Off-Road Car Design Help

[BlueCanary]

EDIT: So, I fixed the original problems of the rover (thanks everybody for the help), with a fancy suspension and reaction wheels and SAS to hold it steady, but I figured it would be worth keeping this thread as "Unanswered" since the advice in it might be helpful to other people and I would like to find different/more efficient ways to do things.

Advice given:

(I'll update this with stuff soon, don't have the time right now)

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I am making an off road utility vehicle sort of inspired by the warthog from halo, and although I've got a prototype that functions ok it's got a lot of issues, particularly with the way it drives on rough terrain.

It flips on pretty much any turn above 14m/s, which I guess will be a problem whatever I do because of the high center of gravity, but it would be nice to get some improvement on this, I was thinking maybe some sort of suspension system might help, but I haven't been able to make one that doesn't double the part count and isn't too heavy.

Also, when going over jumps it tips in the air and flips on landing, I can't see any particular reason why, but if the wheels leave the ground for even a fraction of a second the vehicle will flip on landing.

I don't want to add too much weight or parts because I want it to be air transportable and have the best acceleration it can, which is making fixing it particularly difficult.

So, what I am looking for is help with minimizing rollover and improving it's handling in general, particularly on hills or over jumps. Any suggestions are very much appreciated.

This is the craft in question:

Edited July 26, 2015 by BlueCanary

[Claw]

The CG looks plenty low in that. There are a couple things that might be contributing to the flippy-ness..

- Make sure your rear wheel steering is off. At any appreciable speed for light vehicles, rear wheel turning will cause instability.

- If you have any torque wheels hiding in there, it could be giving you troubles. If there is too much torque, it'll cause issues while you are driving because the drive keys are mapped to the same keys as rotating. So when airborne (or even a little loose on the ground) the torque can contribute to flipping. However, having some torque with stability assist on can be very helpful, so long as the torque isn't overpowering.

Also, there will be a side effect from messing with the wheel steering. The bad thing about doing this, is that those wheels have a bug in the brakes where after you right-click the wheel, the brakes are virtually non'effective. You can manually fiddle with the .craft file to fix them which I can point out to you if you want to do that. Or, if you aren't opposed to add-ons, use the ModuleWheelFix from the stock bug fixes in my sig.

Cheers,

-Claw

[BlueCanary]

The CG looks plenty low in that. There are a couple things that might be contributing to the flippy-ness..

- Make sure your rear wheel steering is off. At any appreciable speed for light vehicles, rear wheel turning will cause instability.

- If you have any torque wheels hiding in there, it could be giving you troubles. If there is too much torque, it'll cause issues while you are driving because the drive keys are mapped to the same keys as rotating. So when airborne (or even a little loose on the ground) the torque can contribute to flipping. However, having some torque with stability assist on can be very helpful, so long as the torque isn't overpowering.

Also, there will be a side effect from messing with the wheel steering. The bad thing about doing this, is that those wheels have a bug in the brakes where after you right-click the wheel, the brakes are virtually non'effective. You can manually fiddle with the .craft file to fix them which I can point out to you if you want to do that. Or, if you aren't opposed to add-ons, use the ModuleWheelFix from the stock bug fixes in my sig.

Cheers,

-Claw

Thanks for the reply,

I've got rear wheel steering on an action group so I can switch it on for parking and slow cornering and off for handling at speed, but it's still very prone to rollover. Maybe somehow changing the instant full wheel deflection to gradual application of steering could help?

Their aren't any torque wheels in there, and I have attitude control mapped to WASD and rover wheels to the arrow keys, so that shouldn't cause issues, but I've tried your suggestion of having some torque and SAS and it does keep it stable in the air perfectly, which helps things a lot. It would be nice to find a more realistic solution though.

That brake bug explains why it tips forward on braking though, I'd rather not add any more mods because my KSP crashes enough as it is though so I guess I'll just have to design to minimize the problem.

[Sharpy]

...First, remap your driving keys to something else than rotation keys. Say, unmap camera control from arrows and assign vehicle control there.

Then give your vehicle a good reaction wheel or two, turn SAS on with stability assist, and have your right hand on arrows, your left hand over Q/E and A/D. Turn with Left+Q, Right+E and if it starts flipping, compensate with A or S. Learn this control scheme and you'll be ready for Munar Derby.

[BlueCanary]

...First, remap your driving keys to something else than rotation keys. Say, unmap camera control from arrows and assign vehicle control there.

