My Trex 600N 3Ding

Chinook Tandem Heli Build Thread

Aerobatic, DCP 30%, Ch5 mix 90%, gyro 35%


Flight with flybar weight added



4th flight


1st flight



Materials:
1) 2 x Trex 450 RotorHead CC and CW modification, $800 HKD
2) DIY Body Frame 1.5cm fiberglass (can use metal cutter) , $50
3) metal bearing mount x 3 pairs, $150 HKD
4) 5mm copper tube , as tandem torque shaft, $30 HKD
5) Miter gears x 2 pairs . spare parts from gas heli torque tube, $54 HKD
6) TH2 mixer ~$1200
7) Pitch gyro Align 500X (old version), Yaw: E-sky 704A HH gyro $230 HKD
8) 500T. 1900kv @15T
9) Towerpro 9g servo x 6 = $180 HKD, servo wire extension x 3
10) Fiberglass 325mm blade 2 pairs, $ 70 HKD
11) 45A Himodel Heli ESC $140, AR6100 6Ch receiver, Align 3A BEC , 3s 1800 lipo

Flight 1:Failed , due to bent hollow main shaft from Ground Resonance?? Vibration caused by too high headspeed and the 2 towers shake like crazy.
Flight 2:Successful hovering , but lots of hunting due to unwired GY401. Resolved using cheap E-sky 704A gyro on HH mode without gain wire connected.
Flight 3:
Successful level flight. Used 2 HH gyro. Need to stregthen frame for the torsional stiffness.
The driving shaft may need 4 bearing support rather than 3. Trex600N needs only 3 bearings. Maybe the shaft-->miter gear connection allows more vertical/ horizontal clearance.
Flight 4:
Vibration comes from torque shaft alignment and frame torsional deformity. Problem solved with additional frame support and realignment of torque shaft bearing mount.
Perfect hovering and forward flight. Very stable Headlock yaw and pitch control.
Flight 5:
Try adding the flybar metal weight (~1.8g). It makes the Tandem much more stable and real. I can off my fingers off the Tx for 10 seconds now.You may need to reduce the gyro gain then.
The front rotor vortex is rather interesting. I intentionally reduce the pitch gyro gain <40%>30cm in a sudden. First I though it is low voltage throttle cut. Then I remember it is what Joe mentioned. You must increase the throttle stick (as much as 2/5 throttle ) to regain altitude. This is real fun to see it happens!
I also observe another interesting phenomenon that does not happed in single rotor heli. When I do a fast piro, the whole bird seems obtunded after turning 180degree. I guess the front rotor turned into a position where the rear rotor was before. The turbulance will then counteract the coming rotor a bit. Anyone can confirm this?
Need to increase TH2 setting DCP gain , as 30% mixing still have Front Vortex Interference on slow FF. The remote Ch5 DCP gain works great as I dial it up to 90% in very windy condition >20km/hr.
Did some aerobatics today and fast FF is perfect.

Change bearing of Align 600L brushless

Mine is over 300 flights and the motor bearing is still fine and I decided not to change it. The bell is nicely balanced . The rear bearing is notched and grainy.

Procedure:

1) mount the 600L on a motor mount. Place the mount on a clamp.

2) Use a DIY tool, or a rotory saw blade driver with teeth 29mm apart. This can turn open the base cap. The base cap has loctite with the stator base.

3)Use a bearing clamp to remove the stator from the base cap. Or you can punch the stator out with the base cap supported.

4)The front bearing, magnet bell can then be removed. There should be a copper washer, of same size as the Trex 450 main gear washer.

5) This is the most difficult part. To remove the rear bearing, one has to punch from the other side of the stator. Align put lots of loctite on the rear bearing. You need a hex socket (size6/8 inch?) to bear the stator base. I use a 5mm Trex450 main shaft with a 6mm copper tube. Thing is easier if you get a 6mm shaft to punch out the rear bearing. Remember another copper washer is underneath the rear bearing.

Trex 600 CF Flybarless

After my experimental Flybarless Trex450 , I decide to convert my Trex600 as well. I forsee the fast cyclic response is good enough for 3D.




Using 15mm linkage ball. 8cm linkage rod.
Extend the upper swashplate ball distance.
Phase angle washout hold in position with hex nut, at 0 deg.
I use one arm only , but will put another arm soon . As during 3D, a cyclic punch will rotate the arm a bit and result in undesirable/ abnormal cyclic response. In addition, the old design Trex600 swashplate has the upper balls off center ( A design flaw).





Leading edge. But the grip screw nut become the top.
Tx swashplate Ail -44%, elevator 55%, collective 40%
Cyclic 13 deg, collective 12deg.
D/R exp Ail/ elev -30%




Result :
I am very happy with the fast cyclic even at very low headspeed ~1900. The forward flip is 2x faster than my 600N @2100 rpm with light paddle.
In head on wind, pitch up is significant.
Hovering/ Control is much stable than Trex450.
Will try to add a pitch gyro to see if the pitch up/ballooning will disappear.

Short video, cannot record the 3D part because memory card is full.

Coast Guard Build Thread

Hurricane EP550 body and .30 Funkey fuselage with wheel retraction driven by 2 servos.

Steps:

1) Retraction system , waiting PIC burning for slow retraction and LED lighting.

2) Trex 600L motor too tall. Have to put back my 1000kv BL. Then have to gear up with 16T / 50T front gear to achieve HS ~1900.

3) The tail hub have to trim at the link ball lever.

4) Swashplate may hit the fuselage on highest range. Need to trim 3 slots.

5) Battery weight better bear on the frame rather than on the fuselage, as the fuselage is not yet mounted secure enough to the main frame.

6) Hurricane EP550 seems a good fit for the .30 fuselage

7) Thinking of putting some seat and pilot inside.

Trex 450 flybarless (2)

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.