Calibrated Cross-Bow and Ballistics Media (image) Arizona State University Caption The cross-bow was constructed so that each shot could be delivered with a consistent draw force that simulates thrusting spears. Credit Jayne Wilkins, Benjamin Schoville, Kyle Brown. Usage Restrictions Must be used to illustrate coverage of this research only. Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.