Hello Everyone,

I would like to introduce you all to a project I am working on, as the name suggests, its a full scale octocopter. I have been inactive on the forum for a while now as I have been away at college in the USA, however, since I have been here for a while I decided to help some highly motivated students from my high school in hyderabad, CHIREC, to design and build this multirotor.

The motive of the project is to encourage the youth of today to think big and do bigger. In todays world we don't lack anything in terms of technology to bring our wildest fantasies to life and we want students to realize that and work on whatever crazy ideas they have under the proper guidance/supervision. I will be uploading some pics and details about the workmanship that went into it shortly, but for now you can check out the project at -

Instagram - https://www.instagram.com/themannedoctocopter/
Website - themannedoctocopter.com

We also just recently uploaded a video on youtube tracking our progress, the link to which is

We are only a week away from the test flight. Follow and give us a thumbs up and look out for updates!

Thank you all,
Sahevaan Taneja

Wow! 

This is a first-of-its-kind project in India. All the very best for the maiden! 

Could you please share the details of the hardware and electronics you used? Maybe some of us here can give it a try too. 

If you succeed, we might be able to try some crazy stuff like the Latvians.

www.youtube.com/watch?v=EOPZhRJtz9w

Thank you Swapnil.

As for the equipment, we are using the following -

8 x Turnigy CA120 70 150kv motors (from hobbyking)
4 x Monster 2000 200A ESC (from hk)
4 x Fatboy 300A ESC (from hk)
[ You must be wondering why two different types of ESC's, the reason for that is the time deadline. I will be returning back to college in August and we had some delays in receiving the fundings from our sponsors hence only a limited number of each type of HV ESC were available. We had tried and tested the Monster 2000 ESC and it seemed to work perfectly with the setup, however, due to limited stocks we were unable to order 8 of them so we decided to mix and match. From my experience and peoples suggestions, this shouldn't be a problem since both are able to supply more amps than required ]
16 x 6s 6200mAh 40c LiPos
8 x 32x10 Xoar Propellers (Yes, they are paired. We tested with a variety of propellers and seemed to get the best thrust + endurance from the propellers we chose)
1 x DJI A3 Pro controller as the autopilot system. It has a triple redundancy system which we found to be essential if we are actually going to test with a person on board.(If anyone has any experience using/setting up this controller, please PM me.)

For all electrical connections we have used XT 150 connectors and they seem to work perfectly for our application and they are very simple to use as well.

The radio system we intend to use is the Turnigy Taranis. We have multiple telemetry receivers for this radio, however, due it being the heart of the project for control, we might test this system out on a couple of other multirotors and aircrafts before we use it. I am also unsure how we can link up multiple receivers for redundancy (If anyone has experience with this system, please post of how we can go about linking multiple receivers to a single transmitter). For the first few test flights we will be use the JR XG14.

The actual frame of the Octocopter is made with a mix of 6061 and 6063 aluminum alloy.

That is such a huge project. My best wishes.

Quote from: Sahevaan on May 16, 2017, 01:33:26 PM

If anyone has experience with this system, please post of how we can go about linking multiple receivers to a single transmitter).

Firstly, it's easy to use multiple receivers for redundancy. I have one such setup where I use a 2.4GHz + 433MHz combo as one frequency can work in cases the other can't. Also, they don't interfere with each other.

Secondly, the FC can be programmed to return to home (take-off point) in case of signal loss. If that is an acceptable scenario, there's no need for multiple receivers.

If you really need it to be truly redundant, I have a comm system that uses 2.4GHz + 433MHz as well as 3G network for redundancy and range. The algorithm I have for the 2.4GHz + 433MHz part of the system has a very low latency of only 1-3 milliseconds (as opposed to the conventional 20ms).

Regarding the ESCs, it's true that different brands won't cause any trouble as long as they can fulfill the power requirements.

I really wish I could work with you guys on this project! 
I have some more suggestions for making the system more robust and safe (electronically). It would be great to discuss those with you if you have the time.

Hello Swapnil,

We have completely exhausted our budget with all the electronics so we wont be able to invest in a 433 MHz system. I have seen multiple RC jets using two receivers of the same brand (both 2.4GHz) as redundancy incase one does fail. We will be programming RTH on the FC, however, having the transmitter too close to the receiver does cause a low RF signal warning but it does not lose signal and the pilot on-board will have the Tx with him, in order to tackle this problem we thought of mounting two or more receivers (we have 6 in total to use) at different location on the multirotor so that incase one does lose signal, the multirotor wont return to home, rather restore control through the secondary receiver. In case this is possible using the FrSky system, it would be a good option to use.

