Servo gear replacement

[billyd]

I just replaced the gears in one of my 9252 servos. It works great and I saved a bunch of money over buying a new $75 servo.

After I closed up the servo I got to thinking (always dangerous)... was I supposed to align the gears (specifically the one moving the servo arm directly) in any special way radially?I noticed the servo arm gear had stops on it, and when I installed it I simply put the stop inbetween the capture points in the servo body.

As I said, all is working well I have full travel in both directions, I even bumped up the EPA to 140% in the tx and no problems. Did I just get lucky or does the servo just recenter itself based on where it finds those stops post gear install?

[DavidH]

You did correct. The nub on the output shaft gear is positioned between the stops located inside the top servo case.

David

[billyd]

Thanks David. So I guess you don't have to center the servo motor and be sure to get that gear stop in the middle of it's travel?

Does the servo just auto adjust it's center to the stop on the gear? It seems like that's what happened.

Anyway just curious how the servo motor and circuitry knows when to stop so that the mechanical stop doesn't cause a gear to strip.

[DavidH]

The stops are there to control the travel of the servo each direction. All you have to do is install the output gear with the nub between the stops. No centering of the nub on installation. The pot is what controls the travel each direction. The centering pulse comes from the transmitter to the receiver and then to the servo. Pulses from the transmitter is what tells it which direction to travel and how much to travel.

David

[billyd]

I appreciate it !! Nice design.

I wish Futaba made a metal gear set for the 9252's. Maybe they do, but I couldn't find them. The vinyl gears are pretty delicate. Then again, it does protect the expensive parts of the servo by not allowing large forces to get to the motor or in turn to the circuitry.

[DavidH]

Futaba makes metal geared servos that are equilavent to the 9252's. The metal geared servos have plastic gears in the gear train also. It is usually the first and second gears that are plastic. They will break in a crash also. You have to have a weak link somewhere in the gear train or it will destroy the servo.

David