Then give your vehicle a good reaction wheel or two, turn SAS on with stability assist, and have your right hand on arrows, your left hand over Q/E and A/D. Turn with Left+Q, Right+E and if it starts flipping, compensate with A or S. Learn this control scheme and you'll be ready for Munar Derby.

I've tried this and it does help a lot, thanks.

It would be nice to find a solution to rover issues that doesn't mean resorting to reaction wheels though, does anyone know a way to do this? I just think reaction wheels are a bit of an odd way to fix a car.

[colmo]

The amount of grip wheels give when trying to skid or slide is a long-term issue. As wheels are being completely redone in KSP 1.1, apparently much for the better, you could bide your time by using the Rollkage wheels, which slide rather than roll, or TouhouTorpedo's rover wheels, though they've not been updated in a while.

Kerbal Foundries is up to date - lo-fi has put in a lot of work on wheels, they likely perform well.

Edited July 19, 2015 by colmo

[Mad Rocket Scientist]

For suspension, try mounting the wheels on radial ant engines, from between 1 to 3 should be best.

[BlueCanary]

For suspension, try mounting the wheels on radial ant engines, from between 1 to 3 should be best.

I actually just tried this, I'm really surprised how well it works, now it's much more stable over bumps than before even without SAS and torque. Was it you who came up with it or Vagani? So I know who to credit if I release something using it?

[Signo]

To avoid the flipping you could try increasing the wheelbase length and/or go 2WD while driving in high G environments like Kerbin. If you feel like messing around a little bit more you could experiment with camber too: it is a good way to slighlty increase your wheelbase. The wheels you have there are pretty powerful compared to the weight you are carrying around, in my experience they could propel a 10t rover to 25m/s.

[BlueCanary]

To avoid the flipping you could try increasing the wheelbase length and/or go 2WD while driving in high G environments like Kerbin. If you feel like messing around a little bit more you could experiment a little bit with camber too: it is a good way to slighlty increase your wheelbase. The wheels you have there are pretty powerful compared to the weight you are carrying around, in my experience they could propel a 10t rover to 25m/s.

Wait, 25m/s? What planet is that on? On kerbin the best I could get was 24.7m/s with a 1.2 tonne 4x4 quadbike (same wheels as this rover) with extra downforce from reaction wheels.

[Mad Rocket Scientist]

I actually just tried this, I'm really surprised how well it works, now it's much more stable over bumps than before even without SAS and torque. Was it you who came up with it or Vagani? So I know who to credit if I release something using it?

Vagani came up with it first, as far as I know.

[colmo]

Nice tip - the old Damned Robotics rotatrons and hinges made fabulous torsion bar suspensions, but alas the Infernal equivalents now would be much more solid.

[Signo]

Wait, 25m/s? What planet is that on? On kerbin the best I could get was 24.7m/s with a 1.2 tonne 4x4 quadbike (same wheels as this rover) with extra downforce from reaction wheels.

On Kerbin, following a pic of my 8t model, it is capable of more than 25m/s on rough flat terrain. It can turn 360° at full throttle. It fits in an Mk3 bay (alas my Mk3 SSTO does not work as intended yet). It is capable of autonomous landing (and back to orbit) on Mun. Back in 0.90 it was a lot beefier, I miss it sometimes Sorry if I did brag a few, this rover is one of my oldies (retrofitted million times) and I kinda love it.

Javascript is disabled. View full album

Edited July 19, 2015 by Signo
It's not a pic, it's a small album.

[BlueCanary]

On Kerbin, following a pic of my 8t model, it is capable of more than 25m/s on rough flat terrain. It can turn 360° at full throttle. It fits in an Mk3 bay (alas my Mk3 SSTO does not work as intended yet). It is capable of autonomous landing (and back to orbit) on Mun. Back in 0.90 it was a lot beefier, I miss it sometimes Sorry if I did brag a few, this rover is one of my oldies (retrofitted million times) and I kinda love it.

That's really impressive, do you know what about it makes it so fast? I have problems getting much above 21m/s with a purpose designed 0.6-tonne, low drag race car.

As to my original problem, I've almost fixed it with addition of suspension and torque for righting it when flipped, but I'm going to leave this thread as Unanswered to see if anyone has different/better solutions and general rover help.

[Signo]

I have a few ideas but to be honest I do not really know why. My prime suspect is that I do not use angle snap for wheels, but I could be wrong.

In case of flipping you just need to open the cargo bay to get back on your wheels.

[BlueCanary]

I have a few ideas but to be honest I do not really know why. My prime suspect is that I do not use angle snap for wheels, but I could be wrong.

In case of flipping you just need to open the cargo bay to get back on your wheels.

