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This paper discusses the measurement of cord loads in pneumatic tires using a direct load transducer. Such an instrument is described in detail together with results of numerous tests. Tire engineers will find this paper of value since it outlines methods for determining cord loads under actual tire operating conditions.

Strain gage instrumented transducers were used to measure the cord loads at a number of locations in several different automotive tires loaded against both flat and cylindrical road wheel surfaces. The two basic types of cord load fluctuation encountered in all automobile tires have been identified from these measurements, and the most severe location for cord load fluctuations has been closely bracketed. By these measurements, it has been possible to show that for each tire definite relations exist between the cord loads induced while running on a cylindrical drum and while running on a flat surface. The maximum cord load fluctuations in a tire are the same for the NBS roadwheel and flat surface when the tire is loaded against the roadwheel with a load of between 85 and 90% of that used on the flat surface.

A summary is presented of measured elastomeric composite response suitable for linear structural and thermoelastic analysis in aircraft tires. Both real and loss properties are presented for a variety of operating conditions including the effects of temperature and frequency. Suitable micro-mechanics models are used for predictions of these properties for other material combinations and the applicability of laminate theory is discussed relative to measured values.

A method has been developed for calculating the internal temperature distribution in an aircraft tire while free rolling under load. The method uses an approximate stress analysis of each point in the tire as it rolls through the contact patch, and from this stress change the mechanical work done on each volume element may be obtained and converted into a heat release rate through a knowledge of material characteristics. The tire cross-section is then considered as a body with internal heat generation, and the diffusion equation is solved numerically with appropriate boundary conditions at the wheel and runway surface. Comparisons with buried thermocouples in actual aircraft tires shows good agreement.

Rolling resistance measurements were made on a sample of twenty-four retreaded and four new truck tires spanning a variety of constructions, tread patterns and tread depths. Examination of the results showed some relationship between three construction features and the resulting rolling resistance values. These are (a) Radial or bias carcass construction, (b) Tread pattern, and (c) Tread depth. The latter two characteristics can over-ride radial or bias construction effects. The effect of tread compound could not be analyzed in this limited test program. Good quality retreaded truck tires can exhibit comparable rolling resistance with new truck tires.

Methods are presented for calculating dynamic contact patch areas of an elastically supported cylindrical shell used to model the dynamic rolling of a loaded pneumatic tire. These areas are shown to be influenced considerably by rolling velocity, constructional parameters of the tire, and its loss characteristics. Dynamic pressure distributions within contact patch areas are obtained analytically, and the techniques involved are given. The shell is used as a basis for calculating load carrying and drag properties of a pneumatic tire so that various tire parameters may be approximated. The results given here are typical of information obtainable from such a model.

The problem of wear of an aircraft tire during touchdown is examined from two points of view. In the first, a simplified analysis of the elements of the problem is shown to lead to a dimensionless description of the process. In the second, small scale experiments using this dimensionless variable as a parameter are shown to correlate well with observed wear.

Mechanical energy loss, in automobile tires, as well as other products made of cord reinforced rubber composites, is a major source of energy-consumption. To minimize the energy loss, it is essential to increase the understanding of the way in which internal losses in a composite depend on the loss characteristics of the constituents used to fabricate it. In this paper, the application of the viscoelasticity theory in predicting the loss characteristics is discussed in detail. The scope and the limitations of the linear theory, the relations between the effective loss characteristics and constituents’ properties, and the numerical methods for predicting the loss moduli are discussed. Some numerical results are presented .