My Octo Doesn’t Lift Enough or Fly Long Enough – What Can I Do?

[questech]

Hello Everyone :nevreness:

My goal is to build an octocopter that will be able to lift a 15lb to 25lb payload and fly for at least 15 minutes (hopefully more).

The problem I’m having is with reading the specs of the components.

Some are only in Chinese, some are inaccurate, and there doesn’t seem to be a strong standard to make an apple to apple comparison.

So I built what I thought would be a heavy lifter, only to find out that it isn’t quite up to the task.

Here are the components I’m using (won’t include Naza and other components non-essential to flight time and lift):


* Hobbyking X930 Glass Fiber Octocopter Frame 895mm (Heavily Modified)
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=26455

* (8) NTM Prop Drive Series 35-36A 910Kv / 350W
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=14847

* (8) HobbyKing F-30A 30A SimonK Brushless ESC w/ 3A 5V UBEC

* (8) 11X4.5 Props

* Turnigy nano-tech 6000mah 3S 25~50C Lipo Pack
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=20681

** Weight of the craft: 8.5lb
** Weight with 1 Battery: 9.5lb
** Weight with 2 Batteries: 10.5lb
** Weight with 3 Batteries: 11.5lb

*** Flight time with 1 battery: 6.5 min
*** Flight time with 2 batteries: 12.5 min
*** Flight time with 3 batteries: 11.5 min

As you can see, the weight of the 3[SUP]rd[/SUP] battery (approx. 1lb) nullifies the benefit of the additional 6000mAh and actually reduces the flight time.

Now this one is a big problem for me because my camera and gimbal weigh 5 or 5.5lb:

*** Flight time with 2 batteries and a 5lb payload : 3.5 – 4.2 min.

-----

One thing that I noticed in hind sight is that my battery is only 25C rated, and my motors max out at 38 amps. HobbyKing sold me the motors and their listing suggested 30amp ESC.

My tests showed that the max amps that I could draw with a 12” prop was 23.6 amps and with an 11” prop the max was 20.1 amps.

Because of my tests I felt comfortable with the 30 amp ESCs, but I’m wondering if the battery’s 25C rating is responsible for the low max amp readings or that the HK specs are just off??

I have some questions:

-- Would a higher C rating battery actually give me better (higher amperage readings) test results?

-- Would a higher C rating give me more lifting capacity?

-- Would a higher C rating give me more flight time?


-----

**** Here is the million dollar question… What do I have to do to upgrade the above octocopter to lift 8lb and fly for at least 15 min?

-- I like these motors, they’re smooth and I feel I can trust them… Is there anything I can do to get more lifting capacity and flight time out of them?

-- What motors would give me the results I’m looking for?

-- Would more cells make a difference?

Any advice and feedback is greatly appreciated!!!

Anthony

 

[SleepyC]

Those motors are completely wrong, and you won’t lift anything with a 3S system.
You want to look for a motor that can lift at least 1500 - 2000 grams at 50% throttle per motor.
And can spin a minimum of 15 inch props.

I have a heavy lift hex that can easily lift 15 lbs and it’s a 6S system using 60 amp sec’s, Avroto 3520 400KV motors and 15/5” t-motor props.
With (2) 6000mah packs i can get around 12 minutes at 10 lbs and around 10 min at 15 lbs.

You need to go in a whole different direction.

Avroto 3520 motors: http://montorc.com/avrotolift3520400kv.aspx
Maytech 60 amp ESC’s: http://www.uavrotorking.com/product/maytech-60amp/
T-Motor Props; http://www.helidirect.com/t-motor-15x5-carbon-fiber-prop-p-31445.hdx?

 

[questech]

Hello SleepyC,

Thanks for the feedback.

Once I built the octo (my first build) I realized that I probably built a great GoPro platform.

I do want to get the most out of what this is though.

My ESCs will handle 4S but the motors (as you can see from the link) only list that they can be used with 3S. I'm sure that if I am careful not to exceed the Amps or Wattage I could probably use a 4S.

That frame only has enough room for 13" props, which I'm picking up tonight.

Do you think that going from a 25C battery to a 45C battery of the same mAh will net me any better results?

