Parametric analysis of the stability of a bicycle taking into account geometrical, mass and compliance properties

Some studies of bicycle dynamics have applied the Whipple Carvallo bicycle model (WCBM) for the stability analysis. The WCBM is limited, since structural elements are assumed to be rigid bodies. In this paper, the WCBM is extended to include the front assembly lateral compliance, and analysis focuses on the study of the open loop stability of a benchmark bicycle. Experimental tests to identify fork and wheel properties are performed, this data is used in the stability analysis for ranking the influence of design parameters. Indexes from the eigenvalues analysis are applied in a full factorial approach. The results show that introducing front assembly compliance generates a wobble mode with little effect on self-stability. The forward displacement of the centre of mass of the rear frame and the increment in trail lead to large increments in the self-stability, whereas increments in front wheel radius and wheelbase reduce stability

Model Based Analysis of Shimmy in a Racing Bicycle

In this paper we are presenting a model of a racing bicycle, developed in Modelica language within the Dymola environment. The main purpose is to investigate the dynamic response of the bicycle and its modes of vibration, referring in particular to shimmy. This phenomenon occurs at high speeds and consists of sudden oscillations of the front assembly around the steering axis. Lateral accelerations on the horizontal tube of the frame can reach 5-10 g with a frequency that varies between 5-10 Hz. Even if it is quite uncommon, shimmy is a topic of great relevance, because it may be extremely dangerous for the rider. Thanks to this model, we can show that the main elements which contribute to the rise of the oscillations are the lateral compliance of the frame and the tyres’ deformation

Advances in Mechanical Systems Dynamics 2020

The fundamentals of mechanical system dynamics were established before the beginning of the industrial era. The 18th century was a very important time for science and was characterized by the development of classical mechanics. This development progressed in the 19th century, and new, important applications related to industrialization were found and studied. The development of computers in the 20th century revolutionized mechanical system dynamics owing to the development of numerical simulation. We are now in the presence of the fourth industrial revolution. Mechanical systems are increasingly integrated with electrical, fluidic, and electronic systems, and the industrial environment has become characterized by the cyber-physical systems of industry 4.0. Within this framework, the status-of-the-art has become represented by integrated mechanical systems and supported by accurate dynamic models able to predict their dynamic behavior. Therefore, mechanical systems dynamics will play a central role in forthcoming years. This Special Issue aims to disseminate the latest research findings and ideas in the field of mechanical systems dynamics, with particular emphasis on novel trends and applications

Pneumatic Tire

For many years, tire engineers relied on the monograph, \u27Mechanics of Pneumatic Tires\u27, for detailed information about the principles of tire design and use. Published originally by the National Bureau of Standards, U.S. Department of Commerce, in 1971, and a later (1981) edition by the National Highway Traffic Safety Administration (NHTSA), U.S. Department of Transportation, it has long been out of print. No textbook or monograph of comparable range and depth has appeared since. While many chapters of the two editions contain authoritative reviews that are still relevant today, they were prepared in an era when bias ply and belted-bias tires were in widespread use in the United States and thus did not deal in a comprehensive way with more recent tire technology, notably the radial constructions now adopted nearly universally. In 2002, it was preposed that NHTSA should sponsor and publish electronically a new book on passenger tires, under editorship of the University of Akron, to meet the needs of a new generation of tire scientists, engineers, designers, and users. This text is the outcome. The chapter authors are recognized authorities in tire science and technology. They have prepared scholarly and up-to-date reviews of the various aspects of passenger car tire design, construction and use, and included test questions in many instances, so that the book can be used for self-study or as a teaching text by engineers and others entering the tire industry

Proceedings of the 2018 Canadian Society for Mechanical Engineering (CSME) International Congress

Published proceedings of the 2018 Canadian Society for Mechanical Engineering (CSME) International Congress, hosted by York University, 27-30 May 2018

Measuring and Modeling the Mechanical Properties of Bicycle Tires

It has been shown that tire deformation can play an important role in the stability and handling of a bicycle. It is expected that an accurate understanding of tire behavior is necessary for correct understanding of rider behavior and that correct understanding of rider behavior is necessary for optimizing bicycle design. That certainly has been the case for motorcycles. Several instances of published bicycle tire stiffness data exist, but they seldom agree with each other, do not all measure the same properties, and often are missing key pieces of test configuration data, such as tire size, rim width, inflation pressure, or vertical load. In this project, three different test devices specific to bicycle tires were developed. Measured bicycle tire stiffnesses are presented for 14 different tires ranging from 22 to 50 mm wide, at inflation pressures from 2 to 11 bar (29 to 160 psi), under vertical loads from 304 to 731 Newtons (68 to 164 lb); for a total of about 120 different parameter combinations. Normalized cornering stiffness was found to vary from below 0.15 to over 0.35, which is ±40% from the average, and normalized camber stiffness varies from below 0.0075 to over 0.015, which is ±33% from the average. Based on numerical simulations, this is more than sufficient to influence bicycle stability and handling. Tires approach the camber stiffness necessary, without slip, for the net ground reaction force to be in the plane of the wheel, obeying the so-called tangent rule, but most tires with most inflation pressures and under most loads presented here fall below that. A numerical model, based on an analysis developed by Rotta for slender toroidal tire cross sections in contact with the ground, was also developed to provide insight into how the tires generated the forces they do and attempt to predict them from simpler measurements. Although actual values generated by the model do not exactly match measured values, the trends in contact patch size and lateral stiffness values generated do correspond well with measured data as parameters vary, such as inflation pressure, vertical load, and rim width