I tried making my own version of your design and it got up to about 24m/s, I think it might be the weight providing downforce to get more traction and the low drag of the spaceplane parts. Either way, it's a really practical, low part count design. I wonder if it would work as well in a larger version, possibly with mk3 parts to give enough space for a little garage for a quadbike or something?

[ErikTheAngry]

I initially thought those were structural pylons. Hitting spacebar would be hilarious.

[Signo]

I tried making my own version of your design and it got up to about 24m/s, I think it might be the weight providing downforce to get more traction and the low drag of the spaceplane parts. Either way, it's a really practical, low part count design. I wonder if it would work as well in a larger version, possibly with mk3 parts to give enough space for a little garage for a quadbike or something?

Nice to hear you found it helpful.

I had a try with Mk3 parts but my design was pretty ugly and scarcely functional. I am looking forward the next stock wheels upgrade to try again.

If you are looking to have extra fun you might want to try a real banking one with a short wheelbase to simulate the bike feeling.

The "bike" in the pics got just a few d/v less than the "car".

Javascript is disabled. View full album

[GarrisonChisholm]

On Kerbin, following a pic of my 8t model, it is capable of more than 25m/s on rough flat terrain. It can turn 360° at full throttle. It fits in an Mk3 bay (alas my Mk3 SSTO does not work as intended yet). It is capable of autonomous landing (and back to orbit) on Mun. Back in 0.90 it was a lot beefier, I miss it sometimes Sorry if I did brag a few, this rover is one of my oldies (retrofitted million times) and I kinda love it.

http://imgur.com/a/tENDB

That is A) Functionally awesoome, and , looks like something from Space 1999- and so N^2 awesome.

[ajburges]

That is A) Functionally awesoome, and , looks like something from Space 1999- and so N^2 awesome.

Ditto.

The mk2 cargo bay body is a great idea. The doors are perfect for a self righting mechanism with some small torque to ensure it's on a side. Should also be less twitchy than large landing legs. Also makes a good spot to hide sensitive instruments.

Dang! I swore of rovers until 1.1 but this has inspired me.

[BlueCanary]

Ditto.

Dang! I swore of rovers until 1.1 but this has inspired me.

Yeah, the new 1.1 rover wheels. What do you think we'll be getting from that? I couldn't find anything definite other than "much better" said by Squad. Personally I'm most hoping for the ability to skid for handbrake turns and drifting and a little more realism, and maybe some way to trade off torque for speed or increase power consumption or something to get faster wheels.

[Signo]

That is A) Functionally awesoome, and , looks like something from Space 1999- and so N^2 awesome.

Ditto.

The mk2 cargo bay body is a great idea. The doors are perfect for a self righting mechanism with some small torque to ensure it's on a side. Should also be less twitchy than large landing legs. Also makes a good spot to hide sensitive instruments.

Thank you guys. I appreciate.

[Starwhip]

In my experience, you don't have much to worry about in terms of roll-overs until you're going about

.

Sometimes I put landing legs in the craft to roll it back over if it flips.Other times I spam reaction wheels. Back in 0.90.0 you could turn docking mode on to lock rotation and still drive, and the reaction wheels would keep you rock steady.

Give it some control surfaces for downforce and disable their inputs. That usually will keep you planted on the ground.

Other than that, the most important thing I've learned is to not push your craft too hard. Don't try to turn it when you're going at top speed, don't go at top speed on rough terrain, stuff like that.

[BlueCanary]

In my experience, you don't have much to worry about in terms of roll-overs until you're going about

Sometimes I put landing legs in the craft to roll it back over if it flips.Other times I spam reaction wheels. Back in 0.90.0 you could turn docking mode on to lock rotation and still drive, and the reaction wheels would keep you rock steady.

Give it some control surfaces for downforce and disable their inputs. That usually will keep you planted on the ground.

Other than that, the most important thing I've learned is to not push your craft too hard. Don't try to turn it when you're going at top speed, don't go at top speed on rough terrain, stuff like that.

http://i.imgur.com/ZfQ2GmL.png

.

Well, that thing is awesome. Kind of worried how it's heading directly for a tree though. I'm going to try control surfaces for downforce again though, kind of don't want to use them on off-road type rovers because they'd make jumps less fun, but I'm making something now where I can really see them helping.

[Anglave]

On Kerbin, following a pic of my 8t model -snip- this rover is one of my oldies (retrofitted million times) and I kinda love it.

Don't suppose you'd share the craft file? I dig the idea of using the cargo bay as a body, but I don't see how you attached all the parts?