The ShenDrones Krieger is an exceptionally compact mini racing quad that packs the full FPV featureset into an X-quad in which each prop almost touches its adjacent props. It is a quad built for one thing: speed. The camera, VTX, flight controller and PDB all reside in a miniscule area where the props do not sweep in the center of the quad and grow upwards, not unlike a tower. The camera mount offers an incredible range of tilt, up to 50 degrees.
Note: This build log was written in November 2015. A lot of stuff has changed in the miniquad scene since then. If you are reading this log – PLEASE do not buy Afro ESCs. Pick up a set of Littlebees, or better yet check out our ESC Buyers Guide for some up to date tips.
I had one goal with my Krieger: I wanted to truly build a monster. It will ultimately be swinging 6-inch tri-props on 4S lipos. Its thrust-to-weight ratio is going to be ridiculous.
To accommodate these monster props, I bought the “DTF 225” variant of the Krieger. This has arms with a cross-section of 225mm, the smallest size you can get while running 6” props.
I really liked the OSD in my ImmersionRC Vortex and intend to continue adding OSDs to all of my future quads. The Krieger has a very small flight stack, so I needed an OSD that would be integrated onto either the FC or the PCB. Enter Power-OSD, which offers a combination PDB, 5V and 12V voltage regulators with filters, and a built-in standalone OSD. The extremely minimal interface is the kicker, only displaying voltage, current and battery consumption, just like I like it. Look out in the future for a separate review on the PowerOSD as well as a quick build log.
Here is the full list of the rest of the components I used in my build:
- Krieger DTF 225 (Amazon)
- AfroESC 30A flashed with BL Heli
- Cobra 2206/2100kV Racing Motor (Amazon)
- Naze32 Rev6 FC (Amazon)
- PowerOSD PDB/OSD (Quadrevo)
- FX799 5.8GHz 200mW VTX (Amazon)
- LemonRX micro 8ch PPM receiver
- Sony PZ0420M CCD FPV camera (Amazon)
I started by soldering together my PowerOSD so that each “arm” had a positive and negative wire running to it. I then mounted the PowerOSD on the Krieger base plate using nylon stand-offs. These stand-offs don’t actually come with the Krieger so if you don’t have any spares, make sure you pick some up. I grabbed a kit from Amazon with a ton of spares for $8, here. Once I had fastened the PDB to the base plate, I cut the wires so that the ESC was laying on each arm in the place I wanted it to be.
When constructing the PDB and associated wiring, you need to be careful that there is nothing hanging “out” of the left and right sides of either the PDB or flight controller. If anything is, you will not be able to fit the tower which protects the stack and holds the camera on the top of the quad. You can see this tower inserted here:
As you can see, if you let the ESC wires “fold over” the edges, they risk contacting carbon fiber, which is conductive. Here is another picture of the final configuration of the Power OSD on the Krieger base plate without the tower installed.
Once I had the Power OSD laid out, I started working on my ESCs. I went with Afro ESCs because I needed 30A ESCs but didn’t really want to drop $30/pc for the KISS ESCs. After finding out that the giant capacitor on the top of the Afro’s hits the top of the main frame of the Krieger, I regret that decision. It’s mostly cosmetic, but it bugs me nonetheless. Since this build, a plethora of great, inexpensive 30A ESCs have come out that do not have these caps, such as the LittleBee 30A. I would recommend using these over the Afro.
The stock AfroESC, which is running SimonK, needs a little work before it is “Krieger-worthy”. I started by removing the stock wrapping. Once I am finished with the ESCs, I will re-wrap them with extra large heat shrink. Next, I removed the positive leads going to the JST/servo connector and the the motor wires. I will be soldering my motor directly to the ESC.
I don’t plan on using the onboard ESCs on these things for anything so I simply removed the positive wire from the servo connector on all of them. This is also necessary when you are flashing them with BL Heli.
I re-glued the protective heat shrink on top of the JST wire pad. This was actually ultimately somewhat of a mistake – I should have shortened these wires at this point. Finally, I removed the power cables for the ESCs so I could solder on the pre-fabricated harness I had already created.
Once the ESCs were prepped, I put the arms on the Krieger so that I could start laying things up. Not pictured is me applying some superglue to the edges of the arms to protect against delaminations after the hundreds of crashes this thing is sure to see.
This is where I discovered there was no way the AfroESCs were going to sit flat on the Krieger due to their massive capacitor:
This isn’t the end of the world, I’ll just add some padding on the outer portion of the arms so the capacitors don’t get popped off in a crash. It’s mostly a cosmetic inconvenience. Again, I would highly recommend going with the Littlebee 30A ESCs or similar inexpensive opto ESCs on the market these days.
