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Servos

I frequently see 9g mentioned in servos. I searched the web but couldn't find any worthwhile answers. At first I thought it meant 9grams but the weight of the servo isn't 9 grams, so have to be something else.

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    I'm voting to close this question as off-topic because it is not at all about Arduino.
    – Chris Stratton
    Apr 15, 2018 at 1:49
  • If servos isn't an integral part of Arduino, then what is? I don't expect arduino to rotate a wheel from thin air.
    – Prashant Sharma
    Apr 15, 2018 at 19:02
  • The idea of servo weight seems irrelevant to me as I see servos measured in kilograms. I tend to think this measurement have to do something with servo's power, like how big things it can move.
    – jutky
    Nov 26, 2020 at 22:14

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According to Flite Test web site, the 9g reference is the weight without the wire lead. They measured one model at 8 grams rounded down. I suspect the weight also ignores the horn as well as the wire.

The article referenced on the web site calls the weight reference as a standard, which means that it more likely allows for heavier or lighter servos as long as the size of the servo matches.

If you purchase a servo for a model known to use a 9g servo, you know the hole you have to build for it to fit. If you purchase a 5g servo, it will be a different hole and you may have a 6 or 7 gram weight, but the servo fits as it should.

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  • So the "9g" is a standardized case size for servos?
    – chrylis -cautiouslyoptimistic-
    Apr 14, 2018 at 23:29
  • I should have put standard in quotes, as anybody can state a standard, but it's the consistent use of 9g for servos of a particular size, regardless of weight that makes it work in this sort of circumstance.
    – fred_dot_u
    Apr 15, 2018 at 0:08
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From a model airplane perspective...

The "9g" is supposed to mean 9 grams in weight. Each vendor has their own way to define their weight.

  • with wires
  • without wires
  • with or without control horns
  • "about the same as a competitor's 9 gram servo"

Most are not accurate.

It is not a standard for size, and has nothing to do with hole size or screw spacing

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According to the link it is.

However, if you look at this more detailed datasheet, it shows 14.7 g.

Probably it's the weight of the motor part itself, not the plastic enclosure around it.

Btw, most websites (without actually using data sheets), mention a weight of 9 g.

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