Differential Thrust question/OpenTX/Taranis X9D

[basslord1124]

This may honestly be a waste of time kind of question but it's an observation I made while researching how to do differential thrust on a Taranis X9D.

So in my earlier days of RC, I had a Spektrum radio. Kinda got locked into Spektrum as that's the only radio that worked with my first micro BNF planes...and this was before I knew about OpenTX. The Spektrum did well, but I couldn't justify spending so much money for extra channels that I was needing.

With the Spektrum I had it set up for my FT Seaduck which used differential thrust. The set up worked well and I could turn it off and on with a switch. And from what I could remember, this was how the functionality worked:
-Throttle stick, functions like normal
-Rudder control - left stick movement, right motor speeds up....right stick movement, left motor speeds up.
The speed of the motors of course relied on the position of the throttle stick...and would only seem to speed up when the appropriate rudder input was applied.

NOW, since digging into Taranis/OpenTX and figuring out on how to do it on this radio, it seems there's a slight change in how it's programmed. Been using this video for reference:

As well as some others. And the one thing I have noticed that is different is this:
-When applying rudder input regardless of direction...the one motor will speed up obviously, BUT the other motor will slow down.

At first when I heard this, I thought the concept was a little odd to how the Spektrum was programmed (and I am really "assuming" that's how it was....that's just what it sounded like to my ears)...but in reality, it does make for a much better and more effective yaw control with the differential thrust.

 

[Tench745]

This may honestly be a waste of time kind of question but it's an observation I made while researching how to do differential thrust on a Taranis X9D.

So in my earlier days of RC, I had a Spektrum radio. Kinda got locked into Spektrum as that's the only radio that worked with my first micro BNF planes...and this was before I knew about OpenTX. The Spektrum did well, but I couldn't justify spending so much money for extra channels that I was needing.

With the Spektrum I had it set up for my FT Seaduck which used differential thrust. The set up worked well and I could turn it off and on with a switch. And from what I could remember, this was how the functionality worked:
-Throttle stick, functions like normal
-Rudder control - left stick movement, right motor speeds up....right stick movement, left motor speeds up.
The speed of the motors of course relied on the position of the throttle stick...and would only seem to speed up when the appropriate rudder input was applied.

NOW, since digging into Taranis/OpenTX and figuring out on how to do it on this radio, it seems there's a slight change in how it's programmed. Been using this video for reference:

As well as some others. And the one thing I have noticed that is different is this:
-When applying rudder input regardless of direction...the one motor will speed up obviously, BUT the other motor will slow down.

At first when I heard this, I thought the concept was a little odd to how the Spektrum was programmed (and I am really "assuming" that's how it was....that's just what it sounded like to my ears)...but in reality, it does make for a much better and more effective yaw control with the differential thrust.

If for whatever reason you don't want the one motor to slow down, you can add differential to the mix. Or, you could do negative differential and only have the motor slow down.

 

[basslord1124]

If for whatever reason you don't want the one motor to slow down, you can add differential to the mix. Or, you could do negative differential and only have the motor slow down.

Thanks for the tip. I'm kinda in the middle what I will end up doing. Probably end up being a thing I tweak as I go. I do think I may go with the approach in the video, but set the opposing motor to not slow down too much for starters.

 

[Tench745]

It's actually super easy to only make motors speed up, but that does have its drawbacks. If you had things set up so each motor only speeds up, then when you're at full throttle, the motors can't speed up any more and you have no differential thrust. The up-side of having one motor slow down is that if you're at full throttle you still have some yaw control.

I was playing with this on my Dumod build, making it so the motor won't stop as I taxi around for a more scale appearance.