Quadcopter build - Motors, battery and weight reduction

Hey guys, 

Not new to this community but it is my first post here. So I'm building a quad for this project that I've been assigned to in my company. It is required to be able to lift a 1kg payload(camera for surveillance). I'm adding a 2 axis gimbal for stability. 

So after all considerations(including approx weight of motors(220g), battery(700g), gimbal(300g) and payload(1kg) ) the all up weight for my quad is approx 3 Kg. So that would obviously mean that i would require a minimum thrust of 6Kg from my motos. Now I know this is super inefficient and I should consider building a hex or octa instead but the project dictates 3 separate designs(one quad, one hex and one octa) so I have to design the quad to fly, and be stable as well. 

A few specifications of the quad: 

Pixhawk Px4 flight controller 

2D custom built Gimbal + 1 Kg payload

2.4 Ghz Radio transmission-reception + 433Mhz (3dr) Telemetry Kit + 5.8 Ghz video transmission - reception 

Okay so 3 things that I need to ask

1. What KV motors and Props should I be looking at. I know that obviously I should practically try out the thrust of the motors, but its in the design phase so I have to give KV motor ratings and Prop size as well. So what motors+Prop combination can get me to lift this huge baby. 

2. I NEED to maximize flight time as much as possible. This will also lead onto my third question about weight reduction. What capacity battery along with C rating of battery should I be looking at?? (This obviously is related to the motors and ESC max current rating as well I know) 

3. I need to reduce the weight to improve the flight time, what are the possible ways that I can reduce the overall weight of the quad? 

Also with a payload of 3.5KG i.e. 2Kg + 3.5Kg = 5.5Kg AUW, for 11KG thrust with hex what motors and battery(ies) should I be looking at?

This is my first ever quad design(I am an Electronics and Telecom Engineer so not a noob in terms of electronics aspect) And I really hope you guys can help me out with these newbie problems of mine. Thanking everyone in advance! 

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This is not really a good project for a first effort. If you are serious I have an absurdly optimized, new quad with a DJI E1200 power system (highly recommended) and a Pixhawk. It is a custom, exotic mapping quad. Could fly 1kg for 30-40 mins with 6s 15-30 AH worth of batteries and UHF radio/telemetry.


If you don't mind me asking, why would you say its not a good first effort? 

I checked out the DJI E1200 Power system and it is insane!! The thing is according to its specs, it recommends 1200-1400g/motor whereas mine would require 1500g/motor (2*3KG), so how much problems would that cause? Although I am really serious and if youre willing to share your design with me I'd be more than grateful. ( I wont copy it ofcourse because its professional work I need to submit, will just take a hint of how I can improve my design) 

EDIT : Also the weight of the motor is 205g/motor, that would add an extra 600g to my design, making the weight/motor 1650g/motor, which I guess really does exceed the recommended specs. 

Thank you. 

Marc Dornan said:

This is not really a good project for a first effort. If you are serious I have an absurdly optimized, new quad with a DJI E1200 power system (highly recommended) and a Pixhawk. It is a custom, exotic mapping quad. Could fly 1kg for 30-40 mins with 6s 15-30 AH worth of batteries and UHF radio/telemetry.
An E1200 quad can carry 6kg AUW, so a well designed frame can easily haul 1kg of payload and lots of battery.what I mean is that this is ambitious for a first project. You will spend a lot of money and time doing this - making what sounds like a high spec work tool

The path of least resistance is to purchase an S900 or a from DJI and add a Pixhawk. Or look at a Matrice 100 system -- why do you need a Pixhawk anyway? The M100 has full autonomy and is ready to roll complete with a 3 axis camera that will be better than anything you can mount.

As for my machine it was made for high end industrial mapping. It is a work tool. Some clever guy in Canada designed it. I meant to use it for IR scanning but another more modest platform was used. It has barely been flown so I was going to sell as an Ag Mapping solution. It could just easily be a long endurance surveillance drone. I can post pics to give you ideas but I would also sell it. In any event you cannot beat the E1200 IMHO.

Oh and you will not find 50g motors to do what you want. Those are for toys! 200g is what you will be needing.

I know it is a very ambitious first project, Im interning at a company and they just want designs for 3 multi copters. designing the quad was becoming the toughest because of the whacky specs they've given to me. As far as cost goes, that is not an issue since this is going to be an industrial project.

So I checked out Tiger motors and a motor they have known as the MN5212-340 (340KV). 

So according to their charts using an 18'' prop along with a 6s 22000 mAh battery, the motor should give a thrust of 1310g at 50% throttle. (http://www.rctigermotor.com/html/2015/Navigator_0206/287.html)

What would your advice be on this configuration? Is using a 6s1P battery okay or impractical? Im sure its gonna weigh a lot too. 

And as far as the DJI E1200 goes, I pitched it and got turned down, apparently some problems regarding using DJI parts for the project, idk the exact reason behind it, but it got turned down. 

Thank you for the help so far! 

EDIT: I edited the stupid mistake of using 55g motors for my design, THANKS a lot for pointing that out!! 

Marc Dornan said:

An E1200 quad can carry 6kg AUW, so a well designed frame can easily haul 1kg of payload and lots of battery.what I mean is that this is ambitious for a first project. You will spend a lot of money and time doing this - making what sounds like a high spec work tool

The path of least resistance is to purchase an S900 or a from DJI and add a Pixhawk. Or look at a Matrice 100 system -- why do you need a Pixhawk anyway? The M100 has full autonomy and is ready to roll complete with a 3 axis camera that will be better than anything you can mount.

As for my machine it was made for high end industrial mapping. It is a work tool. Some clever guy in Canada designed it. I meant to use it for IR scanning but another more modest platform was used. It has barely been flown so I was going to sell as an Ag Mapping solution. It could just easily be a long endurance surveillance drone. I can post pics to give you ideas but I would also sell it. In any event you cannot beat the E1200 IMHO.

Oh and you will not find 50g motors to do what you want. Those are for toys! 200g is what you will be needing.

Hi

What kind of UHF radio/telemetry are you using?

Marc Dornan said:

This is not really a good project for a first effort. If you are serious I have an absurdly optimized, new quad with a DJI E1200 power system (highly recommended) and a Pixhawk. It is a custom, exotic mapping quad. Could fly 1kg for 30-40 mins with 6s 15-30 AH worth of batteries and UHF radio/telemetry.

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