Brushless main motor with brushed tail - conversion notes
Hobby King 10A ESC
weight: 9.6g
LVC pre-set to 3V per cell but don't trust it. Heli has to stop flying before this point is reached anyway:
Tail rotor authority OK but as throttle is moved higher to compensate for dropping voltage the pitch to tail mixing becomes less and less accurate resulting in too much right rudder (torque compensation) being applied by the radio. This has to be removed on the rudder input resulting in a half left deflection on the stick. Then when throttle is increased to make heli climb it has to be taken off to counter the increased torque. It's possible to fly but quite tricky.
Heli will still hover at this point but it's not safe to fly as any punch out will cause barely controllable yaw and the battery has reached about 80% discharge. On a good battery 7 mins is the limit.
Max current seen driving this motor: approx 6A
This ESC starts motor much more smoothly than the 30A and will run it at much lower RPM. A much better fit for this application. Both motor and ESC remain cool during normal hovering flight.
Only settings available for this ESC are Battery type, Brake on/off, Direction of rotation.
This ESC can be re-flashed with BL-Heli
ESC to motor connections:
Yellow ESC -> red heat shrink
Red ESC -> black heat shrink, middle motor wire
Black ESC -> remaining black motor wire.
Revo mixing
DX6i settings:
To get the brushed ESC to arm we need zero "throttle" input and for the gyro to set its neutral rudder position where we need it we need to give it neutral rudder. Unfortunately these two conditions don't coincide, nor are they what we need for actually flying where we need full left rudder at zero throttle and neutral stick. So to make life easy we set normal mode to the initialisation conditions and idle-up to flight conditions. Connect the heli battery with the DX6i set as follows:
Gyro in non-heading hold mode (1) (heading hold doesn't work with the inertia of the original tail rotor system)
Flight mode to NORMAL (just so that we can conveniently set the initial conditions and then switch to IDLE UP for flying)
Once the gyro has initialised at neutral rudder position, hold the rudder full left to give the zero signal for the brushed ESC to arm. Then if you don't want the tail rotor to spin up, while holding left rudder, switch to idle-up which gives full left rudder signal with the stick in the neutral position.
Revo mixing:
NORM STUNT
UP 0 UP <- 100%
DN <-125% DN <- 125%
Pitch Curves:
NORM: 50,25,50,75,100
STUNT: 0,44,63,80,97
HOLD: Not used
Throttle Curves:
NORM: 0,25,50,75,100
STUNT: 0,25,50,75,95
HOLD: all zero
Gyro rates:
0: <- 67% (heading hold regime - not used)
1: 15% (yaw damp regime - this is the one we use)
Travel adjust:
all 100%
D/R & EXPO
NORM: 100% INH
STUNT: 100% INH except rudder which is 100% +40%
SWASH MIX, MIX 1 & 2
all INH
REVERSE
THRO: N
ELEV: R
GYRO: N
AILE: R
RUDD: R
PITCH: R (doesn't affect anything since we don't use the transmitted pitch signal for anything and revo input is taken before the reverses are calculated)
Timer:
Down : 5 mins
Trims:
throttle & rudder: zero
Forward: 2
Left: 6
Switching to normal flight mode switches the REVO MIX, THROTTLE and PITCH settings. Revo mix takes a percentage of the pitch output and feeds it into the rudder output. After much trial and error ( and using the incredibly useful MONITOR page in the DX6i) I settled on 125% LEFT of the pitch signal in the lower half of the curve and 100% LEFT in the top half. Then it was just a matter of test flying to find the tweaks for the pitch curve to give the correct rudder output to balance the main rotor torque. The gyro takes care of the rest by damping the yaw.
The hard part to figure out is how the various reversals in the settings work out.
First thing to note is that the settings in the REVERSE menu are applied last so pitch setting doesn't affect anything to do with the revo mixing. Rudder reverse, of course, does as it is applied as the last stage after mixing just before output.
The pitch curve appears to be handled internally as negative for less than half stick and positive for more than half stick. This gets multiplied by the left or right REVO setting, Left being negative and Right being positive. As the final stage the rudder REVERSE setting is applied.
So for the set up above it works like this:
< 1/2 stick: -(pitch) x -(left revo) = + which is reversed by REVERSE to give - (which is left rudder for heli)
> 1/2 stick: +(pitch) x -(left revo) = - which is reversed by REVERSE to give + (which is right rudder for heli)
You might be thinking that this could be simplified because you could switch the revo to the right to take out the first sign reversal and therefore not need the final rudder reverse but then the rudder input from the stick ( as opposed to just the revo) would be in the wrong sense. So it works backwards from what we need to get the stick and the heli to correspond (REVERSE) which then requires the REVO to be in the left sense for it all to multiply out correctly!
Mods:
