Rover question, specifically wheels

[kodemunkey]

Does anyone find on the Mun / Duna that wheels just won't work?

[Trux]

Have you broken them by any chance? Could you please provide a picture so we can help

[Horn Brain]

Sometimes on the Mun I had trouble with traction. I could still drive, but not nearly as fast as on Kerbin, and the vehicle seems "jerky"- like the wheels are catching on the ground and giving me a little boost and then spinning freely and then catching again. I'm not sure what's going on. Maybe the Mun's lower gravity doesn't provide enough normal force to the wheels and they're slipping?

Edit: I'm using the golden Apollo rover style wheels.

Edited August 15, 2013 by Horn Brain

[itsme86]

Knowing which wheels you're referring to would also help. Different wheels have different characteristics.

[Fuzzy Dunlop]

With the ruggidized medium wheels I seem to have an issue where on certain sections of terrain they give almost no grip - then on the next section they work fine. And there seems to be no logic to which sections have this behaviour so I think it might be a bug.

[katateochi]

Also which mode, staging or docking, are you driving in?

I always drive in docking mode so the reactions wheels are not tipping the rover forward. Also I always have RCS thrusters facing straight up to push the rover down for increased traction.

[boxman]

They definitely dont have as much traction on Mun especially if it is a lightweight rover. But it could also be the angle of the rover wheels, so would help if you could post a screenshot or even better a video of the issue.

[Spartwo]

It's a bug It happens everywhere.

[Kunzite]

I always drive in docking mode so the reactions wheels are not tipping the rover forward.

In the latest version of KSP you can right-click the command module and disable reaction wheels. Driving in docking mode is an old solution to a problem that is no more.

[Rufus Callahan]

The reaction wheels do help keep small rovers more stable on the surface of the mun (or wherever) while driving in docking mode, which means docking mode driving is still useful.

[Nexustrimean]

A Picture would really help.

[ZenithRising]

Just got my first rover to Mun! And yeah, I unfortunately discovered that all my Kerbin testing of the design was worthless in 1/4 gravity.

I discovered that turning off the Reaction Wheels helped a lot. But still, it was very unstable, and had trouble with traction. Any faster than 10 m/s and the slightest vector change would send it tumbling. Hills were . . . challenging. Still, it drove around a bit and (with some reloaded saves), made it back to Kerbin.

I've got a pic, and I'd love suggestions for my next version. I'd like something stable with as high a top speed as possible. I'm already figuring on getting the center of mass as low as I possibly can. And possibly making it heavier in general? Are four wheels more stable than six?

[sporkafife]

I made a large Kethane mining rig which was 3 orange fuel tanks and it could drive over to a lander with a specifically placed docking port to transfer fuel ready to be sent back to Kerbin. However, in the lower Mun gravity, the suspension didn't get pushed down as much and the docking ports no longer line up... It took hours to get it all down on the surface and build the stupid thing, now it's useless XD

[Monkeh]

Add some tiny rockets to the top facing upwards to provide some downforce.

[kodemunkey]

thats another question, how do you dock rovers?

[Monkeh]

By adding a docking port and then driving them together.

Like this:

Be careful though it ends up like this with 2 FPS:

[kodemunkey]

I've tried that, but it doesn't seem to want to let the rovers dock?

[koshelenkovv]

With the ruggidized medium wheels I seem to have an issue where on certain sections of terrain they give almost no grip - then on the next section they work fine. And there seems to be no logic to which sections have this behaviour so I think it might be a bug.

Also their suspension acts strange - suddenly springs contract fully as under heavy load and stays this for some time. Then springs fully extends and wheels lose traction and all rover jerks as if there is no suspension at all, and brakes do not work.

So far only black wheels demonstrated this behaviour.

Drive controls remapped on IJKL so not messed with WASD movements.

[zarakon]

I never really liked the new rover wheels. Nothing I've been able to make with them comes close to the performance of my old rovers that just used landing gear, rockets, and RCS

[Jackissimus]

I made a large Kethane mining rig which was 3 orange fuel tanks and it could drive over to a lander with a specifically placed docking port to transfer fuel ready to be sent back to Kerbin. However, in the lower Mun gravity, the suspension didn't get pushed down as much and the docking ports no longer line up... It took hours to get it all down on the surface and build the stupid thing, now it's useless XD

Yeah I just did basically the same thing with the same result. I have a smallish stationary kethane mining rig and a huge tanker that lands next to it and drives on the big wheels to dock with it. I even installed four docking ports each at a slightly different height, see I was thinking ahead. It didn't work though, I still can't dock with the miner. I think it's really tough to dock with these heavy things, because the magnetic force cannot pull such heavy craft together, and the ports have to be aligned just way too perfectly (not only vertically, but also horizontally and at 180deg angle).

I think I am will give up and just install KAS. I was trying to avoid it, I heard it has issues sometimes, ripping your vessels apart, I don't save very much ...

[British_Rover]

Yeah I just did basically the same thing with the same result. I have a smallish stationary kethane mining rig and a huge tanker that lands next to it and drives on the big wheels to dock with it. I even installed four docking ports each at a slightly different height, see I was thinking ahead. It didn't work though, I still can't dock with the miner. I think it's really tough to dock with these heavy things, because the magnetic force cannot pull such heavy craft together, and the ports have to be aligned just way too perfectly (not only vertically, but also horizontally and at 180deg angle).

I think I am will give up and just install KAS. I was trying to avoid it, I heard it has issues sometimes, ripping your vessels apart, I don't save very much ...

I just got my massive, at almost 47 tons empty its not the heaviest cargo I put into LKO but it is the most awkward, KMD_MK2 into LKO. I initially was going to use docking ports for the kethane transfer but I decided against it and installed KAS. My initial prototype was heavier but too unstable for short VTOL hops. The MK2 successfully hopped the length of the KAS runway and landed at about 15 m/s horizontal and 5m/s vertical. I blew out three tires on that landing and I think it is the hardest it can survive.

Here it is in the VAB before being attached to my asymmetrical launcher. My initial plan was to land it on its own fuel supply but now instead I am going to make a gantry system for my heaviest skycrane to set it down on the Mun. I just don't think 753 m/s of Delta V is enough of a safety margin to set it down under its own power.

Of course now that I have it up there I realized I didn't put a ladder on the Can. Good think for RCS packs.

[Jackissimus]

Yeah, so I just installed KAS. I feel a bit defeated, I wanted to use as few mods as possible. After all, I started this thread: http://forum.kerbalspaceprogram.com/showthread.php/39980-Oldtimers-help-me-enjoy-the-game-more!

I was labelled a purist for that thread, so I hope none of the original readers read this now ... But the stock game just becomes boring after a while. I even started using Mechjeb autopilot sometimes

[Tiron]

Also their suspension acts strange - suddenly springs contract fully as under heavy load and stays this for some time. Then springs fully extends and wheels lose traction and all rover jerks as if there is no suspension at all, and brakes do not work.

So far only black wheels demonstrated this behaviour.

Drive controls remapped on IJKL so not messed with WASD movements.

It's an interaction between the terrain and something with Unity's crappy wheel setup. I heard something about imprecision in the terrain mesh: basically, the suspension reacts as if the terrain were slightly higher or lower than what you see (and are driving on), so it pulls up/pushes down trying to conform to where it thinks the terrain is. It's only a problem when it pulls up, because it actually starts trying to pull the rover off the ground, and partially succeeds. The REAL problem there is that if you're on a hill when it happens, there's an extremely high chance you'll be rolling down said hill seconds later if you're at any kind of speed.

Interestingly, before stock wheel were added I used to cruise around with the old Bigtrak rover, and it was actually FASTER on the Mun than on Kerbin. Over twice as fast, in fact. I got it up over 90 m/s one time. But then again, it was completely immune to damage, so when it'd end up in a tumble after catching some air (and at that speed on the mun it catches air off every tiny rise), nothing came of it other than stuff on the outside of it getting broken. I dropped one from LMO one time by accident, and it survived just fine.

But then, I don't think the Bigtrak HAD a suspension, and I also think that's why it never had any of the problems the current rover wheels do. Even TT's Modular Multiwheels have the same suspension problems as the stock wheels, so it's clearly a Unity problem. I've tried disabling the suspensions on the stock wheels to test if I'm right, but only succeeded in making the wheels not work at all, so I'm kinda stuck.

Edit:

Some interesting, semi-random facts I discovered while trying to build a safe-esque manned rover in 0.20:

TR-2Ls have a tremendous amount of friction, which is a large part of why they work so well, with basically zero ability to slip. This includes even the non-tread parts of the wheel, like the sides. One of the results of this is that if you catch air and then come down in a direction that doesn't allow them to rotate, they basically stop dead on the spot, which causes an ENORMOUS G-Force spike.

At about 30-35 m/s ish, this spike gets strong enough to rip the wheel off the rover entirely, and possibly knock the Kerbals out of their command seats just from the jolt.

At around 50 m/s, the jolt from even regular structural members hitting the ground gets strong enough to start breaking off radially attached parts. Things like RTGs, Probe cores, and command seats (the wheels and Kerbals are probably long gone at this point, but only a direct impact will take the wheels off even at this speed.)

From further testing in 0.21, when the new terrain made it worse:

Rovemax 1s basically can't climb hills. And are still the first thing to break off if you go tumbling down one.

Edited August 16, 2013 by Tiron

[Landge]

I found you can attach struts to help anchor wheels to your rover. The big wheels might not let you start the strut on the wheel but you can make the ends connect.

Here you can see how I crossbraced the big wheels at their support beams.

The ruggedized wheels will let you start the strut on them. Here I've crossed braced the wheels for improved handling so they won't spaz out as often.

Under Brakes Action Key settings, remove brakes from some of the wheels. On multi-wheeled rovers I'll remove brakes from the front and rear, leaving the middle wheels to do all the braking. Helps reduce the rover flipping head over heels when braking in low gravity.

Under Gears Action Key settings you can turn off turning your middle wheels. Just let the front and rear wheels do the turning keeping the middle wheels straight.

Edited August 16, 2013 by Landge

[Tiron]

I found you can attach struts to help anchor wheels to your rover. The big wheels might not let you start the strut on the wheel but you can make the ends connect.

Here you can see how I crossbraced the big wheels at their support beams.

*snip*

The ruggedized wheels will let you start the strut on them. Here I've crossed braced the wheels for improved handling so they won't spaz out as often.

*Snip*

Under Brakes Action Key settings, remove brakes from some of the wheels. On multi-wheeled rovers I'll remove brakes from the front and rear, leaving the middle wheels to do all the braking. Greatly reduces the rover flipping head over heels when braking in low gravity.

Under Gears Action Key settings you can turn off turning your middle wheels. Just let the front and rear wheels do the turning keeping the middle wheels straight.

I actually did that with the TR-2Ls, and it didn't help a bit. Their inability to skid at all just makes them generate way too much force, it seems. And it doesn't affect the suspension issue at all. Now if your problem were the joint between the rover and the wheel flexing, it might help. Might, there's some kind of problem when placing rover wheels with SPH symmetry that causes the second one not to attach properly...