KCFrames KC250 - Review & Build Log

Frame Specs

  • Pure "X" design arm layout
  • 250mm diagonal spindle to spindle
  • Quick replacement arm system
  • Lightweight Carbon 1.5 mm Decks
  • 4mm carbon arms
  • Tight center of mass layout
  • M3 x 16-19mm slots for motor mount holes
  • 35mm Aluminium stand-offs
  • Frame only weight : 99g
  • (optional) Brett Collis designed PDB with 5v 0.5A regulator with the option of hard mounting a XT-60 connector or wire harness.

The Parts List

  • KCFrames KC250 Frame
  • RotorGeeks RG20 Esc's
  • T-Motor F60 2206 2100kv V2 Motors
  • DTFUHF Doge Flight Controller (prototype)
  • DTFUHF Reciever (prototype)
  • FX799T 25mW Video Transmitter
  • HS1177 FPV Camera with 2.1mm Lens
  • TBS Triumph Video Antenna

All of the parts
All of the parts #2

The Build

It is worth noting here that I will be building my KC250 slightly different to how the instructions follow. This is for a few reasons. Firstly, I wanted to mimic the setup Luke Bannister used to win the World Drone Prix in Dubai because it looked amazing in the air and obviously won, but I have also moved to running the Lipo underneath on all of my current quads, rather than on the top.

I think it actually improves flight characteristics with the weight being a lower CoG than normal. This pendulum effect seems to give an extra added level of stability when performing hard or fast manouvres, but will also help when you make mistakes and corrections are needed.

The optional PDB by Brett Collis

As you may have noticed from the frame specs above, there is an optional PDB with 30.5mm bolt spacing that will fit right above or below your flight controller for a tidy but practical power wire installation. Due to running the DTFUHF flight controller with onboard-PDB I will not actually need to use the KC PDB, although the KC PDB is very well designed and looks very good. It features a 5v regulator, pads for ESC's and can fit an XT60 in on the side (or you can solder your own pigtail wire in).

With the above in mind, let's start on the build!

1. Slide the long M3 screws through and place on a flat surface.
2. Add 2 M3 washers to each of the outside screws, leaving the center free.
3. Add the battery strap over the bolt. Note: you will have to cut a hole in the middle for the screw to pass through.
4. Place the bottom plate over your battery strap and feed the screws through the plate. The washers in plate should allow it to sit flush due to the height of the battery strap.
5. Slot the arms over the screws and in plate, the center screw is used as a location guide and will secure them further later on in the build.
6. Add the thick square plate on top of the arms, and screw down the short standoffs. Screw the flange nut onto the center screw.

Reverse side with strap

With the bottom half of the quad now assembled you should be able to get a feel for the size of it. The KC250 is one of the smallest quads that will take 6" props, and you can certainly see it here. The unique arm design looks great here with it's weight saving holes and hard corners towards the motor section. You'll also notice how small the main frame body actually is now, but don't be alarmed - we can still fit everything in there with ease :).

7. An easy step here - secure the Flight controller into position - depending on the layout of your controller you will want to rotate it so the USB port is on the side.
8. I now mounted the HS1177 camera bracket using M2x4mm screws, M2 washers (x2) and M2 Nuts (x2). Add a bit of Blue Loctite to stop them from loosening in flight.

Time to add the Motors

For this build I've gone with the new T-Motor F60 series motors. They come in 2206 2100kv form and provide a perfect amount of thrust and torque for 6", whether you are flying 6030, 6035 or 6045 props on 3s and 4s. The motors in their "all-black" finish really complement the frame here and will be perfect for my black and orange colour scheme you'll notice I've done as we move further on into the build.

9. Simply attach the motors with the bolts - ensure your screws are the correct lengths and do not touch the motor windings. Again, use Loctite here.
10. I like to strip the ESC's down to their bare PCB's for the next step, and always do the motor wires first, allowing me to do completely "fitted" ESC power wires for a clean and tidy build.
11. Solder the motor wires onto your ESC's. Do not worry about motor direction at this point if you run BLHeli, we can switch it later in the software.. :)
12. There's a few steps done here. First I've soldered the power wires from the ESC's to the PDB, and I've also added the ground signal wires to the FC. When soldering these, ensure you solder the ESC's in the correct order (1-4).

All the wires soldered in place, note the Receiver wires

I've now soldered all of the required wires onto the flight controller and PDB, leaving just component placement (VTX and Receiver) left. You'll notice right at the front we've got the receiver wires just poking through the underside of the frame - I've left these wires as long as possible so that I can place the receiver literally anywhere in the frame without having to extend the wires. You'll get a bit of wastage doing this, but once you have them cut to length it leaves for a an extremely tidy build.

13. I've found a good location for the DTFUHF receiver, fitting perfectly on the lower rear deck, and trimmed the RX wires down coming from the FC. Double check polarity of the servo connector here.
14. In this stage we've soldered on the FX799T power harness onto the PDB that gives us direct voltage input from the Lipo. I've also added the remaining frame standoffs and the HS1177 camera in ready to connect it up.

Top down of all of the wiring complete

With all the wiring complete we can sit back and admire how good the frame looks with all the components (aside from the top plate) now in place. As I said earlier the body of the frame is quite small, but actually there is plenty of room to fit everything in, and still make it all really accessible if you do have issues, or get any breakages etc.

15. Connect up the FX799T video transmitter and attach to the top of the frame with double-sided foam tape, and attach your antenna pointing out the back. This should be enough to hold it in place.
16. Align the screws holes for the top plate and fasten them, again using blue Loctite. Note the cable tie used to secure the antenna to the frame, this stops any force or strain being put on the SMA connector of the VTX.

