Differential Thrust for Twin Motors

[Oscar]

Last year Dr. John C gave me a set of Durafly Skymule floats conversion kit (Thank you again Dr. John!!!).  So I decided to convert my Skymule to float plane too.  It's a challenge for me (being a noob in model building).  Finally I managed to convert it.  I noticed my Skymule does not have float rudder to control.  Although I can use throttle and rudder to steer, but I am worried it's not that easy.  Then, I found others use 'Differential Thrust' to control the steering.  With a bit of research (thank you Alan B who gave me ideas on how it works) , trials and errors, I finally got it working. 

For others who are interested in setting up the differential thrust, here is how I did it.

Spektrum DX7 (or higher) - I am using DX9
Left Motor in Throttle (CH1)
Right Motor in another channel - I am using AUX4 (CH9).  Assuming you have DX7 and up, you can use AUX2 or AUX3.  I leave out CH5 (Gear) and CH6 (AUX1) because I am thinking to use it for other purpose in the future (like FPV headtracking, LED lights)

Assign a switch to toggle On/Off differential thrust.  Differential Thrust will only be used in water steering.  Turning off when take off and flying. I am using Switch A since I don't have landing gear.
Assign a switch for throttle cut both motors.  You don't have to but for safety purpose (my fingers will thank me)  I am using Switch H to perform throttle cut
Assign a switch to adjust the right motor speed.  You want to synchronize both motors when performing Differential Thrust.  I am using right knob to adjust the right motor
Programming the Mix function.

Here is the video with the setup instruction.   
https://youtu.be/GOhIIhYPc1k


Where to get the float conversion kit - http://parkflyerplastics.com/cart/index.php?main_page=product_info&cPath=28_50&products_id=706

Side Note: Suppose to be look like a Grumman Albatross.  But the final result looks like a bit of everything (GA+CL215+Twin_Otter).  I don't know how well I build.  I guess I will find out in our float flying event.  Hopefully it won't turn up to be a submarine  )

[Candu]

Oscar, I also use differential thrust for my Guinea Pig cargo plane. I tested it for ground steering, taking off, flying and landing. I assigned a switch to turn differential thrust on and off for testing its flying characteristic and found that there is no real advantage in turning it off. Here's a taxi test in my garage over the winter. Note the nose wheel is not under user control.

https://www.youtube.com/watch?v=ydttePbIgdU

Frank

[Oscar]

Yeah.... so cool while taxiing. 

I look forward this year float flying event.   

[gmcnic]

Frank, are you sure that's your garage?  I don't see any tire marks.

Oscar, here's a DHC-6 Twin Otter in differential/reverse thrust action without any water rudders.

https://youtu.be/x2q_tLn8Dfw

[Michael]

I have been unable to set up differential thrust with my DX18.

Oscar, if I bring my radio and new twin-float-plane to the next meeting, will you try to help me?

[Oscar]

Sure.   

[Oscar]

Oscar, here's a DHC-6 Twin Otter in differential/reverse thrust action without any water rudders.

It's so cool. I doubt it can be done in my Skymule. 

[Oscar]

A big thank you Rob D who recorded my maiden flight.     Here is the maiden flight.

https://youtu.be/2DpZ0eyxEZg

On final approach, too slow with sharp turn causing its stall (pilot error).  Minor damage on the canopy with prop marks, aileron hinge went missing. 

And thank you Michael R for the flying advice with the twin motors. (turn with Rudder)

Lastly, thank you Dr. John who gave me the conversion kit. 

[Skyking]

Way to go Oscar- You conquered another milestone.

Ken

[Oscar]

Thank you Ken

[Wingnutz]

Oscar, thanks for all your posts. They keep me up to date with ROGO stuff and show your increasing skill in the hobby. Well done.

[Oscar]

Thank you Bill