Thanks again for your feedback!

 

[questech]

BTW I have already ordered materials to build a much larger octocopter and all of your feedback will guide me to what Motors, ESCs, and Batteries to use.

So Thank You in Advance!!!!

 

[tombrown1]

Going to 45c will probably not help. You need to spend a lot more money to meet your requirements. And you probably have many many more hours of reading to do on these forums before you build it.

You need better low kv motors, much bigger props, bigger batteries at 6s, bigger escs, and a bigger frame to come close to what you're asking.

Best,

Tom

 

[SleepyC]

Going to 45c will probably not help. You need to spend a lot more money to meet your requirements. And you probably have many many more hours of reading to do on these forums before you build it.

You need better low kv motors, much bigger props, bigger batteries at 6s, bigger escs, and a bigger frame to come close to what you're asking.

Best,

Tom

Yep... 10 + lbs of payload = $$$$
15 - 20 lbs of payload = $$$$$$$$$$$

 

[PeterLester]

Lot's of data but no evidence that proper engineering design has been performed. If no engineering, then, at the very least, a solid knowledge of how to use eCalc for Multirotors is critical...... QUOTE=questech;129976]Hello Everyone :nevreness:

My goal is to build an octocopter that will be able to lift a 15lb to 25lb payload and fly for at least 15 minutes (hopefully more).

The problem I’m having is with reading the specs of the components.

Some are only in Chinese, some are inaccurate, and there doesn’t seem to be a strong standard to make an apple to apple comparison.

So I built what I thought would be a heavy lifter, only to find out that it isn’t quite up to the task.

Here are the components I’m using (won’t include Naza and other components non-essential to flight time and lift):


* Hobbyking X930 Glass Fiber Octocopter Frame 895mm (Heavily Modified)
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=26455

* (8) NTM Prop Drive Series 35-36A 910Kv / 350W
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=14847

* (8) HobbyKing F-30A 30A SimonK Brushless ESC w/ 3A 5V UBEC

* (8) 11X4.5 Props

* Turnigy nano-tech 6000mah 3S 25~50C Lipo Pack
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=20681

** Weight of the craft: 8.5lb
** Weight with 1 Battery: 9.5lb
** Weight with 2 Batteries: 10.5lb
** Weight with 3 Batteries: 11.5lb

*** Flight time with 1 battery: 6.5 min
*** Flight time with 2 batteries: 12.5 min
*** Flight time with 3 batteries: 11.5 min

As you can see, the weight of the 3[SUP]rd[/SUP] battery (approx. 1lb) nullifies the benefit of the additional 6000mAh and actually reduces the flight time.

Now this one is a big problem for me because my camera and gimbal weigh 5 or 5.5lb:

*** Flight time with 2 batteries and a 5lb payload : 3.5 – 4.2 min.

-----

One thing that I noticed in hind sight is that my battery is only 25C rated, and my motors max out at 38 amps. HobbyKing sold me the motors and their listing suggested 30amp ESC.

My tests showed that the max amps that I could draw with a 12” prop was 23.6 amps and with an 11” prop the max was 20.1 amps.

Because of my tests I felt comfortable with the 30 amp ESCs, but I’m wondering if the battery’s 25C rating is responsible for the low max amp readings or that the HK specs are just off??

I have some questions:

-- Would a higher C rating battery actually give me better (higher amperage readings) test results?

-- Would a higher C rating give me more lifting capacity?

-- Would a higher C rating give me more flight time?


-----

**** Here is the million dollar question… What do I have to do to upgrade the above octocopter to lift 8lb and fly for at least 15 min?

-- I like these motors, they’re smooth and I feel I can trust them… Is there anything I can do to get more lifting capacity and flight time out of them?

-- What motors would give me the results I’m looking for?

-- Would more cells make a difference?

Any advice and feedback is greatly appreciated!!!

Anthony[/QUOTE]

 

[questech]

Going to 45c will probably not help. You need to spend a lot more money to meet your requirements. And you probably have many many more hours of reading to do on these forums before you build it.

You need better low kv motors, much bigger props, bigger batteries at 6s, bigger escs, and a bigger frame to come close to what you're asking.

