Let's Make Robots!

Servo Standards?

Hey all,

Just graduated from college and started a new job. I finally have time to pursue projects I've always wanted to do.

ANYWHO. I bought a cheap aluminum hexapod frame from the internet that recommended I use Tower Pro MG995 servos. Unfortunately I just found out through online reviews that these servos and their improved models are not so hot, to put it extremely lightly.

I noticed however that a Futuba S3003 I had lying around seems to have a casing with mounting holes that fit flush with the holes in the frame as well.

Are servos in that general size range constructed to have similar mounting setups? Is there a name for the system or class they lie in? Ideally I'd just find better servos to bolt to the frame I already bought.

Bonus points if you can recommend some servos! I'd like to run the hexapod off an Arduino Mega with a driver shield attached.


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There is at least one DIY hexapod posted here that uses the "dreaded" MG995  MG995R servos. I believe given the price they are not such a bad trade off. I can not speak from experience on that point. I am pretty sure the MG in MG995 stands for Metal Gears, something the S3003 doesn't begin to have. As for class of servo, they are standard hobby servos.

You mentioned using a MEGA with a shield. I would suggest you consider the Red Back Spider from Dagu. OddBot has designed it for just such a robot. Bonus, if you run into issues with the board, you can likely get ahold of him here. As he is in China, he may be awake different hours, but, he is more than willing to help when he can.

I wasn't going to use the S3003's, they don't have the specs required for what I expect/plan, especially considering the frame is aluminum. I was mostly just curious if 'standard' servos all have the same mounting dimensioning. 

Incidentally, that DIY hexapod you linked has the same exact frame I have. It's neat to see a video of it in action. Most of the reviews I've seen for the servos note that the zeroing and the accuracy are butt, which makes me extremely hesitant about using them. They're cheap at $10 a pop, but I'd rather front more money for something better made.

Also, that shield looks sweet. Definitely going to consider that!

Great reply, thanks a lot!


To answer you initial question, hobby servos come in a few standard sizes:

- Standard size - aprox. 40x20x36 mm

- Mini size - aprox. 36x15x30 mm

- Micro size - aprox. 28x13x30 mm

- Nano size - aprox. 22x11x20 mm

- Pico size - aprox. 20x9x20 mm

- MAXI size - aprox. 66x30x57 mm

And there are some special sizes and purposes servos, but in a smaller number.

As for MG996R servos, this is a 11kg/cm Standard servo with metal gears. Metal gears are usually used in high power servos, they did not strip very easy but produce much noise. I have 3-4 servo from this type and I'm pretty satisfied with them. One servo though, is not very accurate at finding it's equilibrium. I guess potentiometers used in these servos are not very accurate.

If you have enough money to put into servos, go for digital ones. These are more precise and powerful than analogic ones, but they are priced accordingly.

Or you can go for something like Dynamixel servos, AX-12 for example.

Thanks, that cleared up that mystery for me. I checked some dimensioned drawings for 'standard' servos and confirmed the sizing similarities. Good to know I can plug different servos into this chassis!

I started looking at price tags for servos, and I see why so many people attempted the $10 996Rs at first. I'll probably abandon my plan of choosing servos ridiculously stronger than what I thought I'd need, haha.

I'll still probably avoid the 996Rs as the servos for this project. I'd rather shell out for decent servos and have the option of reusing them for something else in the future.

Thanks for the comment!

How can I control full range of motion on this servo. Bought a chassis from dagu that has it and in every video I see they can control 180 degrees, I can only control about 90 even with all the limits set in the RC