Walkingdad

Hi, new to RC airplanes and site. Need some advice on motor prop ESC battery combo. Building a 1300mm trainer. 650g, 2600 kv motor 30 amp ESC 8.6 prop With a 2200 3S battery 30C. I have burnt out three ESC‘s and one motor and I’m not sure where I am going wrong. I think it may be the prop from my research but Any help is appreciated.thanx

jaka54

Much easier if you started with a 1600cm span, high winged glow trainer!

tedsander

eCalc can give you some estimates about your setup.
You can play with all the possible combinations (battery, ESC, Motor, Prop)
It's all math - so actual use may vary, but should get you in the ballpark. The demo is free, but to unlock all of the database entries for the different possible battery/esc/motor/prop combinations (or to put in your own from the manufacturer specs) it is pretty affordable.
Not every detail it asks for has to be filled in.
They have other variations on this, depending on what your focus is - performance, different types of models, etc. but each needs its own subscription, unless you pay for a "bundle".
https://www.ecalc.ch/motorcalc.php

Walkingdad

So I did a little experimenting, a six or a seven did the trick. I’m more of a hands-on experimental type, but that seems to get expensive.

speedracerntrixie

My Feedback: (29)

Not much info to go on in your post. Typically one would list all the motor specifications. Example would be 28-20 1100KV. The first two numbers I’d the motor diameter and length. It really helps in determining what ESC amperage and prop size. Your motor with 2600KV is better suited for small props or even more likely EDF use. Doing the math, with a 3S battery that motor wants to spin over 28,000 rpm at full throttle. Likely anything larger then a 6x4 prop is going to overload the ESC, not to mention exceed the rpm limits of the propeller. It’s not pretty when a propeller comes apart. I would highly suggest you purchase a more suitable motor for your model.

Walkingdad

Thanx for the info speedracerntrixie. The full size of the motor is 2212. I wish I would’ve had some of that info a lot sooner before I burnt out the three ESC’s. Even more so because I thought I was fine running the seven and your info tells me to run a six, which sounds a little better. like I said I’m still learning and I am a stubborn one who has to actually physically try to ,see and understand.

LLRCFlyer

Hi Walkingdad,

Choosing the right motor/ESC/Battery/Prop combination for a new airplane can be quite a challenge for someone new to the hobby. You state your plane will weigh 650 grams (a little under 1.5 pounds) and have a wing span of 1300mm (50 inches). That sounds overly optimistic by about one to two pounds for that size airplane, unless it is an all foam profile slab model. Once you have a reasonable estimate of the all up weight, then decide how much power you will need. For a trainer, you will want about 80 to 100 watts per pound of gross weight (a little less if it is a sailplane). If you are looking for aerobatic performance, then 100 to 130 watts per pound should provide spirited performance. If you want to do 3-D flying which requires thrust to weight ratios well in excess of 1:1, then about 175 watts per pound usually works well. Assuming your plane comes out at 2.5 pounds (1,135 grams), then a motor rated for a continuous output of 250 to 300 watts should should work well and a 2212 motor rated at 1200kv would probably work ok. The motor you have (2600Kv is a very high speed motor that needs to turn a tiny prop (probably a 4.75 x 4.75 prop) in order to not be overloaded with a 3S battery. You will be much better off with a larger propeller turning about 8,000 to 10,000 rpm. That would take a Kv of 1,000 to 1,200 when using a 3S battery. You might be able to make your 2600Kv motor work on a 2S battery and a smaller (6x3?) prop.

Every electric motor is different and you need to obtain the specific manufacturer's limiting data for amps, watts, volts and recommended propeller sizes (usually available on-line). Most will list propeller sizes and thrust values for different battery voltages. For example, your 2600 Kv motor might turn a 6x3 prop just fine on a 2S lipo battery (8.4 volts) but could be way overloaded with a 3S or 4S LiPo battery. These 3-wire motors are synchronous motors that try to turn so many rpm per applied volt. As the load is increased, the rpm drops further below its rated synchronous speed and it pulls more amps trying to catch up. The Kv rating depicts the unloaded (free running) synchronous speed of the motor per volt of applied power. Your Kv 2600 motor should turn 2600 rpm per volt when there is no propeller attached. A fully charged 3S battery produces 12.6 volts at no load and will drop to about 11.1 volts under heavy load. Without a propeller, your Kv 2600 motor would turn 12.6 volts x 2600 rpm/volt = 32,760 rpm on a 3S battery. The design running speed under load is usually about 80% of the no load speed, therefore your motor under load on a 3S battery should ideally turn 0.8 x 32,760 rpm = 26,208 rpm. An 8x6 prop is way way way too large for your motor. The APC propeller data charts only show loads for their 8x6 electric prop for speeds up to 25,000 rpm and that takes 2.869 HP or 2139 watts. Based on the square rule for power, it would take about 3.15 HP (3,350 watts) to turn the 8x6 prop at 26,208 rpm. That would take 211.77 amps at 11.1 volts. No wonder it fried your 30 amp ESC and motor. I was able to look up a 2212 sized 2200Kv motor (rated 310 watts and 28 amps with a 3S battery) and it suggested a 5x5 prop for a 3S battery and a 6x4 prop for a 2S battery. Also, your esc should be sized such that the motor's amperage demand does not exceed 80% of the ESC's rated amperage. Long story made short... Look up the manufacturer's maximum allowable amperage and wattage. Then buy a watt/amp meter for about $25, plug it in between the battery and your ESC and make sure your battery/motor/prop combination does not exceed the manufacturer's data for either the ESC or the motor.

