover during breaks in wind-surfing.

Seems that after adjusting servo pushrods two or three full turns, the V911 eats batteries faster than it did before. Motors run cool. Maybe the helicopter was unbalanced before adjusting and now uses move power to re-balance into a hover attitude.

Well, I would not be able to undo the trim if I wanted to as I wasn't keeping track. Have six 130mah batteries and no smaller 120mah (normal) batteries.

Not sure what to try to get longer flights again and I am afraid to touch the other two V911's. I figured two of the three would be trashed by now with the way I fly (reckless is an odd word)..
Mar 31, 2012, 09:56 AM
Team WarpSquad
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That's an interesting observation Ribble. Any way to twist it back 2-3 turns to reset it to the position it was before you mechanically trim, just to see if the battery drain continues.

Is the swashplate rubbing the main shaft?
Apr 02, 2012, 02:45 AM
Crash and learn
Everything turns freely. Don't see any swashplate problems.

Only lubrication was a drop of oil on the tail motor shaft because I use rudder a lot while playing in the wind..

Blades are beat up and dented. In next series of flights, I will install new blades and see if that makes a difference.

Will experiment and make the pushrods longer then trim again.
May 05, 2012, 06:29 PM
Newbie to helis


Is there any place I can learn heli jargon? I can't seem to understand anything
May 05, 2012, 06:56 PM
Team WarpSquad
Daryoon's Avatar
Perhaps start with this:
May 09, 2012, 04:15 PM
Newbie to helis
Originally Posted by Daryoon

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