Thank you for your wishes, please do PM me with your number and we can discuss this over phone.

Quote from: Sahevaan on May 16, 2017, 02:08:27 PM
... the pilot on-board will have the Tx with him, in order to tackle this problem we thought of mounting two or more receivers...

Well, a much easier way to tackle this problem would be to directly hard-wire the transmitter to the A3 pro (via SBUS) so there's no signal lag at all and no need for a receiver for the on-board pilot. We can have a receiver multiplexed with the comm handling system for switching between on-board pilot and ground pilot.

Also, if your deadline isn't too close, I can lend my LIDAR and SONAR sensors for your project to achieve centimeter scale precision altitude hold, position hold and obstacle detection and avoidance while take-off and landing.

LIDAR implementation could be better but its very hard on pocket. LIDAR usable for big copters can be very much expensive as their budget has narrowed. However that could be implemented in later stages after maiden after which they may have good sponsors.

Quote from: Balakrishna Reddy on May 16, 2017, 03:19:23 PM
LIDAR implementation could be better but its very hard on pocket....

Ah, but I already have some expensive LIDARs (as well as SONAR modules) with me that I can lend them!      

I'll also have a scanning LIDAR system in a day or two for implementing Hector SLAM.

Wont u guys have issues with the authorities???
But I guess you've sorted that out already....

Also...considering all the equipment u guys have ( and funding) you can easily make a flying airplane that carries a person...
I mean yes...associated risks with N airplane are a Lott more....like it has to take off at a higher speed and might crash at a high speed leading to more fatality...
But it can be made...
I wanted to make one last year... But the 20hp ( minimum) engines I wanted were expensive and pushed the cost of everything beyond budget....
All the best to u guys...👍

Quote from: Imperial fire on May 16, 2017, 03:34:49 PM
Also...considering all the equipment u guys have ( and funding) you can easily make a flying airplane that carries a person...
I mean yes...associated risks with N airplane are a Lott more....like it has to take off at a higher speed and might crash at a high speed leading to more fatality...
But it can be made...
I wanted to make one last year... But the 20hp ( minimum) engines I wanted were expensive and pushed the cost of everything beyond budget....
All the best to u guys...👍

Nice Idea, I like it.
do you mean something like this? https://en.wikipedia.org/wiki/Airbus_E-Fan

Hey there guys, congrats, on first of all taking up such a project. (would have loved to help).
But i think your motors are a little underpowered(correct me if i am wrong).
You could use the Turnigy Rotomax 150cc (i heard it produces as much as 60 kg with a 30").
The rest i think is perfect.

Waiting to see it in the skies.

Well yes small planes like that...
But also a whole bunch of other ultralight aircraft ...the plans for which are available for free...
My favorite one is the DA 11... Made using just a 8hp engine...
But yes airplanes are a whole new field (and issue too)... Coz once u 'fly' an airplane you've officially 'flown' it. ..( unlike a octacoptor which u can hover a little without any issues)
And once uve. Flown it...authorities will come in...followed by media yes 😂😂😂😂

Neways keep this thread active.. I would absolutely love to see ur project succeed 👍💪💪

Quote from: kartp3112 on May 16, 2017, 06:16:11 PM
...
But i think your motors are a little underpowered(correct me if i am wrong).
...

Even if one of those motors gives 20Kg thrust, the total thrust would be 160Kg which should be good enough for a first prototype.

my calculation,
Frame- 20-40 kg. (not sure what your frame weighs)
Electronics, approx 30-35 kg
Rider 50-80 kg.

Hence adding up, upper bound 155kg
Lower bound 100kg.

To be honest i thinkit is a little on the "edge" as it isnt abiding by the ideal 1:2 ratio od weight to thrust.
Again Correct me if i am wrong.

@kartp3112

Their electronics weigh about 41Kg (given I checked the correct web-pages )

If their frame doesn't weigh more than 20Kg, they can still test a payload of about 45Kg (under 2:3 weight-to-thrust conditions).

They can try to reach the ideal 1:2 ratio using higher pitch propellers and optimizing the weight. I think for a first prototype with funding constraints, a WTR of 1.4:2 would be significant achievement.

