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.

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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.

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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.  

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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.

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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.

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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. ;)

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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.

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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 just got some test pieces back for the avionics plates in 5052.  Looks like it should fit in the dome fine, yet gives much more real estate.  I didn't realize until I started building the prototype just how much room I need.  There's potentially a LOT of junk mounted up there depending on what you're trying to do.  I didn't even have my FPV gear yet!

    So, originally, the 2nd and 3rd levels of avionics were spaced up 1" each.  But I think I'm going to push those as high up as I can.  On the order of 1.5-2".  Try to get it as far away from the power section as I can.  Make sense?

  • Any update on when you will have the CF parts?

  • For the guys who ordered the aluminum parts...

    I got word back from the cutter that they can't offer the same pricing I originally paid for these.  (and actually, this completely invalidates tiggy's commentary)  They actually had a lot of problems producing them.  I think the problem was mostly with the extra thin upper deck.  They had to slow down the cutting speed a lot or else it just blew out with a horrible burr on the bottom.

    So, I have agreed to make the upper set in 1/16" aluminum rather than 0.040".  It's just easier for them.  There will be a minor weight increase on the order of...  well 50% for the upper deck, maybe 20% overall for just the frame plates.  We're talking about a few ounces.

    If this is a problem for you, please let me know.

    Further, I'm not sure yet what the actual price will be.  I decided to have 5 sets done in a batch which helps. I will do my best to hold the line on the 3 sets that were sold, as long as I'm not losing money.  But the "retail price" will have to go up a bit.

  • Rob, I'm following the gimbal thread at regroups. I will get the gimbal from rusty next week but haven't decided on the servos yet. What did you settle on?

    Also have you come up with any good legs for it the has room for the gimbal and is the mounting of the gimbal pretty straight forward or will I need some more parts to mate that?

  • HB, the forum software won't let me respond to you inline, even thought your reply is only the first inline so we have 3-4 more levels to go but... anyway.

    Yeah, you could do that. Another option might be to use the CF top and bottom, as well as a 3rd plate being aluminum, so it's a bit of a sandwich.

    But honestly, just the basic aluminum frame is plenty strong. I saw no vibration problems, no arms moving, and the main plates appear to have survived that horrific crash totally fine. The CF frames are more about weight savings than anything.
  • I would think that just having two kits available is the best way to go. Economy aluminum and then CF to keep it simple for you.

  • Rob, do you think I could receive mine by Dec 9? That is the last possible day I can receive it so it can be forwarded to me. Otherwise it will sit until 2013 which would put a damper on my holiday building plans :)

  • Ok, is there anybody else out there interested?

    I have the first batch of 6 sold, and I have an additional order from Dave C which starts the next batch of 6.  I think if I can get to 3, I might go for it all in one go.

    HB, are you interested in upgrading to CF?

  • Rob you should have received my deposit this morning.
  • Hello. Im a little confused are you saying that coaxial props are less efficient than conventional single props?

     

    regards Eddie

This reply was deleted.

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