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Servo centering myth or reality.

Hondo76251

Well-known member
#21
On smaller stuff I do z bends or a piece of shrink tube over overlapping pushrods but I always center my servos first. Sometimes I center with my "Bench" receiver and other times with servo testers, whatever seems easier at the moment. On medium stuff I still do mostly z bends but sometimes use adjusters. On larger builds I almost always use adjusters like shown above...
 

Sero

Well-known member
#23
Servo centring tools IMO are are just more convenient than using the RX. I use a cell phone USB charger to power mine. If the arm doesn't centre perfectly I'll centre manually/un-powered after I put the arm on then use sub trim in the TX to centre when its powered. Or I may put the arm on so that the up elevator has more throw on it than the down elevator for example.

The linkage stoppers/adjusters are great, but I avoid them when I can as I had the lock screw on my elevator come loose during flight once. The lesson: use thread locker. Also you don't need to put a nylock nut on so it spins on the control horn, just use thread locker on that too.
 
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BATTLEAXE

Well-known member
#24
Pro tip- when setting up symmetrical opposing servos like for the ailerons, you need to use the double arms to get them to manually center the arms evenly. The splines on the servo that grip the arm have an odd number of ridges. The arms will only center if facing one direction. If you use the double arms you will find one will go on perfect and the other will go on of center. The one that is off center you turn 180 degrees will go on center to match the other. Then you trim off the arm that isn't needed. Result- two opposing perfectly symmetrical servos with the same range and motion of travel.
 

sprzout

Knower of useless information
Mentor
#27
With a nylock locknut, you could back it off just enough to let it pivot freely.

FYI. Sometimes rotating the servo horn 180 degrees can make a difference on if the horn is centered or not. Especially if the number of teeth on the servo output is an odd number.....
Or blue Loctite. I did that on a combat wing with those very linkage stoppers, and it worked out great. Plus, it's removable if I need to pull them off to put onto another plane.
 

Bricks

Well-known member
#28
I'm not sure I'm following but, if you add a few bends making a 'V' shape along you linkage, you could keep your servo arm in the center and trim by ajusting the pushrod 'length':



View attachment 160123

The problem with this set up is you do not have equal throws in both directions with the same amount of servo movement. Say this is an elevator in the picture you are going to have less down then up elevator. If your transmitter has adjustment for throws, but the problem is you loose resolution on the down elevator. Be better to mount the servo so the control arm would be centered. Most servos can be mounted and centered in one direction or the other. More then likely if you mounted your servo the other direction the horn would of been centered.
 

Sero

Well-known member
#29
The problem with this set up is you do not have equal throws in both directions with the same amount of servo movement. Say this is an elevator in the picture you are going to have less down then up elevator. If your transmitter has adjustment for throws, but the problem is you loose resolution on the down elevator. Be better to mount the servo so the control arm would be centered. Most servos can be mounted and centered in one direction or the other. More then likely if you mounted your servo the other direction the horn would of been centered.
When I look at the photo the push rod is 90 degrees to the servo arm and control horn, which would make the resolution/movement distance equal in both directions.
 

Bricks

Well-known member
#30
When I look at the photo the push rod is 90 degrees to the servo arm and control horn, which would make the resolution/movement distance equal in both directions.

It must be the angle of the picture that makes it look off center if it is centered then my apologia.