Help with Spring / Suspension Math

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#1

Hello, for the past few days I have been working on creating a programmed car suspension system. For the time being, I am trying just to mimic one spring which will later be used in the place of a wheel on a car.

  1. What do I want to achieve? I have a spring that works for a bit but then after moving it, it breaks.

  2. What is the issue?

    When just using the “Run” feature in studio it works perfectly fine, however, when actually playing it in studio or in-game, it breaks after I move it around. It looks like the damping of the spring stops working for some reason.

    Also, if I set the network ownership to a player it instantly breaks and flies into the sky.

  3. What solutions have I tried so far?

    I’ve read through almost everything I could find about the problem. From what I could find my damping system might be wrong or I might have to add ‘limits’ to the force being applied to the part, but I am not sure where or how to implement that into my code.

    My code is the following:

local rayParams = RaycastParams.new()
rayParams.FilterDescendantsInstances = {script.Parent}
rayParams.FilterType = Enum.RaycastFilterType.Blacklist
local spring = script.Parent

local suspension_length = 4 -- max length of suspension (raycast length)

local Top = script.Parent.Top -- the spring part

local force = Top.BodyForce
local gyro = Top.BodyGyro

local stiffness = 1 

local lastx = 0

local NumWheels = 1


Top:SetNetworkOwner(nil)

game:GetService("RunService").Heartbeat:Connect(function(dt)
	local raycastResult = workspace:Raycast(Top.Position,Top.CFrame.UpVector * -suspension_length,rayParams)
	local distance
	if raycastResult then
		distance = (Top.Position-raycastResult.Position).Magnitude
	end
    local mass = Top:GetMass()
	local weight = (mass*workspace.Gravity)
	local x = suspension_length - (distance or suspension_length)

	local k = weight/ NumWheels + (stiffness or 0)
	local d = 0.9 * 2 * (k *(mass / 4)) ^ 0.5
	local spring_force = k * x 
	local dx = (x - (lastx or x)) / dt
	local damping_force = (dx*d)

    -- Force = kx + dv
	force.Force = Vector3.new(0,spring_force + damping_force,0)
	lastx = x

	gyro.CFrame = CFrame.new(0,0,0)
end)