New Octo Copter Design/Build Thread

Starting a new thread to show what I'm working on.  I'm building a new Octocopter of my own design.  The goal is to use it for Aerial Photography, lifting a mid-weight camera such as a Sony Nex5.  It will of course be using Arducopter for control.  ;)

I started off researching the various kits on the market, and starting getting analysis paralysis.  I looked at all the options such as Droidworx AD8, Cinestar, CarbonCore, and SteadiDrone.  But I just wasn't happy with the design on them, particularly for the price they ask.  Combined with the fact that I can be pretty frugal, and have a strong DIY ethic, I decided to just design my own.

The basis of the design relies on many of the Hobby King quadcopter parts.  I liked the design of the motor mounts, they are very professional looking, even compared to some of the high end machines.  And I liked that the boom mounts are blocks of aluminum instead of plastic.  Very rigid.  I also liked the look of the dome on their H.A.L. quad, but since they don't sell it seperately, I bought the whole kit, it's only $34, amazing!  I might end up using the rest of it someday, who knows?  So, I basically emptied out their stock of Talon parts, so if you need to fix your Talon quad and the parts are backordered... sorry!

Once that was settled, I set about designing the center frame.  My design required a few things, namely I want all the wiring hidden.  I don't want any spaghetti showing.  Particularly with the ESC's, while still allowing cooling airflow.  This required the center hub to be larger than is typical.  I then needed a smaller subframe to house the avionics.

You can see these plates below.  The larger one houses the HAL dome. You will notice the 3 blue anti-vibration grommets in the middle.  This is the APM1 pattern.  I did that just because.  Maybe I'll use an APM1 as a stand along gimbal controller.  The second plate had grommet mounting for an APM2.  The final plate is the top plate, and has bolt patterns for the Ublox GPS and the magnetometer.


This next photos shows the avionics frame built up with an APM2 mounted.  25mm aluminum standoffs are used. I don't like the plastic standoffs typically used.  They get loose, and lead to vibration.  They also break easily.  This structure ends up being quite rigid.


Here is the avionics frame mounted on top of the main frame.  Yes, the main frame is HUGE.  I actually don't see the point in having a tiny center frame, and then long arms.  This seems like it just leads to flex, and doesn't leave you with any real estate to mount your avionics.  


This photo shows one of my design features.  I put some cutouts on the bottom frame for weight savings, and then made matching cutouts on the top frames.  This creates some nice conduits to run wires neatly.


Here it is with the HAL dome mounted and one of the Talon arm mounts bolted in.  I'm really happy with how stiff the assembly is already.


Here it is with one of the arms mounted.  These are the short 220mm arms, I also got some of the 320mm arms.  One may wonder how I'm going to get away with such short arms and 13" props....  Astute readers will know what I'm planning already. ;)


This last photo shows one of the ESC's in position. This is a Hobby King F-40A, it's somewhat larger than typical 20A units which is partially why the frame is so big.


That's it for now.  I had the plates cut out of aluminum to start with because it's cost effective.  If it all works out, I'll probably have it redone in carbon fiber plate for the weight savings.  I was a little uncertain about the weight, but it looks like the frame will come in at 1070g all in aluminum.  That's about 300g heavier than a Droidworx AD8, but not too bad. It will drop about 1-200g if redone in CF.

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  • I flew two packs last night.  Went well other than a flip on takeoff due to PID settings.  After I got it tuned in, this thing is insane!  I am quite sure it has more power than my helicopter.  It's like a rocket. I'm going to have to power it with 4 4S 5000 batteries because it can draw far too many amps at full load, so I'm still trying to fly it gently.  Either that or reduce Thr_Max to 500.  

    I think I got almost 15 minutes from 2 4S 5000 batts.  That beats the eCalc prediction a bit.

    I still want to fly it in some wind before declaring a success.

    Oh, and those motor mounts are ridiculously soft.  I bent 3 when I flipped, but didn't break a single prop!.