Good luck!

Walkingdad

Thanx LLRCFlyer. You gave me everything that I was looking for and more. I didn’t realize how deep all of that actually goes, I thought just throw a motor in there and a propeller with a battery and a speed controller and off you go.(exaggerated.) i’m only a few months in, but I have learned a lot with help from experienced people like you.. I would like to post some pictures, but I’m a new member so it will not allow me yet but I will as soon as I can. it is a foam board plane and I finally got it to fly with a 7 inch propeller but drop down to a six and may even drop further to a five because I did end up burning out that motor also so in total three speed controls and two motors on this one. I don’t plan on doing any 3-D with this particular one, I just want to get my flying skills up and my knowledge.. I was also thinking of dropping down to the 2S battery and giving that a shot. Also, this way I didn’t have to replace the motor but looks like I will have to either way, but I have a spare exactly the same. What size motor would you recommend for this?

LLRCFlyer

Walkingdad,

I would suggest a SunnySky 2212 - 1250Kv motor. My experience with SunnySky motors has been very positive on several different sizes and Kv rated motors and they have moderate prices. Buddy RC has them for $16.99 and they ship pretty quick. I have used several of their 2212 motors, but never the the 1250Kv version.. I used their 2450 Kv versions on 3S batteries for fast pylon racers turning very small props very fast. Check out their 2212 - 1250 Kv specs here:

https://www.buddyrc.com/products/sun...33002364108886

Their description gives the performance specs with several different prop sizes and it should provide a little over 1000 grams of thrust depending on the prop. Max current is listed as 25 amps for no more than 10 seconds and max continuous power is 375 watts. On the BuddyRC website, you can browse the various Kv ratings and see quite a range of performance for the the same 2212 frame size motors. The SunnySky 2212 -1250 motor should turn a 8x6 prop ok on a 30 amp ESC. I think you will find all the information you need at the URL listed above.

Also on a slightly different trainer topic, here is a suggestion if you are just trying to learn to fly and want a very good trainer option. I would suggest the $200 HobbyZone Aeroscout S2 1.1 meter wingspan ready to fly airplane. I bought one last October for my club to use as a trainer. So far it has about 400 flights and 45 hours of flight time on it, still looks like new and it is one I fly when the wind picks up. See it at this URL:
https://www.horizonhobby.com/product...HBZ380001.html
I have been training students since the 1970's and so far the AeroScout is by far the best trainer I have yet run across. Fly it on a buddy box with an instructor and you can easily learn to fly on a single airplane with minimal damage. It may be ugly, but it handles wind and gusts really well, easily operates from 2" mowed grass runways and is aerobatic enough that you won't out-grow it in 6 months. It has an upset recovery button on the transmitter that will quickly bring the plane back to upright level flight if you get disorientated. The Ready To Fly version comes with an entry level 7 channel Spektrum DXs transmitter ($115 separately, but the RTF version is only $20 more than the Bind And Fly version without the transmitter.) While the DXs is limited in functionality, it makes a great buddy box for use with a Spektrum transmitter with wireless trainer link capability.

Enjoy!

LLRCFlyer

Walkingdad,

Upon further inspection of the Buddy RC SunnySky motor listings, and assuming you want to stay with 3S batteries, I think the SunnySky 2216 - 1250Kv motor would be a better choice, even though it will need a 40 amp ESC. The 2212-1250 motor would need to run on a 4S battery to get the performance you want. Try this link to see the $25 SunnySky premium 2216 motors. Altitude Hobbies has good prices on ZTW and Hobbywing ESC's. Both of these ESC''s have switch mode battery eliminator circuits (SBEC) to drive the receiver and servos. A switch mode SBEC is better than a cheaper linear BEC because it does not waste power dropping the output voltage through a resistor like a linear BEC does. I have purchased from Altitude Hobbies on multiple occasions and their service has been very good.

https://www.buddyrc.com/products/sun...-shaft-version
https://www.altitudehobbies.com/coll...ess-32-bit-esc
https://www.altitudehobbies.com/coll...s-40a-ubec-esc

Sorry for any confusion.

Walkingdad

Excellent LLRCFlyer. With the info you have provided I can tell you have been at it for a while. A little deeper than I can understand but I understand enough for now. I really appreciate everything you taught me. I will apply what I have learned and post some updates later on, hopefully I will be able to do videos.

LLRCFlyer

Hi Walkingdad,

I'm glad I could help. I forgot to send a you a link to a watt/amp meter. Here is a link to the one that I use. It has proven to be very easy to use (up to 180 amps) and has saved me from ruining several motors and ESC's. Best $25 you can spend on electric model accessories.

https://www.motionrc.com/products/gt...yzer-gtp180awm

Good Luck