Hello all! I'm new on here. Really new to RC. my Dad got me an RMRC surfer foamy and we've flown it a few times, but recently crashed it hard. So i have it fixed now but need a new servo. There is no data on the servo. When i look on line i see most servos rated for 4,8 volts. My battery puts out 11.1 volts or around 12 really i guess? So maybe that means i have more questions. 1) Is there a breakdown i can read somewhere that explains the battery, motor, servo voltage relationship? 2) I see metal or plastic geared servos, is one better than the other and is weight a consideration? 3) What is some good stuff to read to learn about this hobby? Thankyou!
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Don't worry about the voltage going to the servos. No matter what voltage your flight battery is, the receiver gets only a certain voltage and it's the receiver that powers the servos. Usually, the BEC (Battery Eliminator Circuit) that's is generally built into the ESC (Electric Speed Controller) scales down the voltage before it goes to the receiver.
If you are replacing a single servo like the elevator or rudder, you can simply do just the one. If you are replacing an aileron servo, it might be best to either get that exact same servo from the spare parts listing for that plane or replace them in pairs (one on each aileron) so they match well. Metal geared servos will take a hit better than plastic servos. For your application, I suggest a 9 gram servo, metal geared will suffice. Then there's analog and digital servos but at this stage, it's not that important to get into it.
A LiPo battery is made of cells, each one having a max charge of 4.2v or a starting voltage of 3.7. Your battery is a 3-cell, hence 11.1v. Motors are designed to accept multiples of cells. In your case, that motor takes 3 cells. The "KV" of any given motor means that it will spin a theoretical maximum (without prop or load) to KV x volts x cells. EG, a 1000kv motor running on a 3-cell LiPo battery has a theoretical max speed of 1000 x 4.2v x 3 = 12,600rpm. ESCs are rated in terms of amps. Don't use a higher cell count battery on a motor and ESC that wasn't designed to take it or something will burn up. -
Thanks xviper, I'tll be fun learning from you guys. :Cool:Comment
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Well I finally had time to look at servos and I'm wondering what it means when it says they're not suitable for large fixed wing air craft. My plane is an rmrc surfer. Is that considered large? Do you have any recommendations on brand or are they pretty much all the same? My plane didn't come with any assembly instructions and no parts list so we just had to wing it pun intended.:) Do you guys have any idea where I could get a parts list from? Thanks!Comment
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Is your surfer a 1500mm wingspan? If it is, this is not considered a large plane. Servos are generally sized in terms of "grams". A plane like yours would most likely take 9g servos, digital or analog, plastic or metal geared. You can buy servos at your local hobby shop or online from a place like MotionRC. Or you can shop for them at HobbyKing. They have a warehouse in Oregon.
Big, heavy planes, especially of wood, fiberglass and plastic construction (and some large foam planes) tend to have big control surfaces (ailerons, rudder, elevator) and require stronger servos to make them work (these have been called "giant scale" planes). The bigger the control surfaces, the more wind they need to defect and hence, the bigger the servo needs to be.
Your plane is going to be very similar to this one:
Check out the parts list for this one and you can mimic what needs to go into yours.
Here is a thread about your plane. I'm sure you can get whatever information you need to get your plane flying.
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