throttle servo question/problem

[orthobird]

i have a JR HV 8911 that i had installed into my 3dhs 120" extra , 40% , with DA 170.

on my carb, the spring on the throttle horn is still there, but i have undone the tension on it.

after about 60 flights or so, seems the servo went out on me this wednesday.



i took the plane off, all was good. i started the IMAC basic sequence.

did my roll, then the shark tooth, and on the down side, the throttle was "stuck" on low idle.



i landed the airplane by killing the motor, then i brought her in, tested everything ,seemed to work.



went back out, took her off again, and after the shark tooth, again, throttle stuck. will not respond. i landed the airplane ,and then the throttle servo stopped responding.



anyone else have a problem like this?

how long do you think the throttle servo should last?



seems to me that the throttle servo takes the most stress from all other servos. this is my 3rd throttle servo to go bad on a gas airplane.



what throttle servo do you all use?

 

[Flyin4fun]

well, you are using a Digital servo that has between 200 and 470 oz. in. of torque depending on the voltage that you are using.

There are basically only 2 reasons that you would burn out a 8911 HV on throttle.

(1) the end points for idle and/or full throttle are binding.

(2) chaffing of the servo wire



You will get many answers on correct throttle servo setup and I will not tell you what to do, I will only tell you what I do and I have not had problems with throttle servos burning out.

(1) I never disconnect the throttle spring from tension. (don't need to).

(2) I always get rid of the throttle idle set screw on the carb. (that way at low throttle you are not sending vibration through your linkage to the servo.

(3) I set my high throttle end point (a few clicks) back from where the butterfly ends (no need to peg the butterfly on full throttle to get max rpm).

(4) I use a small piece of Nyrod (split the metal linkage)between the carb and throttle servo. (this greatly reduces the amount of high frequency vibrations that would normally get to the servo without it)(been doing this from my 4 stroke slimmer days).



Believe it or not I have used Hitec 225MG servos (66 oz. in. on 6V) for years without fail.

 

[stangflyer]

Flyin4fun;17684 wrote: well, you are using a Digital servo that has between 200 and 470 oz. in. of torque depending on the voltage that you are using.

There are basically only 2 reasons that you would burn out a 8911 HV on throttle.

(1) the end points for idle and/or full throttle are binding.

(2) chaffing of the servo wire



You will get many answers on correct throttle servo setup and I will not tell you what to do, I will only tell you what I do and I have not had problems with throttle servos burning out.

(1) I never disconnect the throttle spring from tension. (don't need to).

(2) I always get rid of the throttle idle set screw on the carb. (that way at low throttle you are not sending vibration through your linkage to the servo.

(3) I set my high throttle end point (a few clicks) back from where the butterfly ends (no need to peg the butterfly on full throttle to get max rpm).

(4) I use a small piece of Nyrod (split the metal linkage)between the carb and throttle servo. (this greatly reduces the amount of high frequency vibrations that would normally get to the servo without it)(been doing this from my 4 stroke slimmer days).



Believe it or not I have used Hitec 225MG servos (66 oz. in. on 6V) for years without fail.

I too started using Nyrod on all my throttle linkage set ups. They seem to release some of the vibration energy that a solid rod does not. I also set my end point just shy of where my throttle stops at both ends, whether open or closed. I try to take as much stress off the servo as possible. I've used digital servos for throttle on my gassers all along with no failures. With the exception of Nyrod on the linkages, I did the same epa's on all my glow (shudder) motors as well.

17688=11953-Banane09.gif]

 

[orthobird]

Flyin4fun;17684 wrote: well, you are using a Digital servo that has between 200 and 470 oz. in. of torque depending on the voltage that you are using.

There are basically only 2 reasons that you would burn out a 8911 HV on throttle.

(1) the end points for idle and/or full throttle are binding.

(2) chaffing of the servo wire



You will get many answers on correct throttle servo setup and I will not tell you what to do, I will only tell you what I do and I have not had problems with throttle servos burning out.

(1) I never disconnect the throttle spring from tension. (don't need to).

(2) I always get rid of the throttle idle set screw on the carb. (that way at low throttle you are not sending vibration through your linkage to the servo.

(3) I set my high throttle end point (a few clicks) back from where the butterfly ends (no need to peg the butterfly on full throttle to get max rpm).

(4) I use a small piece of Nyrod (split the metal linkage)between the carb and throttle servo. (this greatly reduces the amount of high frequency vibrations that would normally get to the servo without it)(been doing this from my 4 stroke slimmer days).



Believe it or not I have used Hitec 225MG servos (66 oz. in. on 6V) for years without fail.

stangflyer;17688 wrote: I too started using Nyrod on all my throttle linkage set ups. They seem to release some of the vibration energy that a solid rod does not. I also set my end point just shy of where my throttle stops at both ends, whether open or closed. I try to take as much stress off the servo as possible. I've used digital servos for throttle on my gassers all along with no failures. With the exception of Nyrod on the linkages, I did the same epa's on all my glow (shudder) motors as well.

thank you both!!

now i know why i hame burnt out the servo!!!

when i do set up the servo on the end points, i listen to the servo binding, and back off once the buzzing stops. but, what i am not considering is probably that when the airplane engine is running, there is fro and back movements of the carb/motor, etc... and then, it probably binds as you have mentioned!!!



thank you Guys!! i will now go and correct this on all my airplanes.

 

[Tswhite70]

+1 for the nyrod and endpoint adjustments. I can beat the 225MG though, I use the HS-81 nylon gear on all my planes. .09 sec and 41oz-in at 6v with good centering at just over half an ounce in weight.



tsw

 

[yakken]

i use metal gear servos. savox 1258 or spektrum 6040. thousands of flights and no problems yet.(knock on wood)

 

[stangflyer]

Tswhite70;17785 wrote: +1 for the nyrod and endpoint adjustments. I can beat the 225MG though, I use the HS-81 nylon gear on all my planes. .09 sec and 41oz-in at 6v with good centering at just over half an ounce in weight.



tsw

Yikes... HS 81's are great little servos, but Nylon gear train in a big 150cc'er? I'd be pretty reluctant to give that a whirl. Also, only good for six volts. No way I can hook it up to my 7.4 systems without a regulator. And that kind of defeats the purpose of HV servos and 7.4 systems. Been quite satisfied with the HS 5665's I am now using for gas pedals. Whatever works though right?

 

[Tswhite70]

No HV for me yet, running LIFE packs so no worries on the voltage. I guess I should have qualified my comment that I've been running them on 50cc and smaller. So maybe not the best suggestion for a 40% plane. :culpability: Then again we're just talking about something strong enough to move the carb butterfly and then handle vibration over a long period of time without getting sloppy or failing.



tsw

 

[Bunky.F.Knuckle]

I'm overly leary of just 2 mounting points for a servo vs. 4.



Now, if you were talking about a choke servo, it would be a much different story.



I'm using about anything I have laying around as a spare servo for throttles. But, throttle is as vital as a flight control as far as servos go, in my opinion. I will put the best on there as I can afford at the time.



Also, nyrod for a throttle pushrod?? I haven't used nyrod in 15 years. Nyrod went out the door with glow fuel powered airplanes. Nyrod will expand and contract with heat. Of course, I only will use a short section of threaded rod for throttle pushrods.

 

[Bemeson]

I do not use Nyrod either.... I use a 440 rod with it threaded on one end and I solder a threaded brass piece on the other side. I use dubro ball links on both sides. I set up my throttle very carefully and I check for binding before and during motor run up. I use either 1257TG if standard volt and 1267SG for HV. I have over a 1000 flights on one 1257TG and its still going strong.



Brian