  • I think. Do have the jp1 jumper n place. I think I will go with these 3536-910Kv motors you suggested. They say 3s and 10" props. I will be using it with 4s and 10" props. Should be able to lift more than a P&S camera. If not then I will move to 12".
  • I think I didn't explain clearly. I'm not referring to the ESC's signal wires. I'm using external BEC and connect that to the APM and then run another +- from APM to Rx. The APM's - is all tied together and so is the + and I think it's the same on my receiver. The ESCs I cut the + and usually just connected the signal but will now start connecting signal and ground. I'm using their PDB so it's probably getting the ground from their.

    I'm going to go with new motors because of the reserve power. What would you recommend over the ones you have? Same power range is fine and I will go with 12" props also.

    Then I will need to buy just the arms and motor mounts from HK and you will supply the rest?

  • Very clean! I like the wire labels. What are the dimensions on the copper washers or can you include that and the acrylic separator? Earlier you mentioned selling more of a complete kit minus the 2 quads at HK. Will you still be doing that? I'm waiting for the HK quads to get back in stock and then I will order a few and wait for the rest of the parts from you.

    Is that an APM2 with built-on GPS? No reception problems with it under the aluminum? I'm using the same on a 3DR frame with fiber stackup over it and gets great reception. I was considering getting the APM2.5 for this octo and going with the separate GPS to put it more on top. I've always wondered if it improves reception a lot by mounting on a riser like the DJI does.

    Do you see an advantage to running full servo wires to the APM instead of just the signal wires? I normally just connect the signal wires and then have one +-s interconnecting the APM and Rx. Are you doing it for -+ redundency or to keep the cables better seated?

    I haven't decided yet on the motors ESC. I like the idea of using the 10" props, standard 3DR motors and ESCs because I can interchange repair parts between the two but I'm concerned with the lessoned lifting capacity. My idea is to carry a decent camera mount and a canon 60D and FPV camera and associated gear and also get decent flight times. 15 minutes? Do you think that is going to be asking too much in terms of lifting capacity? If so then I will just get the same ESCs and motors your using. Didn't see where you listed the motor type.

  • DwarfStar Flies!!!


    I took it out for it's maiden flight tonight.  It flew perfectly right out off the start.  Marco suggested some Stab and Rate P gains, I started with those, perfect!

    It flies beautifully!  Absolutely not a hint of any kind of problem with the overlapping props.  If noise is any indication, since it's just got that sweet APC SF hum.  The arms don't move, nothing.

    I'll post up more pictures later on.  I'm tired.

  • OK I'm looking forward to your redesigns and also for HK to get the quads back in stock :) I will probably get the CF if you will have those soon. Any idea yet on prices?

  • Well, I didn't quite get it airborn on the weekend.  I spent too much time actually flying my helicopter, which isn't a bad thing!

    I did get power to the APM and ESC's and tested the motors.  So far so good.  All bolted up, the structure is quite rigid.

    I have plans to redesign the avionics decks already.  In my zest to reduce weight, I cut too much material out, and now I don't have enough surface to mount things on.  The upper two levels can be actually quite a big bigger in diameter than they are without fouling the cover.  So I'll do that too. 

    The bottom decks, I don't really have any changes in mind, except possibly different hole mounting patterns for the landing gear a camera gimbal.

  • Interesting, HK just came out with a H.A.L. Hexacopter.

    I like the designs on the HAL, but the only thing "heavy" about them is the weight! LOL

    The design of the hex is interesting in that apparently they've never heard of FEA.  The top plate design is a total fail.  Why did they scallop it out like that?!  Removed like 80% of the strength.  I like the landing gear however.  I'll be waiting for those to hit the parts section.

    I wonder if they're going to do an Octo, and if they will ever release the 3-axis camera mount that they hinted at in the H.A.L. quad kit months ago.

  • Robert, which is the ext. diameter of the arms of your octo?  I think I have a good idea how to fix them to the plates and have a more rigid structure.

  • how come you don't use plywood for your plates?

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