How to prevent my car from rolling over when turning (and how to tune the wheels)

[HyperDraco]

Good day,

I like cars... quite a lot. I like making cars too, in KSP and modding the ones I own in real life too. However my automotive creations in KSP all have a tendency to roll over and send my framerates into the abyss if I do as much as touch the yaw controls at a speed higher than standing still or 10 m/s. Then there's the issue of wheel tuning, I try to change the parameters as much as I can understand. But alas, sometimes it just fails and makes my car start drifting madly. Point is, all of my cars are quite well optimised to stay on the ground, Low CoM, Good Downforce and a somewhat medicore wheelbase. I have no clue why they keep turning (in the shape of an arc) over and crashing. I have trying to solve this for months now and to no avail. 

Thanks for the help,

Hyper

(I can post the craft files and images if required)

[ubkwy]

You could try adding some monopropellant thrusters and using RCS to keep your vehicle stable, not 100% sure it will work though.

[Geonovast]

I've found that having any reaction wheels on the rover set to 'SAS only' helps.  That way they'll try to keep the rover in position instead of apply torque from your input.  I also put that setting on an action group toggle, so that if I end up jumping in an low gravity environment, like say on Minmus, I can quickly toggle the setting and orient the thing correctly before landing.

[Okhin]

I'm not using pitch / yaw / roll controls for rover. I've mapped wheel acceleration and wheel steering to my numeric pad on my keyboard. that way I do not move the mass of the vehicle when turning, just the wheel.

A SAS module definitely helps. Building wide cars with low CoM is also very helpful.

[HyperDraco]

Thanks for the suggestions

On 11/2/2020 at 8:30 PM, Geonovast said:

I've found that having any reaction wheels on the rover set to 'SAS only' helps.  That way they'll try to keep the rover in position instead of apply torque from your input.  I also put that setting on an action group toggle, so that if I end up jumping in an low gravity environment, like say on Minmus, I can quickly toggle the setting and orient the thing correctly before landing.

I do have SAS Wheels (about 4 of them) but I haven't set them to SAS Only, I'll try that right away.

On 11/2/2020 at 8:49 PM, Okhin said:

I'm not using pitch / yaw / roll controls for rover. I've mapped wheel acceleration and wheel steering to my numeric pad on my keyboard. that way I do not move the mass of the vehicle when turning, just the wheel.

A SAS module definitely helps. Building wide cars with low CoM is also very helpful.

That's quite interesting (smart frankly), I will try that out too now.

On 11/2/2020 at 8:27 PM, ubkwy said:

You could try adding some monopropellant thrusters and using RCS to keep your vehicle stable, not 100% sure it will work though.

I tried that on my car earlier, it worked kind of but at super high speeds (200+ m/s) it gets unstable with RCS. (Yes this is an incredibly quick car)

[HyperDraco]

14 hours ago, HyperDraco said:

Thanks for the suggestions

I do have SAS Wheels (about 4 of them) but I haven't set them to SAS Only, I'll try that right away.

That's quite interesting (smart frankly), I will try that out too now.

I tried that on my car earlier, it worked kind of but at super high speeds (200+ m/s) it gets unstable with RCS. (Yes this is an incredibly quick car)

@Geonovast I tried the SAS Only option, it helped slightly.

@Okhin I remapped the wheel controls and it helps when drifting. It helps a lot.

@ubkwy RCS made my thing blow up somehow so I must be doing something wrong here.

Any suggestions on how I should adjust the wheel settings? I currently have Spring and Damper set to auto, Friction control set to 4.3 on the front and 5 on the rear. Auto traction on the front and 5 on the back.

[king of nowhere]

14 hours ago, HyperDraco said:

I tried that on my car earlier, it worked kind of but at super high speeds (200+ m/s) it gets unstable with RCS. (Yes this is an incredibly quick car)

200 m/s is 700 km/h, or 400 mph.

is it really surprising that at such speed the car is unstable, and that you cannot control it? it's already a wonder you don't break your wheels. I don't think there's any realistic way, short of glitch exploitation, to keep anything stable that fast.

[HyperDraco]

5 minutes ago, king of nowhere said:

200 m/s is 700 km/h, or 400 mph.

is it really surprising that at such speed the car is unstable, and that you cannot control it? it's already a wonder you don't break your wheels. I don't think there's any realistic way, short of glitch exploitation, to keep anything stable that fast.

I mean it definitely does stay stable on the runway, I used a massive amount of down force through spoilers, vents and wings (along with the general body shape) to keep it pressed at higher speeds. In that it's perfect, for a straight line it can go from 0 to 320 to 0 in about 16 seconds (this is in m/s).  However if I try to turn above 20 m/s it starts tilting over and blows up consequently.

Furthermore in the straight run, it faces no issues, it's only when I turn it that it faces these issues. I also have some sort of active aero in this car (the regular untouched control surfaces) work well.

Edited November 5, 2020 by HyperDraco

[HyperDraco]

Here are some photos for reference to the car's design.

