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Help! Any clue what's wrong with my servos?

#1
So this is my first scratch build and I had a really hard time setting up the elevon servo motors. These servos are killing me. When I finally think that they are working, they just shut down and freeze. Sometimes they cause the prop motor to stop working also, I guess it's something to do with the transmitter and receiver.

Anyhow, here is a video showing the problem I'm having. Any clue to why the servos keep shutting down?

https://streamable.com/uapgy
 

FastCrash45

Well-known member
#2
So this is my first scratch build and I had a really hard time setting up the elevon servo motors. These servos are killing me. When I finally think that they are working, they just shut down and freeze. Sometimes they cause the prop motor to stop working also, I guess it's something to do with the transmitter and receiver.

Anyhow, here is a video showing the problem I'm having. Any clue to why the servos keep shutting down?

https://streamable.com/uapgy
Weak BEC on the esc? May work until a load is on them then nothing.
 

FastCrash45

Well-known member
#3
So this is my first scratch build and I had a really hard time setting up the elevon servo motors. These servos are killing me. When I finally think that they are working, they just shut down and freeze. Sometimes they cause the prop motor to stop working also, I guess it's something to do with the transmitter and receiver.

Anyhow, here is a video showing the problem I'm having. Any clue to why the servos keep shutting down?

https://streamable.com/uapgy
On review finally it looks like that one servo has a flat spot in the gears where it can't make the return once it goes full deflection
 

Ryan O.

Well-known member
#4
So this is my first scratch build and I had a really hard time setting up the elevon servo motors. These servos are killing me. When I finally think that they are working, they just shut down and freeze. Sometimes they cause the prop motor to stop working also, I guess it's something to do with the transmitter and receiver.

Anyhow, here is a video showing the problem I'm having. Any clue to why the servos keep shutting down?

https://streamable.com/uapgy
What ESC/BEC are you using?
I also used to have a Flysky and it never worked so if this is your first time with the radio that coould be the problem. if you can find a nearby friend with a different radio system that is willing to try the same thing that shouod answer your radio question. There are plenty of people in the hobby that likely would live to test it so I would do that first.
 
#5
On review finally it looks like that one servo has a flat spot in the gears where it can't make the return once it goes full deflection
The other servo does the same thing. I issue is with the rod attached to the control horn, I think the rod bends and makes the servo's arm bend and the gears inside. However, if this happens in flight, then I'm screwed! The servo can still handle what i'm asking it to, but it just freezes and wouldn't do anything. Is there a way I can ignore the warning it's giving?
 

Ryan O.

Well-known member
#6
On review finally it looks like that one servo has a flat spot in the gears where it can't make the return once it goes full deflection
Nice observation, I have used those servos before and they would be a little inconsistent until run a for a few minutes.
 

FDS

Well-known member
#7
It sounds like the servo linkage is binding. Are you using linkage stoppers?
The servo movement needs to be dead in line with the control horn and the control horn needs to be over the hinge line. Get a few pictures of your set up so we can see what’s where.
 

Andrew

G'day Mate
#8
I can see the control rod bending at full deflection stalling the servo causing the receiver to "brownout", causing power signal warning tone (from TX) followed by ESC start up tone when the receiver recovers power. That servo that stop working is definitely broken now.
Also check the plans, there should a deflection gauge to show how much the elevons should move, I can see you have way to much, move the rod 1 or 2 hole's in on the servo arm, and remember to put in some reflex to the elevons. Also one servo needs reversing.
 
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#9
I've watched yur video a few times and here's what I noticed:

Your push rods seem less than perfect. They shouldn't flex like that during operation.
Make sure you use the right gauge of spring steel, avoid mild steel.
I would suggest taking the arm off the servo and testing the servos without any load.
After you make sure your servos are good you should probably redo your push rods and make doubly sure they a are straight between the Z-bends and that the ends of the Z-bend cannot hook up to either the servo or rudder control horn. I crashed one of my FT Vectors at like that.

