How to create multiple clock in one viwer

i try to create dataSourceClock for each dataSource, but it not work
const clock = new Cesium.DataSourceClock()
clock.startTime = start.clone()
clock.stopTime = stop.clone()
clock.currentTime = start.clone()
clock.clockRange = Cesium.ClockRange.CLAMPED
clock.clockStep = Cesium.ClockStep.SYSTEM_CLOCK_MULTIPLIER
clock.multiplier = 1
const dataSource = new Cesium.CustomDataSource()
dataSource.clock = clock
dataSource.entities.add({
availability: new Cesium.TimeIntervalCollection([new Cesium.TimeInterval({
start: start,
stop: stop
})]),
position: positionProperty,
orientation: new Cesium.VelocityOrientationProperty(positionProperty),
model: {
uri: process.env.BASE_URL + ‘/assets/drone.glb’,
color: Cesium.Color.BLUE,
colorBlendMode: Cesium.ColorBlendMode.MIX,
minimumPixelSize: 180,
scale: 1
}
})
this.$_viewer.dataSources.add(dataSource)