|Aug 16, 2013, 05:31 PM|
Lifting a 2.4KG Quad - Tmotors, 6s, Lots of data
After testing three motors on everything from 3s - 6s batteries and 10" to 12" APC props I thought I would share my findings.
Tmotor AT 2216 1250kv
Tmotor MN 3110 700kv
Tmotor MN 3110 470kv
10 x 4.5 MR
10 x 5.5 MR
10 x 4.7 SF
11 x 4.7 SF
12 x 4.5 MR
12 x 4.7 SF
6000 mAh 3s
5000 mAh 4s
4000 mAh 5s
3700 mAh 6s
After reading the 'Project Sponsor Quadcopter 6S HV Flip FPV!' thread...
I was inspired with flohio117's 6s project and wondered how it could help me with my 2.4KG quad challenge. My quad is heavy because I fly stereo GoPros which in turn leads to a heavy battery for counter balance. But I still want it to be small enough to go in hand luggage. Ideally flying on 10" props. 11" would be ok as well if I have to. Maybe 12's?
Until now I have been using Tmotor AT2216 1250kv with APC 10 x 4.7SF props on 3s batteries. It works well...
...but everything is on the limit and the motors and ESC's are always very hot after flying.
Flohio177 explained how raising the volts (4s, 5s, 6s) will drop the amps needed to fly leading to cooler components and longer flying times. Sounds perfect. But which components can take 6s?
His project uses Tmotor MN 3110 470kv motors
and the Tmotor 30A ESC Pro...
An alternate (half price) ESC may be the Hobbywing Platinum 30A-Opto Pro
which I suspect,after reading both manuals, is an identical ESC.
All are rated up to 6s.
I was also interested to see how the Tmotor MN 3110 700kv would fly...
And although only rated to 4s. I wanted to try it on 5s and 6s. Keep this in mind when looking at the results. The 700kv motor is NOT rated for 5s and 6s batteries so using it this way could lead to bad things :-)
My quad is a custom, folding frame with a Copter Control 3D fight controller. I have an older build log if you want to see more..
I did not retune it for each test but it did fine for hovering. I also lengthened the arms to just fit a 12" prop.
This is 'reasonably' scientific but all data was gathered from flying a 6min hover and eyeballing the throttle percentage while looking at an onboard amp meter display. It took a few days to complete so different weather will affect the numbers as well as slightly different weight due to props and batteries. I added a little 'weight factor' in my numbers to make it a little more even. Either way take the numbers as guidance rather than perfect measurements. See my pretty spread sheets and charts below.
The charts have a...
Black line for mAh per min used
Purple bar for amps use to hover at the start of the 6 min flight
Green Bar for throttle percentage at the start of the flight
For the 470kv motor I made a bunch of videos of the different combos at full throttle. Some don't even get off the ground and some zip away at full force. Here are twenty prop battery combos in a playlist...
and a few teasers...
Hope you like my USPS mail box landing gear :-)
Efficiency and flight time is one thing but flight performance is another. I really didn't like the 12" props much although the MR style was better than the SF. The problem with a big prop is it catches a lot of wind and has a more difficult time keeping steady. It is also slower to spin up and down when getting signals from the flight controller. All of this leads to a 'floppy' flight experience. They are super efficient though for hovering.
On the other end of the scale smaller props on a heavy quad like this mean you need a lot of throttle to get off the ground. Once you get above 65% to hover you really give up a lot of control as a quick dive or descent will be difficult to stop as you just don't have the lift as you max out your throttle. 50% to hover really is a good spot if you can get it.
One great thing about the higher s batteries was the lack of sag in the power as the voltage runs down. On my 3s setup, performance would fall off pretty quickly as I am pulling those high amps. So hovering at 65% to start would be 80% six mins later. On a 6s setup 65% to start hovering would still be under 70% six mins later. It pretty much held performance through the full voltage drop.
I have not tested max flight time as I limited each flight to six mins, but you can work it out from my mAh/per min numbers in the charts. I know on one 6s flight I did go until my beeper hit 3.5v per cell and it was over 13 mins. Can't remember which combo now though.
Higher volts and lower amps are much more efficient than my current set up and the smaller props handle better for flight characteristics, especially against the wind.
If I am prepared to push the 700kv motor to 5s (I think 6s was too much heat) I can use those lovely 1055 MR props and hover at 50% while using 40% less mAh per min than my current setup. If I go to 6s on the 470kv motor I can stay with in the recommended limits. I would have to accept hovering at 65% on the same 1055MR prop, but with the bonus of being almost twice as efficient as my current setup.
