What initial velocity will you apply to the balls?
Why did you choose Explicit Dynamics over Transient Structural?
I recommend you first try Transient Structural. In the example below, I have created a 1 m/s downward velocity.
To simplify this model, I suppressed Bolt Pretension. That can be unsuppressed. The Analysis Setting needs to have a first step to load the pretension and a second step where it is locked, both of which have Time Integration turned off.