Is this why the SRV seems to spin out so badly?

[bangermsuk]

i like you to try and get an kamaz truck that weights 9.50 tonnes in space, compare to srv 4.5t that is lightweight materials/space tyres and composite chasis , really doesn't compare? or shouldn't be.

has its says on the wiki it a recon vehicle not a rally spec car and shouldn't be driven like one especially in odyssey terrain at present is terrible over populated with rocks.

Scarab

Lightweight, all-terrain wheeled vehicle designed for exploring planetary surfaces. Equipped with a turret-mounted, dual-plasma repeater weapon. — In-Game Description The Scarab is an explorer SRV produced by Vodel. It enables fast traversing of the surface of planets and moons, enter...

elite-dangerous.fandom.com

 

[AkenBosch]

That's mostly how physics work anyway, a spin out will always try to balance itself toward a full 180°, more than that will require to actively steer in the opposite way once reaching the 180° to allow the vehicle to keep the turning momentum.

Another thing I missed to mention before, is that even though I can't be sure of that, I'm rather convinced the SRV has no differential mechanism, or a fully locked one, end result should be the same. Great to get yourself out of a pickle if you only have a single wheel making contact with the ground, but absolutely terrible whenever you have to turn at speed (both wheels on the axle will be forced to spin at the same speed in a turn, even though the outermost should spin faster than the innermost, since it's traveling on a wider arc).

If anything, I always found the rover physics surprisingly accurate. It's no Assetto Corsa or Richard Burns Rally, definitely has its quirks, but not bad for something "tacked on" a spaceships game.

 

[DemiserofD]

You have way more front end grip than rear, think of it like throwing a hammer handle first.

That would make sense, except spinning out only happens when you're actively accelerating. If you just hit the handbrake, you skid sideways evenly. If what you say were true, then the added drag of the front would apply regardless of whether or not you're accelerating or using the handbrake.

 

[Riverside]

If what you say were true, then the added drag of the front would apply regardless of whether or not you're accelerating or using the handbrake.

It does But if you hit a rock or something that's going to unsettle the car. one side suddenly slows, the SRV's gonna spin.

The handbrake visually locks up all wheels, but steering ability is retained as though at least the fronts are still turning, I think the hand brake is one of the more arcade-like aspects of the SRV's handling. If you lock up all the wheels it should just plough straight on (I mean along it's last vector not necessarily the direction the vehicle is pointing), with only a rudder effect of the steered wheels carving through sand/snow to make it actually turn.

 

[DemiserofD]

It does But if you hit a rock or something that's going to unsettle the car. one side suddenly slows, the SRV's gonna spin.

The handbrake visually locks up all wheels, but steering ability is retained as though at least the fronts are still turning, I think the hand brake is one of the more arcade-like aspects of the SRV's handling. If you lock up all the wheels it should just plough straight on (I mean along it's last vector not necessarily the direction the vehicle is pointing), with only a rudder effect of the steered wheels carving through sand/snow to make it actually turn.

I mean, yeah, if you run into something it'll spin. But if you don't, you'll just slide sideways. By contrast, if you're accelerating, you'll spin and end up backwards. The same difference applies if you just set the throttle to zero; when you land, you'll generally just skid sideways.

If it were purely based on the drag of the wheels, then it would spin no matter if you're accelerating or not. In fact, if you had your Wheels turned right, then the increased drag of the front wheels should actually force you back on course. But the opposite of that happens, instead.

 

[Riverside]

I mean, yeah, if you run into something it'll spin. But if you don't, you'll just slide sideways. By contrast, if you're accelerating, you'll spin and end up backwards. The same difference applies if you just set the throttle to zero; when you land, you'll generally just skid sideways.

If it were purely based on the drag of the wheels, then it would spin no matter if you're accelerating or not. In fact, if you had your Wheels turned right, then the increased drag of the front wheels should actually force you back on course. But the opposite of that happens, instead.

I think I've already covered these points:

You have way more front end grip than rear, think of it like throwing a hammer handle first.

tbh I don't think the SRV driving model actually simulates understeer/push at all, and that alone is enough to make spinning out the driving model's only option to simulate exceeding available grip.

 

[DemiserofD]

I think I've already covered these points:

I'm not sure how much clearer I can be. If those points were true, then it would spin automatically when you side sideways, regardless of whether you're applying thrust or not.

If you are NOT applying thrust, you slide sideways, like so:

If you ARE applying thrust, instead you spin.

If this were based on the drag of the front wheels, there should be no difference at all, especially not if the wheels are turned the opposite direction. Instead, the opposite happens:

 

[AkenBosch]

Seems like you keep forgetting that rear wheels are both pushing and steering to close the turn as well.

 

[DemiserofD]

Seems like you keep forgetting that rear wheels are both pushing and steering to close the turn as well.

Even that should only counteract the observed effect.

What we see is the SRV rotating along the path of the biggest red arrow. If the back wheels thrust had an impact, it should only counteract that rotation. Even if they only served as drag, you would still see only counter-rotation.

Instead, you see only clockwise rotation, and that doesn't make any sense at all unless the outer side is being actively pulled down into the ground and accelerating the rotation.

