Critic of Graupner MC12
I was wanting to :
. Have a simultaneous control on propulsion and lifting (as on full size similar hovercrafts, which are one-engined)
. Be able to tune the ratio lifting power /propulsion power, with ability to maintain lifting motor at a minimum value.
. Open similarly both front chambers (braking function)
. Open differentially front chamber when rudder is moved.
I've bought the radio Graupner MC12 for that purpose. It is my first radio and so, my first programmable radio.
It takes some time to define what to do.
I've not found Graupner manual very clear, and informations on radio screen are a bit cryptic.
After some time i found a solution slightly satisfactory.
Pilot mode adopted is rudder/depth on right stick, and power/ailerons on left stick (mode 4).
That solution drives to :
. Left stick : power rise from bottom to top
Left stick lateral move open right or left chambers. This is without interest, but is a side effect of the given programming.
. Right stick : control rudders.
When this stick is set low, the hovercraft front chamber which is on same side as the rudder direction opens.
Stick in lateral middle position, stick low opens both front chambers (Braking)
Mixing being permanently active, front chambers opening command moves even when the stick not low. To not have undesired opening, a lot of play was set in the command, and the chambers only began to open at half the servo displacment. This is not the best solution, but if you find better, i will be very happy to read you...
Programming adopted on Graupner MC 12
. Pilot mode : Mode 4
. Model type : VC (Voltige/Nautic/Car). Mixage Delta : On
Front chambers are plugged in place of elevons (Servos 2 on left and 3 on right)
Rudders are plugged on servo 4
Propulsion power on servo 1, lifting power on servo 7
You have to note that electronic variators i'm using must bet set to '0' to be able to start motor (for safety reasons). If you want to set a minimum lifting power to avoid the risk of cutting totally lifting when at high speed, you need to use another mixing from 1 to 7 selected by a switch, superposition of both signals allow to get a low point on the power. Same result may be obtained with a 'dual rate' command but that function don't exist on this channel.
Permanent value of mixing (mixer A) 25 to 65 % depending mini and maxi required for lifting. (my personal set : 25 %)
If you rise %, Lifting motor will go faster fo a given propulsion power, gas in high position. But it will go slower fo a given propulsion, on low power.
It must be noted that minimum value for lifting power is also set by offset parameter of channel 7 (my personal set : 60 %)
Travel adjustment also defines minimum and maximum power...
My setpoints :
Travel adjust ‘low’ : -100 % (impossible to adjust with this radio, because it is not possible to attain the negative zone)
Travel adjust 'high', from 0 to 100% depending your lifting power needs. My set : 0% (there is some margin, so...)
To arrive to tune mini and maxi, you have to play with all these parameters (To ease the process, unplug propulsion, and take into account that slightly increase battery power)
Second mixer (mixer C) is set to shutdown totally lifting for :
. Starting variator
. Cutting lifting without switching off the model
My set : 60% (sum of both mixers 1->7 must be around 100%, plus a compensation for offset).
Attention, this mixer is commanded by switch 3, which command also Snap roll on this radio. The Snap Roll mixer (SRE) must be set OFF, else switch 3 lock commands.
Switch set closed when low (activated), that gives :
. Switch low : no lifting, ready for motor start
. Switch high : lifting set at a minimum value
Propulsion power : Depends of your motor, choose yourself. Began with a low setup, That also limits electric consumption.
Travel adjust 'low' : -100%
Travel adjust 'High' : +35%, which give the maximum, so you can see there is margin...
Commande of elevons (servos 2 and 3):
. Neutral commande servo 2 ‘Sub-trim’ : -150
. Neutral commande servo 3 ‘Sub-trim’ : +150
. Travel adjust canal 2 : - 0%, + 150 %
. Travel adjust canal 3 : -150 % , +0%
You have to adjust ‘dual rate’ values, which here defines delta mixing value (Don't try to understand, that's what is written in the manual…)
Dual rate channel 2 : 100 % give equal opening on left and right.
Dual rate channel 3 : 125 % (maximum) increase travel of servos 2 and 3 when stick is set low.
Mixing direction to elevons differential : Channel 4 to 2
In ‘Delta’ mode, channel 2 is used for elevons differential command, channel 3 command depth.
% mixing 4 to 2 : 45% - 55%. My setpoint : 55%
Not too high, because that drive to excess chamber servo travel.
Rudder (channel 4)
Neutre : 0 %
Amplitude: -100 %, + 100%
# : Indifferent - : Not available
Pilot mode : Mode 4
Program mode : VC (voltige/Nautic/Car), with Delta mix
Travel adjust (Amplitude)
Lift fan power
Sub-trim (Offset) & Sens (dépend de votre installation de servos)
Lift fan power
Dual rate & Exponentiel
Function ??, left-right balance, must be 100
Function ??, set to maximum
Lift fan power
E-F : 0%
LDE : OFF
SRE : OFF -> (if ON, commanded by switch N°3, so problem with mixer C)
DLT : ON (delta mixing)
Free use mixers
A17 : CH1 -> CH7 : 25% Active permanently (ON)
B42 : CH4 -> CH2 : 55 % Active permanently (ON)
C17 : CH1 -> CH7 : 60 % , commanded with switch N°3
Radio Graupner MC12 critic
Box : black, sober and elegant, that changes from the horrible chromed box you find with some competitors.
Screen : Cryptic informations, a few added characters may greatly help.
Too much savings were done on the screen.
Each command is described by an abbreviation, which only became understandable after some use. They are in english, if you don't speak english, tooo bad, you will never really understand the system.
. Sb-trim : Sub-trim, in fact this is the 0 adjustment (offset in english !)
. Trv adj : Travel adjust
. D/R : Dual/rate (selected by an optional switch)
. Exp : Exponentiel. Servo will move on exponential curve related to stick position.
. Exp offset : 0 set for exponential adjustment
. Rev-Norm : direction of the servo (reverse – normal)
. Mix : Mixer
Trigram for description :
. mixing SRA : Snap-Roll
. mixing E-F : Elevons to ?
. mixing LDE : Landing ? Automated landing (only adjustment is automatic …)
. mixing DLT : Delta
TMR : Timer : from the beginning of your flight/race...
CHn : Channel n or Servo n, depending context. Differentiate both is important, and if you do have mixing, that is really ambiguous.
For example, in our case (voltige mode, delta mixing) :
Functions TRV ADJ and SB-TRIM are about servos 2 and 3
Functions D/R and Exp are about functions 2 and 3 (resp. function ailerons and depth function)
Same button is used for function mode selection (when set high) and channel selection (when set low).
That does mean you cannot go back, only go forward. That is frankly nagging, and you waste 75% of your time to loop review all functions.
That two commands may have been separated, with for each, the possibility to go back.
Moreover, Each servos/channel function (which are similar for each channel) is chained with mixing, which are common to all channels, so you will review the mixing many, many times...
For marginal equipment savings, probably under 6 euros (4 to 8 character in addition on the screen, and 1 to 3 added buttons), ergonomy of this radio was compromised.
Manual is not the best, especially for beginners. It consider many things as implicit. The core market of this radio being mainly for low experienced people, that manual goes totally aside the cible.
This radio is the lowest cost of programming radio, it is simple and well manufactured, but i find it's ergonomy and it's manual badly designed.
This is a very common model, and maintnance may be easy.
Some people have recommanded me radio Multiplex cockpit MM, for the easyness of programming, though it seems that it does'nt have free mixers, which don't allow to create the system described here.