As a part of the HVOSM development process, Calspan employed the services of professional stunt drivers in 1968 to perform maneuvers and stunts with an instrumented vehicle and, thereby, to generate vehicle response data in violent maneuvers for use in investigating the validity of the computer simulation. One of the included stunts was a fifty foot jump from a take-off to a receiving ramp. The degree of achieved correlation between analytical predictions and experimental measurements was found to be remarkably good in all of the included maneuvers and stunts. At the time, it was jokingly pointed out that Calspan had unintentionally developed a capability for the design and staging (i.e., via animated perspective displays on motion picture film) of auto thrill shows. A related, "far out" suggestion was the design of ramps to produce a combination of jump and rollover (i.e., a "spiral" jump), such that the stunt car would land on its wheels after passing over an obstacle in an inverted condition.
Subsequent to completion of development and validation of the HVOSM simulation in 1970, the thrill show ideas were given somewhat more serious consideration. Such an application would constitute both a challenging dynamics problem, similar in nature to a particularly violent single-vehicle accident, and an attention-getting demonstration of capabilities. It also had the appeal of a "fun" project to relieve a steady diet of crash protection studies.
In November of 1970 Raymond R. McHenry contacted Mr. W. J. Milligan, Jr., President, J.M, Productions, Inc., of Hamburg, New York, regarding his possible interest in the design of a new auto thrill show stunt and/or the establishment of speed and dimensional tolerances for existing stunts. The occasion of the contact was a newspaper item about Mr. Milligan's organization of a new national auto thrill show. As a result of subsequent discussions, J. M. Productions gave Calspan a purchase order to support an analytical study of the spiral jump stunt concept. The HVOSM simulation does not, of course, provide direct guidance for invention. Its application is equivalent to performing experiments with a fully instrumented-vehicle. Therefore, the analytical study of the spiral jump stunt concept consisted essentially of a trial and error process of exploratory changes in ramp configurations. The initial simulation study indicated that the combined needs to run both ends of the automobile over the same ramp profile in sequence and to generate a large roll acceleration in the 40 MPH speed range would create a serious problem in achieving acceptable pitch and yaw behavior. The limitation to the speed range of 40 MPH, which is based on space restrictions that generally exist for thrill show performances, produced a corresponding limitation on the time in the air that was available for the 360 degree roll- over. Thus, a large roll velocity (approximately 230 degrees per second) had to be generated to achieve a "wheels down" landing on the receiving ramp. The sequential traversal of the take-off ramp by the front and the rear wheels, when combined with the nonlinear suspension characteristics during the traversal (i,e., front suspension "bottomed out" throughout the roll impulse) was found to create a response sequence in which the rear wheels cleared or only lightly touched the "roll-impulse" end of the ramp.
As a result of this sequence, the initially predicted responses retained a "nose-up" attitude during the entire jump and were found to include excessive yawing. Attempts to achieve a corrective pitch impulse at either of the rear wheels were unsuccessful, The rear wheel that was moving up fastest cleared any ramp configuration that the "bottomed out" front suspension had traversed, An impulse sufficient for the desired pitch response, when applied at the other rear wheel, acted to excessively reduce the roll velocity. Therefore, it became necessary to consider minor vehicle modifications to achieve the desired combination of linear and angular velocities at the end of the take off ramp. The necessary vehicle modification consisted of an auxiliary contact point on the rear axle, for which the primary loading occurred on the last ten feet of the take-off ramp. The additional contact on the rear axle was also found to require a relatively low side-force capability to avoid unwanted yaw accelerations.
McHenry Software, Inc. (MSI) has created the McHenry-HVOSM (m-hvosm), as part of their msmac3D Program, See also
- McHenry James Bond Stunt,
- '3-D' or not '3-D', THAT is the Question! and
- The Astro Spiral Jump-An Automobile Stunt Designed via Simulation
- 2017 2018 Jaguar rollout rollover stunt We designed the stunt again with msmac3D for a different vehicle as further proof of the validity of the msmac3D/hvosm program