KlappQuad

I recently built a foldable Quadrocopter for FPV, the KlappQuad.

It’s basic form is inspired by the FQuad from Warthox. I own one of these and like it a lot, but I always wanted a foldable version. Also, in order to use a brushless gimbal for the camera, the frame needed some other modifications.

The KlappQuad has a 3 piece body. The lower two plates form the rigid body, holding the foldable arms and the landing skid in place. Also the RC receiver, the flight controller and the AV sender are mounted on this rigid section of the copter.

On top of this section, hold by four soft rubber spacers, a third plate is mounted, holding the gimbal assembly (including it’s electronics PCB) and the LiPo battery (to provide inertia). Since they need to have clear view to the sky, the GPS antenna from the flight controller and the OSD (also containing a GPS antenna) are mounted on the top plate. The rubber spacers (in conjunction with the high mass of the LiPo battery) provide decent vibration decoupling of the camera from the rest of the copter.

 

I use a Naza Light as flightcontroller and it’s GPS antenna is supposed to be mounted on a small spike in order to get best reception. To minimize the folded size of the KlappQuad, I mounted the GPS antenna on a foldable retainer:

 

I machined this retainer out of brass stock on my lathe. The three pieced part took about 2hrs to produce (I’m somewhat out of practice and was happy to have something to machine after a while).

Folding the KlappQuad is a little bit more sophisticated than simply folding all four arms backwards:

In order to minimize the folded length, the two arms on the back are not only rotated to the back but also retractable. The arms are not hold in place by a single bold (like the front arms) but by two bolt heads, running in grooves on the under side of the arms. Milling these grooves was a nice and easy job for my Pleasant Mill…

One bolt head is guiding the shift and rotation of the arm with the long groove visible in the image above. The second bolt holds the arm in is “flight” end position. The groove for the second bolt is open at the end of the arm and visible in the following picture of the folded copter.

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The above picture also shows the position of the front ESCs. The both ESCs for the back motors are concealed between the two lower plates in the back of the copter.

Since all arms slide partly between the two lower two plates when folded, using cable binders to mount the cables from the ESCs to the motors on the arms wasn’t an option. Instead, I drilled small holes into the arms (1mm diameter) and used 0.8mm silver wire to fix the cables to the side of the arms.

Here are some pictures of different stages of folding/unfolding the copter:









 

The folded copter measures LxBxH 47 x 14 x 14 cm with props and 36 x 14 x 14 cm without props. So it fits easily into a small suitcase (including RC transmitter, and some clothes).

The total weight (ready to fly, including Gimbal, GoPro Hero 1 and a 2400mAh LiPo battery) is 1150 gramms.

Last but not least:

It flights great so far. Here’s a video I shot entirely with the KlappQuad. I wanted to know if it would be possible to use this copter to shoot an “action scene”. A friend of mine an his son were so kind to help me out as actors :)

Two tricks

IMG_0399.jpegIn this post I’d like to show you two little tricks concerning 3d printing. I didn’t invent the first one (it’s rather a well known procedure to stick foil to smooth surfaces without bubbles), but as far as I can tell, the second trick is something new.

 

1. No bubbles, no troubles

When printing with a heated build platform, it turns out, that Kapton tape is a great surface for ABS printing. The only problem is, that normal Kapton tape is rather fragile and easily get ripped off the build platform when removing printed parts. Therefor I use 10x10cm sheets of glass with a layer of Kapton tape on top as exchangeable build surfaces on my heated platform.

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One problem is to get the Kapton tape on the glass, well aligned and without bubbles.

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The trick is to use soap, water and a scraper. Here’s a short how-to video, I made:

2. Snap-in, not snap-off

I recently designed a printable Tricopter:IMG_2055.JPG

One special thing of this design is, that the Tricopter is foldable for easy transport:

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For this, the printed center piece (below the plywood platform) has two snap-in hinges for the front arms:

I’m sure, there are several other applications for this technique.

