Pitching Machines

The first arm machines that were used were unguarded, leading to some very tragic accidents. Arm machines then needed to be heavily guarded, limiting the vision advantage. Due to the enormous recoil generated by the arm, the machines also had to be bolted to concrete pads, making them stationery and not available for field or fungo work. Even today arm machines remain bulky and massive. The strengths of this design were some level of vision and timing. The weaknesses were that it was limited to only fastballs, completely immobile and still carried a concern for safety.

The innovators of the wheel machines saw the ability to throw curve balls as the ultimate feature in pitching machines. While the initial wheel machines threw curve balls, they ignored the need for portability and for guarding throwing wheels. Slowly improvements were made to introduce some portability and fungo capabilities but essentially the basic design has stayed the same.Source Sports Attack