How to build a multi-rotor...

Hi all!

I just registered to DIY drones after loitering for quite a while. I'm planning to build a quad or hexacopter and I'm just overwhelmed but the possibilities.

My main problem (I guess) is that I have no R/C background whatsoever. So the problems begin already with selecting a frame - do I want a quad or a hexa. Fiberglass, carbon or alu-frame? How big? What kind of motors? What batteries? Etc...

Does anybody know any place in the web where somebody who is new to the flying thing can find compressed basic knowledge?


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  • Rui Manuel, WOW! Thank you! That was some extensive piece of information!

    To give a bit more background, I worked in the defense industry, and drones fascinated me already for a while. I also definitely am a helo-person.

    The whole thing is gonna be 75% curiosity and "boy-toy". Just do it to get into the matter. 25% it will have practical application or hopefully lead to one. I'm a volunteer in inland water rescue in Finland and we very often go out for missing person searches on or from the lakes (and there's lots of those here - lakes as well as searches!). Especially at night, that is tedious and you can drive just 7m past a body and not see it. One of the things I wanna test somewhen later is, if a quad which is auto-following our cruiser or boat in some altitude with an FPV cam and IR illuminators can be of actual practical use in those tasks.

    So my primary technical interest is (semi-) autonomy and extensive airtime plus a certain weather-resistance. Extreme maneuverability or payload capacity is not really important.

    The budget - the budget is rather limited. I don't have that kind of budget that I could just go and order an rtf quad from udrones or anywhere else. It's gonna be a process. First the frame and maybe the motors, next month the APM and some sensors, then the R/C, the FPV system...

    Finally, one quick and dirty question which I couldn't figure out from the website yet. Do I need a PC/laptop with GCS software for auto-follow me or can this work with an ardustation too?

    R.D.: I would love to start one :D. As my project proceeds, I'll surely start a section about it on my private website.

  • Greetings T.Stefan, There will be joy - there will be despair.

    Here is one of the best information resources I have found. it covers everything you will need inititally. I suggest you also check out the various individual build logs of interest to you, its a very well organised forum. Double check important stuff from forums, wrong advice is always possible.

    Good luck

  • Welcome to the crew Stefan!

    Yes it can be confusing especially with no R/C background but.. you can learn this stuff.

    From the perspective of flying, I seriously 2nd Monroe's recommendation of a sim. You can start doing that inside a week or less to get an idea of what it takes to control a flying vehicle. There are about 3 commercial choices of sims and a couple free ones available. All require an interface that looks and works like a RC Transmitter. Commercial route will cost around $200. 'Free' route - price of the interface box

    You need to answer the question, "What is your budget?"

    I know of no single site with all the answers. Want to start one?

    You will be integrating several disciplines into a quadrotor.What kind of resources do you have? Tools and space are important but you could do this on your kitchen tableif you buy a complete kit from 3DR. If you have tools and a workspace, you can go the route I did and homebrew all but the electronics.

    To answer questions of frame, 4, 6, 8 motors, etc is a bit early yet. Build what you can afford after a sim.

    Don't forget, there is a Buy, Sell, Trade section of this group.

  • Hi Stefan,

    Multicopters where my first experience in air RC (so far I had only driven cars), so, for what I've learned here are some basic stuff you may consider :

    1 - have lots and lots of patience. You will crash, you will have to replace parts, that's a fact. You will have to bear situations of extreme despair and frustration, but, success dependes on the ability to stand up after each fall :)

    2 - begin by buying a cheap frame.This one is very good to start, some 20amp ESCs like this, and motors. Motors seem to be always a difficult thing to choose because of the wide variety. I find the Emax GT 2218 930kv very reliable and also the sunnysky x2212 980kv like this. sunnysky may be a bit cheaper than emax. You will need motors with 700 / 1000 kv. Don't use too high kv motors since you will have too fast reactions and less torque, and choose carefully watching if the amps required are within the ESC capacity.

    3 - there's not a place where you'll learn everything, once again you will need patience and read a lot of foruns and opinions.

    4 - Propellers. You will need both regular propellers (counter clockwise rotation) and pusher propellers (clockwise rotation). For this frame, I would suggest something like 9x4.5 or 10x3.8 max. The smaller the propellers the best, but you will loose lifting capacity, so once again is a bit of test and fly. There's a very usefull site wich can give you approx. values for props, motor and battery configurations. DO NOT and I repeat, DO NOT use cheap propellers. I have found the APC to be the best so far, but hey are a bit hard to find. APC SF (slowfly) 10x4.7, 10x3.8, 9x4.5, etc, once you are already mastering and want to have a more rigged multi, you can to to the carbon propellers, but for learning and crashing, they are too expensive. If you use cheap propellers, you risk them to break in mid air giving you unnecessary crashes.

    5 - Electronics. Be very carefull with solderings and plugs. Avoid plugs when you can, since they may become loose due to vibrations, causing small glitches wich will lead to crashes. Choose a reasonable 3s or 4s lipo battery (for starters I think a 3s will be enough) with 2.2 or 3000mAh and a discharge ratio of 40C or 30C (2.2 or 3). The discarche ratio will tell you how much amps the battery can provide at a given time, so, for instant, if you're using 4x20amps ESCs, and you need maximum power from them, you will need 80amps. A 2200mAh battery with 20C discharge will give you 2.2x20=44amps max at a given time, so you will need a higher C ratio, like 40C (2.2x40=88amps). If you use a 3000mAh you will only need 30C wich already provides 90amps. Aim a bit higher always or the battery will start to warm and loose efficiency.

    6 - Be very carefull handling LiPo batteries, use low voltage alarms, and automatic chargers that monitor and balance the battery. A overcharged or short circuited battery can explode or catch fire.

    8 - To balance and calibrate your quad (I sugest a quad to start, since if you crash, there will be less parts to replace), you will have to read instructions on how to do so and ask for some help. Also, read some past posts, but that's a bit of a trial and error science.

    9 - The radio. You find some cheap 9 ch radios today at around $100 or so, however, as everything, you get what you pay. I prefer a 2nd handed Futaba, than a cheap new radio, but that's me :)

    10 - The simulator is a great peace of software, you can learn the basic maneuvers and see how each control affects what, however, you won't have the "real feel" of the quad. Each aircraft has it's own center of gravity, weight, thrust ratio, etc, and you will have to slowly learn to feel it. I remember my first times where scary. The props rotating scared the sh1t out of me :D I begun by lifting only 10cms or so from the ground, then, 15, and so on, with very small inputs on the radio. That's a very progressive process and after you can lift it and have it hovering, it's time for the more difficult stuff... control it with it's front towards you. You get a bit lost when it comes to orientation because multicopters are very symetric, so it's hard to tell where's the front and where's the rear in mid flight, especially if it's far and in a low angle. If you have it well tuned and calibrated, when you loose orientation, the best thing is to let go of the sticks and then use just roll or pitch to see how it responds untill you get orientation.

    3DRobotics will sell complete kits with apropriate motors for their frame, and if you are not sure what to buy, that's a good alternative, however, for begginers I think that's too much of a good frame to submit to the initial crashes


    I think this is enough to get you started. A very importante safety tip : propellers WILL cut you hard and deep if you don't be carefull. When you are not going to fly, always (and I really mean always), remove the props. A small current spike may cause a motor to spin at full speed and cause a severe injury.


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