Let's Make Robots!

HS-311 Servo

Hi everyone,

I was hoping someone could answer a question for me. I'm in a group that's making an R/C hovercraft and we want to save weight. I was wondering, what would be the smallest batteries we could use while still being efficient and cost-effective? I've tested it with AAs only to this point and so far it looks like it'll work with three of those.


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How in the world are we supposed to answer this? 

Is your hovercraft 2 inches across or 20 feet? Are the motors gas or electric? What size motors? What kind of current do they draw? Etc. Etc. Etc.


They are light, produce gobs of current, and not too pricely compared to AA rechargeables. They require a Li-Po charger.

And yeah a relavent title and a better description, will get you better answers ;)

The hovercraft is no more than 25 cm across and 40 cm long. I was mounting a couple cardboard fins on on the servo to serve as rudders behind my thrust fan.

Thanks for the suggestion JerZ. I totally forgot to mention what I was using the servo for. We've moved to a HS-55 servo now and we've mounted our motor onto it, deciding to go with vectorable turning instead of rudders. Would we be able to power this servo and the controller receiver (20mAh each I believe) with a couple large watch batteries outputting 3V, or would they not supply enough current?

Chris, try not to be so belittling when answering questions in a forum called "ABSOLUTE BEGINNERS". I believe it's called that for a reason.

Watch batteries would be absolutely inadequate for a project like this; LIPOs are the way to go. 

I'd suggest a setup very similar to an RC aircraft, using a 2 cell LIPO of 1000mAH or so giving 7.4V and a brushless motor, for which you'd need an ESC (electronic speed controller).  The ESC takes a standard servo control signal to control the motor speed.  You could also use an aero propellor for this, ducting off some of the down thrust for the vector steering.

A standard RC receiver will give you three, four or more channels for servo and motor control as well as regulating the LIPO voltage down to 5V for the servo supply.  The RC transmitter would be the costliest part of the setup, but you can find basic ones on eBay for pretty low cost.

If this approach appeals, I'll post back later with more detail when I have more time.

you can't hover without motion. I believe you would be better off to have a motor for propulsion, and, one for lift. It is my understanding that racing hovercraft use a single engine to minimize weight.