Speaking of technique, slightly off topic, but maybe also interesting:
A “mechanical disadvantage” of Tricopters versus Quadrocopters is, that in order to countervail the unbalanced torque of the three propellers, one of the motors needs a tilt mechanism (Quadrocopters use two CW propellers and two CCW propellers to self balance the propeller’s torque).
This tilt mechanism is usually one of the more complicated parts to build on a Tricopter. Here’s the tilt mechanism I designed for my printed Tricopter:
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Flying high

IMG_1168.jpgBesides 3D printing, I have recently started a new hobby: flying a RC Quadrocopter. To be more precise, flying a Quadrocopter with “FPV” (if you’re interested in what lured me into this, watch this video on YouTube…)

Anyway, since I’m relatively new to flying radio controlled stuff, I still crash the thing more than I fly it. Recently things really went out of control and I crash landed my Quadrocopter in a forrest, 450m away from its start position.
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About 4 hours search time later (on the next day), my brother in law (who was part of  the little search party) found the crashed thing. Of course, since the (LiPo) batteries were (still) connected for about 24 hours, they were fully discharged (and thus damaged). Also the Quadrocopter’s props and frame were damaged. But on the bright side, we were able to recover all motors and the (rather expensive) electronics, including the FPV related stuff (AV transmitter, camera).

Although it might be possible to repair the broken original frame, I decided to rebuild the Quadrocopter from scratch. And of course, I printed all custom plastic parts on my MakerBot :)

There aren’t many parts needed for a Quadrocopter’s frame: It’s more or less just four arms with the motors attached to one end and a center plate on the other end, forming the typical X shape.

The center plate is also where most of the electronics are mounted: the Quadrocopter’s gyroscope controller (which stabilizes the whole thing when airborne), the battery pack and, of course, the RC receiver. The four ESCs (Electronic Speed Controllers), driving the brushless motors, are mounted directly on the arms (i.e. nearby the motors).

In my case, due to flying the whole thing with FPV, there is need for some additional electronic components: an AV transmitter, a camera and the OSD (On Screen Display), consisting of three  separate PCBs. The OSD isn’t mandatory for FPV, but it’s quite handy to see the battery’s remaining capacity, the Quadcopter’s GPS position and height and such, overlaid in the transmitted video.

So here’s the design I came up with:

For the arms, I use 10x10mm wood profiles. It’s cheap, it’s light weight and it’s tough!

The four arms (each 25cm long) fit into the holes on the center plate. They are hold in place by  M3x25mm bolts, for which I drilled a 3mm hole through each arm after inserting them into the center plate. The exact positions of the holes are already printed into one side of the center plate.

The motors are bolt to small platforms which are attached to the outer end of the four arms:

I used M3x20mm nylon bolts (not printed…) to secure the motor platforms.

The separate holders for the additional electronics (AV transmitter and OSD main PCB) are attached to their respective mounting places on the side and the back of the center plate. The RC receiver and the Gyroscope/Main controller are mounted on top of the platform with double-sided adhesive tape (the Gyro with additional rubber foam padding to reduce vibrations):

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The FPV camera is mounted on the front of the center plate. Above it (on the left side in the following picture), the OSD’s GPS receiver is mounted on the top of the center plate (double-sided adhesive tape):

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As mentioned before, the ESCs (which control the brushless motors) are mounted directly on the arms. So is the RC receivers additional antenna unit:

On the bottom side, you can see a x-shaped structure. This holds the third (and final) PCB of the OSD, containing the current measurement unit which allows the OSD to measure and display up to 50A current. The x-shaped holder and the velcro tape for later holding the battery pack are bolt down to the center plate with help of the four M3x25 bolts (see above).

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Well, that’s about it, so far:

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The feet in the above picture are currently simply four pieces of 6mm aluminum pipe. I plan to replace these by 6mm carbon rod, with nice, printed landing plates:

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Unfortunately, these aren’t ready, yet. I’d like to build these with some kind of suspension in order to soften rough landings. But I’m still in process to design a simple, light weight and effective way to build this…

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That leaves me with a last important question:

Will it blend fly?

The whole Quadrocopter, including the full FPV equipement, battery pack and preliminary feet weights only about 650 gramms, which is well under the theoretical maximum flying weight (including payload) of the original Gaui 330XS hardware.

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Unfortunately, it’s raining outside, so I couldn’t test it in the wild. But I couldn’t resist to do a short hovering test in my living room. You must know, that my living room is rather small and stuffed with furniture, so it’s kind of hard to do test flights there, especially for a not-so-experienced pilot as myself.

But see for yourself:

Well, this looks promising!

So far I’m quite happy with the results of 3D printing structural parts for a Quadrocopter. The parts are quite sturdy, yet light weight. And if  I’ll brake any part of the Quadrocopter in the future, the replacement is always just a quick print away!

Of course, I’ve published the designs of the printed parts on Thingiverse: http://www.thingiverse.com/thing:4812