I really like the MR props. They are stiff and responsive but only cost around $3 per prop. The range is expanding, but there is no 11" flavor until later in the year. Judging by my 1147SF data and extrapolating, I can imagine getting a 50% hover on either motor without breaking the limits while being twice as efficient as my current setup.
|Aug 16, 2013, 10:12 PM|
As you know I have the 3110 700kv too. I absolutly love them and chose them over the famous mt4006 for my qav500g.
I have been contemplating the use of 5s myself but didnt want to damage my motors. So Thank you for testing this out! Now to get some 5s ESCs.
Your test result show the new MR props to be promising. I have seen comments from others that they cause vibrations due to harmonics. So the extra performance is great but the video results suffer. What is your opinion on that?
Thanks a bunch
|Aug 16, 2013, 10:53 PM|
you know what i like about this test. you proved me right again that the 470 on 6s is by far the best motor. i tried telling you lol. but either way this is awesome you tested it so others that dont understand can see. if i was you id had bought a bb gun and shot my neighbor lol. i have a feeling you will end up going with the 470 kv motors on 6s like i orignally told you. your quad hovers at 16A thats pretty crazy mine hovers at 7-8. it shows how much more efficient you could beby going to a lighter frame. either way the 470 on 6s is still a huge upgrade and will allow you to fly longer than you were great test and happy flying!
|Aug 16, 2013, 11:47 PM|
Flohio...You have a point there. What would hold me back on the 6s may be the size of the batteries. the 500g has a height limit of 38mm so unfortunately i think that might be an issue for some others too with other frames. Its neat to see that such a low Kv can still hold up to a higher Kv on 4s as far as % to hover.
This test has certainly steered me to 5s with my 700kv
|Aug 17, 2013, 12:05 AM|
I have not seen video problems but I have only flown them with video on the old 1250kv setup. I will put the gopros on and go for a fly around and see.
|Aug 17, 2013, 12:19 AM|
I agree 6s is the most efficient of the test. Presumably 7s and 8s are better. But lets say I wanted to fly at a higher altitude or had to use smaller props then there is a good argument for the occasional 5s on 700kv - it works.
But nothing can deny it. On most of my charts 4s 700kv is a match to 6s 470kv for hover power but 6s is always better on mAh and that is important for longer flights.
For sheer lifting power the 6s can be beaten if you are prepared to push the 700kv to 5s but hey that just gives me another idea. Why not 470kv on 7s :-)
Regarding the 700kv on 5s. The ESC's handled it fine and in these simple tests the motors were warm but not hot using the smaller MR props. They are way cooler than my 1250kv setup that I have been flying for a year so they should hold up I think. Only time will tell.
I will certainly be keeping the 470's on 6s. But I have a liking for those 700's as well. Lucky I have a few frames.
PS. No bb's tonight. I am staying indoors :-)
|Aug 17, 2013, 12:21 AM|
Don't blame me if you burn up those motors and if you do don't post it as Flohio will laugh at me and make me feel bad.
|Aug 17, 2013, 12:45 AM|
I am going to try out the hobbywing ESC's. HiModel is the first site I have seen that lists the two types separately.
Bullet connectors on the board like Tmotors which the call type B...
Or with wires that will allow me to remove the bullets and solder the motors which I prefer...
They also have the programmer board if you want it...
I plan to test out the different timing options.
|Aug 17, 2013, 12:59 AM|
|Aug 17, 2013, 01:12 AM|
|Aug 17, 2013, 01:18 AM|
Im not sure if you would want to but if you ever had the funds id say get a naza and use it as your test FC because you could put it into gps hold and let it hover and get the closest to real hover times and amp draw. it would be easier because you wouldnt have to adjust the throttle to hold its altitude like you have to do on a CC3D. you never know what you really might be hovering at because a CC3D doesnt have a baro so it can't truely hover without adjusting the throttle all the time.
|Aug 17, 2013, 01:32 AM|
Thats true. But enough testing. Time to go and fly. I am going to build out the 470kv version tomorrow and I have some hobbywing ESC's ordered for a second setup on the 700's. Really there is no advantage to the 700's unless you push them on 5s where they get more lift (but use more mAh). 470 6s beats 700 on everything 'legal'
Thanks again for your original thread. Now I have to go and sell some stuff :-)
|Aug 17, 2013, 01:39 AM|
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