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Old Aug 28, 2012, 01:38 AM
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7oneWo1f's Avatar
United States, MN, Minneapolis
Joined Nov 2011
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programmable servos for 3D flight

So, what's your experience for servo arm travel versus torque, speed, stripping gears, and 3D flight?

I use 5065MGs on my MXS. This are digital programmable servos with provisionable center, end points, and failsafe.

I am wondering what the trade offs are with regard to setting up the servo with reduced travel.

I.e., if I set up the servo arm swing for ~+/-60 degrees corresponding to end point adjustments of +/-150% on my DX8, it seems to me that I would gain resolution and lose speed.

How will this affect snap rolls and pop tops?

Intuitively, I think the wider swing will also be less likely to strip gears.

On the MXS, I had the servo programmed to probably +/-35 to +/-40 degrees of swing. I am thinking about going +/-60 degrees of swing for +/-150% on the DX8, and not using the G10 control arm.

I stripped a main gear recently (bent a tooth) while doing flat spin out of a high energy pop top, with full throttle and full rudder deflection in the flat spin. I tried to pull out of it but the rudder was stuck. I called bad servo on the way down (though the peanut gallary said it was dumb thumbs), and cut throttle right above the corn. The corn saved the plane.

On the ground, the rudder seemed to start working again (ugh, now they really wouldn't believe me, but upon inspection, the rudder servo would stall if there were light resistence placed on the rudder in one direction. Tonight I disassembled the gears and examined them with a loupe, and a tooth was bent and the gears would not mesh at that tooth. Reputation saved. (Not really, I did have a dumb thumb incident a few flights later, but lucked out with not much damage).

Feel free to educate me. I've only been flying for a little over a year, and my knowledge is based on RCG and thinking about things...but, I'm no mechanical engineer so maybe I have some things backwards.
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Old Aug 28, 2012, 03:17 AM
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theKM's Avatar
central PA.
Joined Sep 2004
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5065's, for some reason or another... are not as rugged as analog HS65's. All 5065's have had a shorter lifespan (gears, slop, electronics, whatever).

as for geometry and what the servo can do for you, that's just a question of load: size of control surface, how freely the surface is moving, loss of mechanical advantage with longer arms/throws, and how fast you want to be flying when you hit full deflection.

For learning 3D, 45 degrees throw on elevator is ideal for a number of reasons, but not the least of which is that you give a bunch of mechanical advantage back to the servo.
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Old Aug 28, 2012, 01:38 PM
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7oneWo1f's Avatar
United States, MN, Minneapolis
Joined Nov 2011
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Thanks theKM.

Based on replacing the gears in an HS5065MG, the gears are the same (Hitech part number 55315). It might be the electronics, digital jitter, or something else.

I think I am going to pull the control arm back on my MXS when I replace it, and see if I can still get full rudder throws. I think I will be able to no problem. I'm thinking my pop tops might become a little less crisp, but I don't know. Gotta experiment I guess.
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Old Aug 28, 2012, 06:56 PM
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United States, NC, Hertford
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Hs65s blow back under heavy loads. Where the 5065s will do everything they can not to. The digitals will burn out or bust gear while they try to hold position.
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Old Aug 28, 2012, 08:40 PM
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That is a plausible/believable explanation, losifanatic. So, which would be better? Seems the blow back.

I just checked, and the servo does have an overload protection output power rate setting for V2.0 5065MG servos. You can set it to off, 10, 20, 30, 40, or 50.

I just checked on some threads at helifreak, and some 5065mg user recommended a setting of 20 for 20% power reduction.

I just pulled out the manual sheet that came with my new servo, and it says something a little different:

Quote:
Overload protection: This function is to protect the servos from the overload condition. Once the servo is overloaded for a certain period of time, the motor output will be reduced to the level that the user programmed to the servo. Please note that this function is deactivated (off) in the factory setting.
.

So in this case 20 would be an 80% power reduction.
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Old Aug 28, 2012, 08:51 PM
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United States, NC, Hertford
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I have just resently turned on my overload protection on all my servos. I set them all to 20. I was having issues of my digitals burning up when l was being really mean to my planes. So far l havent had a servo go out since l turned on the protection. Though l still am in the middle of a repair to my 42" slick so l havent tested my 5065s yet.
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