Does trimming put stress on servos?
09-24-2003 | 11:27 AM
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From: Kennewick,
WA
Does trimming put stress on servos?
Got to thinking yesterday about servos and had a question, although it's probably minimal.
When you install your radio gear, everything is done in the servos neutral position. So when you take the plane out to fly, and you realize that you need to make a few trim clicks one way or the other, the servo is now out of neutral position and is "working" even if you aren't moving that control. SO the servo is drawing power to hold that trim position.
Wouldn't that reduce battery life and servo life?
When you install your radio gear, everything is done in the servos neutral position. So when you take the plane out to fly, and you realize that you need to make a few trim clicks one way or the other, the servo is now out of neutral position and is "working" even if you aren't moving that control. SO the servo is drawing power to hold that trim position.
Wouldn't that reduce battery life and servo life?
09-24-2003 | 12:14 PM
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From: Toronto, ON, CANADA
RE: Does trimming put stress on servos?
Servos only drain power when they are trying to hold the position they have been told to hold.
The control stick and the trim slide together tell the servo where to go to. The servo will move to that position. Anything that tries to move the servo from that position will cause the servo to try harder to keep itself in position.
Trying to think of an analogy... how about the cruise control on your car.
You set it to 50, the car travels at 50. On the flat sections, the car has to fight air resistance which is trying to slow the car down, so the car automatically "presses the gas pedal" to keep the speed constant. This "draws energy". The car hits an up-hill, the gas gets pressed harder to keep speed. This draws even more energy. The car goes down hill, and the slope counter-acts the air resistance so the pedal is released.... draws less energy even though it is keeping speed. Hits a really steep down-hill, you have to press the brake, consuming energy...
Change the cruise control setting, and the car needs to use energy to adjust to the new setting.
Basically, the position of the stick, and trim, sets the "cruise speed" of the servo, and the energy required to keep the servo in that position dictates the amount of power the servo consumes from the battery. Strong forces on the control surface, regardless of the servo position, will require large amounts of enery to counter-act. No forces on the control surface will require no energy to counter-act.
gus
The control stick and the trim slide together tell the servo where to go to. The servo will move to that position. Anything that tries to move the servo from that position will cause the servo to try harder to keep itself in position.
Trying to think of an analogy... how about the cruise control on your car.
You set it to 50, the car travels at 50. On the flat sections, the car has to fight air resistance which is trying to slow the car down, so the car automatically "presses the gas pedal" to keep the speed constant. This "draws energy". The car hits an up-hill, the gas gets pressed harder to keep speed. This draws even more energy. The car goes down hill, and the slope counter-acts the air resistance so the pedal is released.... draws less energy even though it is keeping speed. Hits a really steep down-hill, you have to press the brake, consuming energy...
Change the cruise control setting, and the car needs to use energy to adjust to the new setting.
Basically, the position of the stick, and trim, sets the "cruise speed" of the servo, and the energy required to keep the servo in that position dictates the amount of power the servo consumes from the battery. Strong forces on the control surface, regardless of the servo position, will require large amounts of enery to counter-act. No forces on the control surface will require no energy to counter-act.
gus
09-24-2003 | 01:45 PM
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RE: Does trimming put stress on servos?
Backwing, you are correct in your thinking. If a surface is deflected into the airstream, the air will push on it (and the servo), and it WILL put more strain on the servo than if it were straight.
But the amount is so minimal, that throughout a day of flying, you may reduce your battery life by about 30 seconds.
But the amount is so minimal, that throughout a day of flying, you may reduce your battery life by about 30 seconds.
09-24-2003 | 03:11 PM
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From: Laurel, MD,
RE: Does trimming put stress on servos?
There is no magic "center" for servos, as I think Gus was saying. So holding the servo off center is no different from it holding at any other point.
However, as Minn said, your controls surfaces do have force on them when deflected, and even some force on them when "not deflected", In fact, I doubt you really ever "know" where the "zero force" point is for a control surface. The servo also has to work against the weight of the control surface and any forces created by the hinges or anything else. And if you add in things like turbulance that is constanly trying to "flutter" a control surface, I think it's safe to say that a servo in flight never has 0 load, no matter where the surface is. The good news is that the load is going to be small, and like Minn said, it's not noticeable.
However, as Minn said, your controls surfaces do have force on them when deflected, and even some force on them when "not deflected", In fact, I doubt you really ever "know" where the "zero force" point is for a control surface. The servo also has to work against the weight of the control surface and any forces created by the hinges or anything else. And if you add in things like turbulance that is constanly trying to "flutter" a control surface, I think it's safe to say that a servo in flight never has 0 load, no matter where the surface is. The good news is that the load is going to be small, and like Minn said, it's not noticeable.
