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This paper presents trailer sway testing results of a 5th wheel RV toy-hauler being towed by a conventional “dually” pick-up. Tests were performed at various speeds, trailer gross weights, king pin weights, and tire pressures. Results validate the understanding that 5th wheel trailers, at 20% pin weight generally have substantially better sway damping than conventional trailers. Tests at 10% pin weight show trailer sway damping is substantially reduced, but still is well above minimum industry accepted standards. Much of the improved sway damping for 5th wheel trailers can be attributed to the forward hitch location and not just the higher hitch loads that are typically used.

Eight 3-wheel passenger vehicles of both one-front and one-rear wheel configurations were tested and compared to similar-sized 4-wheel vehicles. The tests produced measures of overturn resistance, oversteer/understeer, transient responses to control and external disturbance inputs, and braking performance and stability. A comparison was also made of a 4- to 3-wheel conversion, and the effects of various handling modifications were evaluated. The results indicate that a properly engineered 3-wheel car can be made as stable as a properly engineered 4-wheel car, although the single front wheel configuration may be less stable in limit maneuvers.

A significant aspect of trailering safetyis the ability of a combination vehicle to stop with the same effectiveness as the tow vehicle alone. This paper describes the operation of electric and surge brake systems and presents analytical equations which can be used to predict stopping distances of these combinations as well as those trailers having no brakes. Comparisons are then made to full scale brake performance tests with seven different trailers. Problems are discussed and recommendations for a trailer-alone brake test procedure are given.

Full-scale vehicle response tests were conducted on five vehicles using a crosswind disturbance test facility capable of providing a 35 mph wind over a nominal 120 ft test length. The vehicles were a Honda Accord, Chevrolet station wagon, Ford Econoline van, VW Microbus, and Ford pickup/camper. Results showed that passenger cars, station wagons, and most vans have virtually no crosswind sensitivity problems, whereas the VW Microbus, the pickup/camper (in winds higher than 35 mph), and cars pulling trailers do have potential problems. Key vehicle parameters dictating this yaw response sensitivity are the distance between the aerodynamic and tire force centers, tire restoring moment (including understeer gradient), and the basic aerodynamic side forces. A simple analytical relationship in these terms was developed to predict steady-state yaw rate in steady winds.

This paper describes the results of a test program to evaluate various roadway disturbances present in the driving environment. The specific objectives were to pare down the list of possible roadway disturbances to the worst cases, identify handling problem areas, find meaningful response parameters and compare responses of different vehicles which might influence the results. The program provided an accident data analysis, survey questionnaire results and full scale test results which found the pavement/shoulder dropoff (requiring an edge climb maneuver) to be the most severe and most likely disturbance to result in lane exceedance. This occurs when the vehicle is scrubbing one set of tires on the shoulder edge (or encountering the edge at too shallow an angle for climb), thereby climb), thereby requiring the driver to apply a large steering deflection to get the car to climb back onto the pavement. In this case the vehicle will “spin out” if the speed is high enough.