private Momentum computeMomentum(RigidBody elevator, ReferenceFrame frame) {
    elevator.updateFramesRecursively();
    TwistCalculator twistCalculator = new TwistCalculator(world, elevator);
    twistCalculator.compute();

    MomentumCalculator momentumCalculator = new MomentumCalculator(twistCalculator);
    Momentum momentum = new Momentum(frame);
    momentumCalculator.computeAndPack(momentum);

    return momentum;
  }