<html><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><div>Comments below:</div><div><br></div><div apple-content-edited="true"> </div><br><div><div>On May 22, 2008, at 8:05 AM, Scott wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"> <div> <div><span class="611385614-22052008"><font face="Berlin Sans FB">There was some of the typical RC discussion at Hemet - and one topic that came up, as it usually does, is servo wear and replacement. With today's digital servos, I have the following questions about digital servo replacement;</font></span></div> <div><span class="611385614-22052008"><font face="Berlin Sans FB"></font></span> </div> <div><span class="611385614-22052008"><font face="Berlin Sans FB">1) what are the symptoms of a digital servo that is starting to wear out?</font></span></div></div></blockquote><div><br></div>In flight, the plane will lose the "locked in, tight" feeling that it (if initially properly set up) had when new. You'll think that you're flying in light turbulence even though it may be calm out. Other symptoms to look for are the plane doesn't consistently roll axially anymore (assuming it once did!), due to the servo endpoint having changed slightly due to the change in pot resistance from the wearing in the pot element (I check this in flight with multiple up and down line rolls in both directions, 3 or 4 rolls in a row). If you measured your aileron deflections you would likely find that one or both of the aileron "throws" had changed from their initial settings by 0.1 or 0.2 degrees (assuming you had accurately set them with a precision instrument to begin with).</div><div><br></div><div><blockquote type="cite"><div> <div><span class="611385614-22052008"> <font face="Berlin Sans FB">- poor centering ?</font></span></div></div></blockquote><div><br></div><div>Yes, but you will only be able to see it if you put a long pointer on the servo, put the radio in "servo sweep/test" mode, and look for a slight pause as it passes center. I use my laser deflection system to check for this when the servos are installed in the plane.</div><br><blockquote type="cite"><div><div><span class="611385614-22052008"><font face="Berlin Sans FB"> </font></span></div> <div><span class="611385614-22052008"> <font face="Berlin Sans FB">- does this equate to a louder 'buzz' at center</font></span></div></div></blockquote><div><br></div><div>Sometimes, but not usually (more likely on the rudder if the cables are tight).</div><br><blockquote type="cite"><div> <div><span class="611385614-22052008"> <font face="Berlin Sans FB">- is the only way to tell this to put a servo on some sort of protractor and look at the centering?</font></span></div></div></blockquote><div><br></div><div>See above.</div><br><blockquote type="cite"><div> <div><span class="611385614-22052008"> <font face="Berlin Sans FB">- does thee servo draw more current?</font></span></div></div></blockquote><div><br></div><div>Not significantly.</div><br><blockquote type="cite"><div> <div><span class="611385614-22052008"></span> </div> <div><span class="611385614-22052008"><font face="Berlin Sans FB">2) What tests can be performed either 'in the plane' or 'outside the plane' to determine if a servo needs to be replaced?</font></span></div></div></blockquote><div><br></div><div>In the plane, see above. Outside the plane, I mounted a laser emitter to a servo arm, clamped the servo to a lightweight, portable vise, pointed the "dot" at a point on the wall, put the system into "servo sweep/test mode", and look for a pause or slowdown as it passes through center (same as the in-plane test).</div><br><blockquote type="cite"><div> <div><span class="611385614-22052008"> <font face="Berlin Sans FB">- In plane testing would be ideal, but we must compare against a 'new' servo, so maybe this is not practical.</font></span></div> <div></div></div></blockquote><div><br></div><div>No need to compare, new servos don't exhibit any of these characteristics (at lease the ones I use don't).</div><br><blockquote type="cite"><div><div><span class="611385614-22052008"><font face="Berlin Sans FB">Any thoughts on the above would be considered.</font></span></div> <div></div></div></blockquote></div><br><div>For the guys flying glow, you can expect the servos to show signs of pot wear (primarily to vibration) on the ailerons at around 35-50 flights, closer to 80-100 on the elevators and the rudder. And contrary to popular belief, it doesn't matter "whose" motor mount you are using, the answer is the same. It's also good practice with glow setups to change out the servo gears every other time you change the pots.</div><div><br></div><div>For electric the magic number is around 180-200 flights, with the culprit being pot wear due to the wiper sweeping back and forth over the element under normal usage (i.e. simply wearing out).</div><div><br></div><div><br></div><div>As always, YMMV </div><div><br></div><div>Jerry</div><div><br></div><div><div>Budd Engineering</div><div><a href="mailto:jerry@buddengineering.com">jerry@buddengineering.com</a></div><div><a href="http://www.buddengineering.com">http://www.buddengineering.com</a></div></div></body></html>