Perpetual chain movement

Phaser 3
1

Hi I’m trying to modify this example https://labs.phaser.io/edit.html?src=src/physics/matterjs/chain.js&v=3.24.1, in a way that the chain will perpetually move frome left to right like a pendulum.
I properly set inertia and friction to 0 but the chain will ultimatly stop moving.
This is my code :

var config = {
    type: Phaser.AUTO,
    width: 800,
    height: 600,
    backgroundColor: '#1b1464',
    parent: 'phaser-example',
    physics: {
        default: 'matter'
    },
    scene: {
        preload: preload,
        create: create,
        update: update
    }
};

var block;
var cursors;
var prev;
var prevConstraint;
var velocity = 10;

var game = new Phaser.Game(config);

function preload ()
{
    this.load.image('block', 'assets/sprites/block.png');
    this.load.image('ball', 'assets/sprites/shinyball.png');
}

function create ()
{
    block = this.matter.add.image(400, 50, 'block', null, { ignoreGravity: true, inertia: Infinity });
    block.setFixedRotation();
    block.setMass(500);

    var y = 150;
    var x = 400;
    prev = block;

    block.setFriction(0.000);
    block.setFrictionAir(0.000);
    block.setFrictionStatic(0.000);
    block.setBounce(1);

    for (var i = 0; i < 12; i++)
    {
        var ball = this.matter.add.image(x, y, 'ball', null, { shape: 'circle', mass: 0.1, inertia: Infinity });
        
        ball.setFriction(0.000);
        ball.setFrictionAir(0.000);
        ball.setFrictionStatic(0.000);
        ball.setBounce(1);
        //ball.setInertia('Infinity');

        prevConstraint = this.matter.add.joint(prev, ball, (i === 0) ? 90 : 35, 1);
        prev = ball;



        y += 0;
         x -= 35;
    }


    this.matter.add.mouseSpring();

    cursors = this.input.keyboard.createCursorKeys();
}
var lastpos;
function update ()
{

 

    if (cursors.left.isDown)
    {
        block.setVelocityX(-20);
        this.matter.world.removeConstraint(prevConstraint);
    }
    else if (cursors.right.isDown)
    {
        block.setVelocityX(20);
    }
    else
    {
        block.setVelocityX(0);
    }

    if (cursors.up.isDown)
    {
        block.setVelocityY(-20);
    }
    else if (cursors.down.isDown)
    {
        block.setVelocityY(20);
    }
    else
    {
        block.setVelocityY(0);
    }
}

Do you have a clue about how I can do it ?
Thanks