I developed the Rekon 4 FR to create a sub 250g freestyle platform that gests as close as possible to a “classic” five-inch quad. And while performance was the main objective, I still wanted it to be practical for everyday use:

– A robust frame with quick swap arms that can take hard crashes and offers good component protection.

– The option to carry light HD cameras (Naked GoPro, SMO, Insta 360).

– Compatibility with a widely available battery sized (650-850mah 4S).

– And finally, have some margin towards the sub 250g goal, so you do not have to worry about every gram of wire or tape you add to your build (if you are choosing the frame kit instead of the BNF).

Why 4 inch?

1.A 4” platform can be built sub 250g pretty comfortably and you will be able to carry a relatively large battery for 4-6min of aggressive freestyle. The disc load is lower than on a sub 250g 5”, making it less floaty and having more momentum when you “throw” the quad during freestyle tricks.

2.A 4” quad can carry a naked GoPro type camera easily and without a noticeable impact on flight performance. The analogue version is still sub 250 with a 25g naked GoPro and a 650mah 4S (unfortunately the digital version is not since the vista adds around 14g) 

3.4” t-mount props have gotten pretty mainstream and there is a decent choice and availability (which is not the case for 3.5”)

Motor & prop choice

The motor and propeller configuration was crucial to achieving the desired flight characteristics. After weeks of testing, I finally settled for an intermediate stator size with an aggressive kV. A stator larger than 1804 (e.g. 1606, 2004, 2204) didn’t seem to offer any noticeable improvement of flight characteristics while adding a significant amount of weight. Anything smaller than 1804 just did not have enough torque to make the quad feel locked and snappy enough. 

The best performing props were the Gemfan 4023 tribades. They are more on the aggressive side in comparison to the HQ T4x2x3 and while they can be pretty amp hungry on the relatively high kV 1804 motors, they ensure the quad has an impressive punch! 

Specifications

Product name: Rekon4 FR Freestyle FPV Drone 4S HD Version
Weight:161.2g

Rekon4 FR Freestyle Frame
Model:4-inch Frame
Wheelbase:180 mm
Size:180*140 mm
Power plug:XT30

Zeus F722 mini Flight Controller
MPU:BMI270
CPU:STM32F722 RET6
Input Voltage:3-6S Lipo
BEC Output:5V/3A,9V/2A

Zeus 28A BL_S 3-6S 4in1 ESC
CPU:EFM8BB21F
Input Voltage:3-6S Lipo
Steady Current:28A
Peak Current:35A（10 Sec）

CADDX Polar vista kit
Operating frequency:5.725-5.850 GHz
Input power:about 7.4-26.4V
Channels:8

Rekon 1804 3500KV motor
Motor:KV3500
Input voltage:3-4S
Recommended blade:4 inches

Gemfan 4023 4-inch 3-blades propeller
Quantity:4 CW & 4 CCW

Package Included:

1x HGLRC Zeus F728 STACK
1x CADDX Polar vista kit
1x Rekon4 FR Freestyle Frame
1x Rekon 1804 3500KV motor
8x Gemfan 4023 4-inch 3-blades propeller
1x Hammer Antenna (L Screen Printing)
1x receiver (optional)

Recommended Battery:

4S:550mah-1000mAh