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Laser Cut MultiWii based quadcopter

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Picture of Laser Cut MultiWii based quadcopter
This is the second version of a small quad copter that I designed and built. It is designed so that the only power tool required to build it is a laser cutter.

You can get multicopter frames for cheap from a number of sources, but I wanted something that was more customizable and hackable. The cost to build the actual frame by itself for this quad (including glue, etc) is only about $50. The rest of the costs are probably similar to what it would cost to build a quadcopter using a commercially available frame kit. I also believe it to be more sturdy and easier/cheaper to repair than a lot of quad frames on the market. While learning to fly with version 1 of this quad, I crashed it repeatedly, several times into a tree. After several hard crashes I did break one of the motor mounts, but a little bit of wood glue and some clamps and it worked as good as new.

While I think this makes a fine first quadcopter for people (it was essentially my first), having some knowledge of building and flying RC  vehicles will help. I've tried to be thorough in both documenting the build as well as providing sources for the materials and parts.

Let me know if you have any questions, problems or suggestions.

 
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mrpi641 month ago

Looks awesome; may just try it!

Very very good! This was VERY informational and will help me tremendously with my quad! One thing, you use 10A ESCs and the motor's max amp draw @3s is 9.5 which is cutting it very close to 10A. I recommend you use a slightly higher ESC like a 12A. Or is there some other reason you used 10?

dylanfm (author)  Enjoying Electronics2 months ago
That is good point about the current draw of the motors. What happened is this was the 2nd version of the quad and in the first version I started with the same motors and smaller props with a 2s battery before moving up to the 8" props and the 3s battery. Since it always worked on rev 1 I didn't think to upgrade the ESC on this rev 2 quad I documented here. I still haven't had any problems or burnt up any of the ESCs on either rev of this design, probably because the max current of the motors at 3s is 9.5A IF you are using a 9x5 prop which I am not. My guess is that i'm drawing ~8A max with the 8x4.5 props and even that is probably for short periods of time only. Still a little close to the max ratings for my tastes, but like I said I haven't had any failures.

For the Octocopter I am building now (which uses different motors) I have ordered some of the Afro 12A ESCs (http://www.hobbyking.com/hobbyking/store/__42546__Afro_ESC_12Amp_Multi_rotor_Motor_Speed_Controller_SimonK_Firmware_.html) mostly for the extra features, not for the higher current capabilities. Physically they are little bigger than the 10A ESCs I used in this quad, but they could probably be zip-tied into place.

Thanks for the comment and good luck on the quad,
Dylan
dchall89 months ago
I love flying toys. Perhaps that's why I pursued aerospace engineering. And that's why I quickly lose interest in quad copter electronics projects. But I always look at the aerodynamic features as well as weight and payload. Don't get me wrong. It is great that the Arduino and other electronics packages have become affordable so as to enable the electronics oriented folks to get into RC flying. Y'all are pushing the envelope for the rest of us.  I look forward to the day when I can send a HD camera up to 500 feet, direct it through a pattern covering a square mile, and have it automatically come back with an SD card full of images.  Oh and I want the software to make a Google Earth type mosaic out of the images.  A year ago that was a lifetime away.  Now it could be a year or so away. 

Regarding your airframe, have you considered what you could do with corrugated plastic as a frame?  I'm not suggesting corroplast for this project, but it might give you ideas for a different design.  Another idea would be thin foam sheet glued together with either CA or Gorilla glue. 

When I was in college we built an airplane and glued the wing ribs together with Gorilla glue.  It wasn't called that at the time but that urethane adhesive is what has become G-glue.  It would be my first choice for any wood project.  The glued bond is much stronger than the wood itself. 

Regarding your vibration issue: you know that nice stiff wooden frame?  It's transmitting the vibrations from the motors to the camera.  This is a spring/mass/damper problem.  In stiffer systems wood can be used as the damper.  This time it is not so much.  Adding mass is the approach, but you don't want to add mass that isn't doing any damping.  You only need it at strategic points.  You might wrap some rubber bands around the arms at various points.  Or put some blobs of putty on the frame as a damping material/mass.  Try it at different locations and test the results.  Vibration damping without sophisticated equipment is very much a trial and error project.  Or instead of painting it, 3M makes a spray on undercoat for cars.  That stuff works well to dampen vibrations.  You do not necessarily need to coat the entire frame.  Spot spraying often works best especially if you know exactly where to spray (lots of research needed).  Another approach would be to use two pieces of 1/16 inch wood and glue them together with a very thin coat of silicone caulk.  The caulk in between the wood will absorb the vibration.  Try gluing the wood together before cutting.  E-6000 is another glue that might work and stay soft enough to absorb the vibes.  There is another add-on you might try.  It is called Peel & Seal and is used to stop roofing leaks on houses.  It costs about $17 at Lowe's for a lifetime supply.  Cut some small strips and stick them on at your favorite strategic locations.  It is a foil backed viscoelastic material where both the foil and the goo absorb vibrations at different frequencies.  Good luck with your project!
dylanfm (author)  dchall89 months ago
Thanks for all the suggestions. I hadn't really considered too many other materials for the frame, but you make some interesting points. I have drawn up a design for a fiberglass frame as well as a carbon fiber/balsa wood plane/quadcopter hybrid that I may build some day. I have used Gorilla glue for other things and agree that it is good stuff. For this frame it seemed like CA was good enough, but it is possible that extra mass of the Gorilla glue might help with vibration issues.

