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Help Understanding Motor Size/KV/Power

jamieFL

New member
#1
IMG_20140628_142958.jpg
I am building a V-Tail and have almost everything decided/purchased except the motors/props/esc. The weight minus the Naze32 flight controller and OSD module is 430 grams and the average weight of my 2200mah 4S batteries is 250 grams. The booms are currently 11.5 inches long and will be shortened once my prop size choice has been made. The motors ar 56 grams each (224 grams total) and esc are 32 grams each (128 grams total). With the flight controller, OSD, and wiring, I will estimate the total weight of my V-Tail to be 1200 grams.

What my problem is, is that I am powering my V-Tail with a 4S battery and I don't know how to find amps/thrust/best prop size. If I were able, I would use the lighter 3S, but I already own 5 of the 4S.

Unless someone changes my mind, I am going to use the SunnySky X2212 motor in either 980kv or 1400kv. I have copied the motor specs below. I am currently using the 980kv motors on my Titan Tricopter and I built a very light simplecopter tricopter for a friend and used the 1400kv motors (3S) on his. Both fly well but his is definitely snappier.

My V-Tail is going to be an FPV platform and I would like it to be quick, agile, and have good battery life. The charts do not include stats for 4S, so the best I can do is estimate. I know that the 980kv on 4S with 9x5 props work well. The motors don't even warso up. Battery life is about 8-10 minutes.

Does anyone have experience they can share. I am looking for recommendations choosing motors, props, and boom lengths for an approximately 1200 gram V-Tail. Thank you.

X2212-1400kv
2212-1400kv.jpg

X2212-980kv
2212-980kv.jpg
 
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FinalGlideAus

terrorizing squirrels
#3
If you want fast and agile on 4s get the 1400kv's. They are a powerhouse rocket ship with HQ 8x5. If you want effiency go for the 980kv using 10x4.5. They are both really nice motors.
 

jamieFL

New member
#6
FinalGlideAus, Thank you. I took a look at the link you provided and then saw this...
http://www.rcgroups.com/forums/showthread.php?t=2157642

The SunnySky motors will easily pull 30a. I had never thought about going to a smaller but faster spinning motor until I clicked on Soma's profile to see what else he has done. He recently tested the Tiger MT2206-2000kv motor. He recommends this ESC...
http://www.himodel.com/electric/Sun..._BLHELI-Multi-20A-OPTO_Tube_installation.html

Tiger-MT260 2000kv.PNG

These motors and ESCs are lighter and at over 1000g thrust at 100%, plenty powerful. Other than cost and short supply, are there any drawbacks? Can anyone lend an opinion?
 

nilsen

Senior Member
#7
Hey Jamie,

This really does work ecalc

I paid the 2 or whatever Euros for the full version so that I could choose the motors (as the trial version only gives you a random subset).

Anyway playing around with the figures, battery sizes, rotor sizes, esc wattages and motor KV I was able to choose what I needed which in my case was a aerial platform and I was able to do it at the max efficiency for, in my case, hover.

Give it a try!

Hope this helps,

Cheers
 

jamieFL

New member
#9
nilsen,

Thank you. I will look into that. One question though...I noticed that neither of the motors I am currently looking at are in the motor list. Are they included in the pro version?

FinalGlideAus,

Thanks again. I will be looking forward to your reply.
 

FinalGlideAus

terrorizing squirrels
#10
FinalGlideAus, Thank you. I took a look at the link you provided and then saw this...
http://www.rcgroups.com/forums/showthread.php?t=2157642

The SunnySky motors will easily pull 30a. I had never thought about going to a smaller but faster spinning motor until I clicked on Soma's profile to see what else he has done. He recently tested the Tiger MT2206-2000kv motor. He recommends this ESC...
http://www.himodel.com/electric/Sun..._BLHELI-Multi-20A-OPTO_Tube_installation.html

View attachment 26683

These motors and ESCs are lighter and at over 1000g thrust at 100%, plenty powerful. Other than cost and short supply, are there any drawbacks? Can anyone lend an opinion?
Considering your apparent experience (apologies if I'm wrong), what you want to achieve and the design of your copter I would suggest going with the 2212 1400kv motors and getting 30a ESC's. They will still make you smile trust me. :) just make sure you use HQ brand 8x5 props and not some other crappy brand like Gemfan. Props make a huge performance difference.

Running the MN2206 2000kv's on 4s is still very experimental. The ONLY esc you should run with that setup is the KISS esc. Any other esc will likely fry the motor or have sync issues. I have this setup on my Franken-Warp and tried the Sunrise 20a's but had major dramas. Soma and I have been working on this setup for a while now. He is away on holidays right now so can't update that page. Not only that, but the motors are running that hard that magnets are being pulled off the motor bell because of the power. I have found a solution but it means playing with an expensive new purchase. What I'm trying to say is there is a LOT of fiddling to do on this setup and if you're not careful you will burn motors.

