New experimental impossible tilt for the BabyTri

[Kevin_Erik]

I added the tilt to my Tri-Mini until the Tri-Baby is operational again. Granted this isn’t made for this frame but I wanted to try it anyway as It’s windy as all-F outside. (Hovered inside) Anyways, I added a servo quick disconnect rather than having to disassemble the frame to swap a servo out. Should have the baby up in the next few days if all goes well.

Note: I have a tilt-mech for the Tri-Mini in transit from my print house. Whats shown below is a Nylon / Kevlar mix.

Yes those are F80 motors… 🙂

[LitterBug]

Made it out to the field for a quick FPV romp with BabyTri#1 over the weekend. This is my hotrod build that I have to detune because it is too responsive on every axis:

[chilternflyer]

Stainless steel gears aren’t the answer. We should be using a bigger servo!
I have v2 and a 3.5 big tricopters. They use David’s tail mech with the 210 servo.

So far I have three 210 servos. I have also bought lots of spare gear sets.

I’ve got two remaining servos that have backlash and one that became so bad that I had to scrap it.

The pressure on the small pins (axles) eventually leads to failure of the mounting of the last gear (before the output shaft). It turns the hole into a slot where it fits into the plastic base (that holds the motor and the gear train). Changing the gears doesn’t help in this case!

[chilternflyer]

Terje:
I’d like to remix your design to make it fit a 210 servo and offset a 2217 and 2213 motors. I’d also like to make it as one solid piece due to the torque and gyro effect of the bigger motor and prop combo.

You kindly published the fusion 360 file for it on thingyverse but it only contained the bodies.
Would you mind sharing the full design file with me?

[Terje]

So far I’ve gotten 0 feedback on whether the impossible tilt works or not, and/or reports on broken servos.

Until I get some feedback, I will hold back on releasing any files.

[Kevin_Erik]

I have it working on the Tri-Mini but will not rebuild the Baby till later this week.

I can say this about the Mini though… Default PID’s and the Tail is silky smooth without a hint of wag. Keep in mind that this is just the in-house hover checks but even this was very surprising.

[LitterBug]

I’ve been flying this on two Baby tris. Had a few pilot induced config issues but will be getting more time on the frames now that the weather has turned for the good. Also have the Impossi-Tilt on a Mini and will be finishing up a second mini in the near future. Have a variety of servos including two RCE 210s, a Turnigy 211, and will putting a beefy BMS-A207 https://www.blue-bird-model.com/products_detail/50.htm on the new mini.

Not sure why it would cause more broken servos unless it’s being set up in a bind.

LB

[Kevin_Erik]

The current design should produce far fewer servo failures due to the crash induced torque now being signifigantly reduced. (Woot!) Thus far i am really impressed by the look, fit and feel of the new mechanism. Beyond all that, I strongly feel that this Tail-Mechanism should replace the default one currently offered by David. Maybe make it the standard for Tri V5 and beyond?

[LitterBug]

Was comparing the BMS-A207 to a BMS-210 last night. It will need approximately a 1.2mm shim under it to get the gear spline to match up.

[chilternflyer]

Fair point.

I’d like to try your design on a big tricopter because that is really where it would make all of the difference.

Could you publish an STL for the motor mounting that will accommodate a 2217?

[Kevin_Erik]

Here is the Impossible Tail Mechanism installed (inverted) on the Tri-Baby. It’s printed from a Nylon / Kevlar mix that should be unbreakable.

Notice that the Video Antenna is now mounted aft, well clear of the receivers antennas. Beyond that, the in-house test flight had a bit of minor wag which was easily isolated by increasing the Yaw P&D Gains. Initially the Yaw was set to the Defaults (70/45/20) but increasing it to 100/45/40 removed almost all traces of wag. I figure that the tail response was too slow and thus increasing the rates helped.

I’ve included the Diff and log-file of the test flight for reference.
# Triflight on Betaflight 3.2.2 v2 / MATEKF405 (MKF4) 3.2.2 Dec 31 2017 / 15:24:22 (30f68c8) MSP API: 1.36

# resources
resource MOTOR 1 C08
resource MOTOR 3 C09
resource MOTOR 4 NONE
resource MOTOR 5 NONE
resource MOTOR 6 NONE
resource SERVO 1 C06
resource SERIAL_TX 2 NONE
resource SERIAL_TX 11 A02

# servo
servo 5 1090 1964 1533 100 -1

# feature
feature ANTI_GRAVITY
feature DYNAMIC_FILTER

# map
map TAER1234

# serial
serial 30 32 115200 57600 0 115200

# aux
aux 0 0 0 1700 2100
aux 1 1 2 925 1300
aux 2 2 2 1300 1700
aux 3 28 2 1700 2100
aux 4 37 1 1700 2100

# master
set gyro_sync_denom = 2
set gyro_notch1_hz = 0
set gyro_notch2_hz = 0
set dshot_idle_value = 400
set motor_pwm_protocol = DSHOT1200
set failsafe_off_delay = 30
set failsafe_throttle = 1100
set failsafe_kill_switch = ON
set failsafe_procedure = AUTO-LAND
set align_board_roll = 180
set bat_capacity = 1000
set ibata_scale = 179
set servo_center_pulse = 1520
set servo_pwm_rate = 250
set tri_tail_servo_speed = 265
set tri_servo_feedback = RSSI
set pid_process_denom = 2
set dterm_lowpass_type = PT1
set dterm_lowpass = 70
set anti_gravity_gain = 3000
set yaw_lowpass = 40
set p_yaw = 100
set d_yaw = 40

# rateprofile
set rc_expo = 20
set rc_expo_yaw = 20

Attachments:

1. Test-Flight.zip

[Kevin_Erik]

@chilternflyer The 2217 motor should fit fine. I use a 2207 motor and the only difference is that yours is 10 mm taller.

[LitterBug]

@chilternflyer there is also the impossible tilt that was designed specifically for the larger tricopters. There are different height motor holders for taller motors. The rear pivot point also has more clearance for the taller motors. https://www.thingiverse.com/thing:1035497

Cheers!
LitterBug

[Kevin_Erik]

There is a limit to how tall of a motor can be compensated for as the mount can only be so deep until it contacts the frame. In those situations it may require that the Servo and the motor-mount be elevated (shimmed) to accommodate for the motors swing.

[Kevin_Erik]

Tomorrow i will be able to fly the Tri-Baby and provide plenty of feedback. Very often i fly agressively so a crash is likely.

[Author]

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