• This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn more.

Electric setups

igneous

Junior Member
#1
For some reason I seem to be the only one so extremely confused by how to design an electric system. I'm talking about top to bottom: what receiver should I use, if I need a mixer (for a flying wing) what do I use and how do I set it up, what ESC do I use, what battery do I use, when and how should I use the same battery that powers the motor to power the receiver and servos? That kind of stuff. I have yet to find any good online resources for learning about it, if you could point me in the right direction that would be awesome. Or even better do an episode about it.

Thanks!
 

bicyclemonkey

Flying Derp
Mentor
#2
Most planes will have a recommended setup in the instruction manual or plans whether its a kit or ARF. All the info for the motor you choose will be listed in the product page for that specific motor. Like this for example:

http://www.hobbyking.com/hobbyking/store/__14401__Turnigy_G25_Brushless_Outrunner_870kv_.html

It states the following:

Required;
50A ESC
3S~4S Li-Po / 10 ~ 14-cell Ni-MH/Ni-Cd
11x8 ~ 14x7 prop
Suitable for sport and scale airplanes weighing 3 to 5.5 pounds (1.4–2.5kg).

Do you have a specific plane in mind you need help with?
 
#3
You are correct, the info is out there but there is no "one stop shop" for it all. And that's what makes a forum site like this awesome. Between myself, a modeler and supplier and the varying knowledge on here, we should be able to get you up in the air in no time. With that said, starting from Forward to Aft you need: A prop, a motor, an ESC to run the motor, servos, a receiver, a BEC to run the servos and receiver if the above mentioned ESC does not have one internally, a battery to run the system and finally a transmitter. You mentioned a "flying wing", that typically means that the surfaces are going to be an elevon (elevator/aileron) mix. This will require some mixing so a computer radio is in order or you can use a mixer. The receiver is dependent on your radio and somewhat on your transmitter and the rest is totally dependent upon your plane. Wing span, wing area, weight, etc. So..........what plane have you got or looking to get?
 
#4
I'll try to explain everything you need to know...

First and foremost, you need a radio system. It's best to get the best possible if you know you are staying in the hobby so you won't have to spend extra money upgrading in the future. Something like a stock turnigy 9x is perfect for beginners and experts alike (Once you get into more complicated stuff you can upgrade the filmware to er9x for more options, but don't worry about that for now)
Another GREAT radio is the dx7. Seriously consider getting one if you plan to stay in this hobby for good.
You normally get 1 receiver with the transmitter you buy, but you'll probably have more than 1 plane in the future right? This means you'll need more receivers- 1 per plane

Extra rx for 9x- http://www.hobbyking.com/hobbyking/store/__12339__Turnigy_9X_2_4GHz_8Ch_Receiver_V2_.html
Extra rx for dx7-http://www.hobbyking.com/hobbyking/store/__11965__OrangeRx_R610_Spektrum_DSM2_6Ch_2_4Ghz_Receiver_w_Sat_Port_.html


The plane you're buying or building needs to have a power system that fits its needs specifically. Normally kits have recommended parts. If that's the case, just get what they tell you to and you'll have a flying plane.
Some don't provide what you need. You'll need to know the weight of the airframe and a general size prop. Look through some motors and look at the specs of thrust and prop size. If those meet the needs of your plane, then that is a good motor to use. KV is rpm per volt. It's important to know that higher kv motors like smaller props and lower kv motors like bigger props. A 2200kv motor with a small (6x4) prop is great for a fast parkjet. A 1300kv motor with a bigger (9x5) prop is better for slow flying and 3D. I can't cover all of the rules here though.

Now that you have a motor that looks to be good, you need a way to connect that to the rx. A speed control does exactly what it's name suggests- Provides power to the motor to make it spin faster/slower. You'll need to look at how many amps the motor draws in the specs. If it says it draws 15a, then you'll need an esc (speed control) that can handle 15a or higher. It's good to go overkill on the esc but for 15a, you don't need more than a 20a speed control.

Next you need a battery. Again, look at the specs of the motor and see how many amps it draws and how many cells it will run on for what you want. It says 15a and will run on 2-3 lipo cells. 1 cell is 3.7 volts. The more cells, the more power. So you decide you want more power and go with a 3s battery. You'll need to find a 3s lipo that can deliver 15+ amps to the motor.

