Car chassis bug

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#1

Hey there, I am trying to make a car suspension/chassis for a model which contains multiple mesh parts. I am following this great tutorial by @sleitnick (How to Rig a Car) and I highly recommend checking it out if you want to rig your own car.

Problem

My issue is when I test the suspension the wheels start glitching it messes up the whole chassis, the wheels are connected the the chassis with cylindrical constraints and spring constraints

Narrowing down the issue

I have tested and found what may be the underlying issue, which is the Mass part. The Mass part is basically there to control the centre of mass of the car as using the actual mass of the car is unreliable so the Mass part’s property of Massless is set to false while all the other meshes of the car are set to true

However, when I change the Mass parts property of Massless to true the car’s chassis starts to function normally or if I increase the y axis position of the Mass part it solves the issue as well. My problem is that I want to simulate a realistic centre of mass so I need the Mass part to keep its original values and position. (see video below)

Increasing the SpringConstraints FreeLength also solves the issue but again the suspension height increases and makes the chassis look weird.

Video of the issue: mass part glitch bug

What may not be the problem

  • I do not think it is a collision issue because I have the set existing CollisionGroups for the Car body meshes and Car wheel meshes so they do not collide but if there is a way to check collisions e.g if a part is colliding with one part please do let me know

If there are any more solutions please do let me know, thank you!

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#2

Are you playing with the constraints and spring forces at all? These will be affected by the weight of the parts and vice versa. If the additional weight of the Mass part is throwing things off, its probably because the extra weight now needs to be accounted for in the constraints and springs… try to increase the stiffness and the force and see if it helps.

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#3

Hi there thanks for your reply - I have tried changing the spring forces of the wheels but now it doesnt really glitch out but this happens:

image
image1913×783 77.2 KB

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#4

Just to prove this point even further I have removed every single body part of the car to show it is not a collision issue and in fact something to do with the car not being able to handle e.g the weight, constraint issue

image
image1527×787 56.9 KB

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#5

I have experimented with another car model in the past and it was rigged perfectly (in the same way) as the current car I am using; however, the mass part has the same size (4x4x4) as the previous model so I am not sure why this car suspension is glitching out while the other one is not?

Previous car rig working:

image
image1103×435 74.7 KB

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#6

Have you tried just importing over that chassis to your new body?

#7

I am unable to import it as it is a step-by-step procedure you have to follow but I double-checked I did all the steps correctly but it still does not work.

Here is the rig and even without the body it still glitches out:
car.rbxl (33.7 KB)

I would appreciate if you could take a look

Edit: This is the tutorial I followed (How to Rig a Car)

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#8

Here is the working rig (light-blue) and current rig (blue) side by side to compare
car.rbxl (34.5 KB)

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#9

Soon as I get home tonight I’ll check this out I’ve had the same problem recently myself @ 8 50 PM EST if this remains unsolved

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#10

Let me upload what i have… all i changed was the free length of the springs (from 2 to 4)… i dont see any issues on my end, it moves freely whether or not i set the platform to massless or not… try it out:
car.rbxl (34.9 KB)

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#11

Unfortunately, I have already tried this but it makes the suspension height increase and I want the height to remain similar e.g this is what it looks like with FreeLength changed to 4:

image
image1021×455 80.4 KB

#12

But your mass part then will collide with the ground, maybe try to spread out the mass part so u can make it thinner, then you can lower the free length of the springs.

Let me keep messing with it.

#13

The Mass part’s CanCollide property is set to false so collision shouldnt be an issue and the Mass part is supposed to be into the ground (a bit) to simulate a realistic centre of mass/gravity so drifting/driving would be easier and the car wouldnt tilt over easily etc.

Let me keep messing with it.

Appreciate it :slight_smile:

#14

ok here u go, springs at 2 and i dont see the same issue, it moves freely:

car.rbxl (34.9 KB)

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#15

Wow! How did you fix it? I have spent hours on this and still couldnt figure it out.

What did you change?

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#16

I made one of these cars from the same tutorial and had the same issue. I found there were 2 issues that where causing my problems.

Issue 1:
The mass part has too much mass. Try either changing the size to reduce the volume, or change the density to a value less than 0.7.

The mass part being too massive caused the springs to compress too much and glitch.

Issue 2:
The free length of the spring is too short. Try increasing the values across all 4 wheels and see what happens.

This was the only thing that caused me issues in the past and always resolved after playing around with it a bit.

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#17

I re-aligned the orientation of all the springs and the constraints to be the correct way, and then i changed your force back to 10,000 and then just played with the free length.

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