Edited November 5, 2020 by HyperDraco

[Mikenike]

I personally think that the car may not be wide enough. This behavior can occur with very thin cars, because the wheelbase compared to each other are too close, so bring your wheels out a little. It may look hyper ugly, but it may help. Also, try clipping wheels together, or near each other. If you want, clip those basic steerable wheels (early tech tree ones) to the sides of the car, it may help. As a person who got a 2.5m rover up past Mach .9 it can help to add wheels to prevent flipping.

[king of nowhere]

i would never try to make a steep turn above 10 m/s on a low gravity, even with a rover i consider stable.  my rover stops at around 40 m/s, and at that speed i would never try to turn except by the smallest possible increments. and it would take a huge amount of time braking.

it's normal. it's how physics work.

[Mikenike]

16 minutes ago, king of nowhere said:

i would never try to make a steep turn above 10 m/s on a low gravity, even with a rover i consider stable.  my rover stops at around 40 m/s, and at that speed i would never try to turn except by the smallest possible increments. and it would take a huge amount of time braking.

it's normal. it's how physics work.

Its on KERBIN. For now at least. @HyperDraco doesn't need answers on Minmus, yet.

[Okhin]

4 hours ago, Mikenike said:

I personally think that the car may not be wide enough. This behavior can occur with very thin cars, because the wheelbase compared to each other are too close, so bring your wheels out a little. It may look hyper ugly, but it may help. Also, try clipping wheels together, or near each other. If you want, clip those basic steerable wheels (early tech tree ones) to the sides of the car, it may help. As a person who got a 2.5m rover up past Mach .9 it can help to add wheels to prevent flipping.

Instead of bringing your wheels out, you can try to aim for a more trapezoidal shape. Keep the front wheel as is, it helps to turn, but widen the rear wheels. Also, maybe tilt them a little bit on the car axis, to win a little bit more of ground surface (in which case you do not want them to steer)

[HyperDraco]

2 hours ago, Okhin said:

Instead of bringing your wheels out, you can try to aim for a more trapezoidal shape. Keep the front wheel as is, it helps to turn, but widen the rear wheels. Also, maybe tilt them a little bit on the car axis, to win a little bit more of ground surface (in which case you do not want them to steer)

I have tried this with the final iteration of the craft and it does seem to help.

5 hours ago, Mikenike said:

Its on KERBIN. For now at least. @HyperDraco doesn't need answers on Minmus, yet.

The car is solely meant to be a Kerbin racer for now.

7 hours ago, Mikenike said:

I personally think that the car may not be wide enough. This behavior can occur with very thin cars, because the wheelbase compared to each other are too close, so bring your wheels out a little. It may look hyper ugly, but it may help. Also, try clipping wheels together, or near each other. If you want, clip those basic steerable wheels (early tech tree ones) to the sides of the car, it may help. As a person who got a 2.5m rover up past Mach .9 it can help to add wheels to prevent flipping.

I have tried the clipping wheels part with the final (or most recent) iteration of the car and it seems to help with super-high speed stability. However turning wise, it doesn't help all that much. I might bring the wheels out a bit and might adjust the car shape to make it look less hyper ugly. So I definitely will try doing that soon. I have put one of the early game wheels (smaller due to TweakScale) on the front of the car to act as sort of bumper guard during braking, I will try that on the rest of the body too now. I'll try the rest of these out soon.

Thank you very much, I'll try once again to see if it works. 

[HyperDraco]

22 hours ago, HyperDraco said:

I have tried this with the final iteration of the craft and it does seem to help.

The car is solely meant to be a Kerbin racer for now.

I have tried the clipping wheels part with the final (or most recent) iteration of the car and it seems to help with super-high speed stability. However turning wise, it doesn't help all that much. I might bring the wheels out a bit and might adjust the car shape to make it look less hyper ugly. So I definitely will try doing that soon. I have put one of the early game wheels (smaller due to TweakScale) on the front of the car to act as sort of bumper guard during braking, I will try that on the rest of the body too now. I'll try the rest of these out soon.

Thank you very much, I'll try once again to see if it works. 

I just tried expanding the wheelbase and decided to make an entirely new craft instead but on the same platform as my other car but with individual wheel KSP-grade suspension (by which I mean you can toss the craft off of the top of the  VAB and land it flat on the  wheels without a single thing breaking. I know but hey Cubic Octagonal Struts and Ant Engines are OP suspension wise).

Adding outer wheels and clipping more wheels helped a lot. Now I have a 25% higher chance of recovery from imminent death when my craft hits 90 degrees. It's an increase from the previous 0% chance.

[Klapaucius]

Another thing you can do is to right click the wheels and lower the slider on the friction control.  Especially if you are using the WASD keys as opposed to a joystick, you are stuck with all or nothing as far as turning the wheels. Knocking off some of the friction will allow them to slide and help ameliorate the flipping.  You occasionally spin out, but at least you won't destroy your vehicle.

Edited November 11, 2020 by Klapaucius