This equation will help you find how many amps the battery can deliver:

A(amps)= Mah X c rating

Mah is the capacity and c rating is how fast the battery can discharge power. Say the battery is 1500mah, 20c. The equation would go like this:

1.5 X 20 = 30 amps

So a 1500mah 20c 3s can deliver 30 amps- way more than you need for the motor that only pulls 15a. If you want a long flight time go with this battery since the motor won't be pushing the battery all the time. A lighter plane can be achieved with a smaller battery (1000mah 20c = 20a) but flight times won't be as long. Never use a battery that can't supply at least the motors max draw.

Something to add about escs- Most under 50a have something called a built in bec. A bec supplies power to the rx and servos. You don't need to buy and install an external bec unless you are using more than 5ish servos.

The dx7 and turnigy 9x both have mixing built in for elevons, vtail, etc... You won't need a v-tail mixer for any plane as long as you don't use gyros. You don't need to know about all that just yet.



Ask anymore questions you have. I tried to cover all the basics you need to know. If there's any mistakes, would someone please correct me :) It took a while to type all that and I'm not so sure its mistake free lol
 

bicyclemonkey

Flying Derp
Mentor
#8
that's where the help of forums come in. The best way to start to judge what motor/prop/ESC to use on a plane that doesn't have a recommended setup it to start with the flying weight and narrow the motor choices down the watt per lb. rule.

This is taken from RC airplane world:

Here are some Watts per pound values that you should be able to relate to your model...
Less than 50W/lb - very lightweight / low wing loading slow flyer.
50 to 80 W/lb - powered gliders, basic park flyers and trainers, classic biplanes and vintage ('Old Timer') type planes.
80 to 120 W/lb - general sport flying and basic/intermediate aerobatics. Many scale (eg warbirds) subjects suit this power band.
120 to 180W/lb - more serious aerobatics, pattern flying, 3D and scale EDF jets
180 to 200+W/lb - faster jets and anything that requires Arnie-amounts of muscle!


Also, if you know what size prop you want to run on your plane, you can start by picking a motor that can handle that size prop and falls within the watt/lb rule...
 

Tritium

Amateur Extra Class K5TWM
#9
It also doesn't hurt to look at specs of many different planes either in catalogs or online. Look at type of plane performance wise, weight, motor size / wattage, prop size, esc required, battery voltage used and flight time per charge. These values can allow you to make educated guesses about what will work for your own builds.

Thurmond
 
#10
that's where the help of forums come in. The best way to start to judge what motor/prop/ESC to use on a plane that doesn't have a recommended setup it to start with the flying weight and narrow the motor choices down the watt per lb. rule.

This is taken from RC airplane world:

Here are some Watts per pound values that you should be able to relate to your model...
Less than 50W/lb - very lightweight / low wing loading slow flyer.
50 to 80 W/lb - powered gliders, basic park flyers and trainers, classic biplanes and vintage ('Old Timer') type planes.
80 to 120 W/lb - general sport flying and basic/intermediate aerobatics. Many scale (eg warbirds) subjects suit this power band.
120 to 180W/lb - more serious aerobatics, pattern flying, 3D and scale EDF jets
180 to 200+W/lb - faster jets and anything that requires Arnie-amounts of muscle!
Too complicated for a newbie.. I barely understand that yet!
 

bicyclemonkey

Flying Derp
Mentor
#11
That couldn't be more simple...If your plane weighs 2.5 lbs, you need to have a motor that pulls 200-250w. All motors will show you what it's rated for in watts.
 
#12
When choosing a motor, I don't look a watts, I look at thrust and amps pulled. That's all that needs to be known

And besides, there's so many planes out there that need a power system that doesn't follow those rules that it's barely relevant
 

ananas1301

Crazy flyer/crasher :D
#14
When I try to figure out a setup I always look at the motor first. What both of you said is correct and either way you do it will be fine. Personally I can get along much better with the thrust and amps version of RCjetflyer2. Of course other people like Josh Bixler are used to the watts system and tell us in the epised that this has a 1500Watts of power system. Both not wrong and really doesn´t matter. The only important thing is to choose a high enough ESC and a battery to deliver the right amount of power for your 1500Watts of however much you need.

@byciclemoney: No not only the 37A. If you tell me that the motor draws 37A I can´t really figure out where to use it. I can only guess. I would need the thrust that the motor could give me max! So if with 37A I have a thrust of 3kg then I´ll use this for a 1,5kg Balsa Extra to have a nice thrust-weight ratio and enough power for all maneouvers.
 
Last edited: