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Help! Bad Servo?

#1
My servos on my versa are really sloppy. They were never perfect, but one of them has gotten really bad with the other seemingly not far behind. I noticed a lot of oscillation in flight today, so I grounded it quickly and noticed how far I could move the control surface.


They are the Emaxx 9G servo's I bought from FT and have 10-15 flights on them. I checked the voltage coming out of the RX and it was 4.98v. I also swapped to a different ESC to make sure that wasn't a problem. I'm afraid I'll be cutting up my plane.

Any ideas on what I should do next? Is this a symptom of stripping gears?

Thanks!
 
Last edited:

quorneng

Active member
#2
endfim72
Looking at the video the servo arm is actually moving when you move the elevon.
So any (or all) of these could be the problem:
1, The holes in the servo arm and/or horn could be worn.
2. The servo arm could be moving on its splines.
3. The whole servo could be loose.
4. The servo the gear train could be damaged.

As a mechanical engineer I must say the geometry of your linkage is far from ideal.
The elevon horn is working at a very poor mechanical advantage so any 'slop' in any part of the system will result in free play at the control surface.
It is a good idea to use the outermost holes in the servo arm coupled with the longest horn possible to get the travel required. This set up will minimise the forces in link and its bearings at each end.
 

stay-fun

Helicopter addict
#3
The elevon moves a lot, while the servo horn itself isn't moving much at all. I agree with quorneng, a geometry issue, and from my perspective slop in the linkage stopper, either where it connects to the horn or the rod, or both.
 

herk1

Trash Hauler emeritus
#4
To me it looks like the servo is no longer securely attached inside the wing. You could confirm it by removing the pushrod (first remove the linkage stopper then remove the pushrod at the servo arm), then gently push the servo (maybe by sticking a skewer stick in the slot for example) to test for looseness (and see how it's different from the other side).

I have never liked the idea of unnecessarily installing a servo inside a sealed-up wing, where it's not serviceable without cutting into the wing. That's why I mounted the servos on my Versa Wings as shown in this photo:
 

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