The above has kept me busy and stopped me from giving much updates on this forum but hopefully I can get some spare time soon to give updates.

All that said, if installed on the right quad they give butt clenching performance. Here is a video of my Franken-Warp
http://youtu.be/sPpryPy6yqk

Check here for the build info. Still much updating to go.
http://forum.flitetest.com/showthre...ate-Speed-(code-name-stupidly-powerful)/page7
 
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#11
Considering your apparent experience (apologies if I'm wrong), what you want to achieve and the design of your copter I would suggest going with the 2212 1400kv motors and getting 30a ESC's. They will still make you smile trust me. :) just make sure you use HQ brand 8x5 props and not some other crappy brand like Gemfan. Props make a huge performance difference.
No. You are not wrong. I am new to electric flight and multi-rotors even though I've been in the RC Modeling hobby for almost 30 years. My first RC plane was a Sig Kadet Mk II that I built when I was 16 years old. I can look at something and build it, and I can follow someone elses specs easy enough. That is what I have done twice now. Even though I based this V-Tail on the Batbones, I am trying to build something of my own...hopefully with the performance of the 250 mini quads.

Based on your strong recomendations, I will be using the Sunnysky X2212-1400kv motors with the HQ 8x5 props. Now I can rebuild my rear booms without the motors being swept forward and shorten them to around 8 inches...mabye shorter.

On my Titan and 980KV motors I used the HobbyKing Blue F30A ESC flashed with SimonK. Is that my best choice?
 

FinalGlideAus

terrorizing squirrels
#12
Yes the Blue Series or F30a flashed with SimonK will work fine for lower KV motors like the 2212 1400 even on 4s. The guys from simple copter use this setup all the time although I think they use a different prop and F30a ESC's.

Note that just like the 980kv, the 1400 is not rated for 4s but will take it happily. If you fly around at WOT for 5 minutes straight that may be different but we don't do that with Multicopters so we can get away with it :)

With this setup on a quad you'll give the 250 quads a run for their money (well maybe not mine :D ). Keep me informed of how it flies. I think you'll be impressed with the power.

Oh and I started flying control lines back in my early teens. Couldn't afford RC gear when I was young. :)
 
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FinalGlideAus

terrorizing squirrels
#14
Lol I taught my next door neighbor to fly control line just so I had some to fly combat with. There was only two of us so I used launch him and while he circled high I would start mine and attach it to a tethered dolly I made up on a table that when I pulled a string would release the dolly and I would (sometimes) takeoff when it rolled to the edge. Then we would both move 10 meters over to get away from the launch table (we flew over thick grass) and start combat. All that combine with the tiny Cox .049 fuel tanks and their "emotional" starting tendencies we usually were lucky to get a minute of combat before someone ran out of fuel. I still smile when I think of those times. Actually not when you got your finger struck by the prop while trying to start it in the middle of winter with glo fuel and oil all over your hands. :)
 

nilsen

Senior Member
#15
nilsen,

Thank you. I will look into that. One question though...I noticed that neither of the motors I am currently looking at are in the motor list. Are they included in the pro version?

FinalGlideAus,

Thanks again. I will be looking forward to your reply.
Here you go. If you need any more calculations, let me know, but it looks pretty good with the 980KV

ecalc.png

Cheers
 
#17
I also started out as a young teen in control line. My first was a small balsa 1/2a that I modded to add ailerons. Then I built a. 40 sized Duster. I cannot remember who made the kit, but I would not be surprised if it was Sig. Those were the good old days weren't they?
 

FinalGlideAus

terrorizing squirrels
#18
I also started out as a young teen in control line. My first was a small balsa 1/2a that I modded to add ailerons. Then I built a. 40 sized Duster. I cannot remember who made the kit, but I would not be surprised if it was Sig. Those were the good old days weren't they?
Now you're making me feel old...
 

Craftydan

Hostage Taker of Quads
Moderator
Mentor
#20
I wouldn't take those calculator's data tables as gospel for what's available on the market. The data in them is generally good, and the caluclations are a fair first guess, but the data itself is incomplete . . . very incomplete.

I don't buy high-end brand-name motors, or even comon motors, but 3/4 of my motors aren't in there, including my sunnysky 2216-1250kv motors.

Dunno of they have a 2212 1400kv in a *pure* multirotor varient, but as long as you can deal with the long shaft, these are available:

http://www.buddyrc.com/sunnysky-x2212-9-1400kv-ii.html