rtstestpilot

My Feedback: (2)

Hey guys, the club I belong to have started to fly SSC with H.O.R.'s built from SttB. We love the way they fly but after about a half dozen flights or so, the throttle servo is "burning out"; we have lost 3 servos on 2 different planes so far. The props have all been ballanced. After 6 or so flights you can't throttle back or kill the engine. If you rotate the servo arm by hand, is feels like a brand new servo. Once it is hooked up to a receiver and you rotate it by hand, it will stick in random spots for a brief moment then go back to acting like it's not powered at all. All this happens just from normal flight, we haven't even used them for their intended purpose yet. Does anybody have any ideas or suggestions to remedy this? We are really looking forward to using our new planes but at the rate this is going would be cost prohibitive, let alone the inconvenience and safety issues. Thanks, Todd

rrh

Throttle servos can be tricky to set up so that you don't stall the servo - the throttle bore is fully open but the servo is still trying to push farther. You have to get the linkage just right. Here is a way to simplify it AND save your servo when you lawn dart. Two separate linkage rods inside the friction fit of the fuel line that slip on impact but open and close the throttle fine.

draftman1

hey Todd, what brand and model are you using? RH's hook up is good also.

rtstestpilot

My Feedback: (2)

Thanks for the tip on the slippable linkage Randy; what a great idea! This isn't the problem yet, our linkages aren't stalled. We have used both a regular and a micro servo with the same outcome. I really think that since it is being mounted directly on the motor mount and is taking every vibration that the engine throws at it, that it is shaking the holy electrics out of it, so to speak. By the way, what plane do you fly and what is the plane in the picture?

rtstestpilot

My Feedback: (2)

I built the 15 size H.O.R. with a new magnum 15. The servos "were" a hitec 81 micro, a jr micro, and a futaba standard. Every one failed with about the same amount of time of engine running as the others.

draftman1

yeap, the good ol 81. those gears will strip when you look at them. I went to all 82mg for all of my combat and small stuff

rtstestpilot

My Feedback: (2)

I'd like the chance to get to strip the gears, so far all the gear trains are in mint condition.

draftman1

wow, it must be a fuel thing then. fuel getting into the servo and fouling it out . thats the only thing I can think of

rtstestpilot

My Feedback: (2)

I guess it could be fuel, I didn't even think of that. I'll have to open a couple of them up and see. I just figured the engine vibrations killed them.

rrh

I've run a number of different servos for throttle successfully right there in the middle of the heat, fuel goo and vibes and they all worked fine until some fatal combat blow ended their life span. I have had hs81s croak in the box just because I looked at them on-line. I bet there is one dieing right now because we are thinking about it...

Blue Note

I will confirm that the fuel spray will kill your servo every time. Just a matter of how long it will take. Get it out of the fuel residue somehow ( shield it or move it away from the engine ) and it will do MUCH better. Good luck.

BNC

Clean

No lie on the 81's. Hell I had one die in Columbia just because I ran it into some pink styrofoam.

GSJames

I would bet that it's oil from the fuel exhaust getting into the pots. I use CRC Electronics Cleaner (you can get it in the Automotive section at WalMart) to clean off the servo after each flight. You might also put an exhaust deflector on the muffler to make sure that the exhaust is not getting on any of the servos.

The slip joint throttle pushrod WILL save your gear train in a crash. Make sure that at full open throttle the pushrod is pointing straight forward. That way when it hits something the load is a straight compression load and not a torque load on the gears.

Also, try putting a standard Battle Axe/Avenger/PhencePost foam wing on your HOR fuselage. You will be surprised at the increase in turning performance and the reduced amount of stalls, snaps, etc.

Have fun!

rtstestpilot

My Feedback: (2)

Well, I opened up the cases of 2 of the servos and they were spotless inside. The hitec 311 standard servo when hooked up with the motor/circuit board removed doesn't respond to signal input initially. If you rotate the armature you can feel resistance in a couple of spots. You can actually spin the shaft and it will take off, move the stick one direction or another and it will stop at a certain point. If you rotate the servo horn (the pot is still inside and attached) it has the same reaction as moving the stick. It's almost like the motor isn't getting full power. The pot works. I haven't ran the jr micro simply because its a pain to get the circuit board and motor out and will assume ( I know, I know) the same thing. Are there brushes in these small motors? If so, it almost acts like they need replaced.

Clean

normally there is a pot in there somewhere, normally on the output shaft, that turns with the arms. It is part of the feedback loop.