Best,

Tom

Yes, yes I agree, much more research, but I already have a good start thanks to you and others that have offered their comments, so thank you, I appreciate it!!

It may seem simplistic, but I totally get the "You need better low kv motors, much bigger props, bigger batteries at 6s, bigger escs, and a bigger frame to come close to what you're asking." comment. 2 days ago I hadn't yet fully understood the orchestration.

I believe that I now have to choose the right motors and then build everything else around that choice to accommodate them.

So now my pursuite is to find the right motors... Your suggestions are welcome!

BTW this is my first Octo build, and the last RC build that I did was 30 years ago on a gas powered Chipmunk and I haven't had any RC activity since, so I'm essentially new at this.

Thanks Again Tom!!

Anthony

 

[questech]

Yep... 10 + lbs of payload = $$$$
15 - 20 lbs of payload = $$$$$$$$$$$

Hi :tennis:

I'm willing to put in the investment, I just don't want to throw money down the drain, which is why I'm researching.

When I decided to do this, I purchased a DJI Phantom with Gimbal, GoPro, and FPV setup to learn on.

So I taught myself to fly and then I immediately tore the thing down and reverse engineered it to see how it worked and how all of the components fit together.

My next step was to build something, anything that I could test my knowledge and see if it would actually fly... intro to my first octocopter build.

At this point I had no knowledge of any formulas/calculations so I simply purchased a cheap frame (4 of them and redesigned it for durability and to experiment with designing) and because I had no knowledge of the requirements, I followed the recommendations of HK as a starting point, which is the setup that I'm flying.

Now to be honest, this thing flies beautifully with a light payload, like my GoPro and its tiny 2 axis gimbal, and I've gotten over 13min of flight time so far, and I think with tweaks (less weight, different batteries) I can get at least 15min of flight time.

So I believe the experiment has been nothing short of successful. I have a great GoPro platform, a lot more knowledge, I made some new friends, and I'm building my next project... All good :nevreness:

Thanks for all of your input!!

Anthony

 

[questech]

Lot's of data but no evidence that proper engineering design has been performed. If no engineering, then, at the very least, a solid knowledge of how to use eCalc for Multirotors is critical......

Hi Peter,

No evidence of proper engineering and design??

There was no attempt at proper engineering and design :highly_amused:


But seriously, I didn't know where to start, so I just started experimenting and as always, I learn as I go.

Look at my reply to SleepyC for an explanation of my process.

I agree, my next step (before I spend lots of money on my next set of motors for the new octo) is to learn how to use eCalc for Multirotors.

That app is pretty strieght forward, I find the hardest part getting the data to fill in the blanks.

I know that you guys must have ways to get the data, or know how to extrapolate other information and come up with a close guess of what the missing data might be, but I'm not there.

So any help that you can offer in this vein would be greatly appreciated!!

Thanks for the feedback !!

Anthony

 

[questech]

Quick Update:

Even though I'm a filmmaker (one of my businesses) and have lots of buds with RED cameras, I think I will lower my requirements for this next build to carry an Up To 10lb camera and gimbal combo for 20min... I'll build a RED platform once I get more demand for it.

Thanks Again !!

Anthony

 

[tombrown1]

10 pound camera/gimbal for 20 minutes? I'm pretty sure nobody in the world has accomplished this.

You might squeeze out 10-12.

T-motor motors are excellent and have a proven track record.

 

[Thalios]

Also get some real batteries, not Crappy Nanotech which are the worst at sustained voltage, capacity versus weight and lifespan. On real batteries compared to these crap, you can save anywhere from 50g to 400g per battery!

 

[tombrown1]

Also get some real batteries, not Crappy Nanotech which are the worst at sustained voltage, capacity versus weight and lifespan. On real batteries compared to these crap, you can save anywhere from 50g to 400g per battery!

What are these real batteries you speak of?

 

[Thalios]

There are tons to choose from.

I own about 15 different brands of batteries for all kind of purposes and the nanotech have been the worst by far.

Thunder Power, Dinogy, Desire Power, Pulse Ultra, and many other are really nice ones.