Servo questions, size and precision

[Andy.T.]

Hello, I have a couple servo questions that I didn't quickly find already discussed. So far, the planes I've built have been single engine swappable sizes mainly. 9g servos have all been fine. I've used these specific 9g servos in half a dozen planes or so recently to decent effect. I've seen ~15% either DOA or die first time I plug them in, but I assume this is relatively normal for a 3-5$ servo.
But these questions I am curious about because the next two build project both represent an aspect of RC that will be new for me. First up is size based. I am planning on building an FT Guinea Pig this winter. I'm curious, at what rough model weight or size or speed etc, would be good to move up to a bigger, presumably stronger, servo? I think I've seen mention of 12g and 17g servos being a thing.
Second question is related to precision of the servos themselves. These cheap servos, I don't know that they have a large degree of precision. It's always seemed to me that they only provide limited amounts of positions as they move through their motion range. Another winter build will hopefully be a 3d plane. going to start w/ FT-3D, and eventually probably a FT Edge. Is it recommended to use anything different for aerobatic planes' servos?
Thanks in advance!

 

[Merv]

...I've seen ~15% either DOA or die first time I plug them in, but I assume this is relatively normal for a 3-5$ servo....

I use the cheapest 9g servos I can find, about $1 each. My doa rate is about the same, maybe a bit less, 5-10%.

...I'm curious, at what rough model weight or size or speed etc, would be good to move up to a bigger, presumably stronger, servo? ...

I would use a larger servo on a plane 150% of the standard FT plane. Anything over 2 pounds or so.

... Another winter build will hopefully be a 3d plane. going to start w/ FT-3D, and eventually probably a FT Edge. Is it recommended to use anything different for aerobatic ...

I fly both the FT3D & Edge with 9g servos. They work great for me.

 

[Andy.T.]

I use the cheapest 9g servos I can find, about $1 each. My doa rate is about the same, maybe a bit less, 5-10%.

I would use a larger servo on a plane 150% of the standard FT plane. Anything over 2 pounds or so.


I fly both the FT3D & Edge with 9g servos. They work great for me.

Great, thanks! Good to know I'm not doing something silly and unknown with the servos causing an oddly high DOA rate. Also super good confirmation on the rough size plane to upgrade servos on. FT Guinea Pig page in the store lists a model weight of 2.2lbs, but 9g servos. Seems like that might be a good one to put 12g's in tho, eh?
Do you ever replace the cheap servos proactively? If so, whats your criteria for replacing servos in planes? It'd be shame to find out it was time to replace a servo when it crashed a plane, even when it's 8$ of foam board. Oh! And, some of the planes might be slightly inconvenient to say the least to rip out servos; do you plan on ease of access for servos as a factor in design?

 

[Merv]

...Seems like that might be a good one to put 12g's in tho, eh?...

If I had 12's on hand, I would consider using them. But I wouldn't special order them, the 9's will likely work just fine.

...Do you ever replace the cheap servos proactively? If so, whats your criteria for replacing servos in planes?...

I always check the servos after a crash. Apply a bit of resistance to the servo arm as it makes it's way back & forth. They will generally begin to have a catch somewhere in the travel before they completely give out.

...do you plan on ease of access for servos as a factor in design?

Yes, I have recently begun to use 3D printed servo trays to make changing them or transferring them to a new air frame, far easier than hot gluing them in. The servos are screwed to the trays.

The servos generally last much longer than the planes and are transferred several times to new air frames before they give up the ghost.

 

[Mr NCT]

The servos generally last much longer than the planes and are transferred several times to new air frames before they give up the ghost.

Me too! I give them a pretty good test between planes, but I have some that are in plane 3 or 4.

 

[Andy.T.]

If I had 12's on hand, I would consider using them. But I wouldn't special order them, the 9's will likely work just fine.

I always check the servos after a crash. Apply a bit of resistance to the servo arm as it makes it's way back & forth. They will generally begin to have a catch somewhere in the travel before they completely give out.

Yes, I have recently begun to use 3D printed servo trays to make changing them or transferring them to a new air frame, far easier than hot gluing them in. The servos are screwed to the trays.

The servos generally last much longer than the planes and are transferred several times to new air frames before they give up the ghost.

cool, makes sense. I suppose I'll just try a Guinea Pig with standard 2836 1120Kv @ 3S and 9g servos and see if I end up needing to adjust anything. I thought I remembered seeing a thing or two once referencing not enough power on a twin C pack. That seemed surprising tho, as I'm pretty sure two of the orange 2836's w/ a 10x6 is well within spec for the motors and to my testing make 1.1-1.2kg of thrust per.
Do you mind sharing any pictures of the servo trays in use? I'm having troubles envisioning what they would look likeand be easier to work with. I've been super excitedly awaiting a 3D printer getting up and running on my workbench, but the loaner I got seems to have come to me with a jam in the extruder and I haven't taken it apart yet.

thanks again!

 

[Bricks]

When it comes to foamies precision is usually not a great consideration when it comes to servos. Putting together a large 3D plane is a different story where servos can run $150 to $500 each, where precision and speed are paramount, provided the pilot can make use of them..