Once all of the ESCs were hooked up to the PDB, it was time to take them inside and program them. In the case of these Afro ESCs, I needed to first flash BL Heli before programming. Look for a future article on how to flash Afro ESCs with BL heli. Note that since the Afro ESCs will never support the special bootloader mode that most Silabs ESCs (like the littlebees) have, you cannot program them or adjust them from the Cleanflight app. You will need to make each adjustment individually.
Next I started to fiddle around with the motor placement. Since the arms on the Krieger are so damned small, the ESCs almost hit the motor bell. I’m not willing to totally butcher my cobra motors by cutting off everything but a few mm of motor cable, so I came up with an “interesting” layout solution:
My logic is that most hard crashes are going to occur with the quad going either forwards or backwards. By pointing the motors sideways such that the wires are extruding into the left and right sides of the Kriegers, I believe they will still remain relatively safe and I get to keep from cutting them down to a few mm with some clever routing. As you can see, I made sure to apply some extra-large heat shrink on the inside of the ESC before soldering the motor wires. This heat shrink is particularly thick and will protect and partially insulate the ESC from the carbon fiber arm.
Here, all of the motors and ESCs are installed. At this point, it’s time to take the quad inside again and adjust the motor direction using BL Heli. As you can see, I should have cut down the length of the ESC JST (servo) leads before shrinking the heat shrink.
Now that the power system is installed, I turn my attention to the flight controller and RC receiver.
I’m using a Naze Rev6 board in this build. Keeping in mind that the Krieger will not fit anything to the left or right of the stack, I soldered the data pins inward and the I/O pins outwards. I started by just soldering all of the pins on (minus the 2 extra ESC outputs for hexacopters). I will remove them in the future after I decide what features I want and which I don’t want.
Next I hooked up my ridiculously small lemon RX PPM receiver. I’m very impressed with this little guy. I should have ordered more of them. As you can see, to fit the PPM receiver pins inboard, I needed to bend them slightly to pass around the ESC pins. There is still PLENTY of contact room for the pins.
Here is the stack fully assembled. I am powering the RX directly from the Power OSD (power goes into the Lemon RX’s bind port), which then powers the Naze through the PPM connector. After setting up the Naze and receiver, I shrink wrapped the receiver to prevent it from shorting to the Naze. It is velcroed on top of the Naze.
One thing to note with the Krieger is that it does not come with the nylon hardware you see pictured here. I used all M3 hardware:
4x ~15mm screws
4x 15mm male-female stand-offs
8x M3 nylon nuts.
The PDB is kept isolated from the carbon fiber by nylon nuts underneath it, which also holds the four screws in place.
The final part of the Krieger build is assembling the camera tower. I started by doing a loose assembly to get a feel of how it will go together. Even though my VTX (a FX799) is quite small, it still barely fits inside of the tower. Larger VTX’s will definitely not fit.
The upper metal bar in this picture slides up and down along the tower, depending on where you have the camera. There are several 3D-printable designs online which can latch on to these bars to allow for a HD camera mount.
The 90-degree SMA angle adapter does not come with the Krieger kit, neither does a washer that you must insert onto the SMA adapter to get the VTX to fit flush against the carbon fiber and not flop all over the place.
Since you have to use a washer, it will be really difficult to get the press fit that you normally get with SMA adapters. This means you’ll need to zip tie the antenna in a vertical alignment. This is called out in the Krieger build manual. I wish they could have figured out a way to make the carbon fiber slightly thicker or added a bushing to the kit to get the exact spacing needed, but I guess I’ll have to live with it.
I decided to mount my flight camera to the tower with M2 standoffs and screws. The holes on both the camera and the front of the tower are too small for M3 screws. This configuration actually ends up working quite well, recessing the camera lens enough to protect it and holding it securely in place.
I’m actually a big fan of the Krieger’s camera mount design. When the nuts holding the two copper rods to the carbon fiber is tightened, the camera is quite secure. However, you can still move tilt it backwards or forwards with a little bit of force. The little dots guide you to different tilt angles so you can easily remember which angle works best for you.
Once the tower is built, mounting it to the rest of the quad is actually pretty easy. The nut-hold down design looks kind of funky from first glance, but it is actually pretty intuitive. The nut actually butts up against the PDB board, which holds it in place and makes screwing it down pretty easy.
And that’s it! This is the completed quad, just needing some set-up in cleanflight before it goes out for its maiden flight.
References and links:
Discussion (RCGroups): Link
Build Video (YouTube – FLYiPILOT)