robotics Uncategorized: cardboard howto paper quadcopter robotics
Keeping with our recent all-multirotor all-the-time theme, it’s time for another how-to post! Plans are afoot, and scheming has been schemed. The flying robot skeletons have been piling up in a corner of the workshop, and after several revisions we’ve narrowed down the design to something worth sharing.
Maybe you want to build your own? Maybe you want to take this design and mod it for agility, weight, or style. Awesome. First, here’s the base pattern:
(updated on 04/15/2012)
First off, you’ll need some tools:
- CNC laser cutter. In theory, you could cut these parts out with an x-acto knife, which is madness. You’ll want to borrow a laser cutter. Honestly, you should just buy one. They’re the absolute best thing in the world, and the prices are dropping very fast. Check out Hurricane Laser, for example. Or TechShop.
- Scissors, for cutting tape.
- Soldering iron, and solder.
- A can of Super77 spray glue.
- 60degree hole chamfer. Handheld is fine.
You’ll need the following build materials. For my examples, I use cardboard sheeting from ULINE.
- Several sheets of 4mm cardboard. The thickness matters, if you change the thickness, make sure you update the tab cutouts to match. They’re 3x the thickness, or 12mm.
- Brown paper packing tape for sealing the edges. The clear stuff doesn’t stick very well. You can also use fiber reinforced tape.
- 4×4″x1/8″ black ABS plastic sheet. You can also use heavy card stock, sheet metal, acrylic, or aluminum bar stock.
- No. 127 Black ESD or similar. 7”x1/8″
- One 14oz ZipLock plastic container, or other lightweight 5″ diameter bowl.
- Double sided copper clad PCB board, you’ll need about a 0.5×0.5″ square piece.
- 4 paperclips.
For electronic components, you’ll need the following:
- 4ea 22mm brushless outrunner motors. I’ve used both Cobra 1300kV and DiyDrones 850kV motors.
- 4ea matching prop adapters for your motors and propellers.
- 4ea regular propellers. GWS 8×3, GemFan 10×45, etc. Yes, 4ea. You’ll want extras, lots of extras. You’ll break a lot of props at first.
- 4ea reverse propellers.
- 4ea ESC controllers for your motors, with an on board BEC. I use 20A NextLevel controllers.
- 20mm heatshrink, for the covering the copper clad power board. Electrical tape works too.
- 6mm heatshink for covering connectors and wires.
- 0.1″ spacing jumper wires, female socket. For the battery power sense line.
- Controller board. I use the Quadrino Zoom.
- Cable assembly for Quadrino Zoom.
- Spread spectrum 2.4ghz transmitter and receiver. 6 channel or better. Spektrum DX6i, etc. There are 4 control channels, and 2 mode channels. You’ll need another two channels if you want to add head tracking later.
- 2-4ea, 2000-1300mAh 3S LiPo battery. Trust me, you’ll want more than one. Your motors must match the battery voltage. I use Turnigy batteries.
- Lipo battery charger.
- Battery connector plug and wires. I use XT60 plugs.
- Sparkfun Blutooth module, if you want wireless telemetry. Totally optional.
- Nylon mesh wire sleeve. I use this to protect the motor leads from prop strikes. Also optional.
It’s a lot of parts and pieces, it’s true. Depending on where you source things from, and how fast your shipping times are, it can take up to a month for all the parts and pieces to arrive. HobbyKing has notoriously long wait times, for example. If you care about customer service and speed, order domestic. I recommend Innov8tive Designs.
Got all your parts and pieces? Great! Let’s get started…
(**Hey, what’s with those holes in the picture? How come they’re not in the plans? Turns out the tend to cause frame failure for really hard landings, so I took ’em out. Amazingly, it still flew after one of the arms bent…)
robotics: cardboard guestblog robotics tricopter
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This tricopter frame design is decently ridged, it’s not extremely crash resistant, but it does fine with a few hard landings. This is the first flying revision, so there is plenty of room for design improvements. Improve and share! Available under a creative commons ShareAlike-NonComm-Attrib license.
Source files here: 24cmTrV2.zip
You’ll also need a few build materials:
- Lasers, or a lot of time and a sharp knife.
- Glue: less is more!
- Itoya- O’Glue, school glue, etc.. some kind of water based glue
- Hot melt glue – hot glue gun
- CA glue – super glue
- 3.2mm rod, carbon fiber, fiberglass, wood, or a glue-able plastic
Arms are each made from 4 laminations of 3mm cardboard. To better resist bending, cut the outer two arm laminations parallel to the corrugation, and the inner two perpendicular.
Cut 5 base plates and 1 top plate. Three of the base plates will go on the bottom part of the frame, and the other two will combine with the top plate to make the upper part. For maximum durability, rotate each plate lamination 120 degrees so that the corrugations criss-cross when you glue them. You may need to adjust the motor mounts and servo profile in the tail arm to match your parts.
