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Oct 27, 2008, 03:47 PM
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Moving servo arms by hand.


Hey guys. I was taught not to move servo arms by hand when they are not plugged in and powered up (or when they are, for that matter). The reason being, that you could strip or damage the gear train and mess up the potentiometer. Anyways, I have always got on to people in my design project when they do it. One guy I have been telling not to, for 4 years now, and he still does it, I'm thinking he might be just to annoy me because he knows I hate it. Sometimes when he is asking me a question about how to do something and he has a servo in his hand, he will just work the arm back and forth almost 90 degrees while he is talking to me. I tell him there is a right and wrong way to do things, the right way being to plug the servo in and center it with a transmitter, the wrong way being to move them by hand.

Am I just being anal, or is there really something wrong with moving servo arms by hand?

Jonathan
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Oct 27, 2008, 04:17 PM
Registered User
Within reason, moving an unpowered servo by hand will seldom do any harm. Doing so while powered up very well can damage it either mechanically stripping gears or excessive current drain causing possible damage to electrical components.
Oct 27, 2008, 04:24 PM
k2k
k2k
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k2k's Avatar
I do it all the time when I'm setting up a plane and I've never damaged a servo. I also put back pressure on servos while driving them with a servo tester to test them for gear problems before I install them. You can feel any problems through your fingers. I wouldn't recommend trying to force a servo into reverse travel while powered up, but short of that any servo worth having in your plane should take up to stalled condition without damage. It's the sudden application of a large force like banging a flap on landing that will strip a gear.
Oct 27, 2008, 05:37 PM
Registered User
richard hanson's Avatar
some of the very small 6-7-8-9- gram servos have crude drive trains and YES moving them by hand can strip them.
Some others will strip by simply stalling them

I have repaired them for others (and me) and that was why they were damaged
Oct 27, 2008, 09:03 PM
Inciting Riots
village_idiot's Avatar
JR S241 servos will definitely strip if you move them by hand. Conversely the Spektrum DSP60 digital servos are programmed by turning the arms when the servo is connected to the programming devices.
Oct 28, 2008, 03:37 AM
Registered User

Servo - Do not turn by hand


Not recommended, a servo is designed to be driven upwards from the smallest gear.
Many users are unaware of the actual amount of pressure they can apply when turning a servo by hand, well above a servo's usual rating. Some servos, mainly the large powerfull (e.g. yacht sail servos with long arms) and the smaller park flyer type have been presented with bent pins (which the gears spin on) or damaged cases with pin holes elongated [by the pressure applied when turning by hand] which permits slop, rapid wear and often later jamming of the servo gear train, refer pictures under:
Servo - Installation - Correct Mounting for longer life

29Oct08: refer also post #11 below
"Also, if you figure out how fast the motor is turn when you move the servo arm, the motor becomes a generator. It can cause harm to the control electronics.- Brian, an EAJ"

Much more information available under sub sections
"Glitches & Jitter in Receiver, Servo & ESC - Causes and Cures"
"Servo - Alterations, Calculators, Databases, Leads, Repairs, Convert to an ESC or winch & FAQ."
below
"Radio Systems, Accessories, Alterations and FAQ" at
Alan's Hobby, Model & RC FAQ Web Links

Alan T.
Last edited by A.T.; Feb 06, 2013 at 03:06 AM. Reason: update url.
Oct 28, 2008, 09:40 AM
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udogigahertz's Avatar
Quote:
Originally Posted by richard hanson
some of the very small 6-7-8-9- gram servos have crude drive trains and YES moving them by hand can strip them.
Some others will strip by simply stalling them

I have repaired them for others (and me) and that was why they were damaged
If servos can't stand that "torture", don't put them in your plane!

Moving a servo by hand is a good test of quality, if they fail .... don't use them.

Udo
Oct 28, 2008, 09:47 AM
Registered User
richard hanson's Avatar
Quote:
Originally Posted by udogigahertz
If servos can't stand that "torture", don't put them in your plane!

Moving a servo by hand is a good test of quality, if they fail .... don't use them.

Udo
The little bitty ones will fail this and the lead screw servos used in the teensy weensy Vapor and heli will NOT move by hand.
And they are great little servos.
Oct 28, 2008, 09:59 AM
Inciting Riots
village_idiot's Avatar
The S241 is a pretty good servo, except for turning the arm by hand. It all depends on the amount of reduction in use.
Oct 28, 2008, 10:34 AM
Registered User
Never had a problem moving servo arms, but then do not use the little ones nor the digital ones. And yes, I have replaced lots of stripped gears but that was always a result of a crash. I do own one of the nifty servo testors and it centers them for me when I am setting up the plane. All of my servos are standards and usually ball bearing ones at that.

Cheers,

Chip
Oct 28, 2008, 10:50 AM
Electric Airplane Junkie
bhchan's Avatar
Also, if you figure out how fast the motor is turn when you move the servo arm, the motor becomes a generator. It can cause harm to the control electronics.

Brian, an EAJ
Dec 07, 2010, 09:01 AM
Registered User
Hi Gentlemen,
I was curious if any of you might know of a part that would be appropriate for this application. I am trying to control a potentiometer (270 degree turning radius) with a servo (or whatever would work) via a flexible, high torque cable. The idea is to have a servo that can be programmed via a USB controller to give commands to the servo and thus turn the potentiometer that it connects to. The challenge is that I'd also like to have the potentiometer be manually turnable while connected to the servo and still be aware of its position. In other words I would need a servo with a turning radius of at least 270 degrees and could be turned by hand and would be aware of its position. If anybody knows of a servo like this I'd greatly appreciate a link in the right direction! Thanks guys!
Dec 07, 2010, 09:32 AM
AndyKunz's Avatar
You should post this over in the DIY Electronics area. You'd find a lot more info.

Andy
Dec 07, 2010, 09:38 AM
Registered User
godfrey's Avatar
I have never stripped gears in a servo by turning them by hand, but I tend to do it gently.

Alan is correct. They are designed to be driven upwards from the smallest gear. I don't think turning it into power generating unit is going to affect the logic on the servo - but I've been wrong before.

Quote:
Originally Posted by diyguitarmods
.
I have no idea what direction to point you in other than any website that sells small robot parts. Driving servos via a small microcontroller has been popular for many years.
Dec 07, 2010, 08:08 PM
Suspended Account
Some servos move freely by hand.
Some servos don't move by hand. Never force it or you will break a gear.

Never move any servo by hand while power is applied and TX is on. You will break gear or burn amplifier.
Last edited by John Kim; Dec 08, 2010 at 11:52 AM.


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