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Servo on the way out?

Old 02-19-2013, 05:32 PM
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grosbeak
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Default Servo on the way out?

My 50cc SBach has one aileron servo in each wing - Hitec HS-5625s. The one in the port wing sings at while idling at center; I suspected the linkage at first but I've had it off and apart and it appears to move smoothly. In addition, the port wing servo will not hold the aileron up when the Rx is off. That is, if I deflect the starboard aileron up (as in, towards the sky) with the rx off, the servo holds it there. On the port side the aileron sags to just below neutral.

Is this servo on the verge of failure?
Old 02-19-2013, 07:20 PM
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nitro wing
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Default RE: Servo on the way out?

those symptoms are somewhat normal, the singing/ buzzing/whining when powered up and sagging when power is off.
This servo is on the weak side for this application and size aircraft though.

130OZ @ 6 volts is enough for sport scale but well below what most are using for 50cc aerobats, never mind 3D
Old 02-19-2013, 07:21 PM
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Default RE: Servo on the way out?

It is normal for hitec digital servos to buzz around the center position. The sagging of one servo implies the gear set is little bit loose. As long as the servo can hold the control surface in place (without play) when power on, it is in good shape.

What is the torque requirement for the aileron servos for SBach 50cc? 5625s are rated at 131oz-in @ 6v which probably is a little bit of low for 50cc.
Old 02-20-2013, 05:08 AM
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Default RE: Servo on the way out?

The controls sag on most digital servos when power removes, no problems with the gears.

I agree, I wouldn't run those servos on an SBach 50cc unless you're going to take it easy flying it.
Old 02-20-2013, 05:51 AM
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Default RE: Servo on the way out?

I've run 5625s on Ailerons of 50cc birds many times and fly nothing close to easy. I've never had a problem.
Old 02-20-2013, 07:15 AM
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Default RE: Servo on the way out?

I respect the talent it takes to fly 3D well, but I'm not the least bit interested in doing in myself. This is an IMAC plane.

As for the servo specs, I have no idea - this plane is discontinued by the manufacturer. It has flown with the current servos for at least two years.
Old 02-20-2013, 07:50 AM
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Default RE: Servo on the way out?

If you aren't going to be pushing the plane, I'd run it. Worst case is it dies, but the plane should still be controllable enough to get it on the ground?
Old 02-20-2013, 09:37 AM
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Default RE: Servo on the way out?

What RX are you using? Some of the Futaba HS Rx do not support digital high speed mode on all servo channels. For example the 6008HS supports the high speed mode only on the first four channels. The buzzing occurs only on the high speed channels if high speed mode is selected. Typically ailerons will be connected on 1 & 7. In this case, if high speed mode is enabled, channel 1 will buzz but channel 7 will not. Racked my brains as well till if figured out this. If thats the case, look at going to normal mode (see the manual for how to set this) and all servos will be ok.

If the servo allows the control surface to drop when the TX is switched off, it just means some play in the gears. It varies from servo to servo. The 3010s on my airplanes do not allow the surface to move when the RX is off but the 5625s do.

Ameyam
Old 02-20-2013, 11:51 AM
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Default RE: Servo on the way out?


ORIGINAL: ameyam

What RX are you using? Some of the Futaba HS Rx do not support digital high speed mode on all servo channels. For example the 6008HS supports the high speed mode only on the first four channels. The buzzing occurs only on the high speed channels if high speed mode is selected. Typically ailerons will be connected on 1 & 7. In this case, if high speed mode is enabled, channel 1 will buzz but channel 7 will not. Racked my brains as well till if figured out this. If thats the case, look at going to normal mode (see the manual for how to set this) and all servos will be ok.

If the servo allows the control surface to drop when the TX is switched off, it just means some play in the gears. It varies from servo to servo. The 3010s on my airplanes do not allow the surface to move when the RX is off but the 5625s do.

Ameyam
Hey Ameyam,

It is a Futaba R6008. I burnt out a couple of throttle servos during setup and learned that HS mode was the cause, so it's on normal mode now. Good catch!
Old 02-20-2013, 12:44 PM
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Default RE: Servo on the way out?

