I've been working on an accessory-cage based quadcopter design to have a modular way of adding and removing components. The intent is to avoid the rubber-band and tape method of attaching components to the airframe. The accessory cage is comprised of four vertically-oriented carbon tubes and is meant to hold everything but the motors. There's a 3D-printed stage for each component; the flight controller, battery, ESCs, etc. each sit in their own carriers that slip on and off and can be repositioned as one sees fit. I have a basic "starting point" CAD model for an accessory stage, and I modify it as needed for whatever component I want to add.

The design needs some refinement: I'm going to implement a better thermal break between the motors and the [low-melting temperature] PLA airframe. It also has underside LED lighting (not visible in the pictures) that I would like to make removable for wiring access in the next version. I designed and printed prop guards but haven't installed them because I don't want to mess with the aesthetic and add too much weight, so instead I have minimalist stainless spring-wire prop guards in mind for v2.

Once I'm really happy with it my hope is to upload the files to the Thingiverse for those with a 3D printer, if anyone is interested. I'll also include the "starting point" file for the accessory stages, as well as the Inventor part files (2009) for anyone with access to that program.

You'll note in the pics that the flight controller is simply supported in its stage, so I should also work out an isolation web for it (maybe something like a shock mount for those old-timey microphones).

Views: 3170


Developer
Comment by RoboCopter on August 20, 2013 at 9:44pm

Very cool Justine! Keep up the great work! What kind of flight times are you getting?

Comment by mP1 on August 20, 2013 at 10:44pm

Why is the battery hung so low ?

Comment by Erman Ozen on August 20, 2013 at 11:22pm
Battery is probably low for better stability but may be too low and could result in impact on a hard landing.
Comment by Jim James on August 20, 2013 at 11:31pm

Way Awesome killer job


Developer
Comment by John Arne Birkeland on August 21, 2013 at 2:32am

Making a multicopter bottom heavy does not make it more stable. A multicopter is inherently unstable and fully relies on active stabilization to fly. Meaning that you want the CoG to be neutral to make it easier for the autopilot stabilization to make quick adjustments, resulting in a more stable copter.

Comment by Crashpilot1000 on August 21, 2013 at 3:25am

Putting the FC up is a real plus of that construction! Besides keeping mag disturbances low, it also helps the baro in ground effect, especially on small copters.

Cheers Kraut Rob

Comment by R. D. Starwalt on August 21, 2013 at 4:05am

The battery location looks like a effort to provide balance in the vertical axis, origin being the thrust line on the motor arms...I guess.

+1 with JAB, it does not really help as the controller should be able to handle all the details.

-=Doug

Comment by R. D. Starwalt on August 21, 2013 at 4:23am

A+ Justine. All our 3D printer fans will probably cause a spike on the server where you keep the files.

I enjoy and applaud the time you put into the project.

Build on!

-=Doug

Comment by Gsouth on August 21, 2013 at 4:57am

I'm new to this hobby and am in the middle of the rubber band and tape build methods. Your modular concept is wonderful. The need for it has lingered in the back of my mind as I try to stick stuff onto the frame but I never thought of the next step of solving the problem as you have.

It seems to me that accessibility to any components that need to be read or adjusted is important also. Trying to read the flashing led's on the APM hidden in a smoke brownish case is difficult. The two lights on the bottom of the GPS are also hard to see. Maybe I'm overemphasizing this aspect because as technology such as Andropilot are developed the need for indicators on the copter is less.

The aesthetics of the design increase its appeal.

Comment by Justine Haupt on August 21, 2013 at 5:52am

Wow I'm glad people like it.

Flight times: Rather terrible right now. I haven't flown continuously for long enough to time it accurately but I'm pretty sure it's in the 4-5 minute range with a 2.2Ah battery. I wonder just how far away it is from the best-efficiency scenario with the 8x5.4 props on it now, so I have 9x4.5, 9x4.7, and 10x4.5 on order, as well as a 3Ah battery. Will do a lot of experimenting because I don't feel like reading a textbooks worth of aerodynamcs to figure out what the best prop should be, and ecalc doesn't have the no-name motors I used. Input would be welcome but I understand this is a known challenge with long flight times.

Re battery position:

It's not where it is for CG reasons. I wanted to keep the top half of the cage available for a camera, sonar, and maybe eventually LIDAR (although I could just use longer graphite tubes of course). Having it where it is gives my hands comfortable access to the connector on the APM power module. Originally I had clips built into the landing skids that held the battery as high as possible while still being underneath, but I realized even that should be modular. It may wind up sliding back up as I add downward-looking sensing capabilities. Being inside/between the landing skids, it have found it to be fairly well protected, though. It's crashed a few times now (nothing too terrible yet) but the batter doesn't come into contact with anything.

A bigger problem I found is with the telemetry antenna. Two times now I landed with enough ground speed for it to roll over and the SMA edge-mount connector broke off. I fixed it once, and the broke it again the next day. What I did last night was add a small length of coax cable between the board and the SMA connector, and the connector is attached to a separate plastic module by means of shrink tubing, so there's a nice flexible joint there now. I'll photograph that when I get a chance.

I forgot in my previous post -- in my excitement of getting it flying this past weekend I made a youtube video (just a slide show with a poor quality video at the end): http://www.youtube.com/watch?v=rXtjjwk0ZKQ

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