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Electric noob here

#1
So much jargon and acronyms I can't figure out a dang thing.

I'm building the Sea Duck and don't have a clue about electric motor power requirements nor the whole motor/ESC/battery config.
Only used electric in RC cars 25 years ago when the most important thing about power was # of windings and batteries were NiCads.

Finally making the switch due to noise, mess, power, availability and awesome new planes like these FT examples.

Can someone help match up what I need for the Sea Duck? Not looking for supersonic but rather power with good handling.

TIA
 

PsyBorg

Wake up! Time to fly!
#2
So much jargon and acronyms I can't figure out a dang thing.

I'm building the Sea Duck and don't have a clue about electric motor power requirements nor the whole motor/ESC/battery config.
Only used electric in RC cars 25 years ago when the most important thing about power was # of windings and batteries were NiCads.

Finally making the switch due to noise, mess, power, availability and awesome new planes like these FT examples.

Can someone help match up what I need for the Sea Duck? Not looking for supersonic but rather power with good handling.

TIA
Usually on FT kits there is a spec sheet that lists what electronics were used for original build. If you are cutting the parts yourself those same parts are listed on the sales page. You can get the FT pre selected and packaged power packs for them or you can source your own parts staying close to recommended gear as possible.
 

Ketchup

4s mini mustang
#3
So much jargon and acronyms I can't figure out a dang thing.

I'm building the Sea Duck and don't have a clue about electric motor power requirements nor the whole motor/ESC/battery config.
Only used electric in RC cars 25 years ago when the most important thing about power was # of windings and batteries were NiCads.

Finally making the switch due to noise, mess, power, availability and awesome new planes like these FT examples.

Can someone help match up what I need for the Sea Duck? Not looking for supersonic but rather power with good handling.

TIA
From what I have seen the FT power pack C twin is a good fit. The power packs are a good way to get flying before completely understanding everything about electronics. They come with good quality components and will last a while.
Now I don't know much about motor size requirements and usually just go by feel, but I can explain what a lot of the numbers mean.
the numbers like 2204 and 2215 are for the motor's physical size in mm. The first two are width and the next two are height in mm. Here's where it gets confusing though, there are two places that you can measure from. You could measure the size of the outside of the motor, or you could measure the stator size. Since there is no industry standard you have to be careful about this when choosing a motor because one 2215 can be a lot smaller than another. A way I found to get around that was to look at the actual listed measurements of the motor instead of the numbers. If the motor measurements in the description are larger than the motor numbers, then they are probably measuring the stator.
For example, you can find a 2826 on hobby king, and under the specs you see that the "product size" is 28mm wide and 27mm tall. Since that is pretty close to 28 and 26, you can assume that they measured the entire motor to get the number 2826.
The next number is kv. Kv is rpm per volt, so if you put 12 volts into a 1000kv motor under no load, it should spin at 12000 rpm.
In summary, a 2204 2300kv motor is a motor with either a stator or bell size of 22mm wide and 4mm tall that spins at 2300 rpm per volt.
I managed to find a pic of a labeled motor:
mini-quad-brushless-motor-anatomy-bell-magnet-bearing-stator-winding-shaft-diagram-1024x768.jpg

This is a website that explains a lot of motor stuff a lot better. Some of the info is for quads but lots of the general information will be good to know for planes too. https://oscarliang.com/quadcopter-motor-propeller/
I know that you just asked for help finding a power system but I felt like giving you a bit more information to get started since you said that you didn't know much about electric and stuff.

Also welcome to the hobby and the forums!
 

quorneng

Elite member
#6
HH
In some respects you don't have to do any 'figuring' if you follow the FT motor/prop/ESC recommendations. They are proven to work well.
 
#7
Forgive me for being old-school but I like to learn what I'm building and off the shelf kits don't really aid that process.

I have many fuel planes that I would like to convert. This will require knowledge that I cannot gain by using pre-configured power packs.
 

Bricks

Master member
#8
Me personally have converted a couple of glow to electric, I now have a tendency to not make the conversion. When going with bigger planes the cost of batteries and associated parts adds up to more then just flying nitro. On smaller then .40 size not as bad but getting into the over .40 size and up is expensive. I now tend to change glow to gassers in the .40 size and up. Flight times go way up running gassers a 6 ounce tank on my Evolution 10cc gassers is 20 minutes plus depending on how I fly.
 