Servos scare me the most in my planes. I will use one for a year, maybe two, then move them from elevator/ ailerons to throttle, rudder or retracts. I can stand to lose one of those in flight, but not elevator or ailerons. On a new servo, I also like to work it for an hour before using it in a plane. If a new servo goes out when new, it will usually stop working within that hour. After that, I feel good about it in my plane.

I haven't used any digital servos yet so I don't know about the buzzing. But on a analog servo, if it's buzzing, it's drawing amps from the battery. It is also looking for center or is binding. So it's best, if you have one that is buzzing, to look for the reason and fix it.

Frank
Old 02-20-2013, 01:17 PM
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Default RE: Servo on the way out?

Digital servos buzz, they are constantly finding center. It's normal, there's nothing to fix.

Just the weight of the control surface will make them buzz a little. They do it a little less when they get some time on them.
Old 03-16-2013, 06:02 PM
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Default RE: Servo on the way out?


ORIGINAL: grosbeak

My 50cc SBach has one aileron servo in each wing - Hitec HS-5625s. The one in the port wing sings at while idling at center; I suspected the linkage at first but I've had it off and apart and it appears to move smoothly. In addition, the port wing servo will not hold the aileron up when the Rx is off. That is, if I deflect the starboard aileron up (as in, towards the sky) with the rx off, the servo holds it there. On the port side the aileron sags to just below neutral.

Is this servo on the verge of failure?
John, when apart you should be checking that the pivot holes in the case are not becoming oblonged. I bought a 50cc airframe that had been flown with 5625 servo's on aileron duty. It worked for the previous owner, but I would not trust them on a 50cc aileron (single servo/side) application. I beleive you have been handed some good advice, with genuine concerns about operating at the top end of this servo's spec's. My advice would be to upgrade these two servo's in a timely manner. Let's call it an investment. These (5625's) might be better suited as elevator servo's on your next 30cc build. A saved Sbach, surely justifies a new 30cc airframe.
Hope this helps, enjoy your season ahead.
-Snuts-

P.S.
Your Sbach recommends a minimum of 180oz/in servo's on the ailerons.
Old 03-18-2013, 08:29 AM
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Default RE: Servo on the way out?


ORIGINAL: snuts


ORIGINAL: grosbeak

My 50cc SBach has one aileron servo in each wing - Hitec HS-5625s. The one in the port wing sings at while idling at center; I suspected the linkage at first but I've had it off and apart and it appears to move smoothly. In addition, the port wing servo will not hold the aileron up when the Rx is off. That is, if I deflect the starboard aileron up (as in, towards the sky) with the rx off, the servo holds it there. On the port side the aileron sags to just below neutral.

Is this servo on the verge of failure?
John, when apart you should be checking that the pivot holes in the case are not becoming oblonged. I bought a 50cc airframe that had been flown with 5625 servo's on aileron duty. It worked for the previous owner, but I would not trust them on a 50cc aileron (single servo/side) application. I beleive you have been handed some good advice, with genuine concerns about operating at the top end of this servo's spec's. My advice would be to upgrade these two servo's in a timely manner. Let's call it an investment. These (5625's) might be better suited as elevator servo's on your next 30cc build. A saved Sbach, surely justifies a new 30cc airframe.
Hope this helps, enjoy your season ahead.
-Snuts-

P.S.
Your Sbach recommends a minimum of 180oz/in servo's on the ailerons.
Snuts, thanks for the tip. The pivot holes are not elongated, but I will be replacing the servos. I have a pair of Savox 251MGs on order - they're rated to 222 oz/in.
Old 03-19-2013, 05:13 PM
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snuts
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Default RE: Servo on the way out?

Pat yourself on the back, smile and say what a smart fella you are for the upgrade. Beats the guilty feeling you would have had, should you have lost it. Now start looking for another airframe for your 5625's.
Ha-ha.

-Snuts-

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