Basic landing gears - Never stop or permanent "jumping"

[SurekUr]

Hello everyone!

I'm sorry if I re-asking this question but I can't find the exact same problem, that I have.

I just started to play KSP some days ago. Right now I unlocked the "Avilation" tech node, so I can build some simple airplanes. My planes are flyable, and controllable quite good, everything working right except the landing gears.

At this point i can work with two type of landing gears: LY-01 fixed landing gear and LY-05 steerable landing gear. If I using LY-01 (It is a nightmare to place this correctly) my plane starts permanently "jumping" like a lowrider from Sanandreas, and its not just annoying but don't get me recover my vessel since its leave the surface before i can press the recovery button. (<-May be some collision problem?) If i use a pair of LY-05 with disable steering and one steerable, my plane stops the "lowrider effect ", but an other problem come up. Its never can stop exactly. I know LY-05 has no brakes but I think - if i shut down the engines - its simple need to stop itself after a while, but no. My plane slow down to 5-8 m/s and after that its never stop exactly, but stop loosing impulse and go forward (or backward) infinitely. Also if I use parachutes to slow down my planes first its work but after its slow down the chutes get cut automaticly , and my plane re-accelerat to 5-8 m/s Its means two thing: 1.) I'm a genius who invented the perpetuum mobile. and 2.) I can not use my planes, since if I go to EVA, my airplane leave my kerbals and they need to run after like a comic book characters... Please help me, my Kerbals are sad.

KSP version: 1.4.4 (Linux build)

Thank you for your replies!

[bewing]

KSP uses a game engine called Unity. Unity uses a physics library called PhysX. Inside PhysX is a bug in their spring equation that makes wheels and landing legs (anything with a "suspension") bounce. Usually it is controllable with some tweaks in your craft design. Unfortunately, we can't fix it since the Unity/PhysX sourcecode is not public.

Planes in 1.4.4 usually bounce like that if the wheels are loaded very heavily. Try removing some fuel and the bouncing may go away.

3 hours ago, SurekUr said:

but after its slow down the chutes get cut automaticly , and my plane re-accelerat to 5-8 m/s

That really has to mean that one of your engines is still on. Or you landed on a hill.

 

[SurekUr]

Thank you for your fast reply!

38 minutes ago, bewing said:

Inside PhysX is a bug in their spring equation that makes wheels and landing legs (anything with a "suspension") bounce. [...] Unfortunately, we can't fix it since the Unity/PhysX sourcecode is not public. 

Maybe that is why God used Bullet physic when created real world. Anyway set damper strength to 2 solved my bouncing problem. Now I can use the landing gears with breaks, and finally stop my airplanes. My kerbals happy again.

 

44 minutes ago, bewing said:

That really has to mean that one of your engines is still on. Or you landed on a hill.

I landed on the runway, and on the flat grass near to the space center and I'm sure the engines switched of. Now I can stop my plane with the brakes but if the brakes are off the vehicle still self accelerate itself, with no reason (also before I "start the first stage" Its start slowly accelerated(Maybe because my front gear is at a bit lower than the pair on the back, so the lifting vector of the wings pointing bit forward when the plane is on the ground, otherwise if the velocity is 0 the lifting power is also must be 0.  Maybe a floating point number rounding problem at the datatype KSP contains force vectors can cause something like this?)). Its not big problem since I can use brakes, and the game enjoyable again, thanks to you!

[CrashyMcCrashFace]

It can be fixed by weaking the spring strength and dampening. The problem gets more complex when landing on different planets.

[bewing]

The runway is perfectly flat. That is, it does not follow the curve of the surface of the planet. So things will tend to roll toward the center of the runway. But they tend to do it fairly slowly -- at most a few m/s at a time. Planes on the grass do not accelerate by themselves, unless there is a problem with the installation of the game.

But if your kerbals are happy for now, that's good enough. And welcome to the forums!