Ok, so one of my big concerns is servos. I've learned ANY brand CAN fail. Obviously you stick with the ones you know and trust or have been used successfully a lot by others. But is there a VERY good device you can buy to test servos out? Something you can just plug in and let run diagnostic tests? Maybe detect torque so you can see if it's still has original torque or if the motor is getting weaker.

Signal loss? I don't even know what you'd look for but can anyone help me with how to check and test your servos after you've flown with them for a while (or even buying NEW ones to make sure you don't get a lemon that will fail)?

Good Morning, Although I am not any kind of Expert I am perhaps a long term survivor. So RP80 one practice I have always done for as long I can remember using servos with both new servos and used servos.

Its called by some of us 'burning in the servo' It is simply running the servo continuously back and forth for about ten minutes. In the case of new servos I always do this before installing in the airplane and yes have found some to fail in this way but the rate is quite low maybe 1-2%.

For used servos going into a new airplane: First I carefully move the arm with the servo unplugged from stop to stop looking for gear problems and indeed any slippage doing this is a problem. Next I will plug it into my servo driver listening for any continuous running of the motor, thats bad. At this point I set the servo driver to manual and while holding the servo up to my ear manually go from stop to stop with the servo driver. Doing this you will soon develop an ear for what a heathy servo and gear train sound like. Last I simply Burn in the used servo on the continuous cycle mode with the servo driver as I noted above for new servos.

My orginal servo driver I purchased late sixties or early seventys as an electronics kit was an Ace Servo-cisor and finally gave up two years ago so in the video is my replacement a cheap Hong Kong unit I paid under twenty bucks for and there are many servo drivers out there on the market now.

Anyway here is a short video of it set in the 'cycle' mode to illustrate what I am talking about..

http://www.youtube.com/watch?v=y5hCC...h_0PWTkXPcXnWA

John

I have one of these and it works great. http://york-electronics.com/index.htm won't tell you torque, but will tell you if you have other issues and is great for setting up your servos without a radio.

Cool! thank you guys! John - have you had any servos fail on your plane after havinng done these tests? Or have you been 100% sucessful?
thanks

Any thing can fail at any time. Example when will that light bulb burn out? No way to tell. You can look for clues. Moving the arm by hand feeling for a " skip" in the gears. A sound that you haven't heard before. Or as you return to neutral the control surface wobbles back and forth.

Ditto on what has been said. I take my burn in a little longer, normally 30 minutes. Just me, it's probably doesn't need to be that long. I also grab the output wheel during cycling and add some resistance. This is my way to check the gears. I also do one other thing. I put an amp meter in line with the servo and check it's idle current and it's operating current. Check this against specs. A failing servo motor will draw more amps and is a sign of going bad. I don't measure torque either. I just use the manufactures data. Observation is the best preventive measure you can use. Watch and listen to the servos, they will tell you when they start to go bad. When flying, if it doesn't feel right, land and check it. I've seen too many flyers continue to fly when they comment on soemthing feeling different. just use common sense.

RP 100% is a difficult number to acheve and While I cannot claim that with any accuracy as its difficult to know 'But' I do believe my little procedure I outlined to help reliability to a considerable degree.

Now I have had many destroyed and stripped servos from flutter especially in pylon racing but that is totally unrelated to electronics. Servos are often accused of being causes of that but that is not really the case and it is entirely an outside causes (in my opinion).

Another cause of servo failure also totally outside the electronics factors and that is simple 'Hanger Rash' such as banging control surfaces on doors jams etc.

A Servo tester and an amp meter allows you to test the servos. A digital position readout is a useful addition.
With the one I have, 1000 1500 2000 are the three prime positions of concern.
1500 is obviously 50%, and is very useful when you are setting linkages, etc.
Once a model is trimmed, checking the servo positions can also be useful if you want to eventually fine tune
linkage, etc, or transfer to another TX.

ok, thakns for the additional info. What amp meter can I buy that will work for our scenario. Also chuckk2 - what tester do you have that you mention?

Hanger 9 makes a current/voltmeter. HAN172
A servo tester and readout from the same company that made the
two separate units I use. The separate units can be used independently.
Use the web to find best price, etc.
http://www.hobbylinc.com/htm/emo/emoemo1001.htm

Her's a great one.
http://www.vexacontrol.com/xciter_details_1.html
I've been using one for years and I always use Futaba servos. There's no sense in saving a few bucks on servos when it comes to a model worth over $1000. Dan

Not an expert, but I test all my servos prior to use, the Brand names get an hour on the servo tester and the cheaper chinese servos will get longer

Its hard to test under actual conditions though, and sitting on a servo tester is not the same as the vibration in a helicopter or plane.

I have had several servos develop issues (surprisingly they were the Brand names)

Usually problems will become apparent before a total failure (not always) but fortunately this was the case for me. The Hitechs were on the collective of a 450 Helicopter and started to develop slight jitters during normal operation.. I noticed it during a preflight so I replaced all servos and the 2nd batch are still fine.

The Futaba Tail servo did the same thing, after about 600 flights it started making a screeching sound, (like a dry bearing in an electing motor) then within minutes of ground testing it failed completely.

Careful preflight and ongoing monitoring "might" catch an impending failure before flight..

This video shows how I test my servos - but usually only for an hour.

http://www.youtube.com/watch?v=kY5Uf3Y5GMI These two servos have been working flawlessly on two helicopters for over two years and many hundreds of flights.

A servo tester is a good way to compare servos - here is a demo of a faulty servo beside two good ones.

http://www.youtube.com/watch?v=BgoztDiEZ7k

Fortunately, the motors and signal processing components usually outlast the gear trains and potentiometers. Gears are easy enough to test for, and pots show up as a case of the jitters at some point in the servo's travel. Testing like these guys are talking about will ferret out the servos that are defective from the factory, and from there it's highly unlikely you'll get a failure other than gears or pots for years to come.