AddTorque not increasing relativeVelocity magnitude of a collision

I have 2 rigidbody objects that will collide with each other. One is spinning (like a propeller) using Rigidbody.AddTorque() in FixedUpdate() and the player will control this object and must ‘smash’ it with the other object.

Now I’m trying to calculate the force at which the propeller object impacts the other object.

I’ve been using if (collision.relativeVelocity.magnitude > minimumMagnitude) (if true, then apply damage, if not, then no damage is applied) to measure this force and so far with other objects that are not spinning using AddTorque(), this works quite well, but for some reason the AddTorque() is not adding to the relativeVelocity so the measured number is always quite a lot lower than it’s supposed to be.

What am I doing wrong here?

You can use

collision.rigidbody.angularVelocity to find the Angular Velocity from the other colliding object.