About RC servo motors

[jbeech]

Without fail, every customer brings up the question of the motor within our servos sometime during the conversation. The facts are, all servos - any brand - use one of three types; a DC-motor, coreless, or a brushless. Another fact is nobody seems to have a ready source for showing you how they're different, and more importantly, why you pick one versus the other. So I set out to write an askJOHN on the subject. Doing it right required me to sacrifice some motors (I cut them apart on the lathe). Why? It's because nothing beats show-and-tell. Bottom line? Whether you favor Futaba, Hitec, or Savox instead of ours, this is solid information for everybody - here's the link:

https://www.promodeler.com/askJohn/talkRADIO/about-RC-servo-motors

 

[AKNick]

Nice Work John! I'll have to brew a cup of coffee and read through it. You spend some time on this one!

 

[dhal22]

Someone should just conjoin 2 opposing brands servos together and let them fight it out. Your Futaba against my Hitec or whichever brands and have a tug a war fight.

 

[AKNick]

Someone should just conjoin 2 opposing brands servos together and let them fight it out. Your Futaba against my Hitec or whichever brands and have a tug a war fight.

That would be better than robot wars... LOL

I finally read through the entire article. It's a little winded and redundant, but lots of rich information in there to take home.

 

[jbeech]

Tell 'em what you're gonna tell 'em, tell 'em, then tell 'em what you told them. Time proven.

 

[AKNick]

Tell 'em what you're gonna tell 'em, tell 'em, then tell 'em what you told them. Time proven.

So that was the plan all along? LOL

 

[jbeech]

Actually, it's very difficult to judge the effect of a lesson on students when you're not in a classroom, e.g. to see their reactions concurrently so the usual tactics include the three R's . . . repetition, reiteration, and reapproach. Note; in a prior life I was a secondary education math and science teacher. That, and questions about servo motors are really common during inquiries about servos. Moreover, you may have noticed there are three totally different approaches occurring concurrently, two for visual learners and one aimed at integrating readers. In truth, there was a lot of effort put into this because I wanted to nail it down.

 

[Snoopy1]

Thanks for doing that long and interesting read. The mechanics of the motor and gearing is reasonably straightforward. But one of the most important aspects of a servo is the control system of which very little is discussed. You can have the very best motor and gear set but if the electrical controller is a bad design the servo will be useless.

 

[jbeech]

Ahhh . . . now you get into the territory of trade secrets. For example, this is why some servos squeal, approaches to PID tuning, etc. To be honest, this is a depth well beyond the scope of anything i'd ever endeavor to speak to within an askJOHN. Specifically, the purpose is to educate modelers broadly instead of delving into engineering discussions where eyes glaze over. Bottom line? This is an über competitive business and whilst there's nothing new under the sun, because modelers hate servos that buzz, we expend a lot of time addressing this and would rather keep our mouths shut as to why our servos are comparatively quieter than our oriental competitors' offerings, to which I'll add, I seriously doubt anybody has a bad offering else they don't last long in the market.

 

[Snoopy1]

You do not have to get into the minute details of design. But you have to agree that a little more info to the modeller on the capability of the electronics would be helpful.
For example. Resolution, step function, watts required to hold for example 100 oz-inch. this just a few that I can come up with at this time. It would be nice to know a few of these parameters but it will turn out like “C “ ratings on batteries not worth the paper it was written on.