How do I design this rover in a way that it doesn't flip over when braking on the Mun?

[smjjames]

I'm just wondering if there is a way to design this rover so that it doesn't flip over when I brake on the Mun? Also, ways to make it control better at higher speeds. I know I could just add more weight or just go slower, but I'm wondering if theres any design ways that can help.

Part mods that I have (just for general info and to show what I do have)

KAS

MechJeb

Hangar mod 2.0.2.2

B9 Aerospace

procedural fairings

Edited January 16, 2015 by smjjames

[Itsdavyjones]

One way is to disable the front wheels ability to brake. Had the same problem with my airplanes upon landing. Another way is to have a monoprop rocket or RCS to push the rover down while braking.

[KerbMav]

Make the rover longer, disable brakes on the front wheels (not sure if this requires TweakableEverything or some other mod), use an anti-lock braking system (do not keep the key pressed ), add some reaction wheels and a probe core/pilot with SAS capablity.

[smjjames]

How do I disable the brakes for the front wheels? Only options I have are 'lock steering', 'disable motor', and 'invert steering'.

I've also noticed that using a 6-wheel configuration helps some with control and also with the flipping over (mainly because heavier)

[jman508]

you could try to move the center of mass closer to the ground.

im not good with off world rovers. so yeahhh

if your looking for fast breaking you could put a little rod pointing out of the front of the rover you could put a wheel or 2 on it and then it wouldn't flip when breaking.

you could also make the rover just bigger. the wider and longer it is the better. then it becomes harder to flip.

[tomf]

I normally put reaction wheels on my rovers. When braking, accelerating and steering you can apply teh counteracting force with the reaction wheels to keep the rover level.

[smjjames]

I normally put reaction wheels on my rovers. When braking, accelerating and steering you can apply teh counteracting force with the reaction wheels to keep the rover level.

How do you do that? I thought the reaction wheels were automatic. I'll give the reaction wheels a try.

[eddiew]

Reaction wheels, SAS on, and linear (LIN) docking mode. Docking mode will try not to let you flip, you can basically bang it to 4x timewarp and as long as you stay under your wheels' maximum speed, it'll all work out I have some tiny rovers (fit in a 1.25 fairing) that never fall over, just because I drive them in this mode.

Rotational (ROT) docking mode will let you flip it back over if you do still manage to get its legs in the air.

[Anquietas314]

How do you do that? I thought the reaction wheels were automatic. I'll give the reaction wheels a try.

Drive the rover using linear docking controls. The reaction wheels (with SAS on) will automatically try to stop the rover from rotating, meaning you don't flip as easily . If it still flips afterwards, then you can add the linear RCS thrusters pointing upwards (to help push the thing to the ground) or make the rover longer and wider.

EDIT: ninja'd

[Foxster]

Sounds like good advice above but I usually just stick some landing gear well out the front and as it tips forwards that saves it from going over.

Some RCS can be handy for righting an upside down rover.

[RexKramer]

Using smaller wheels might help in a couple of ways also. It will help keep your center of gravity lower, and less grip may induce less torque to the vessel during braking.

I also like the wheels you are using, but sometimes smaller wheels make more sense. The rover you have in the original post is very light, those large wheels are overkill IMO.

[smjjames]

I was using the bigger wheels because better traction on slopes, but okay.

[Fearless Son]

Traction is mainly a product of gravity, the weight of the rover pushing downward on the surface it is rolling over. Heavier rovers need more traction to move up steeper slopes. However on the Mun, all that is much lower, and traction runs into diminishing returns. Given a light enough rover, you do not need too much traction to climb gentle slopes.

[smjjames]

I meant the steeper slopes.

Anyways, I decided to completely start over because one of the side struts somehow connected itself into the battery and other stuff that KSP registered as being connected to the battery, couldn't figure out how to get it off, so I just decided to redo the whole thing.

[KerbMav]

Waaait a minute - docking mode changes the behaviour of SAS? Or do you just mean that the linear controls are safer?

I usually remap the keys under the rover tab in the settings to the arrow keys (unbinding the camera too of course!) and use them to drive around.

[Anquietas314]

Waaait a minute - docking mode changes the behaviour of SAS? Or do you just mean that the linear controls are safer?

Not exactly. Basically, by using linear docking mode, pressing W just means "forward" and not "rotate in specific direction blah and go forward". Remapping the controls is of course an alternative way to do that, but docking mode is less of a hassle tbh.

[Laie]

How do I disable the brakes for the front wheels? Only options I have are 'lock steering', 'disable motor', and 'invert steering'.

"Disable Brakes" is only available in the hangar during assembly. As your rover is already in the field, your only options are a) starting over or editing the savegame in some way (swapping vessels, or just retroactively disabling the brakes through savegame edit). This kind of savegame-editing isn't complicated, all it requires is a text editor and some common sense.

[cantab]

"As your rover is already in the field, your only options are a) starting over or editing the savegame in some way (swapping vessels, or just retroactively disabling the brakes through savegame edit).

Or c) Tap the brakes, don't hold them.

Or perhaps best of all, d) Don't use the brakes to slow down, use reverse! That's much gentler than braking.

[eddiew]

Not exactly. Basically, by using linear docking mode, pressing W just means "forward" and not "rotate in specific direction blah and go forward". Remapping the controls is of course an alternative way to do that, but docking mode is less of a hassle tbh.

That. In LIN docking mode, forward (W) will leave it to your wheels to go forward, without pushing the nose down.

It's very noticable with LIN, and SAS either off or on however - SAS really fights to keep your rover in the same plane it was when you first turned it on, i.e. the right way up with all wheels planted, facing the same direction. Without SAS, you'll bobble around over the terrain as before. You'll need to toggle it on/off briefly as terrain inclination changes and your wheels start lifting off, or in order to change course. You can also use docking ROT mode (spacebar) to have SAS torque make the turn, rather than rely on the traction of your wheels, but this can lead to a major side-skid and potential flip.

For comparison with all the people saying 'make it longer/wider,' here is my standard unmanned Mun rover:

One probe core, one round battery, one small reaction wheel. Tiny wheelbase. Never flips because the torque of that little wheel is so huge compared to his tiny 370kg body Small fuel tank is just enough to get him onto Mun's surface from LKO (barely) then ejects. Rovers are so much more fun in docking mode. You stop fearing them and start driving them 20km to a new survey mission, because it was already 'close enough'

Edited January 16, 2015 by eddiew

[smjjames]

Thanks for the help guys.

[Anquietas314]

Without SAS, you'll bobble around over the terrain as before. You'll need to toggle it on/off briefly as terrain inclination changes and your wheels start lifting off

SAS was changed a while ago (0.21?) to allow the ship (or in this case, rover) to accommodate user input or large unintended attitude changes (steep hills for example) without having to toggle it. Of course, it's occasionally very stupid about that ("Your plane has the pitch control to hold this attitude, but it takes ~70% control input to do it? Okay, I won't bother!"), but usually it works well enough.