Heavylift Motor/Powerboard Choice

Vortex

Vortex

Member
Some time back I started putting together a SJ8 and bought everything I needed to run it on 6S. Back then there weren't too many options and I ended up having to shelve the project and wait for the technology to catch up. What I did get was a set of AXI 4120/20 motors which at the time were the best choice but have since been passed by quite a few better, more powerful, lighter and more efficient motors.

I have been looking at motors to replace the AXI's and have come up with a few that have stood out but I really can't decide which is the best for my needs.

These are my design parameters


  • Need to be able to lift a MTOW of 18-20kgs
  • Run 6S

These are the motors I'm considering and undecided on.....If I am missing something better suited please let me know


  • KW10 V2
  • T-Motor MN3520 400kv
  • MK3644/24

I have MK flight control and after seeing the new MK-QUAD2XLCOMBI I'm thinking it might be simpler to use this instead of the Herc III Octo board I had planned to use. Anyone had any experience with these?

Thanks and I look forward to the replies

Regards,

Lance
 

maxwelltub

maxwelltub

Member
I personally love the tiger motors, but haven't tired the these other options. The tiger motors seem to have the great build quality but I was also also coming from cheaper brands before. I find that reading the motor chart is the best way to find the motor that has the thrust you need for the least amount of energy. So if your AUW is 20kgs, pic a motor prop combo to give you at least 40kgs of thrust at full throttle and uses the least about of juice. Thats my method at least.
 

S

Silverburn

Member
I do it slightly differently, but I guess everyone does!

1. Determine your AUW.
2. Then divide by 8 (for an octo).
3. This gives you the thrust per motor needed to maintain hover.
4. Try to find a list of motor/prop combo's that can deliver this at 50% throttle.
5. Narrow that list down to the ones with the most grams per watt at 50% and 75% throttle. <50% is never really used, and >75% you want power at the expense of efficiency. Most people fly in the 50-75% range.
6. Run it through ecalc to make sure you're not exceeding motor temperatures, battery C ratings, ESC loadings etc.

If you have any left on the list after that - and haven't died from "Excel poisoning" - those are your motors :)
 
Last edited by a moderator:

S

Silverburn

Member
A personal note about t-motors.

I'm a big fan of tmotors, but recently I've notice they do not respond well to even minor crashes. I've had to replace 2 MN3508's after an unbalanced tip over on take off (landing leg was caught in grass), and one on landing. They still ran, and the bell was still tight, and bearings were still smooth, but the vibes had doubled.
I also had a "semi-controlled fall out the sky" from 15m on my TBS Disco, and it landed upright in grass. Nothing was broken, but all 4 motors needed to be replaced. They all still ran, bearings were still smooth, but were very vibey when under power.
 


BorisS

BorisS

Drone Enthusiast
Vortex said:
Some time back I started putting together a SJ8 and bought everything I needed to run it on 6S. Back then there weren't too many options and I ended up having to shelve the project and wait for the technology to catch up. What I did get was a set of AXI 4120/20 motors which at the time were the best choice but have since been passed by quite a few better, more powerful, lighter and more efficient motors.

I have been looking at motors to replace the AXI's and have come up with a few that have stood out but I really can't decide which is the best for my needs.

These are my design parameters


  • Need to be able to lift a MTOW of 18-20kgs
  • Run 6S

These are the motors I'm considering and undecided on.....If I am missing something better suited please let me know


  • KW10 V2
  • T-Motor MN3520 400kv
  • MK3644/24

I have MK flight control and after seeing the new MK-QUAD2XLCOMBI I'm thinking it might be simpler to use this instead of the Herc III Octo board I had planned to use. Anyone had any experience with these?

Thanks and I look forward to the replies

Regards,

Lance
Click to expand...

Lance have you checked up on the U series motors from tiger, think those are the way to go ! In my eyes just a complete different range of possibility with those now ! Also I am pretty sure that 8s will be the new 6s for 2014 !

Boris
 

Vortex

Vortex

Member
Thanks for the input......I looked at the U series motors but they are 50g heavier than the equivalent pro series motor...That's 400g total!! Motor efficiency is a couple of percent lower also.

Has anyone tried the MK motors and Powerboard??

Thanks,

Lance
 

J

jes1111

Active Member
Your motor choices don't seem to add up - for AUW of 20kg you need 20/8 = 2.5kg thrust at ~50% throttle. The MN3520 motors are not even close to that.

For planning such a heavy bird, definitely use www.eCalc.ch as your starting point for drivetrain choices.

btw - what's the intended payload? Why so heavy?
 

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