Green Vectors

[Redacted]

Something is not balanced, I'll do a swinging arm test and post a video.

[Redacted]

Here is the Swing arm Test-Stand, clearly something is bugged here. From what I can see the entire assembly is being twisted from both sides yet one side becomes dominant causing the entire stand to Yaw. In flight, I'm seeing the exact same phenomena regardless of setting, part placement or symmetry.

Note: The entire assembly is mirrored then symmetry removed to allow for CW and CCW rotations.

 

While for an Aircraft counter rotating props that are not over the crafts center-line will cause significant Yaw. While for helicopters it may produce Roll or Pitch thus causing the cyclic action to fight to maintain stability. This is why your seeing a 20 mps loss on your copter.

Edited April 2, 2020 by Redacted

[XLjedi]

@Redacted  Do you happen to have a link to the craft file?

[AHHans]

2 hours ago, Redacted said:

Here is the Swing arm Test-Stand, clearly something is bugged here.

Yes, if you look at the yellow and purple vectors you see that one rotor generates more lift than the other. AFAIK the helicopter blades stall at a rather low angle of attack, so it might be that the "retreating" rotor stalls, generates less lift, and "retreats" even faster. Does this also behave like that when you set the blades to a low pitch (deploy angle)?

[AHHans]

P.S. I just made my own test, just like yours. (With the small helicopter blades.) And indeed at large deploy angles it rotates (yaws), but at low deploy angles it slows the rotation to a stop. For my "craft" the border was at about 10 degrees deploy angle: above that it will start to rotate, below that it will stop.

Another issue is that it will always rotate in the direction indicated by the green arrows. If it would be really only an instability issue initiated by random motion, then it should randomly rotate in one or the other direction. So there seems to be some systematic asymmetry there with clockwise and counter-clockwise rotating rotors. But it's not a large force, just strong enough to get the craft out of its balance point.

[Edit:] Hmmmm.... maybe it is the green vectors. Maybe the game engine only displays vectors if there is some force and SQUAD introduced some tiny, artificial phantom force in order to get the game engine to display these vectors. Does anyone know how the vectors are drawn?

Edited April 2, 2020 by AHHans

[XLjedi]

49 minutes ago, AHHans said:

P.S. I just made my own test, just like yours. (With the small helicopter blades.) And indeed at large deploy angles it rotates (yaws), but at low deploy angles it slows the rotation to a stop. For my "craft" the border was at about 10 degrees deploy angle: above that it will start to rotate, below that it will stop.

Another issue is that it will always rotate in the direction indicated by the green arrows. If it would be really only an instability issue initiated by random motion, then it should randomly rotate in one or the other direction. So there seems to be some systematic asymmetry there with clockwise and counter-clockwise rotating rotors. But it's not a large force, just strong enough to get the craft out of its balance point.

[Edit:] Hmmmm.... maybe it is the green vectors. Maybe the game engine only displays vectors if there is some force and SQUAD introduced some tiny, artificial phantom force in order to get the game engine to display these vectors. Does anyone know how the vectors are drawn?

Did you try reversing the engine rotation and blade orientation on both engines to see if it then pulled in the opposite direction?

When I did this on my craft, it continued to roll in the same direction... so I thought I had ruled out the green vectors as a result of why my specific craft was losing control at speed.

LOL, that was also my initial question...  @SQUAD  WTH are these green vectors?

Edited April 2, 2020 by XLjedi

[AHHans]

43 minutes ago, XLjedi said:

Did you try reversing the engine rotation and blade orientation on both engines to see if it then pulled in the opposite direction?

Well, I did try setting negative deploy angle before, and it was still rotating in the direction of the green vectors. But when I reverse the rotation of the rotors then I can change the rotation by setting positive or negative deploy angle. So from the four combinations (clockwise left or right * deploy angle positive or negative) only one makes the structure rotate opposite to the direction of the green vectors. 

[XLjedi]

@AHHans  What version of the game are you running?   You should only need to apply positive deploy angle for both CW and CCW rotation.  That was one of the changes they made for cyclic control in 1.9.1.

[AHHans]

5 minutes ago, XLjedi said:

@AHHans  What version of the game are you running?   You should only need to apply positive deploy angle for both CW and CCW rotation.  That was one of the changes they made for cyclic control in 1.9.1.

I tested this in 1.9.1. With negative deploy angle I mean that the blades on both rotors are set to negative deploy angle, so that the rotors push and don't pull without also changing the direction of rotation on the rotors.

[Redacted]

I did a swing-test using the smaller jet engines to verify that this is indeed an issue of the Rotors. Further more I think that the props are becoming disconnected from the rotor as it spins. Possibly leading to the blades fluttering about and their leading edge not facing the correct way. (loss of lift)

[XLjedi]

I'm just about exhausted with reporting errors on this game...

I think this will be my last attempt at helping them fix it.  I give it a very low probability of being addressed.

[XLjedi]

Ya know...  I don't know?  

I'm just not seeing a problem with yaw in this example craft? 

http://www.xl-logic.com/KSP/Example/Green Vector Rotation.craft

I would've thought the green vectors would cause this thing to yaw right or left and they just don't?

I did however go ahead and post a bug report anyway:

https://bugs.kerbalspaceprogram.com/issues/25120

Because regardless of green vector yaw, SOMETHING goofy did get introduced to the aero-modeling with cyclic controls in the 1.9.1 update that now causes the rotor blades to tilt badly in one direction or another at higher speeds.  Aside from looking stupid, I also took a performance hit and lost 20 m/s on max airspeed.