Total cut list:
- 4 arms parallel to corrugation
- 4 arms perpendicular to corrugations
- 2 tail arms parallel to corrugation
- 2 tail arms perpendicular to corrugations
- 5 base plates
- 1 top plate
- 1 set servo retainers – 1.4mm cardstock
- 2 motor mounts – 1.4mm cardstock
- 1 tail assembly top and bottom – 1.4mm cardstock
For the laminations use a moderate amount of water based glue – Itoya-O’Glue is nice. You could use spray adhesive too, but it’s $18/can.
Get two sheets of something really flat, i.e. some scrap acrylic sheet you have laying around. Sandwich your newly glued arms and plates between two of these flat sheets and put a good number of books and heavy things on top (~15kg). This will press the glue into any voids and keep your structural members straight as they dry. If you used the water-based glue, leave the arms to dry for about 24hrs, no peeking!
Now that you’ve waited 24hrs for your parts to dry, retrieve them! As long as you were somewhat careful when you aligned the laminations, you should be able dry assemble your tricopter frame plates and arms. I start gluing the base plate and arms together with about 3mm gap between them- I squirt some hot glue into that gap and press the parts together. Work fast, hot glue works a lot better when it is hot!
Adjust the mounts to fit your motors. Mount your motors to the motor mounts, glue the mounts to the arms with hot melt glue.
Tail yaw assembly, the hard part:
Cut the rod to about 4.5cm or so and slide on your hinge parts, rotating them 180 degrees from each other. The hinge elements should rotate relatively easily but not be loose, or really stiff. Line up the rod flush with the first top tail plate hinge element. Line up your hinge elements with the tail hinge plate top and bottom. Make sure all the hinge elements are straight. Use CA to carefully glue hinge elements to the top and bottom, don’t get glue on the rod! Double check that everything is lined up and let the glue fully set. Now that the glue is set, double check that the rod is aligned with the first top plate hinge element. Carefully glue *only* the top hinge elements to the rod. Trim your servo horn so that its splined hub can fit on the front top hinge element co-axial with the rod, it might help if you sand away any surface features from the servo horn. Double check your alignment and glue the servo horn to the front plate. Allow the glue to set.
Make sure that the servo is centered by connecting it to a powered neutral RX channel.
Carefully partially test fit the hinge on the servo, don’t push it on all the way, I doubt it would survive removal from a snug shaft. Make sure that your hinge is co-axial with the servo splined shaft. You might need to add a shim to the bottom of the hinge or trim the arm a bit to make sure the hinge and servo are co-axial. Carefully fit the hinge hub onto the shaft. I use hot melt glue to glue hinge bottom to the tail arm.
Attach your electronics and go flying!
Some tricopter fundamentals by David Windestål – http://www.rcexplorer.se
|Thing||weight(g)||quan||total weight(g)||sub price||price||Notes||Links|
|Orange 6 chan RX||9.9||1||9.9||5.99||5.99||de-case, and use heat shrink to save weight||HobbyKing|
|servo Plastic||9.9||0||0||plastic might work.|
|kk-board||14.6||1||14.6||14.99||14.99||You will also need a programmer to reflash this with the tricopter firmware. Most any iscp 6 pin will do.||HobbyKing|
|esc||9.8||3||29.4||9.47||28.41||Maybe buy an extra||HobbyKing|
|motor + hardware||20||3||60||10||30||Get at least one extra||HobbyKing|
|5030Prop (ccw)||1.5||6||9||1||6||Get a few extra, especially if you don't have experence flying dynamically unstable rotor craft, ie, collective pitch helicopters||HobbyKing|
|tur 1300||123.2||1||123.2||10||10||Order from domestic HK warehouse, need at least 25C rate, 1000mAh – 1600mAh||HobbyKing|
|Actual4plyFrame||60||1||60||1||1||standard corrugated cardboard, nominal thickness 3mm, density 166.7 kg/m^3 (50mg/cm^2 – one 3mm sheet)|
|Frame assembly structural glue||5||1||5||0||Low-mid temp hot melt glue|
|Composit layer glue||0||Itoya- O'Glue, might switch to contact adhesive, $18|
|CA – Glue||0||Servo retainer/ tail tilt hinge assembly glue|
|HK EMS shipping||1||30||30|
|Total est Weight||332.8||Total Price($)||135.06|
My friend Joachim P., taking some inspiration from the cardboard quad, decided to build a paper tri-copter. Using a pretty ingenious tail tilt mount, his Tri-copter comes in at 357g fully loaded. It also costs around 130$ (sans transmitter.)
Of course, he’s using a gyro only board (the KKmicrocopter controller), so one could probably get a lot more stability with 6DOF or 9DOF board, but I’m impressed none the less.
