加上每秒的setInterval数

I want my sHand to add 6 per second but it works only once, If I try to do something like this: this.sHand++ it works fine and adds 1 degrees per second but I want 6 instead of 1 any solutions?

  data:{
    sHand: 30
  },
  computed:{
    style(){
        return { transform: 'rotate(' + this.sHand + 'deg)'}
    }
  },
  created(){
    setInterval(() => {
        this.sHand + 6  // not working :/
    },1000)
  }
    <div :style="style" class="secondhand"></div>