Temperature Reduction Technologies Meet Asphalt Pavement: Green and Sustainability

This Special Issue, "Temperature Reduction Technologies Meet Asphalt Pavement: Green and Sustainability", covers various subjects related to advanced temperature reduction technologies in bituminous materials. It can help civil engineers and material scientists better identify underlying views for sustainable pavement constructions

Development and validation of a wheelchair caster testing protocol

The majority of wheelchairs delivered in less-resourced settings fail prematurely. This issue has been recognized by the WHO Guidelines that recommend product testing based on field conditions to evaluate and improve wheelchair quality. This work is motivated from WHO’s recommendation and this is first scientific study investigating inclusion of environmental conditions in wheelchair testing. The goals of this work were to develop a testing protocol for wheelchair casters based on field conditions, evaluate the impact of environmental testing factors on quality and make appropriate recommendations for wheelchair testing based on study outcomes. In this study, an evidence-based approach was followed in which wheelchair testing evidence, expert advice, and field evidence were continually triangulated to inform the testing protocol development. A literature review (Chapter 1) was carried out and expert advice was sought to generate a list of testing methods with environmental factors based on outdoor failures. Caster system failure was identified as a key testing gap that poses significant safety risks to the wheelchair users. Development of a caster testing equipment (Chapter 2) and a caster failure checklist (Chapter 3) was carried out through an iterative design and review approach. The checklist was distributed for collecting failure data following psychometric evaluation and revisions. Testing factors of shock, corrosion and abrasion were validated to respective field exposures and caster testing was conducted (Chapter 4). Environmental factors impacted the durability of 25% caster models and altered failure modes for 75% models. Two-thirds of the altered failure modes have significant risk of causing injuries to users and wheelchair failures. About 73% of the testing failures matched with the most common failure modes experienced in the field. Based on study findings, environmental factors strongly influence both the time-to-failure and failure mode for caster models. We recommend that environmental exposure need to be considered as part of wheelchair testing protocols to help improve the external validity of the testing, which will ultimately improve the safety and reliability of the device. These recommendations are discussed along with caster design recommendations and suggestions for future work in Chapter 5

Vibration, Control and Stability of Dynamical Systems

From Preface: This is the fourteenth time when the conference “Dynamical Systems: Theory and Applications” gathers a numerous group of outstanding scientists and engineers, who deal with widely understood problems of theoretical and applied dynamics. Organization of the conference would not have been possible without a great effort of the staff of the Department of Automation, Biomechanics and Mechatronics. The patronage over the conference has been taken by the Committee of Mechanics of the Polish Academy of Sciences and Ministry of Science and Higher Education of Poland. It is a great pleasure that our invitation has been accepted by recording in the history of our conference number of people, including good colleagues and friends as well as a large group of researchers and scientists, who decided to participate in the conference for the first time. With proud and satisfaction we welcomed over 180 persons from 31 countries all over the world. They decided to share the results of their research and many years experiences in a discipline of dynamical systems by submitting many very interesting papers. This year, the DSTA Conference Proceedings were split into three volumes entitled “Dynamical Systems” with respective subtitles: Vibration, Control and Stability of Dynamical Systems; Mathematical and Numerical Aspects of Dynamical System Analysis and Engineering Dynamics and Life Sciences. Additionally, there will be also published two volumes of Springer Proceedings in Mathematics and Statistics entitled “Dynamical Systems in Theoretical Perspective” and “Dynamical Systems in Applications”

Continual improvement: A bibliography with indexes, 1992-1993

This bibliography lists 606 references to reports and journal articles entered into the NASA Scientific and Technical Information Database during 1992 to 1993. Topics cover the philosophy and history of Continual Improvement (CI), basic approaches and strategies for implementation, and lessons learned from public and private sector models. Entries are arranged according to the following categories: Leadership for Quality, Information and Analysis, Strategic Planning for CI, Human Resources Utilization, Management of Process Quality, Supplier Quality, Assessing Results, Customer Focus and Satisfaction, TQM Tools and Philosophies, and Applications. Indexes include subject, personal author, corporate source, contract number, report number, and accession number