Trex 450 Flybarless

Version 1 with direct drive. Poor collective resolution as the gain is et to 35% only.








Version 2 with mixer at hub to half the collective pitch travel, to improve resolution. However, the cyclic pitch travel is also halfed.

The cyclic travel can only be isolated from the collective pitch travel at the swashplate level. That is the swashplate upper/ lower diameter ratio.

TH2 CCPM mixer board from tech product

The rotor phase angle adjuster . 10 minsutes job from a shaft collar and fiberglass. Will make a better one.




****1st version

Direct Swashplate drive the blade grip.

Mechanical Setup:
1) taken away all flybar, seesaw and mixer arm. Direct swashplate drive to gip hub.
2) GY401 as elevator dampenig. Align 500X as rudder gyro
3) towerpro CCPM servo, Hitec 56HB rudder servo
4) TH2 CCPM mixing
5) Main grip leading edge control. Mechanical Phase angle adjusted 11 o'clock.
6) Servo horn distance shorter ??mm

CCPM mixer and Tx setup:
1) TH2 gain : Aileron 60%, elevator 65%, pitch 35% (way too small resolution)
2) Aileron D/R 80, Exp -50; Elevator D/R 70, Exp -50;
3) Cyclic 12 deg; pitch 10 deg

Result :
Hovering
1) Unexpected oscillation at pitch axis. Likely too high pitch gyro gain, sloppy servo , soft head dampening. Touchdown of expensive carbon blade with minimal damage.

****2nd flight
1) Hardening head dampener rubber
2) reduce sloppy servo, use Align 500X as pitch gyro with gain 20%
3) Add mixer arm to increase blade pitch resolution. 2x travel now
4) Servo horn distance same as flybar trex 450
5) Th2 setting: Aileron gain 65%, Elevator gain 70%, pitch gain 45%.
6) Achieved Max. pitch +/- 10deg, cyclic only 8-10 degree ( needs more)
6) Tx Ail. D/R 90, Exp -40; Ele D/R 90, Exp -30.

Result:
Stable hovering. Perfect figure of 8. No oscillaltion. Needs constant attention to roll (cause lack of aileron stabalization). Cyclic response at HS 2000 is almost as fast at HS2800.

N.B. TH2 has a behaviour that trimming on the Tx will greatly reduce the SW travel to the opposite direction. Therefore, all trimming best done mechanically or on the TH2 itself.

Next test schedule:
1) To test backward flight.
2) To test inverted flight.
3) To test 3D performance

Plan:
1) Need to increase inner swashplate diameter and decrease outer SW diameter. This will increase cyclic travel mechanically.
2) resolve some mechanical binding at mixer arm and central hub.
3) Change a more powerful BEC as the clamped BEC current is over 2.6A with 4 servos/2 gyros/ TH2 and receiver.

****3rd flight
Forward flight, stabel, no pitch up problem.
Backward figure of 8, pretty stable.
Pitch gyro gain at 30%. No osciallation as the head dampener is pretty hard.
With a plastic blade the cyclic is very fast and predictable. D/R 100%, Exp -25%
On pumping up/ down collective pitch, the heli may drift a bit ? realted to plastic blade being too flexible?
Plan for hard 3D in windy condition this weekend.




Phase angle set to zero











All linkages are straight now. No slop at all (except at the swashplate itself). Collective control is precise.