With the build process completed we now have to go into Cleanflight and set up the flight controller so that it is aligned correctly, our rates have been entered, failsafe has been set, and any other important configuration chages have been done. Ensuring your failsafe is set correctly is by far the most important, and will save you from damage and other unforseen consequences should something happen during your flying.

Setup and Tuning

1. Connect the flight controller via USB and load up Cleanflight Configurator. Go to the Flash Firmware tab and load up the latest version of firmware for your board and click Flash Firmware. For this board we're using Betaflight 2.6.1.
2. With flashing complete, press Connect to connect to the flight controller, we're going to go through some basic things but once you've done it a few times it will be drilled into your memory and will take a couple of minutes before you can fly! On this page we need to Calibrate the Accelerometer.
3. With that done we'll move onto the ports tab, and we're going to set UART 3 (which our Receiver is connected to), to run as a SerialRX. This will allow the X4R-SB to communite to the FC. If you run telemetry you can set that up here too, it's just a case of selecting your telemetry type from the dropdown. Don't forget to press Save!
4. The Failsafe tab is a new addition in recent firmware updates, and looks a little scary. Most of the default settings on this page actually work very well, just make sure your stage 2 failsafe procedure is set to drop rather than Land, so that the propellors stop spinning once failsafe is entered. This is by far a much safer method than trying to land.
5. This is the main tab that catches people out - if you have rotated the Flight Controller to easily access the USB port you will need to ensure your yaw offset is correct. Other than that ensure you have selected QuadX and enable OneShot125 if your ESC's support it.
6. If your ports tab saved correctly, your Receiver mode should switch automatically to RX_SERIAL, simply selector SBUS as the provider and that should be your receiver setup fully on this page. If you plan to run VBAT to monitor your battery voltage via flight controller you setup your parameters here.
5. PID tuning is a bit of an art, and sadly does not cover the scope of this review, but on the latest versions of Betaflight the stock PID values are actually very good for most quads similar to this design. If your quad does not move in any direction fast enough you can increase the RATE here.
6.There's very little to do on this tab, but it is very useful for ensuring your receiver is receiving your channel outputs (you may need to plugin your Lipo to power the receiver). You can change the channel mapping on this page, AETR and TAER are common layouts, 1234 just declares the switch layout, you can leave those at default.
# Final Pics

The last image, honest!!

One of the most important tabs of the configurator, but also one of the most easily missed. This is where we'll setup our flight modes, arm switches, flight type (acro, horizon etc), and any buzzers if required. I run a super simple setup of only 2 Modes - ARM and AIRMODE - both of which are triggered when AUX1 (Switch F on my Taranis) is triggered up. This will spin my propellers and activate PID's at 0 throttle (using AIRMODE), and I'm ready to fly!

With everything assembled, configured and adjusted - it's now to time to put your propellers on and fly this awesome machine!

Top down view
Close up
Front view

Video & Full Gallery

So let's get onto the maiden! I've thoroughly enjoyed the build of the frame, building quadcopters is a hugely fun passion of mine, so let's now see how it flies!

There's a bit of tuning still required, but otherwise it's flying AMAZING. It has actually put my other setups into question with how linear and good it felt around the mini course we setup. I'd of liked to have put some gates down as well, but sadly the grass has grown huge with the summer weather we've had here in the UK so that will have to wait for another day.. :)

There's a full build gallery with extra photos and media available here.

Final Thoughts

I've built it. I've set it up and configured it. I've flown it, and I've crashed it. Many times I might add.. :) So how does it perform and what do I think?

Well, it's great! I've not had a 6" setup for a good few months after focusing on 5", and actually there's something to be said for swinging that extra inch of prop. It mostly takes away the need to run Tri-blades which means much less amp-draw in flight, meaning better flight times! What do I mean by this? Well, in the corners you have that extra inch of prop to grip in the corners. When you run 5" 2-blade propellers you tend to drift past the corner and often have to over correct to get it to do what you want, where as with Tri-blades it just "grips" the air better and does this all for you, making for a much smoother feel and actually a smoother flight. 6" does exactly that I feel, even more so, meaning you can be super precise but also quick at the same time.

Side view

As for the frame itself, you can really tell how light it is in the corners with full throttle accelerations - it just picks up in no time and gains momentum amazingly. The lightweight design of the frame also means it has a very low drag factor compared to other frames, further helping you accelerate in the air when speed is crucial to "out-run" your mates, or competition :).

Despite its small size, it is very easy to fit all of the equipment in without feeling cramped meaning if you do break something you have ample room to repair or replace it. This is also where the KC comes into it's own league as well - if you do manage to break an arm during a flight, the quick release system will mean you are back in the air extremely quickly, compared to other frames that will need a whole host of dis-assembly. The "KC Mechanism" means you just need to loosen 2 bolts and you can swap an arm out, ready for the next race - other frames would force you to miss races.

In Action!

I would however say if you plan to run a GoPro to record your footage, then you will need to run the Lipo underneath like I have - there is just not enough room on the top plate to accommodate both the Lipo and GoPro. This is absolutely fine of course in flight, and will help with Center of Gravity, but I know people like to run everything on the top of the frame. Similarly, if you are looking to use the KC 250 as a "basher" frame, I would be a little hesitant purely for the fact that this is a dedicated racing frame. It's made light, it's built light, and so there are a few places you could have issues (the cutouts in the arms or the bottom arm plate), but with that being said if you are looking for a quad to use for FPV Racing with your mates or competitively, I would not hesitate to get one.

I've also seen that KCFrames are bringing out a thicker bottom deck and redesigned bottom plate (the square piece), for those having issues with breaking stuff - so that is certainly an added bonus.. :)

Bonus Wallpaper