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'm still flying mine and the only issues I have are how the booms are held to the center piece. You should replace the screw that holds the boom to the center piece with a ss screw like Rob supplied. I ordered some extras from the same place he got his. If you try to torque down on the ones that come from HK, they will break. I also have used epoxy on a few of them because they just wouldn't stay put. Before flying I always grab each motor and try to twist it with a little force just to make sure it's not loose. The motor mounts also can't take any sort of light crash like the props getting bumped on the ground in case of a rough landing. They bend too easily. They will bend before a prop usually will break.

    • Steve, glad you and others are still liking it.  I just ready your post about the gap between the motor mounts and the top plate.  I think that the Talon quads are built the same way, no?  In any case, even if the motor mount was touching the top plate, it would really only be rubbing it, it would not give much support at all.  You'd actually end up wearing both plates.

      That's largely the reason I abandoned the design.  The Talon motor mounts and boom mounts are just not very good.

      FYI, I have one set of aluminum plates left for $50 if anybody wants them.

      If you guys like this design, I really should market my H8.  It's SOO much better.  

      • Hi Rob,

        Anyway you can throw up some info on your H8 before I order any more stuff?


      • Thanks for reminding me about that. The solution I can up with was just just cut down the aluminum spacers on the boom mounts (you said motor mount but i think you meant boom mount) and that really makes it clamp down better. They are just about 1-2mm too long. I just took a dremel to it.

        The other problem is the side screw being too weak from the Talon kit. That was easily solved by using the ss screws you use in the kit. On a couple I had to use some epoxy for extra assurance. Really the problem is the metal is too soft for both the motor and boom mounts but if you never had more than a hard landing then it's ok. I've rolled mine a couple of times because I have very little flat landing space and forgot to plug in all 4 batteries sometimes in the beginning. It actually takes off with 1 3300x4S but you pretty much kill the life span of that battery in the process and have maybe a 4 minute flight ;-)

        For a long time I haven't had any crashes but I'm not flying it as much as my others because I'm having trouble with the gimbal not wobbling back and forth and that was the main reason I built it.

        Would love to see your H8. Start a thread if you haven't already! I'm sure it's a much improved design over this one.

  • Anything new on this Octo. I'm actually getting around to ordering parts to complete the project. I have all the cf parts that I ordered from Rob a year ago :(. Are there any changes I should make from the original design in the way of motors, esc's, props, motor mounts, booms, boom lengths, etc. Any guidance would be appreciated.

  •    I really like what you have done.

    Good job

  • Maiden flight is done!  Wahoo!
    ...some issues with compass wandering, but I'm sure I'll sort that out.

    Very pleased.  Thanks for so many of your help getting this far :)

  • Has anyone found a better alternative to the H.A.L. motor mounts? They are good for one soft hit and even if they are just slightly bent, they have to be replaced because they can crack in flight. Don't ask me how I know :) I think something that didn't extend out from the boom would be more resilient to soft crashes. Just can't find anything in 14mm.

  • Hi Rob,

    Been having a great time with this. Been doing a lot of filming with my nex5 using a pixim camera for fpv. Later I will put in a little circuit so I can switch between the two cameras. Because of the weight, it really feels solid doing fpv. With the changes in v3 the alt hold makes you feel like you are just stuck in the air.

    Yesterday I had a crash or more of a hard landing because of low battery but had my first 2 broken arms. You can see they are not very good CF but they broke in a way that makes them reusable. I had some new spares so didn't need to reuse but it only broke cleanly off at the boom mount so just broke off a perfect 1/2". What I noticed when I changed them is that the standoffs are too long causing the upper CF plate to not make contact with the boom mount. I've been noticing how the arms have a up/down flex when I lift off and land. . It doesn't seem to effect the stability in the air but I would like to get rid of it. I think it must confuse the stabilizer somewhat. I don't know how I didn't notice it before but when I changed out these two arms I noticed there is a more than 1mm gap between the top of the boom mount (the narrow part) and the upper CF plate. I can just shave down the standoffs. It should really make it a lot stiffer in the up/down flex.

  • I think Rob had a crash and didn't rebuild yet but I can say mine is more than a rocket and super steady for filming. I think the power is going to come in handy for lifting heavier cameras. I don't plan to use it for speed. I will start with a sony nex5. I'm not flying with the weight of the camera or gimbal yet so it feels more than overpowered. I've never even tried to push throttle to 100%. I think in a second I wouldn't see it again! I'm in a + config and with 320mm arms. Rob dwarfed his to 160mm if I'm not mistaken. With no so new 4||3300mAh 4S batteries I get 13 minutes. Probably will get down to around 10 with the camera added. I can send you my tuning parameters if you need.

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