Originally Posted by
flyinfool1
To get the real info as to failure modes you would need to pry that info out of one or more of the manufacturers, possible one of the larger dealers. The sample size that any other hobbyist is exposed to is to small to draw a conclusion.
I have had servos fail where they drove hard over to one side. I have had them fail where they simply stopped working as if the power was turned off making them free running. In 45 years in R/C I can only remember 4 in flight servo failures. It is just not real common. 3 Of those were on Helios, the other one was an elevator servo on a 40 size 3D aircraft. I have had other failures but they were all done as a result of stupidity during setup. Maybe I have just been lucky to have such a small failure rate, maybe it is because I never use just enough servo for the job, I don't know.
Will anyone that has connections to a servo manufacturer or distributer chime in here with some real data? I would like to know the real answer also.
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My company was involved in servo manufacturing for 17 yrs (1968-1983). I was aware of all failures reported by customers and in house failures. We cycle tested every servo before shipment and there were a very few that failed in test. I remember one field failure and we found a grain of sand that locked the gear train. Another customer reported a servo reversed in the air and he landed with reversed elevator. My first reaction was this was impossible but later found Mitsumi had changed the way they anchored the magnets in the servo motor and the magnet came loose and rotated 180 degrees under vibration.
I feel vibration is the main cause of servo failure today. If a power connection or signal wire connection breaks the servo is going to be dead. If a pot connection breaks the servo is probably going to drive full travel. I suspect that most servo amplifier failures are caused by over voltage or prolonged high loads from mechanical linkage.
I have been flying R/C models since 1952 and have never personally had a servo failure in the air.