Originally Posted by izzy-israel-73
hi I have been running hitec 225 servos in most of my planes I have had 3 of them bow up and seize but not while flying what could cause this to happen?
Looks like no one ever responded. This is an old question but worth a reply.
Serovos fail for a variety of reasons.
Defect - stuff happens
Wires too small - if the wires going to your servos are too thin they will cause a voltage drop under load. As the servo tries to do its job it will have to draw too much current, will heat up and fail.
Broken gears - This is usually caused by impact with a surface. Common on flaps on gliders. Or it could be that the servo being used is really too small. As a result the gears on the servo are too small for the stress being applied.
Overload - The servo is not strong enough and as a result it is working hard causing it to draw more current than it should which generates heat and can eventually cause in internal failure.
These last two are the most important because they can cause problems with more than just the servo.
Draggy push rods
- If your push rods are draggy the servo is working hard just to move the rod, forget about the surface. This can be caused by a dirty guide tube, something rubbing along the push rod. If you disconnect the push rod from the servo and the surface it should move smoothly and without drag. If it is dragging or stiff you have a problem.
Miss aligned push rods - This is similar to the draggy connection rod issue above. The miss aligned rod will cause a side load on the servo. This can stress the bearings or the case as well as the motor. If it is severe enough it can even cause the servo to get locked in a position which will draw a lot of power and eventually burn up the servo. The servo has to work harder to overcome this issue meaning it will pull more current than it should. You will either end up with worn sloppy gears, worn bearings, or burn out the servo.
These two problems often cause the servo to not be able to center properly. This can leave the servo under load even when you have the sticks centered. This can cause the servo heat up and eventually fail.
This can also put a high drain on your flight pack or the BEC of your ESC causing rapid pack drain. If your flight pack voltage gets too low it can cause a shutdown of your receiver leading to loss of control and a crash. This is a common cause of crashes that are blamed on the radio system but which are really a power issue .that may be caused by a poor servo installation.
If the BEC of your ESC gets too hot due to this constant load it can cause a thermal shutdown, you lose power to the receiver and you lose control of the plane. Again, This is a common cause of crashes that are blamed on the radio system but which are really a power issue that may be caused by a poor servo installation.