ORIGINAL: Rudeboy
So the HS-81 I had on the throttle of my Diamond Dust died after about 15 flights. As far as I can tell, the feedback pot couldn't stand the vibes the West 36 is putting out.
Since it fits the same mount, I'm going to try a HS-85 next...I opened up both servo's and the HS-85 appears to built a little bit more solid.
But I was thinking: the reason the servo died is probably because it is resonating in sync with the engine at some point. I mean, I use HS-81 for the cut-off in Q-500 planes, and those engines aren't exactly soft natured either. They hold up fine in that application..........
Rudeboy, as an
ex-retailer who did in excess of $800,000 business with Hitec RCD across 6 years, I can verify that your first 3 thoughts on this issue go right to the heart of the problem like a guided missile. Uncanny.
1) It is the feedback pot that gets killed when hs-81's are exposed to vibration.
2) The hs-85's f.b. potentiometer is isolated one shaft further away from vibration coming in through the output shaft than the hs-81's pot. Use them!
3) the reason the 81's held for you on Q-500 cut-offs is because with that linkage vibration only makes it past the output shaft, to the pot when the linkage is under tension (which terminates the vibration).
Soo, long story short, in dealing with customers returning failed servos, I found out right away that while the electric flyers got superb reliability from the hs-81's, the glow flyers experienced an atrocious failure rate. And it was almost always the pot that failed.
If you go to the hs-85's for your vibration intensive applications and you are still killing them,
then something truly is wrong with your installation.