Which motors do I use?

[CrusherColin1]

Hi, I am currently ordering parts for a Tarot Iron Man 650 that I will use for AP. I am torn between two motors. The

"Quanum MT Series 3508 700KV Brushless Multirotor Motor Built by DYS"

or the

"Multistar Elite 4006-740KV Multi-Rotor Motor"

I will be using the Qbrain 4 in 1 25A ESC, does anyone have any advice on which one of these motors is generally better in quality and efficiency.

Thanks! Any advice helps! This is my first large quad build.

 

[nilsen]

Hey CC,

What size props are you thinking of going for and are you going 3 or 4s?

The Multistar's will be slightly more efficient on a 12 inch prop on 4s, the Quanum will be more efficient with a larger prop.

For comparison, I run the Multistar "standard" 760kv with a 13 inch prop so if you could fit a 14 inch prop I would go with the Quanum on 4s.

Cheers

 

[CrusherColin1]

3s

Thanks that helps a lot, I was planning on using 3s. I have some already and they tend to be cheaper. I was going to use between 11-14 inch props. I am just looking for the most efficient setup. Will large props cause problems running on a 3s?
Thanks!

 

[jipp]

be sure to post picture of this build as i too want to build a AP bird maybe this winter and i was looking at the tarot 650 hex ( the reason i would go with the hex is because from what i can tell from the picture.. you can run it in quad form or hex.. by just snapping the arm on.. so seems like the right with retractable landing gear, as one option..

also you would have to look at the amps drawn from the motor with different size props.. you would not want to fry a ESC in the air and watch the big girl come down.

from what i understand if you can run 4s you would get longer flight times.. but i do understand using what you have.
chris

 

[CrusherColin1]

How?

How exactly would I find out how many amps the motor will pull with different props?

 

[jipp]

How exactly would I find out how many amps the motor will pull with different props?

first place i would go to is sales literature that tells ya the specs of the motor..

they often include such.. or the webpage selling them may offer there own test. for example cobra are well documented with such info.

if you can not find the info.. you could ask the store selling them if they have the specs..

sorry i have no other ideas. that is where i would start. of course others on here may have first hand feed back for ya which is always a bonus about lost of people trying different hardware on a large forum.

chris.

 

[nilsen]

How exactly would I find out how many amps the motor will pull with different props?

Hi Colin,

I used ecalc.ch which can be used to give you a pretty good idea of how a different setups would work in terms of efficiency, flight times, etc.

The Quanum motors are rated up to 6s, you won't get any lift on 3S unless you swing 18 inch props or something, and even then that is not their intened use.

I did some calculations on Ecalc for you so you can see the efficiency differences.

Multistar 3S 11Inch props


Multistar 3S 13Inch props


Multistar 4S 11Inch props


Multistar 4S 13Inch props


Quanum 3S 14Inch props - note that even with much larger props, on 3s this thing won't fly.


Quanum 4S 11Inch props


Quanum 4S 13Inch props


Hope this helps, feel free to ask anything you want.

 

[CrusherColin1]

THANK YOU!

Thank you this helped a lot and answered my questions completely! I am thinking of going with the 3s 13 inch props or the 4s 11 inch. Do you know why it says the motors will over heat with 13 inch props on 4s? Is there anything I could do to prevent that because that would be my favorite setup.

Thanks!

 

[CrusherColin1]

Efficiency?

I have never looked at a chart like this, is 70% efficiency good, ok, or bad? Would I want to switch to different motors? I am kind of new to this! Thanks for all of your help!

 

[Malcurin]

http://www.tarot-rc.com/index.php?main_page=product_info&cPath=65_75&products_id=1076
i use these with a tarot 680 pro frame on 4s 5000mah bats get about 12 min flight time with 40 amp esc;s and 13x55 cf props. they are pretty good motors came well balanced props didn't but my dubro sorted them out , very nice frame for AP and video with a SJ5000+

 

[Cyberdactyl]

Thank you this helped a lot and answered my questions completely! I am thinking of going with the 3s 13 inch props or the 4s 11 inch. Do you know why it says the motors will over heat with 13 inch props on 4s? Is there anything I could do to prevent that because that would be my favorite setup.

Thanks!

For a particular setup, (motor, prop, prop pitch, AUW, amps and voltage, etc.,) as ecalc calculates, there is an upper load the motor and ESCs can handle. Forcing a motor to spin a prop larger than it can handle too fast, will cause it to overheat.

It's a bit analogous to putting a manual transmission car in too high a gear at too slow a speed and flooring it.

So the general rule of thumb, as you go up in voltage for a particular setup, you need to drop the load, which can be done by dropping the prop size, pitch depth or AUW. Since AUW tends to get worse as you raise voltage, the general solution is to drop the prop size.

 

[nilsen]

Thank you this helped a lot and answered my questions completely! I am thinking of going with the 3s 13 inch props or the 4s 11 inch. Do you know why it says the motors will over heat with 13 inch props on 4s? Is there anything I could do to prevent that because that would be my favorite setup.

Thanks!

No problem Colin,

I run 13Inch props on 4s and the motors bearly get warm, granted they are a slightly different KV but eCalc also says that they will overheat AT MAX. The thing is that you are hovering at about 35% throttle meaning you will hardly ever be at full throttle and if you are it should be for short periods, this isn't a mini-quad after all

Regarding Efficiency, I have tried to work out the most efficient setups and have achieved a theoretical 85% or so, as you can see on the "motor at optimum" section that is where the motors perform their absolute best. you should problalby use a slightly higher KV with a 12 inch prop but I like to under-use my motors and have plenty of headroom.

 

[Ddm5]

Don't even bothering using a 4in1 ESC. Most of the current ones on the market are useless.

 

[Ocean]

Don't even bothering using a 4in1 ESC. Most of the current ones on the market are useless.

+1

My friend regrets it as the worst RC purchase he has ever made.