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.

Views: 81182

Reply to This

Replies to This Discussion

Hi Barry,

Yeah, I did not rebuild after the crash.  In an ideal world, I would absolutely rebuild it, it was a good design.  But I wanted to try a V-8 Octo as well, so I'm playing with that.  I'd love to have one of each, but with limited time and money, I had to make a choice of what to do.

I do still have 2 aluminum plate sets left.

Ever since I completed this octo I've thought about why I didn't consider the V design. I think it's better any many aspects. More room for avionics. Even with all the space you made, it can get a little cramped. Better orientation if flying LOS. I will not be doing that so much so not a big deal but I would prefer it for the occasion that I do LOS. Other is for camera view. Should be more room. I also think it will fly better in forward and banking flight. If you end up doing one, you can count me in for one.

Something else I'm looking to change. Do you have any experience with this wii-esc? I'm thinking to try it on my quad but if it works out then I would reflash the octo also. I set up the bootloader so I can do it via the servo cable.

http://code.google.com/p/wii-esc/

Yeah, I actually started with an H8 idea, but then got sidetracked to the Octo.  And now I've circled back around to the H8.  The advantages I see are:

  • Camera, batteries and avionics can all be mounted on a tray on top of the "dirty" frame, vibration isolated from the motor frame.
  • With camera mounted between the motors, you have unlimited FOV with never any motors in the frame.
  • No need for landing gear, at all, just belly land.  Less weight, less drag.

It's actually going to be a stupid simple design.  Another big plus is the motor mounts will be custom made, but strong.  Cut from 6061-T6 instead of the HK cast alloy mounts. 

I'm designing it to use these new motors which are almost as powerful as the 35-36 motors, but smaller:

http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=...

I'm also designing it around the use of Hobbywing Quattro 25A ESC's.  The whole thing will be very, very simple.  And the frame will be fairly cheap to produce.

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.

Rob,

Can you go into a little detail about how you had the LED Lighting setup? I am trying to work it out but not making any progress.

Attachments:

Hi Jeremy, sorry I didn't respond to the email.  Got lost in the shuffle.

Exactly what info are you looking for?  If I remember, I can send you some photos of my little power distribution board to give you some ideas.  But it was really pretty simple.  I just used an ULN2803 darlington chip to control the LED's, with the signals coming from the APM.  Pretty straight forward and has been detailed in the old wiki... not sure it's been carried over to the new one.

No worries! Summer schedules are crazy all around.

If I know what the parts are and how they are connected, I can make it work. Would it be better to go with a JDRONES IO board or something similar?

Yep, that would work.  I have one of those boards, but never used it yet.  I've just used ULN2803's directly controlled by APM.

If you could post some photos and/or some details on how it is put together that would be great. I'm ordering the jdrones io board today, just have to wait on the shipping to Oahu. Price to living in paradise...so they say.

 

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.

I imagine this very issue is another of the myriad reasons I need to build myself a 3D printer... unlimited nylon mounts.

Jake, if you can do the sketch, I'll be glad to print some prototypes.

Reply to Discussion

RSS

Groups

Season Two of the Trust Time Trial (T3) Contest 
A list of all T3 contests is here. The current round, the Vertical Horizontal one, is here

© 2019   Created by Chris Anderson.   Powered by

Badges  |  Report an Issue  |  Terms of Service