Looking for some help with a foamie rudder setup. It is setup on a pull-pull with fishing line. I am having problems with the servo not holding and jumping. The jumping happens at both throw points and is intermittant. Just wondering if it is a bad servo (very possible given that it is a HobbyKing $2 servo.)

Here is the video of what is going on. Could it be something with the Rx to Servo or someone also mentioned it could have something to do with the fail/safe???

Any ideas???

[youtube]http://www.youtube.com/watch?v=3YPHJgWBgwA[/youtube]

Two dollar servo?

Trevor its difficult to pinpoint exactly what is the issue with that servo whether its a striped tooth easy to do when stringing, tieing a pull/pull or a bad feedback pot but it is highly likely a bad servo. Easily checked with another servo by plugging it into the same port.

John

That looks like a classic bad pot to me. If you'll spend a little more money you can have a good performing servo. Don't expect any of them to last long, especially if you're doing 3D flight with them. For low cost but serviceable servos, look at the Solar line. The one complaint I have is that the wires going into the motor and board don't have any vibration protection, but that's easily fixed with a dab of hot glue. Solars center well and are accurate. For quality and durable servos, look at Hitecs or Futabas.

I can not tell from your video but you may have some negative Ackerman built in. If so, this can be very hard on the servo and cause such problems. You want absolutely no Ackerman or some positive. Positive is safer and will not cause any problems. Akerman, if you do not recognise the term, is the geometry of the set up. You want the line not being pulled to go a bit slack as you move the servo off center yet be just barely snug when at neutral. You do this by having the attach point on either the servo arm or the surface horn being offset from a line through the hinge point. If you Google Ackerman, you should be able to find a detailed explanation of it.

If you flew it and had any type of rudder hit when activating the rudder servo you have hurt the servo. I'd swap the servo with a better, metal gear servo.

I have the same plane. It flies very well in the dead calm morning. I get 3 or 4 every year at home.

Toss the servo and get another one. Is that the 9gram servo or is it a 5gram? I do not remember. I am guessing it is the 9gram. I have been replacing all of my 9gram servos with the EXI's.

http://www.hobbypartz.com/9gexidimeges.html

If it is a 5gram, the Tower Pro's are out of stock.



Buzz.

Looks like the servo pot is bad. Do as John said and just hook up another servo into the same RX port and see what happens. I have been using the Hitec HS 55 in my little electrics, so far no problems that I didn't cause myself. I think they are about $10.00.

I will swap the servo out and see if that helps. It is a 5g. I did buy extras since they were so cheap, but I may throw something better in and see if that solves the problem.

They may have been more like $4 but still ridiculously cheap.