PAW Custom Wheel Settings - Effects?

[Srpadget]

I'm looking for ways to improve the usability of the abysmal wheels (and landing gear, but esp wheels) that we've been stuck with since Version 1.3.  And I am trying to avoid the 'fun' of endless experimentation in Sandbox mode just to rediscover what people here might already know--I don't want to waste my time 'reinventing the wheel', so to speak. 

So what are those PAW "override" sliders actually for?  What is each of them supposed to control?  For instance, what's the difference between "friction control" and "traction control"?  And is there any reason I shouldn't just peg the traction, spring strength, and damper strength to their maximum values?

And for that matter, do they even do anything at all?  My findings from trying to adjust spring/damper settings on Mun and Minmus would seem to indicate they do absolutely nothing whatsoever...

My primary issues: 

1) On the Mun, larger/heavier vehicles (fuel truck massing ~40 tons fully loaded) slide sideways down modest slopes and CANNOT climb back up, even via switchbacking (where by 'modest' I mean "the most level patch of ground in the vicinity--unless I'm watching the navball indications, I have to look closely, possibly from several different camera angles, to tell that there is a slope AT ALL or which direction is downhill")

2) On Minmus, small rovers (~ 1/2 ton) bounce their suspensions in a never-ending, zero-damping spring-action.  While PARKED.  Upon physics load, the rover starts in a neutral position and then the suspension 'sags' (okay, that's as expected as physics kicks in) and then rebounds, sags, rebounds, sags, FOREVER. And I mean FOREVER, not just "for longer than I think it should".  I mean ZERO damping, no matter how long it stays in scene or how high I set the damping slider.  (Note:  so far, I've just played with the settings after arrival at Minmus.  Dunno if maybe the slider might actually do something if I cranked it during construction.)  Bouncy-bouncy-bouncy, through the suspension's full range of motion, on and on and on and on...; it looks like one of those dancing inanimate objects from a 1920s-1930s cartoon short

3) And of course there's the whole issue with landing legs being under-damped and leading to landers going through crazy gyrations, plus the surfaces of all bodies appear to be made of grease so that any object sitting on the surface will sloooooowly sliiiiiiide down any slope no matter how slight...

The second effect is annoying but kind of cute, and honestly doesn't especially impact gameplay.  The third is a bit more problematic, but hasn't caused much in the way of serious problems yet (as long as I remember to record the initial coordinates of any surface bases I intend as permanent infrastructure, and periodically update my .persistent file to move the base back to where it's SUPPOSED to be before it crawls to a steeper slope...) 

But that first one?  There's just nothing as "fun" (in the 'not at all fun' sense of the word) as watching a Jumbo tank full of LF/O just drift away down a two-degree slope and being *utterly unable* to do anything about it--even driving all 6 wheels at full "battery drain" power just changes the angle at which I drift downslope.  Grrr.

And I am really not looking forward to trying to set up a fuel refinery on Ike; I'm guessing that its lower-than-Mun gravity (hence presumably even lower traction/ground friction?) and scarcity of genuinely level ground will make Issue #1 worse, not better...

I did a quick search in Tutorials with keywords "wheel" or "wheels" in their subjects, but didn't come up with anything useful.  "Help me, Jeb-Wan Kermanobi, you're my only hope!"

[bewing]

1 hour ago, Srpadget said:

For instance, what's the difference between "friction control" and "traction control"?

Friction is how hard your wheels/legs stick to the ground (0 = ice, 5 = velcro). Traction control is another name for ABS on cars -- if one wheel loses traction, then the system automatically applies the brakes on that wheel until it stops slipping.

1 hour ago, Srpadget said:

 And is there any reason I shouldn't just peg the traction, spring strength, and damper strength to their maximum values?

If you have a rover with too much "drag" at the front, then it will be unstable and it will try to swap ends. You want highish friction on the back wheels, and lower friction at the front. But having friction be too high overall can result in having your rover roll rather than powerslide -- and if your rover is vulnerable to rolling, this can be the end of your journey. So, for a very stable rover -- you may want lower friction so that catching some air is not as dangerous.

Since Traction Control applies the brakes on the wheels while you are driving, it costs you a lot of your engine torque. If you have it set too high, you will have almost no power for climbing hills.

If your springs are too stiff, you can break your legs/wheels when you hit the ground (after a jump, for example).  If your springs are too weak, your suspension can bottom out -- and then you still can break your legs/wheels. Then again, sometimes you need really stiff springs to prevent infinite bouncing, especially on low-G CBs.

Damping is magic. There is almost always a sweet spot setting that will prevent infinite bouncing -- but it depends highly on the load of each wheel, so nobody can tell you where that sweet spot is for any specific craft.

 

[Srpadget]

On 7/4/2019 at 1:46 PM, bewing said:

If your springs are too stiff, you can break your legs/wheels when you hit the ground (after a jump, for example).  If your springs are too weak, your suspension can bottom out -- and then you still can break your legs/wheels.

Heh - my 40-ton tanker truck, on a run of 100 meters or less, at about 2-3 m/sec, along level ground (as level as I could find, anyway), between my refinery and a rocket landed nearby to refill its tanks?  If it EVER catches air (so to speak...!) for any reason whatsoever, I have WAY bigger problems than wheel settings...! 

But yeah, that's good info to spread around, for those folks who use rovers for speed runs or for long-distance exploration.

On 7/4/2019 at 1:46 PM, bewing said:

Friction is how hard your wheels/legs stick to the ground (0 = ice, 5 = velcro).

YES!  THAT'S IT EXACTLY!  Near as I can tell from that heavy tanker's behavior, the surface of the Mun is entirely wet slush over ice!  So, crank up the tanker's wheel FRICTION overall, but only moderately on the front pair of wheels, and progressively higher on each pair until friction is maxed out on the rear wheels--and then be REALLY careful to keep speeds down (though see above) when backing up (and possibly when returning empty to base).

