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).
Comments
@Justine: That design is rainproof: http://www.microdrones.com/index-de.php ...........
> I am working on something with close to the same intention where I can have more things covered and protected.
Neat. Protection would be nice. I'm trying to think of how it might be made rain proof.
>Wondering how heavy is your setup? Curious as to the size looking like around a 350mm?
I don't have an accurate scale but it feels like it weighs the same as a new 1kg spool of PLA :). Does this size refer to the spacing from one motor to one on the opposite side? If so, that's spot on: 350mm.
10 minutes would be nice and I think that's a reasonable goal for now. I can't imagine how people are getting 30, 40, or 50 minutes. That would be amazing. Right, so many combinations. I do wish it were more straightforward.
I really like the DJI Phantom design and you might be able to tell that this one (I call it "dot") is somewhat inspired by it. In hindsight maybe I would have had an easier time figuring everything out if I bought one ready to fly, so I definitely respect that approach.
Print volume -- yes, I just checked again now that I have access to the information and the arms are actually 162mm long and 53 wide at their widest point (I was going from memory previously). The newer version won't have the same mounting tabs around the motors for attaching the prop guards that I never used, so the wides point will be about 40mm on the new ones.
Justine - that looks awesome, I have been working on (an honestly thowing out) a number of 3D printed quadcopter designs. I am working on something with close to the same intention where I can have more things covered and protected. Wondering how heavy is your setup? Curious as to the size looking like around a 350mm? Your props / motor selection dealing with the weight will be fun to figure out to get decent 10 min or so flight time will be fun. In my quest to build my own - I have since bought a DJI Phantom to learn how to fly, put together a F450, now the 3DR frame quadcopter - so I have boards, ESC, Motors -> DJI 950Kv and 3DR 850Kv - various props to mess with - it is amazing just the motor / prop combination impact, even before the batteries. Next up is a tricopter build and I want to get some 1100/1200Kv motors.
I keep brushing off and refining my designs and I will be keeping and eye out on Thingiverse for yours. One question on that, I have the Cubify 3D with 5.5" cube print ability, I am thinking your arms may be too long for me to print with mine. Keep up the good work, one of the coolest printed designs I have seen yet.
Max size: The arms are split into two parts, and they're about 170mm long and 40mm wide at the widest point. I can get two complete arms on the 200x250mm built plate on my Makergear M2.
Brandon, thanks! Right now they detach with two machine screws each (hex nuts are fused into the one side of the arms). I have 3mm bullet connectors for the wires, but the LEDs from all four arms are soldered to just two header connectors. That was just because I happened to have that connector in my stock and I could make a point of making the arm detachment procedure completely solder free. I don't know if I could do it in under a minute though. Maybe five. It's a REALLY good idea and I will look into the Anderson connectors. But really, if anyone else wants to use this design I suppose it will be up to them to connectorize however they want. This makes me think that it would be neat to make the arm itself an electrical socket; Just Plug the whole thing into the fuselage core like a big connector. But that would be a real design effort and a lot of prototyping I'm sure. Maybe in the future, or maybe if someone else would want to tackle it.
Nice design! How detachable are the arms? It would be really nice if there was a quick electrical/mechanical connection for each arm so that they could be quickly swapped. For a lot of people, downtime is a killer, for both fun and for productivity if you're actually using your copter to do something. Having an arm that is easy to swap, like <1min without soldering, crimping, or any of that, would be amazing. I think Anderson electrical connectors are a good option for the electrical connection--they click together and separate easily, so they could be swapped around to change motor direction.
What is the max size of the printed component? (read: how big is my 3d printer need to be to print these?)
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): https://www.youtube.com/watch?v=rXtjjwk0ZKQ
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.
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
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
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