Plane wheels are bad

[memes in space]

I'm going about 50 m/s and they start spinning out of control. ????

 

EDIT: Okay clearly something is wrong with my plane, because the stock planes work fine. Any idea what's happening?

Edited January 8, 2017 by memes in space

[sal_vager]

Perhaps the wheels are not on straight? We really need your craft file to test, you could put it on dropbox.

[AeroGav]

For each landing leg -

1. press 3 to select "rotate  part" mode

2. Make sure the circular indicator to the right of the symmetry mode indicator shows you are in angle snap rather than fine rotation mode.

3. select landing leg

4. press F to toggle between absolute and local rotation modes.   Make sure you're set to absolute then -

5. rotate the leg one notch to the left , then snap it back to centre again.  This will remove any stray rotation it may have picked up ensure the wheels face dead ahead.

Also ,  (tip from @bewing)  you can use the friction control override to make sure the wheels aft of CoM have more grip than the front.

Finally,  bear in mind high takeoff and landing speeds aren't essential, even for spaceplanes.  A low performance career mode starter plane should probably be lifting off below 30 m/s.    Even this supersonic one isn't that "hot" in the circuit

https://kerbalx.com/AeroGav/Ghoul

Even this long range nuclear SSTO handles decently at low speed

 

 

Edited January 8, 2017 by AeroGav

[foamyesque]

Without seeing a picture of the plane in question I can't say for sure but this issue is almost always caused by an interaction between your aerodynamics and your wheel placement. Your center of drag is ahead of your center of mass, and the usual cause for that while on the ground is your rear gear losing traction and your front gear being pressed down.

 

Fire up some screenshots

[ForScience6686]

One thing I've noticed, planes become a bit unstable on the ground when they are reaching the point where lift will over come gravity.  So if the plane starts to veer (granted everything is aligned properly) it's time to pull back and get in the air.

[AeroGav]

52 minutes ago, ForScience6686 said:

One thing I've noticed, planes become a bit unstable on the ground when they are reaching the point where lift will over come gravity.  So if the plane starts to veer (granted everything is aligned properly) it's time to pull back and get in the air.

Is it wheelbarrowing?    If the front leg reaches further down than the others (often happens if the main legs are same size, but mounted to wing) then the mains lift off first and due to CoL being behind CoM, it rotates forward and keeps nosewheel on the ground.  Not a stable config for a unicycle.

[ForScience6686]

13 minutes ago, AeroGav said:

Is it wheelbarrowing?    If the front leg reaches further down than the others (often happens if the main legs are same size, but mounted to wing) then the mains lift off first and due to CoL being behind CoM, it rotates forward and keeps nosewheel on the ground.  Not a stable config for a unicycle.

Exactly my thoughts, you made it so much more simple to understand.