The control throws are listed as 12° on the build plans. I can't really confirm this but yours look far bigger than that to me.
12° would be roughly 1"1/16 in height for ever 5" in length.
You should double check and if you find them too big there are several things you can try in order:
Make sure your servo rates on the TX are not set to over 100%, this might cause blockages as the servos go past their mechanical end points.
Use one of the "closer" holes on your servo arm which will both reduce the throw and the load on your servo. The video says to use the middle hole, but the srevo horns on the FT servos are tiny. The hole to use youn your servo arms isorobably the second from the center.
Lastly you can dial down the rates on your TX to get to the throws you want but in turn you will lose some of the resolution on your control surfaces and maneuvers will become less precise.
 
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Merv

Well-known member
#10
Binding linkage could cause the problem. It. looks like you have too much throw for a wing. Turn down the throws and see if that fixes the problem. You may need to bend the push rod to keep it from contacting the servo. Sometimes the gears in the servo are bad and bind.
 
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Wildthing

Well-known member
#11
First, you should never turn off the receiver while the battery is plugged in, always unplug the battery first.

I see the right control rod bending, (shouldn't bend) . Take the rods off and check your linkage stoppers and hinges to make sure they all move freely and if that is good use stronger wire.

Lower your rates, you could be going beyond your hinge travel which is causing the extra load on the servos plus bending the rod.

Check all your connections to the esc and rx, could be a bad connection or weak bec that can't handle the extra load. Try a different esc and see if it does the same thing.
 

skymaster

Well-known member
#12
I think like everyone here your pushrods are weak if they are bending while under no load imagine when fighting with the wind they for sure are going to bend more add a ziptie in the middle. i alsa think your problem is the receiver try moving your radio a little farther away from your plane. i had a receiver that whenever i had my radio near the receiver it would keep restarting. you might have a bad receiver.
 
#13
I think like everyone here your pushrods are weak if they are bending while under no load imagine when fighting with the wind they for sure are going to bend more add a ziptie in the middle. i alsa think your problem is the receiver try moving your radio a little farther away from your plane. i had a receiver that whenever i had my radio near the receiver it would keep restarting. you might have a bad receiver.
The wire kind of looks like it came from a spool and was straightened to make the push rods. That leads me to believe it is mild steel. if that is all you have available you could try shrink wrapping a piece of a bbq skewer to the straight bit to stiffen it up. make sure it doesn't interfere with the control horns, though.

I didn't even notice the receiver browning out. I thought that was the Video looping..
As mentioned this could be because the BEC on your ESC can't handle the amp draw of the stalled servo wich causes the voltage to dip below what the receiver needs fro operation. With just 2 servos to supply power to that would be a very weak BEC- or a damaged one...
The receiver should be working with anything from 3V to 10V. I would not put more than 6 Volts into standard servos. 4.5-5 V would be ideal.
Do you have a receiver battery that you could substitue for the ESC? 3 or 4 AA in series cells should do it.
 
#14
Thank you everyone for the help. I will try to do as you suggest. I might end up just getting new electronics gear. I made mistakes when building the plane that are hard to fix after I hot glued everything, but I will try nonetheless.
 

Wildthing

Well-known member
#15
Thank you everyone for the help. I will try to do as you suggest. I might end up just getting new electronics gear. I made mistakes when building the plane that are hard to fix after I hot glued everything, but I will try nonetheless.
First go through all the steps to diagnose what is the problem , whether it is electronic or mechanical that way you know what to watch for. I (we) have all made tons of mistakes but that is part of the learning process , every build gets easier and better. :)
 
#17
Hot glued parts can be easily removed by warming it up again to remove components and IPA removes the glue residue.
Rubbing alcohol or methylated spirits sprayed on hot glue joints will also creep into the cracks and break the adhesion between the hot glue and the surface it's sticking to. Just make sure not to soak your paper to the point it delaminates.