help with counter rotating propellers

[Sydd]

Hi, I'm having issues with counter rotating props.

Spoiler

https://imgur.com/a/IVOEWlh

The first plane, from KerbalX, works fine. My plane (the 2nd) has the same setup but is going to have some weird thrust as you can see in 3rd and 4th pictures, I dont understand why. Any help? I think this might be a bug

(saving the 1st plane's engines as a subassembly and putting them on my 2nd plane works though, until I decide to replace the propellers with bigger ones)

[TheFlyingKerman]

I'd begin with fitting the blades with the angle snap tools, to ensure they are perfectly straight. Then after sending the plane out to the runway, set the parking brake, and then turn on the motors with very low torque/RPM, and that the RPM of the motors and AoA of the blades are all exactly the same.

[Sydd]

After a bit of experimenting, changing the angles of the wings even a little bit towards the up (like on planes such as grumman goose or PBY catalina) completly messes with the CoL in the editor.

I think when CoM and CoL are miscalculated like this, the propellers do some weird stuff. I had to separate them a bit more when they're angled to make the propellers thrust properly in a linear manner with throttle.

Hopefully KSP2 wont have bugs like these

[Leganeski]

I'm just as confused as you are. Despite many attempts, I have never gotten a bilateral counter-rotating propeller plane to actually work either, so I suspect there is a large amount of unintuitive variation dependent on the precise positions and angles of everything.

 

6 hours ago, Sydd said:

until I decide to replace the propellers with bigger ones

This means that your propeller blades are somehow set up incorrectly. However, the second picture makes it look like you did everything right.

At this point, the only thing I can think of would be to check the action groups to make sure that they all do the right thing. In particular, if the main throttle was bound to the deploy angle on the propellers, replacing the propellers could have removed or changed that binding.

 

[Sydd]

Yeah they're setup properly, the thing is the main throttle changes the angle from parallel (0) to 35 degrees and it should increase thrust the same way on both engines, but it doesnt

One engine is going to thrust forward in the around 15° or so and then thrust backward around 30°

And the CoL issue with just a slight angle on the wings and then propellers acting weird makes me think it's just a bug. I built a plane that looks differently, closer to a grumman goose and it works now

Edited January 16, 2023 by Sydd