 

[AkenBosch]

You are either using those arrows the wrong way, or we are not understanding each other at a fundamental level.

If you keep your front wheels steered to the left as in the picture, there will inevitably come a point where the rover will spin back clockwise, getting back straight forward, once it will lose enough forward momentum to have the rear axle get some grip again, leaving the left-steered front axle to roll backward along the path of least resistance. That's also what you need to do once past a 180° rotation to complete it into a 360°.
If you got into a high speed counter-clockwise spin and keep steering left and accelerating, you will definitely not rotate back clockwise, you'll just end up 180° and set wheels straight to keep driving backward for a bit, or steer to the right and complete the spin, or gain enough traction in whatever new direction the rover took and start going that way. The latter happens a lot, and can be mildly infuriating at times.

 

[Crank Larson]

You're giving FD way too much credit. I'm not a game developer or professional racecar driver but I think it's extremely suspicious that we always spin out exactly 180 degrees, every time.

Who's this we? When I spin out it's usually due to my driving and not allowing for the surface conditions (which can be completely different depending on the planet).

FD deserve full credit for the Scarab. It has given me years of top quality entertainment.

Spoiler: Sensible Speeds

Source: https://youtu.be/Hp7R7_GFg2c

 

[dekot]

Who's this we? When I spin out it's usually due to my driving and not allowing for the surface conditions (which can be completely different depending on the planet).

FD deserve full credit for the Scarab. It has given me years of top quality entertainment.

Spoiler: Sensible Speeds

Source: https://youtu.be/Hp7R7_GFg2c

I think you misunderstood something. When you do spin out due to your driving, you will always spin out exactly 180 degrees.

 

[Crank Larson]

I think you misunderstood something. When you do spin out due to your driving, you will always spin out exactly 180 degrees.

I disagree. It's entirely down to your driving.

Spoiler: 1080

Source: https://youtu.be/cfaNq8zenx0

 

[DemiserofD]

I disagree. It's entirely down to your driving.

Spoiler: 1080

Source: https://youtu.be/cfaNq8zenx0

A more accurate statement would be, you tend to stabilize backwards, rather than forwards.

 

[DemiserofD]

You are either using those arrows the wrong way, or we are not understanding each other at a fundamental level.

If you keep your front wheels steered to the left as in the picture, there will inevitably come a point where the rover will spin back clockwise, getting back straight forward, once it will lose enough forward momentum to have the rear axle get some grip again, leaving the left-steered front axle to roll backward along the path of least resistance. That's also what you need to do once past a 180° rotation to complete it into a 360°.
If you got into a high speed counter-clockwise spin and keep steering left and accelerating, you will definitely not rotate back clockwise, you'll just end up 180° and set wheels straight to keep driving backward for a bit, or steer to the right and complete the spin, or gain enough traction in whatever new direction the rover took and start going that way. The latter happens a lot, and can be mildly infuriating at times.

There are limits to MS paint, true.

What I was trying to depict was a player who has already begun a clockwise spin, and turns their wheels counter-clockwise to attempt to correct it. If drag were the most important factor, then every factor would have the opposite effect, and would result in the SRV not spinning out, and instead continuing forward, counteracting the uncontrollable spin.

But what you experience instead is an exponential growth of the clockwise turn until you're backwards. Of course, depending on how fast you're going, it can easily continue and spin you all the way around, but at that point, you're already in a serious spin, and so it's just as likely to keep spinning until it's backwards again. Landing the spin properly so you end up going forwards(without stopping completely, that is), is possible, but is far less likely than the alternative.

The only reason I can see for this to happen is that the wheels providing the most thrust actively suck themselves into the ground. Here, let me try to describe the exact scenario. Start with your Basic SRV. You are moving forward along the path of the white arrow. Drag is equal on both front sets of tires, as described by the yellow arrows.

Next, you begin to turn to the right. This causes the SRV to lean out of the turn, putting more drag onto the leading(outer) tire, and less on the inner tire. This is fine, up to a point; at this stage, the movement and drag is low enough that just by turning left, you can counteract it.

But as you continue to turn, the forces involved continue to increase until eventually, all your weight is on the left side, and the SRV as a whole pitches irresistibly right, curving around the left side of the SRV. This continues until you're going backwards, and when you're going backwards, you can't actually thrust forwards anymore. The tires just won't do it. So you lose that effect, and the SRV stabilizes, just like it would have done had you taken your hand off the throttle...only facing backwards, instead of forwards.

By contrast, if you just take your hands off the throttle entirely or hit the handbrake, you lose this force pulling the outer tires into the ground, and they instead behave as physics expects they should, and skid across the ground.

It's all a bizarre result of a vehicle with too much traction, but which is inexplicably unable to flip itself over unless actively launched by outside forces like impacting a rock or going over a ledge. What makes this all the more confusing is, this traction which causes this effect should, rightfully, also apply to the spinning of the tire, but because of how they coded it, it doesn't apply as much, resulting in the actual applied thrust getting overwhelmed by the drag with the ground.

