V6 FPV Multicopter

Bill of Materials

[Qty. 3] 3/8″ Basswood Square Rods

[Qty. 1] 1/32″ Birch Plywood Sheet

[Qty. 1] M2x8 Screws

[Qty. 1] Cable Ties

[Qty. 1] 20AWG Red Wire

[Qty. 1] 20AWG Black Wire

[Qty. 6] 2900kv Brushless Outrunner

[Qty. 6] Plush 6A ESC

[Qty. 1] 26AWG Servo Wire

[Qty. 1] Servo Terminals

[Qty. 1] Male to Male Servo Leads

[Qty. 1] KK2 Flight Controller

[Qty. 1] 2200mAh 2S Nano-Tech Lipo

 

To construct the frame I began by cutting two 13″ arms from the 3/8″ basswood rods. The arms sweep out 14.5 degrees from the center placing the rear two motors about 7.25″ apart and the front two motors about 13.5″ apart. The cross arms are approximately 11″ long and they have been notched to rest across each other. It is best to cut and align the outer arms to a template before measuring up and cutting the inner cross arms.

The center plate was cut to about 2.5″ x 5.5″ and slotted to mount the battery and radio gear. Before mounting the motors and ESCs I removed the servo wire of each ESC and replaced it with a longer wire. All three of the connections were soldered to the first ESC, but the reamaining ESCs only have a signal wire. I also soldered the supplied bullet connectors to each ESC and motor. The motor mounts are fixed to the frame with two M2x8 screws. The correct rotation for the motors is described in the KK2 motor layout.

The power wires for the front two motor ESCs are daisy chained to the middle motor ESCs to clean up the wiring. In order to support the current of both ESCs I replaced the power wires of the middle motor ESCs with 20AWG wire.

As shown below, only on the first motor ESC are all three servo wires routed back to the flight controller. The remaining ESCs have only a single signal cable routed back to the flight controller. Since the stock leads aren’t long enough, it is much easier to only solder an extended signal wire where necessary.

The center of the flight controller is positioned just behind the middle motors so that the center of the frame is aligned across the sensors (mounted at the top of the board).

I mounted a Pico-Wide FPV Camera beneath the front plate of the frame. The fatshark 5.8GHz 100mW video transmitter is secured on top of the 8-channel 2.4GHz receiver.

Finally, the 2200mAh 2S LiPo was secured beneath the rear of the center plate using a Velcro strap. The props are mounted with the supplied prop savers as they are the easiest and most well balanced method of mounting the props. Flight time with the 2200mAh LiPo is approximately 13 minutes.

I also modified the V6 mixing for better yaw control. The default settings cause the aircraft to sweep very wide as it yaws. Imagine a point at which the arms intersect to the rear of the frame; with default settings it is as if the aircraft yaws about this point. By modifying the rudder mix the yaw control is improved, but it remains quite slow.

CH1 Rudder: 100

CH2 Rudder: 71

CH3 Rudder: 42

CH4 Rudder: -42

CH5 Rudder: -71

CH6 Rudder: -100

 

My current PID settings are as follows (These may still need some adjustment):

Aileron & Elevator

P Gain: 60     P Limit: 10

I Gain: 30     I Limit: 10

Rudder

P Gain: 150     P Limit: 20

I Gain: 50     I Limit: 10

 

After spending an hour adjusting the auto-level settings, I arrived at the conclusion that the control algorithms of the KK 2 are not designed for true “auto-leveling” so much as they are for drift compensation. The algorithms are not calculating the precise angle of the controller, but they are instead compensating for acceleration due to gyro drift. This results in a huge amount of lag compared to that achieved through true auto-leveling with an AHRS algorithm. I eventually installed a MWC Crius MultiWii flight controller with a custom V6 mix. The flight performance far exceeds that of the KK2 in both auto-leveling and yaw authority. A tutorial for writing custom motor mixes for MultiWii can be found here. I also added some LEDs so that it looks like a Cylon Raider ;)

 

The Beginner’s Guide to Multicopters

I often get asked many of the same questions from individuals seeking to build their first multicopter; therefore, I thought that it would be a great resource to offer a manual that accounts for the very basics of multicopters and remote control equipment. Here I will host the manual and keep it updated with the most current revisions. Please contact me if you have something that you would like to see added or corrected. Click on the picture below to view and download the guide.

cover

Micro FPV Multicopter

After giving FPV a go for the first time with my X4 Drone, I found it rather difficult to fly on such a large and heavy platform. I was too overly cautious of crashing. Therefore, I decided to build a durable micro to practice FPV. I began with the intention of making a hexacopter frame, but after damaging two motors I decided to make it into a quad instead. Here I will document the build of the hexacopter up until it became a quad. At this price, I would suggest ordering at least one or two extras of each component.

Parts List:

[Qty. 6] 2900kv Brushless Outrunner

[Qty. 6] 6A Brushless ESC

[Qty. 1] 6x 5030/R Props 

[Qty. 2] 2S 1000mAh Nanotech LiPo

[Qty. 1] Pico 5V Wide Angle Camera

[Qty. 1] Camera Cable

 

I built the frame from a thin sheet of aluminum and some basswood. The arms are made of two 1/4″ x 3/16″ pieces of bass wood separated by several small 1/8″ pieces. This allowed me to place gaps between the arms for the bolts without having to drill out the small holes. This is a schematic of the frame, it can be scaled to fit various size components, but it is designed to be used with the parts listed above:

The aluminum plates and legs were cut and drilled using these templates:

The original model used the standard Fatshark CCD killer camera, but I decided to use the pico camera instead.

After reflashing the 6A ESCs with SimonK firmware, I covered them in black heat shrink and directly soldered them to the motor wires. The motors are all bolted to the frame and the wires secured with small cable ties.

The power distribution includes an additional lead for powering the video TX.

Finally, I assembled the top plate with all of the electronics and a MWC Crius SE flight controller with MultiWii 2.0.

I used the camera with my 100mW Fatshark video transmitter, it should be compatible with any other NTSC FPV setup as well. The pico camera is extremely small, easily hot glued into place and removable if necessary. The weight of the camera is hardly even measurable and it seems to have quite good light sensitivity, even in very low light. I must mention that the props I ordered are very well balanced, perfect for this micro, however, they must be installed carefully as to not damage the motor. To install the props I removed the lower mounting bracket of the motor to expose the base of the shaft near the c clip. Placing the prop around the tip of the shaft I secured the motor in a vice and applied pressure until the prop was completely secured. The key is to remove the lower mounting bracket and ensure that the base of the shaft near the c clip is flush against the wall of the vice, otherwise the force will push the shaft through the bearing and damage the motor. If this happens then the motor will not function properly and must be replaced. Another option is to use the prop adapter supplied with the motors and some 3 bladed props such as the 5x3x3 or 5x3x3R. However, these props and prop adapters are horribly balanced, I haven’t even attempted balancing them yet.

After damaging two of my motors, I decided to make my hexacopter into a quadcopter. I redesigned the frame to resemble my X4 drone. It uses thin aluminum plates and some 3/16″ by 3/8″ bass wood for the arms.

With a 1000mAh LiPo I get about 7 minutes of flight time with fpv gear. The motors supply more than enough thrust to recover from fast drops and the flight controller required absolutely no PID tuning. It is extremely agile, stable and responsive. With such little weight it takes many crashes without any damage to the frame, motors or props.