Rovers? Any tips?

[DaElite101]

So, rovers have been fairly difficult for me to build so far. I fixed the reaction wheels so they don't make my rover stand up on 2 wheels. But my latest rover on Minmus has a difficult time getting over slopes. Is there anything I can do to fix this, besides giving my next rover a fuel tank and engines? I have researched Field Science but not Advanced motors yet.

[foamyesque]

Pictures would help. That said, one thing you can do is boost the friction slider higher, which gives your wheels better grip on slopes. Some downforce from RCS units might help, too, but has obvious endurance problems.

[bewing]

Widen the stance on the wheels. Different wheels have different amounts of power, so if you don't have enough then think about changing wheels (or adding more). Maximize the friction and brakes on low-gravity bodies. Go over sharp angles slowly (like the ones at the edges of the Minmus Lowlands). And adding a rocket motor is a very smart thing to do -- especially on Minmus.

 

This is my lowest-tech minmus rover:

Spoiler

 

Edited August 5, 2016 by bewing

[Foxster]

Here's something that is very fast and really hard to tip over even on Minmus...

Craft file: https://www.dropbox.com/s/k45tbf6yxpmlbii/Ion rover 1.craft?dl=0

It has the added bonus of being able to make orbit...

Edited August 5, 2016 by Foxster

[Zhetaan]

@Geschosskopf, I think, is the expert on this (hence the summons), but this is what I know:

Shut down the traction control on your wheels.  As I understand it, traction control in KSP works as in real life; i.e., it takes power away from wheels that slip (unlike real life, it does not transfer that power to the ones that grip).  The problem is that despite the fancy animations, the wheels code-wise are parts that just drag across the ground, so KSP has no good way to tell whether they're slipping or running correctly.  As you try to go up a slope, the wheels have less power (because they're fighting gravity), but KSP's traction control only sees this as lost power and assumes it's from a slip.  So it responds by taking power away from the wheels.  This causes the wheels to be even less effective ... which KSP sees as a slip.  So it takes more power away from the wheels.  Eventually, you stop.

I am not certain whether you can shut off traction control in-flight or if you have to do it in the VAB, but try it and see how things go.

[Geschosskopf]

18 hours ago, DaElite101 said:

So, rovers have been fairly difficult for me to build so far. I fixed the reaction wheels so they don't make my rover stand up on 2 wheels. But my latest rover on Minmus has a difficult time getting over slopes. Is there anything I can do to fix this, besides giving my next rover a fuel tank and engines? I have researched Field Science but not Advanced motors yet.

As @Zhetaan says, for any rover intended for use out in the field where it has to climb hills, set Traction Control to zero.  If you try to climb a hill with Traction Control > 0, you'll never make it.  Traction Control is useful only if you're trying to do laps around and between the KSC buildings at high speed.

Now, that will certainly help you, but it's not the full story for Minmus.  Minmus has like no gravity, and wheels rely on gravity to work because gravity creates the necessary friction between the wheels and the ground.  Without this friction, you can';t accelerate, turn, or stop very well using the wheels.  So, you have to design and tweak the rover to get a good grip on Minmus.  You have 2 main things you can do here:  provide downforce and tweak the wheels.  Or a combination of both.  Both at the bottom line increase the friction between Minmus and wheels, so the wheels work better.  We'll discuss tweaking wheels first.

Wheels have 4 tweaks you can play with:  Traction Control (already discussed---set to zero as a general rule), Friction, Spring, and Damper.  The last 3 are actually useful but they default to working in Kerbin's gravity, so if the gravity is significantly different, you need to make some changes.  Friction is the 1st thing to look at.  To change it, you usually have to click a button that says "Override Friction" or some such before the slider even appears.  If the gravity is lower than Kerbin's, increase the Friction slider.  If it's higher, decrease it.  The default (for Kerbin) is 1 and often you can increase this up to 5 (depends on the wheel it seems).  I've found that 2 is great for Mun and 3-4 works fairly well for Minmus.  Use the highest setting for the things with even less gravity than Minmus.

Spring and Damper (shock absorbers) are 2 halves of the same whole (the suspension) so should generally have the same value.  If you change one, you should usually change the other to match.  If you increase Spring without increasing Damper, you rover will bounce high and frequently under any gravity.  If you increase Damper without increasing Spring, you make the suspension more stiff, which can result in breakage, explosions, tumbles, and such.  Anyway, both create internal forces between the wheels and the vehicle proper, and these default to be scaled to Kerbin's gravity.  So if you do anything to these settings, generally you tone them down a bit for gravity < Kerbin, and up for gravity  > Kerbin.  HOWEVER, unless you're trying to go as fast as possible, expect to jump moguls, etc (Elcano?). you don't really have to mess with either of these very often.

So that's wheel tweaks.  As an alternative and/or along with, you can create downforce.  This normally isn't necessary on atmospheric worlds because they've got enough gravity to give you enough friction anyway, so no need for spoilers unless you're trying to set the land speed record on the KSC runway.  Downforce is for the low-gravity, airless moons.  What you do here is mount an ion engine on top (usually over the CoM) to thrust the rover down onto the surface.  An ion engine usually provides sufficient thrust and the fuel lasts forever, but then you have to provide the electricity, which might be a problem at night.  If you have downforce from an engine, then all bets are off for the proper wheel tweaks for a given amount of gravity.  You'll have to figure that out for yourself.

 

6 hours ago, Zhetaan said:

@Geschosskopf, I think, is the expert on this (hence the summons), but this is what I know:

I'm hardly an expert but thanks anyway

 

6 hours ago, Zhetaan said:

I am not certain whether you can shut off traction control in-flight or if you have to do it in the VAB, but try it and see how things go.

Unless things have changed recently, you can tweak all wheel settings in flight.  This includes enabling/disabling/reversing sterring, enabling/disabling mortors, and all tlhe Traction Control Friction, Spring, and Damper settings.