Measuring and testing – Frictional resistance – coefficient or characteristics
Patent
1995-05-08
1997-06-03
Noland, Thomas P.
Measuring and testing
Frictional resistance, coefficient or characteristics
73146, G01N 1902, G01M 1706
Patent
active
056356234
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a device which makes it possible to determine the forces present between the tire and the travel surface on which it is rolling and furthermore, in particular, permits measurement of the properties of the tire, utilizing the longitudinal forces. Such properties are, for instance, the rolling resistance and the coefficient of longitudinal adherence. The invention also concerns the methods carried out by means of such a device and, more particularly, the methods for the comparative measurement of the properties of rolling resistance and adherence limits of different tires, or the same properties due to different travel surfaces.
Taking into account all the factors which can play a part during the measurement of rolling resistance, this measurement is very difficult and, as known, there are two major kinds of methods: The first kind concerns measurements on machines, and mention may be made of measurements on a flywheel, the tire to be tested traveling on a flywheel of larger or smaller diameter, and measurements on roller test benches, said rollers having small diameters and producing stresses in the tire far different from those encountered on a flat travel surface, hence the appearance of the machine on a flat travel surface in the form of a belt on which the tire rolls; the second type concerns measurements on actual runways and travel surfaces which are generally carried out with a vehicle, whether an analytical vehicle or a conventional vehicle. With this last type of vehicle, the so-called travel-surface-deceleration method is frequently used, which method is undoubtedly less precise than the others, but gives interesting results, since it includes the environmental factors to the maximum extent.
As to the adherence limit measurements, they are also generally carried out with the use of flywheels in the case of measurements on machines, but they are more frequently performed with the use of vehicles traveling on runways with different variable, travel surfaces. It is obvious that the methods with vehicles and runways require considerable space, in the same way as the methods with flywheels, since the flywheels must be of large diameter.
SUMMARY OF THE INVENTION
The object of the invention is to provide a device which, while simple, permits at least a comparative measurements of rolling resistances and/or of adherence limits within a limited space, or at least a space which is very small as compared with runways or workshops, while permitting rolling on a flat travel surface or one of very little curvature.
The device in accordance with the invention is characterized by the fact that it comprises two dimensionally identical mounted assemblies, assembled by a connecting arm the center axis of which is parallel to the straight line connecting the centers of rotation of the unloaded mounted assemblies, said connecting arm being provided with ballasting means necessary for obtaining the load imposed on each of the assemblies and such that the center of gravity of the device at rest is located between said straight line and the travel surface on which the device will roll, the device furthermore comprising means capable, by rotation of the mounted assemblies, of imparting to its center of gravity a cycloidal movement giving it a given angular position with respect to the plane containing the straight line connecting the centers of rotation of the mounted assemblies which is perpendicular to the travel surface.
By mounted assembly there is to be understood the assembly formed by at least one tire inflated to a given pressure and its mounting rim, said rim being provided with a wheel disk which can be fastened on a hub. The connecting arm which connects the two mounted assemblies can be a rigid connecting bar of any cross section, for instance circular or square, fastened firmly on the two hubs on which the disks themselves are fastened. This arm will advantageously be an arm which can turn freely in the housings provided for this purpose in the
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Journal of Testing and Evaluation, vol. 20, No. 6, Nov. 1992, Philadelphia, A, US, pp. 470-474, Siew-Ann Tan et al. "Laboratory Wheel Tracking Apparatus for Bituminous Pavement Studies".
Soviet Inventions Illustrated Week 8938, 6 Sep. 89 Derwent Publications Ltd., London, GB; AN 89-218769/30 & SU 1434-334-A (Sarat Poly) 30 Oct. 1988.
Compagnie Generale des Etablissements Michelin--Michelin & Cie
Noland Thomas P.
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