#9
Excellent help Thank you very much. Now I just need to figure out the motor/ESC amperage requirements and batteries...
Start by taking a look at the motor's spec sheet (or similar) if available, they can be quite helpful in understanding the capabilities and requirements of a motor. Typically, these data sheets will have specified performance numbers with various combinations of propellers and battery voltage (cell counts). Here's an example, the EMAX MT1806 - Power Pack A's OG motor before the FT radial motors were a thing. Likewise, Power Pack C used to use the EMAX GT2215/09 1180kV and Power Pack B the GT2212 (though I can't remember the specific kV variant).

description_image_MT1806_2280KV_jpg (2).jpg

First, you'll have to make some decisions about what you want the motor to do. If it needs to go fast, choose a prop / cell count combo with a coarser pitch and higher RPM. If you need maximum static thrust, choose the appropriate prop / cell count combo. If you're going for efficiency, there are choices for that too. Once you've got an idea of what sort of prop and battery cell count (a "3s" battery has 3 cells, "4s" 4 cells and so on) you'd like, you can take a look at the specified power and/or amperage figures (if the latter is not present, divide the power by the voltage - Lithium polymer batteries are 4 volts per cell at a moderate charge). We now know how many cells our battery needs to be and how much current the motor will draw.

Choose an ESC whose continuous current rating is above that of the maximum motor current - the closer the ESC's rating is to the maximum current, the harder you'll be driving it and the more cooling you'll need. Also consider features such as having wiring and connecters pre-soldered and the capabilities of its BEC (Battery Eliminator Circuit). The BEC is a small voltage regulator on the ESC that takes battery power and turns it into the 5V needed for the receiver and the servo - a good rule of thumb is to have somewhere around 0.8 amps of BEC current capability per 9g servo. Bigger servos will generally draw more current than smaller ones, as will digital servos over analog.

To find the maximum continuous current a battery can deliver, multiply its capacity in amp-hours (divide milli-amp-hours by 1000) by its specified continuous "C rating". For example, a 2200mAh 35C battery can output (2.2Ah * 35C =) 77A. To calculate approximate flight time, divide the battery's capacity in amp-hours by the estimated average current draw (I use half of the maximum current) and multiply by 60 to get the approximate flight time in minutes: A 5000mAh battery being discharged at 25A will last (5Ah / 25A =) 0.2 hours * 60 = 12 minutes.
 

quorneng

Elite member
#10
HH
I am sure you will learn much about the capabilities of electric by starting from a known set up as for your Sea Duck and simply flying it.
I too am old school so my first foray (2009) into electric RC was a beginners foam 'ready to fly'.
With internet research and through forums like this it did not take long to work out how to improve it to met my own expectations.
From then on it was just a matter of a gradual progression & experimentation to create a wide range of planes, admittedly some more successful than others, but they all flew and many still do.
I have not bought another 'ready to fly' since - except a multi rotor and a single rotor helicopter where by experience simply does not apply. ;)
 

Merv

Legendary member
#11
Excellent help Thank you very much. Now I just need to figure out the motor/ESC amperage requirements and batteries...
The first thing to know, all of the amp ratings are do not exceed numbers. If a motor is rated for 30 amps, don’t exceed that number. Larger props draw more amps & spinning a prop faster will increase the amp draw.

Start with the motor, choose a prop that will not exceed the amp limit. Next choose an ESC that can supply more amps than the motor will draw. Finally choose a battery that can supply more amps than the motor will draw. Remember that the ESC & battery also power the servos, include a bit of overhead capacity (3-5 amps) in your sizing. The battery amp rating is calculated, mah/1000 x C = amps. Example a 2,200 mah 25C can supply 55 amps. (2,200/1000 x 25 = 55). Some batteries have two C rating, always use the smaller number. The larger number is a burst ratting, what the battery can supply for a short time, maybe 10-15 seconds. The smaller number is what the battery can supply for continuous use.

It’s perfectly fine to use a battery and/or ESC that can supply more amps than needed. You won’t hurt anything but there maybe an some excess weight. If your amp draw exceeds any of the ratings, the weakest component will burnout first.
 
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