If you have additional comments and examples to share, please add them to the bug tracker!

 

Edited April 3, 2020 by XLjedi

[mystifeid]

4 hours ago, XLjedi said:

Aside from looking stupid, I also took a performance hit and lost 20 m/s on max airspeed.

Have to admit, this annoyed me too. I had quite a large stable of prop aircraft and it was disappointing to see them lose 20-25m/s. (Curiously, there was one that possibly gained speed.)

Moreover, the ducted blades performance now far outstrips anything the other blades could ever do. I made a plane for a challenge to carry full ore containers with the engine size at 50%. It was never meant to be a fast plane. But with empty ore containers and the (eight smallest ec) engines at 100% it easily hits 325m/s in a climb. Before the changes, it was all I could do to get 300m/s after a lot of attempts. Now that plane does 275m/s and my krappy ore carrier does 325 without trying!

 

Edited April 4, 2020 by mystifeid

[Redacted]

Anyone ever question why the Rotors speed limit is capped at “460”?

One phenomena I’ve seen before is a games “Tick” rate can cause problems with the internal physics and video rendering. What i mean by this is that most games update at a predetermined Hz and the video rendering is often several times faster, in some cases a whole factor faster. What this leads to is a display where parts can become detached as physical behaviors are updated too slowly to be model effectively. (Sound familiar?)

Case in point this can easily be observed in KSP as the physics-warp is enabled. Propellers will appear to separate from the Rotors, increasing their distance as the phsyics-warp is sped up. Now factor in the fact that each Propeller “Entity” is being modeled to provide lift and the whole simulation become garbage rather quickly. However in KSP’s case this garbage can happen without engaging physics-warp. Just spin up a rotor and the whole thing starts to become unstable. Which produces some rather unpredictable results as the Physics engine cant keep up with the rotational speed of the Propellers / Rotors.

Edited April 4, 2020 by Redacted
Whiskey

[Redacted]

Just did a Swing Test Stand experiment using version KSP version 1.9.0, had NO yaw deviation what so ever.

Edit will attempt to load in the craft i was working on to see if this also true here.

Edited April 4, 2020 by Redacted

[XLjedi]

3 hours ago, Redacted said:

Anyone ever question why the Rotors speed limit is capped at “460”?

That one's easy; it's a Unity limitation on max rotation speed.  The devs actually reported that one pretty early on.

You don't even need to use accel speed to see it.  Just stack two rotor engines slap a pair of blades on and watch what happens.

 

[Redacted]

So far the KSP V1.9.0 craft i am messing with is working. Will upload it in a few, then post a link.

[XLjedi]

This is pointless... all we got on our bug report is one down vote and a fanboi arguing the behaviour is "Expected".   

Which honestly, is pretty much what I expected would happen.

[Redacted]

Its the ***-hats like that that end up destroying a community. Saw the same thing with Supreme Commander Forged Alliance. In a nutshell it came down between what the fan-boys wanted and what the modders (such as my self) were offering. They wanted a predictable game so they could continue to use their exploits (in tournaments), while the modders wanted to fix bugs and submit new content. In the end all of the serious modders left, leaving the game is a very sorry state that IMO is still one big exploit. 

Here is the link to the craft: https://steamcommunity.com/sharedfiles/filedetails/?id=2047597700

Its not prefect but compared to KSP 1.9.1 its controllable.

Edited April 4, 2020 by Redacted

[XLjedi]

@Redacted  post your example craft to the bug report... it has a spot where you can upload it.

Links here are worthless.

Edited April 4, 2020 by XLjedi

[XLjedi]

11 hours ago, mystifeid said:

Have to admit, this annoyed me too. I had quite a large stable of prop aircraft and it was disappointing to see them lose 20-25m/s. (Curiously, there was one that possibly gained speed.)

Moreover, the ducted blades performance now far outstrips anything the other blades could ever do. I made a plane for a challenge to carry full ore containers with the engine size at 50%. It was never meant to be a fast plane. But with empty ore containers and the (eight smallest ec) engines at 100% it easily hits 325m/s in a climb. Before the changes, it was all I could do to get 300m/s after a lot of attempts. Now that plane does 275m/s and my krappy ore carrier does 325 without trying!

 

Due to the poor performance of the regular props, I finally started building cowl "turbo-chargers" into my warbird designs so they can fly.

This one for instance:  https://kerbalx.com/XLjedi/F5U-Crusader

Prior to the turbo charger design, I could not adequately power this type of craft.  I particularly like how they are pretty care-free in flight when it comes to maneuvering and recovering speed in the 2/3 throttle range.

[Redacted]

Looks cool m8.

[fourfa]

Oh the hidden counter rotating cowl prop is genius!

[MichaelMoore]

On 3/27/2020 at 12:27 PM, mystifeid said:

I'm gonna go out on a limb here and say that the green arrows show the amount of and direction of the torque of the engines. You've reversed the rotation of one of the engines so the green arrows should point in opposite directions. However you also reverse the deploy direction of the propeller blades on the engine with reversed rotation so that the thrust arrows (I'm assuming they're the pink ones) all point in the same direction. It looks like you might have some vibration judging by the splayed appearance of the green arrows - compare to :

Why is the left gree arrow looking backwards? I don't understand. Or it's just an exampe?

Edited April 9, 2020 by MichaelMoore
wrong words

[mystifeid]

26 minutes ago, MichaelMoore said:

Why is the left gree arrow looking backwards? I don't understand. Or it's just an exampe?

I assumed at the time it was using the right hand rule for determining torque direction.