Suspension settings

[stormdot5]

I've been trying to test out the functions of the suspension setting and thought it would be good to share it here. I tested by using a MK2 Fuselage with wheels on, along with Vernier engines to induce oscillations/simulate bumps. I also dropped it from a launch clamp. I tested with the fixed, and small folding gear. Kerbal engineer was required for precise ride height as it measures surface altitude to centimeters.

 

Spring strength

I assumed this would vary the ride height depending on the setting, and therefore set the suspension travel available. It turns out that setting it below a certain point, depending on the load on the spring, will cause the vehicle to sag or bottom out. This means that there is a certain minimum setting for the weight on your landing gear. If you set it below this then you won't get full travel / bottom out, and your plane is likely to be unstable.

Trying to test the effects of setting it higher showed me that landing gear dropped vertically is incredibly resilient. Once you have the minimum setting as above then it appears you are likely to be able to smash your plane into the ground at any reasonable speed and get away with it. Setting it higher may give you more leeway with high speed impacts with the fixed gear as it may clip through to the ground. Setting it too high for the weight of your plane can lead to it breaking on impact.

 

Damper Strength

This does function as you would expect, dissipating the energy in the suspension over time. Setting it too low can cause the vehicle to become unable to shed the energy from driving. You can determine this using RCS to disturb the vehicle and seeing if settles back to a stable state. It is very obvious when rolling around whether it has enough damping.

Setting this further up can cause the suspension to respond slowly, possibly causing issues with uneven runways or terrain at speed. Setting this high in conjuction with spring strength can lead to brittle landing gear, stiff, but likely to break on impacts.

Peculiarly, setting it to the maximum setting, or close to it, can cause similar effects to too low, where the vehicle is unable to stabilise and apparent phantom forces keep vibrating it on it's wheels.

 

Hopefully some people might be able to use this information to help set up their craft. I think it should be as simple as testing minimum sping strength for the weight using ride height. Then the minimum damper setting for stable rolling. Then if your craft has issues with landing, add spring strength to address breaking landing gear, and damper strength to reduce bounce, in small increments.