The most annoying thing is, the fact it does tend to stabilize backwards shows it really SHOULD be possible to make it stabilize forwards, instead, but it just has never happened.

 

[Crank Larson]

, but which is inexplicably unable to flip itself over unless actively launched by outside forces like impacting a rock or going over a ledge.

Eh? The jets on the wheels simply stick the wheels to the ground better. How would you flip any wheeled vehicle without outside forces (or internal additions such as springs)?!

Rather than overthinking all this, you'd be much better getting in the Scarab and driving it until you understand how it works.

 

[DemiserofD]

Eh? The jets on the wheels simply stick the wheels to the ground better. How would you flip any wheeled vehicle without outside forces (or internal additions such as springs)?!

Rather than overthinking all this, you'd be much better getting in the Scarab and driving it until you understand how it works.

Well, think about a truck that turns too quickly at high speed. It flips over and rolls. If it doesn't do that, it typically starts to skid sideways until it stabilizes in a new forward direction.

Check out this video. In it you can see that one of two things typically happen; either the vehicle turns too fast, the wheels lose contact with the ground, and it flips over, OR it turns about 45 degrees, the wheels lose traction with the ground, and it begins to skid.

In almost all of those cases of skidding, if the driver turned their wheels counter to rotation and accelerated, they could have stabilized and saved it. What causes the crash is failing to turn appropriately, combined with slamming on the brakes. But if an SRV turns their wheels counter to the rotation and accelerates, it actually makes the crash worse. The best thing an SRV driver can do is stop accelerating at all or hit the brakes, both of which are counter-intuitive, because they're exactly the opposite of what happens in reality.

And crucially, none of those vehicles stabilize moving backwards.(some do stop while facing backwards, but that's just because that's where they happened to stop, not because they stabilized there)

SRVs are behaving completely opposite to how they would and should behave in real life. Is it any wonder people get confused?

 

[d8veh]

For ages I've been frustrated by the SRV slipping out and ending up backwards, but I've never really given it much thought until today.

Finally, I fiddled around with it, and have a plausible explanation for why it acts so funny.

In order to make the SRV work on low-g planets, they needed to invert the way real tires work. IRL, tires give you thrust forwards, yes, but also thrust UP, as I've tried to show in this basic diagram:

View attachment 291547

Now, the trouble with this is, if you have significant thrust, it would tend to throw the vehicle into the air repeatedly as you accelerate, with the thrust overcoming the tenuous pull of gravity. The only solution is to instead change the wheel to function more like THIS:

View attachment 291548
This has benefits; the SRV will cling to surfaces like crazy, even things far steeper than you'd expect, and the 'going airborne' problem is solved.

But there's a problem with this, and that problem is turning. In a normal car, as you turn, your front wheels pull themselves up on top of the approaching ground, while the back tires tend to skid through it, pulling the rear wheels down and stabilizing the vehicle.

But if your front wheels are instead pulling themselves DOWN into the ground, then acceleration won't stabilize the vehicle, but instead DE-stabilize it! Every bit of additional force pulls the wheels further into the ground, essentially acting like a giant brake. This causes the vehicle to lean forwards, into the turn, and the more it leans, the more those wheels bind with the ground, and the faster the vehicle turns!

This inevitably results in the SRV constantly and unavoidably spinning 180 degrees, until forward thrust stops digging its own face literally into the dirt.

This also explains why the hand brake doesn't cause this instability; it STOPS all thrust to the wheels, so rather than digging in and spinning crazily and out of control, it simply skids gracefully to a halt.

Now, I'm no physics expert, so I have no idea how to actually fix this. But doesn't this seem like a plausible reason why SRVs are so unstable?

If this IS the case, then perhaps there could be a way to prevent this from happening so much? Maybe a toggle to allow us to stop the SRV from pushing us into the ground? I'd happily learn to deal with an SRV that tends to launch itself into the air, if it means less going out of control and spinning around!

Sorry, that's all wrong. The reason that the SRV is unstable is that they put the cabin on the chassis the wrong way round. Maybe they didn't make it clear enough on the blueprints. How do I know that? Simple! Drive the SRV backwards and you'll find it's completely stable - no spinning out at all. Also, it can climb better.

 

[DemiserofD]

Sorry, that's all wrong. The reason that the SRV is unstable is that they put the cabin on the chassis the wrong way round. Maybe they didn't make it clear enough on the blueprints. How do I know that? Simple! Drive the SRV backwards and you'll find it's completely stable - no spinning out at all. Also, it can climb better.

I thought about that. But that doesn't explain why you skid sideways when you hit the brakes, but spin out when you accelerate, does it?

I guess I'm open to being convinced. If that's really the case, I might try inverting my SRV controls and just driving backwards all the time.

 

[VR andysonofbob]

Flying the SRV is fine and all, but when I touch down, I inevitably catch the forward side wheels, they dig in, and I end up flying backwards, which is just as annoying.

It seems to me you could solve this problem by just having a toggle for the downwards thrusters. If I want to deactivate them, give me that choice.

I don't know if this has been mentioned but I have pretty stopped spinning upon landing now. All I do is briefly take my foot off the throttle when I land then reapply. It seems to stop me spinning