I have played with a lot of things to try to get rid of the vibration in the camera mount. I have tried isolating the mount from the frame with various densities of foam and rubber. I have bought some sound deadening sheet that is used in cars that sounds similar to the Peel and Seal you described (though was probably way over priced) and tried putting it between the frame and mount as well as just putting large pieces all over the sides of the mount. Nothing helped much.

I think there are a number of problems making it difficult to clean up the vibration. The amount of surface area in contact between the camera mount and the frame is too small. I think I need to spread the contact out over a larger area with a layer of dampening material in between. I think the slop in the gears of the servos makes it more susceptible to vibration. I have got interested in brushless motor gimbals and I'm to going to build one of those, possibly out of ABS plastic using a 3d printer and then try some different mounting options. I'm not sure if I can keep the weight low enough with that kind of gimbal or not. I have balanced my props, but I might try balancing my motors also. I should also try putting some of the sound deadening sheet between the motors and the frame.

I have actually built a larger (30" motor to motor) quadcopter with a similar frame (which I should probably do an instructable on). Because of the increased size, It is made out of thicker wood. I haven't actually tried mounting a camera to it yet, but I think it may have less issues with vibration. It also has a much higher payload capability so I have more weight to play with vibration dampening techniques.
balance the props,that should reduce most of all your vibrations coming through the frame.Plenty of good products available for isolating a camera mount,for taking rock steady video and stills,nice job,thanks for posting
dylanfm (author)  godscountry3 months ago
Thanks for the suggestion. I actually did balance the props and it didn't really help much, I don't know why. I think the biggest problem with vibration, which I didn't realize until fairly recently, is how the props are mounted. I think the o-ring style prop saver mounts coupled with the cheap props mean that you can't always get the props running completely true regardless of how well they are balanced.

I have pretty much set this quadcopter aside and have been working on an octocopter. In addition to using collet style prop mounts, the octocopter is designed for mounting vibration damping rubber mounts to attach the camera gimbal. I have also ordered a small brushless camera gimbal suitable for a go pro size camera and I have designed and built a larger brushless gimbal for a larger DSLR like camera (actually it is meant for my Samsung NX1000). While I haven't got the brushless gimbal I built fully tuned yet, it shows promise that it will work. My main worry is if the octocopter will be able to lift the 2.5lbs of gimbal and camera. On "paper" it should, but I need to finish building it to find out. The octocopter frame is cut out and put together, I just need to finish assembling it. hopefully I will do another instructable on that design later.
dylanfm (author) 3 months ago
I used Alibre to create the .dxf file but then open and re-scale it using a program called ProgeCad 2008 smart. For some reason I haven't been able to get Alibre to save drawings so that they are in millimeters when I open them in the laser cutter software which is why I always re-scale it using another program. I just downloaded the file from the instructable and opened it in both those programs so it is still working for me. What program(s) are you trying to use? --Dylan
wolfejoe3 months ago
What program did you use to create/open the dxf cut file? I can't use it on the programs I have.
Balza9 months ago
thank you for your exhaustive answer.
I'm here when you have updates! :)
Balza10 months ago
Beautiful quadcopter!
One question: what is the maximum flight time and how many kg can pull up?
Thanks!
dylanfm (author)  Balza9 months ago
I don't have firm answers for those questions. Based on timed measurements with previous version of this quad i think the flight time should be 9-14 minutes, but I haven't timed it on this version of the quad. I haven't tested what is the maximum weight it can lift, the most I have tested it with is about 0.34kg. I'm pretty sure it can do 0.5kg pretty easily. Going to 9" props would gain a lot more lifting power, but I think the current might be to much for these speed controllers.
boeing_73710 months ago
Excellent, just excellent!
Jared_Reabow10 months ago
hey mate, check out some of the frames ii have made, i hope it gives you ideas, because your current is very basic.
http://diydrones.com/forum/topics/laser-cut-custom-made-frames
dylanfm (author)  Jared_Reabow10 months ago
Thanks for the link, you have some interesting designs there. Basic, durable, and easy to assemble as what I was going for with design. I have some other designs that are a little bit more eleborate that I might build someday, but in general I will probably always shoot of for easy and functional over cool looking.
hcklex10 months ago
Do you have to have the Multiwii control board to just fly? with no Bluetooth or gps
dylanfm (author)  hcklex10 months ago
Well it doesn't have to be the multiwii control board but you need some sort of flight control board. There are a lot of other flight control boards out there with a wide range of prices. I think at a minimum they all have 3-axis gyros, but a lot of them have more sensors. The MultiWii based board I recommened has 3-axis gyros, 3-axis accelerometers, 3-axis magnetometer (digital compass) and an altimeter. It really makes it much easier to fly having all the extra sensors. The only other one that I have used was similar to this one: http://hobbyking.com/hobbyking/store/__21977__HobbyKing_Multi_Rotor_Control_Board_V3_0_Atmega328_PA_.html and it was much harder to fly with it.

Even if you didn't need the sensors you would still need some sort of mixing board to mix all the signals from the receiver before sending them to the speed controllers. The flight control board is what knows to speed up all 4 motors if you move the throttle up, but only speed up the left motors if you move the roll stick to the left, etc.
geekOmat10 months ago
Very nice build. Specially like the idea of using the laser cut material. Also very detailed and comprehensive instruction! Thanks for all this work.
Green Silver10 months ago
Nice build,thanks for posting
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