Funny thing--I actually want/intend/prefer to play Kerbal SPACE Program as, y'know, interplanetary exploration via rocketry (yeah, I know, imagine that).  And yet, what I spend the most time tweaking, am generally most pleased by when it works out, and take/share the most screenies of?  A mining/refining operation and associated trucking infrastructure... 

Edited July 6, 2019 by Srpadget
tweaking wording for clarity

[Geschosskopf]

On 7/4/2019 at 1:59 PM, Srpadget said:

1) On the Mun, larger/heavier vehicles (fuel truck massing ~40 tons fully loaded) slide sideways down modest slopes and CANNOT climb back up, even via switchbacking (where by 'modest' I mean "the most level patch of ground in the vicinity--unless I'm watching the navball indications, I have to look closely, possibly from several different camera angles, to tell that there is a slope AT ALL or which direction is downhill")

The usual cause of sliding downhill is not having enough traction.  Be warned, however, that the higher the traction, the more EC you need to turn the wheel.

The usual cause of being unable to climb hills is having traction control turned on.  As @bewing says, this is like ABS.  If the system thinks a wheel is spinning, it will decrease power to it.  The problem is, the system decides if a wheel is spinning by comparing the expected vehicle speed for the power going to the wheel vs. the actual vehicle speed.  So, when you go up a hill, you increase power and the vehicle slows down due to gravity.  The traction control system interprets this as the wheel spinning and decreases power to the wheel.  So you go slower and apply more power.  Which looks like more spinning so you actually get less power.  This continues until the system totally prevents power going to the wheel.  For this reason, ALWAYS turn traction control OFF unless your rover is intended for the rally race around KSC's roads :).

 

On 7/4/2019 at 1:59 PM, Srpadget said:

2) On Minmus, small rovers (~ 1/2 ton) bounce their suspensions in a never-ending, zero-damping spring-action.  While PARKED.  Upon physics load, the rover starts in a neutral position and then the suspension 'sags' (okay, that's as expected as physics kicks in) and then rebounds, sags, rebounds, sags, FOREVER. And I mean FOREVER, not just "for longer than I think it should".  I mean ZERO damping, no matter how long it stays in scene or how high I set the damping slider.  (Note:  so far, I've just played with the settings after arrival at Minmus.  Dunno if maybe the slider might actually do something if I cranked it during construction.)  Bouncy-bouncy-bouncy, through the suspension's full range of motion, on and on and on and on...; it looks like one of those dancing inanimate objects from a 1920s-1930s cartoon short

The spring/damper ratio (and in fact the whole suspension system in Unity) is borked.  So this is something else you ALWAYS have to tweak.  ALWAYS take this off "auto" and manually adjust the sliders.  I find that a combination of maximum damping and 0.50 spring works well for all environments and for both wheels and legs.

In terms of what these settings do to the suspension, it's not what you'd expect.  They both seem to act like springs, with no actual oscillation-absorbing "damping".  Springs push up and are more elastic (have a higher frequency of oscillation), damping pushes down (and has a lower frequency of oscillation).  Changing the ratio effectively moves the centerpoint and reducing springs decreases bounciness.  You need SOME spring to absorb bumps and also to keep your vehicles from bottoming out under their own weight.  But you want a LOT of "damping" relative to spring to minimize bounciness.  Hence, my preferred ration of max damper and 0.50 spring.

 

On 7/4/2019 at 1:59 PM, Srpadget said:

3) And of course there's the whole issue with landing legs being under-damped and leading to landers going through crazy gyrations, plus the surfaces of all bodies appear to be made of grease so that any object sitting on the surface will sloooooowly sliiiiiiide down any slope no matter how slight...

Legs are just wheels that don't turn so the same rules apply to them for tweaking the suspension.

[Srpadget]

2 hours ago, Geschosskopf said:

The spring/damper ratio (and in fact the whole suspension system in Unity) is borked.  [snip]

They both seem to act like springs, with no actual oscillation-absorbing "damping".  Springs push up and are more elastic (have a higher frequency of oscillation), damping pushes down (and has a lower frequency of oscillation). 

But but but ... Okay, I am an engineer by profession and I think my brain just broke.

Okay, then, that explains why I had concluded the sliders didn't actually do anything.  Here I was, expecting that if I increased "damping" that it might, oh I dunno, "increase damping"!  Crazy, right?

(How do I add an 'eyeroll' to this thing...?  Ah, there it is...) 

[Geschosskopf]

7 hours ago, Srpadget said:

But but but ... Okay, I am an engineer by profession and I think my brain just broke.

Okay, then, that explains why I had concluded the sliders didn't actually do anything.  Here I was, expecting that if I increased "damping" that it might, oh I dunno, "increase damping"!  Crazy, right?

I know  .  I've got an engineering degree, too, but these days I'm only an "engineer" in it's original sense of being an operator of an "engine", specifically a fire engine ;).  But either way, damping should friggin' damp or be renamed.

As I understand things, the Unity 5 wheel system works beautifully (except for a tendency for vehicles to slide slowly down imperceptible grades) on totally "known" vehicles.  That is, the parameters of the vehicle as a whole are constant (IOW, pre-build vehicle) and it's operating in a constant environment (IOW, on Earth).  In KSP, every vehicle is a unique collection of various parts and they get sent to planets with vastly different gravity.  So the system doesn't work so well.  But hey, it's demonstrably obvious that KSP takes place in a separate universe where all 4 of the Fundamental Forces are radically different from what we know, so matter itself is utterly alien and all laws of physics work differently.  Just roll with it