 

Funding constraint reminds me...
What would be the cost of all the equipment that these guys have bought??
(Including batteries ESC motors chargers props sensors.. )
Around 3 lakh??  Or more??

Quote from: Sahevaan on May 15, 2017, 04:54:35 PM
...
We are only a week away from the test flight...

I guess the first test flight will be any day now. Best of luck guys! Make our nation proud! 

Hey guys,

Sorry for the super late reply. I have been busy with other work, however, here's an update and answer to a lot of your questions.

The DJI A3 controller that we have ordered is on the way and should reach us any day.
The package with all the batteries has been stopped by customs and I was just informed that I had to write a 'techinical write-up' and submit a picture invoice. I have just done that. Since it is for educational purpose and we will be sending the excel sheet on the school's letterhead, we might be able to clear our package without further hassles.
We have just finished soldering the connectors to all the motors and ESC's and will be balancing all the propellers in the coming few days (although they come pre-balanced from the factory, we did have some vibrations at lower rpm while testing).

As per the tests, each of the motors with the 32 x 10 wooden prop is producing 26kgs of thrust. We have not even tested the power setups full potential yet because the batteries we were using for testing were 20c and hence capable of producing only 100A (5Ah x 20c) while the new batteries are going to be 6.2 Ah and 40c. Since we have 8 motors, we're looking at approximately 200kgs of thrust at full power.

We have done endurance tests and we are getting about 6 mins of ground run time when the motor is producing 13kgs of thrust and about 5mins when producing 15kgs of thrust. We have also performed amp and power tests. We have videos (although not very professional) while doing them as well. If enough people are interested in seeing them, we can upload them on YouTube.

As for the weight, the frame weighs 28kgs. Each motor weighs 1.3kgs, ESC + Wires and Connectors about 700g and 2 x 6s 6.2Ah batteries about 2kgs. Which totals to about 4kgs of equipment per arm (per motor/esc/battery setup) and 32kgs in total. The figures above are estimates. Once we have all the equipment in hand we will be able measure the weight accurate to the gram.

We spent a total of 10 lakhs in acquiring the equipment, shipping and importing, designing and testing the frame, i.e. all together.

I also have a couple of questions, one of which I will ask now.
Our design allows the motor to be moved inwards and outwards on the arm to allow fine tuning of the dia of the octocopter eventually. Any ideas what the effects would be moving them inwards? Currently they are at their outer most limit at 1.48m from the center of the multirotor. They can be moved in by ~0.2m safely without the blades touching.

I honestly think that they are more efficient the more the distance between them.....
Also having em further apart perhaps allows for better control.. Although that shudnt be a big issue..

I don't understand this part 'will be balancing all the propellers in the coming few days (although they come pre-balanced from the factory, we did have some vibrations at lower rpm while testing)........ Are u having vibrations at lower rpm ?? If yes then how not at high rpm?? Shudnt the vibrations increase at high rpm??

P.s please upload any video u guys have on YouTube as and when you get time...
...a video always teaches something extra.💪👍

Quote from: Imperial fire on May 23, 2017, 01:39:29 AM
...
I don't understand this part 'will be balancing all the propellers in the coming few days (although they come pre-balanced from the factory, we did have some vibrations at lower rpm while testing)........ Are u having vibrations at lower rpm ?? If yes then how not at high rpm?? Shudnt the vibrations increase at high rpm??

Resonance.
https://en.wikipedia.org/wiki/Resonance

Quote from: Sahevaan on May 23, 2017, 12:32:32 AM
...
Our design allows the motor to be moved inwards and outwards on the arm to allow fine tuning of the dia of the octocopter eventually. Any ideas what the effects would be moving them inwards? Currently they are at their outer most limit at 1.48m from the center of the multirotor. They can be moved in by ~0.2m safely without the blades touching.

The further apart they are, the more efficient and stable the system will be.

@swapnil I read the resonance article...I still don't understand...
Don't vibrations become more pronounced at high rpm for the same prop??
Or do we have vibrations at low rpm and then they cancel each other at high rpm??

Swapnil +1 on that. Seems like all the propellers are very well balanced. The vibrations are arising at about 1200-1500rpm (will confirm that in a couple of days once the tachometer is here) are due to resonance, however adding a little bit of dampening material seems to solve the problem significantly. Hopefully with 8 motors the vibrations do not constructively interfere and increase in amplitude. Any thoughts on that?