UPDATE: Build plans are are in the next post. Thank’s Joachim!
robotics Uncategorized: cardboard paper robotics
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I finished another frame this afternoon. Now that I’ve made a few of these, the turn around time is getting shorter.
This time with rubber-band shock landing gear, and card-stock motor mounts. They work better than the old aluminum ones from the previous frame. A friend with a bit more flying experience than I came over to help me grab this video.
The paper shocks aren’t holding up very well, but I think I can fix that.
Cardboard. It’s awesome.
Update: We took it outside and got some test video, this little guy really performs!
robotics Uncategorized: cardboard paper robotics
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It took a few round, and I went down a few dead ends, but today I finally managed to make a flying paper robot. Originally, I started out with a flying sphere design copied wholesale from the JDM Flying Sphere. Eventually I figured out that I didn’t know the first damn thing about making a flying robot and that it would probably make a bit of sense to try and build one that had been successfully flown by more than one other person working for the Japanese military.
So, I decided to build a quadcopter. A few people have built those, and it looked like a simpler problem.
The hardest part about getting started with quadcopters is choosing which of the half-dozen or so control platforms best describes you as a quadcopter enthusiast. I settled on the ArduPilot Mega v2. Then I settled on the MultiWii based Quadrino. Both are perfectly capable of loitering around like a lazy robot, but the Quadrino has a certain simplicity and easy-of-use that I found attractive, so I’ve been using that one the most.
As I had a few 750W motors lying around from the flying sphere experiments I decided to build my first quad out of those. This created a few unexpected problems, and a few very dangerous close calls. With 3kW of motor connected to the frame it was very much a robot, in the kill all humans sense of the word. While I did manage to make it hover, I eventually learned my lesson and decided to go with something a little more petite.
It seems that the point of all these paper robot exercises has been to try and find interesting design patterns that one can use to build cheap, reproducible robots with. With that in mind, the hard part about building a paper quadcopter frame was going to be getting it rigid enough to fly with some semblance of control.
I started with folded up triangle beams, as I had been using these to make legs for the walking robots earlier. Unfortunately, they proved to be difficult to anchor in a cross configuration. I could get one beam rigid, but the other would be split in two. The frame was floppy, and had a very wide profile against the prop downwash, and was a fantastic failure.
After that, I abandon triangles. I decided to try and build laminated cardboard beams in the hopes that they would be rigid enough to make a frame. For some reason I was still hung up on folding, and went with a triangular folded stiffener. It too was a dismal failure. Eventually it became clear, that I was going to have to find some way to make the arms cross each other at the center, and to find some other way of attaching the stiffeners.
In retrospect I probably should have started with slotted construction from the beginning, but sometimes you just have to do things the wrong way first. Maybe it makes for a better story. Maybe it makes figuring out the right way that much more enjoyable once you pull your head out of the… bushes.
Hot off the laser, I slotted the new frame together. Already it was considerably stiffer than any of my previous attempts. By gluing the layers together, I could make the frame stiffer still. The final piece in the puzzle was when I remembered a bit about applying polyurethane to paper my friend Pete told me about when I first showed him my walking robots. After applying kraft tape to strengthen the edges of the cardboard, I sprayed the frame down 3-4 times with an oil based polyurethane wood finish. At 52 grams, the final frame was incredibly light, water proof, and very, very rigid. Surprisingly so!
Impatient for my HobbyKing order to arrive, I purchased a set of 2213/34 Cobra motors from Innov8tive Designs, (highly recommended. Thanks again for the advice!), and set about integrating the electronics. This involved finding a way to attach 4 motor controllers, a radio, battery, and the control board onto the paper frame. It needed to be done in a way that wouldn’t compromise frame integrity, be easily serviceable, and survive multiple crash landings from operator and software error.
By notching the stiffener plates I found a novel way to use large black rubber bands to secure various elements to the frame. They have proven to be very versatile in holding ESCs, cables, and even heavy 4S battery packs to the underside of the frame. The 1.75 cup ZipLock plastic container that acts as the crash dome is even secured with rubber bands.
Without the battery, this little guy weighs 600 grams and pushes approximately 2400. With the hulking 4S lipo pack installed it comes in just under 900 grams and takes off at about 1/3 throttle. As the motors are small enough, I can fly indoors. The motor mounts where the only part where I resorted to using sheet metal, but I’m fairly confident they can be replaced with a heavy card stock. I can probably knock another 50-100 grams off the frame by replacing the cable harness as well.
…but that’s for another day. Now, I must go outside and fly.
If you’d like to make your own, here are the flat patterns. FlyingPaper.pdf
robotics Uncategorized: cardboard paper robotics
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I’ll be giving a short talk on my paper robots tonight at dorkbotsf. Here are a few of the flat patterns should you wish to try and make some paper hexapods of your own. Have fun!