Search Results

Recreational Off Road Vehicles (ROVs) which are sometimes referred to as side-by-sides, have increased in popularity over the last decade. These vehicles are available in many different sizes and performance characteristics from a host of different manufacturers and also have a variety of different missions, just as there are many types of off road terrain. The United States Federal Government, through the Consumer Product Safety Commission (CPSC), has advocated and proposed vehicle handling and rollover resistance standards for the side-by-sides which have a top speed above 25 miles per hour (these are not defined as “low speed vehicles”). For the sake of repeatability, the proposed maneuvers are to be performed on a high friction hard surface (like asphalt) as opposed to the off road surfaces (i.e. grass, sand, dirt, mud. rocks, etc.) that these vehicles are designed to be operated on.

The concept of vehicle understeer and oversteer has been well studied and equations, test methods, and test results have been published for many decades. This concept has a specific definition in the steady-state driving range as opposed to quantification in highly transient limit handling events. There have been specific test procedures developed and employed by automotive engineers for decades on how to quantify understeer. These include the constant radius method, the constant steering wheel angle/variable speed method, the constant speed/ variable radius method, and the constant speed/variable steer method. These methods are very good for calculating the understeer gradient but care must be taken in interpreting the result at the limits of tire traction since lateral tire forces can be reduced on a drive axle when significant throttle is applied.

In the field of accident reconstruction, it is often important to measure the deformation of a vehicle (i.e. automobile, truck, motorcycle, etc.) after a crash has occurred. This data can be used for many purposes including energy calculations for speed loss, measuring roof or other structural deformation, analyzing seat or seat belt component positions, frame or unitized body structure deformation, and for estimating the actual post crash condition of a vehicle prior to the damage inflicted by the cutting and spreading tools used by emergency personnel. Traditionally, vehicle damage was measured using plumb bobs and tape measures or laser transits. However, these methods are not only time consuming but they also require a significant amount of upfront analysis to determine which points on the vehicle to measure at the inspection. In recent years, newer methods such as photogrammetry software and three dimensional scanners have come into play.

It is well known that tire force and moment properties are affected by numerous design variables such as tire size, type, compounding, and construction. It is also true that environmental conditions such as rain, snow, or road surface type can alter the cornering capacity of a tire. In this study, specific environmental parameters related to water on the roadway are varied to study the effects on the force and moment properties of modern radial tires. The parameters under study included translational velocity and water depth during standard sweep testing at two different vertical loads. The force and moment characteristics of seven different tires were tested at the Calspan Tire Research Facility in Buffalo, New York. The slip angle sweep tests were conducted on the Flat Trac tire machine at various belt speeds, normal loads, and water depths.