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The multi-speed internal gear hub of a bicycle is a well-closed gear shifting system that works perfectly under any challenging riding environment, and is developed specifically to improve fragile chain-drive derailleur using planetary gear trains. In recent years, bicycle internal hub gears have been developed toward multi-speed transmission, and in the development process of internal gear hubs, the structure of speed changing mechanism has changed from a single planetary gear train to multiple planetary gear trains, and is becoming more complex. The primary purpose of this Study aims to establish a systemized and efficient design process, and develop an effective theory and method for designing multiple-speed internal gear hubs with the design concept and common features of multiple-speed internal gear hub products developed in recent years, to favor the innovation and development of internal gear hubs. First, existing multiple speed internal hub products are analyzed and summarized for their basic features, limitations, and demands as the reference for the design of multiple speed internal gear hubs, and a catalog of usable planetary structures is systematically established with the coupling and connection of basic high and low ratio speed changing modules. Secondly, usable planetary structures that offer best performance of geometric progression speed ratio distribution of gear hub are matched with gear positions, and a table of gear sequence is confirmed; third, based on the maximum external diameter required by design, tooth numbers for every gear in a hub are defined according to the relationship between tooth number and speed ratio, as well as the gear sequences; and finally, the systematic design process above is applied to the development of an easy-to-use computer aided design software with the lowest possible number of variables using Visual Basic 6.0 for designers, in order to favor the innovation and development of internal gear hubs.

The bevel gears have been widely used for the intersected-axial transmission system for a long time. But mostly them are limited in the category of involute tooth profiles. It is believed that bevel gears with circular-arc tooth profile, similar to the Wildhaber-Novikov circular-arc helical gears, will improve the load capacity of the gear set. The bevel gears with circular-arc tooth profiles was firstly proposed by Kuo and Tsai in 2001. Although these new type of bevel gears can increase the load capacity of transmission, the expensive manufacturing process is still the problem. In this paper, the design parameters of bevel gear with circular-arc profiles developed by Kuo and Tsai are modified. Bevel gear set with spiral point contact path is developed. This improvement makes it possible to manufacturing the newly developed bevel gears in just a simple milling or/and grinding process with circular cutting edges. The manufacturing process is then cost down quit a lot. A method for checking the gear interference is also proposed. Finally, the 3D solid models of the bevel gear with circular-arc tooth profiles as well as the grinding wheel are constructed by using the computer software ¡§Pro/E¡¨. It is believed that the mathematical models and the design method developed in the thesis will provide a useful foundation for the further studies.

In current years, searching for substitute energy such as the wind and ocean power of renewable energy is an important subject due to the petroleum shortage. The gear box is the key mechanism in the system of wind and ocean power. Moreover, the main function of the system is to generate electricity by speeding up the rotative velocity. However, the power of environment changes momentarily and makes the turbine a variable input. In order to improve the efficiency of generating electricity, it should get the constant input to keep the high quality of generating electricity. First of all, the study focuses on the gear box and synthesizes a constant speed mechanism of planetary gear train which degrees of freedom is two. In the mechanism, inputs are the variable speed turbine and a constant speed motor. When they input the mechanism, a constant speed output will be made to supply the generator. Secondly, it is necessary to set up the real object of the constant speed mechanism of planetary gear train. Finally, observing the real condition from the experiment to prove the theory is correct.

A composite skid landing gear design investigation has been conducted. Limit Drop Test as per Federal Aviation Regulations (FAR) Part 27.725 and Crash test as per MIL STD 1290A (AV) were simulated using ABAQUS to evaluate performance of multiple composite fiber-matrix systems. Load factor developed during multiple landing scenarios and energy dissipated during crash were computed. Strength and stiffness based constraints were imposed. Tsai-Wu and LaRC04 physics based failure criteria were used for limit loads. Hashin s damage initiation criteria with Davila-Camanho s energy based damage evolution law were used for crash. Initial results indicate that an all single-composite skid landing gear may not be feasible due to strength concerns in the cross member bends. Hybridization of multiple composites with elasto-plastic aluminum 7075 showed proof of strength under limit loads. Laminate tailoring for load factor optimization under limit loads was done by parameterization of a single variable fiber orientation angle for multiple laminate families. Tsai-Wu failure criterion was used to impose strength constraints. A quasi-isotropic N = 4 (pi/4) 48 ply IM7/8552 laminate was shown to be the optimal solution with a load factor under level landing condition equaling 4.17g s. LaRC04 predicts that failures will be initiated as matrix cracking under compression and fiber kinking under in-plane shear and longitudinal compression. All failures under limit loads being reported in the metal-composite hybrid joint, the joint was simulated by adhesive bonding and filament winding, separately. Simply adhesive bonding the metal and composite regions does not meet strength requirements. Filament wound bolted metal-composite joint shows proof of strength. Filament wound composite bolted to metal cross member radii is the final joining methodology. Finally, crash analysis was conducted as per requirements from MIL STD 1290A (AV). Crash at 42 ft/sec with 1 design gross weight (DGW) lift was simulated using ABAQUS. Plastic and friction energy dissipation in the reference aluminum skid landing gear were compared with plastic, friction and damage energy dissipation in the hybrid metal-composite design. Damage in composites was modeled as progressive damage with Hashin s damage initiation criteria and Davila-Camanho s energy based damage evolution law. The latter meets requirements of aircraft kinetic energy dissipation up to 20 ft/sec (67.6 kJ) as per MIL STD 1290A (AV). Weight saving possibility of up to 49% over conventional metal skid landing gear is reported. The final design recommended includes Ke49/PEEK skids, 48 ply IM7/8552 cross member tapered beams and, Al 7075 cross member bend radii bolted to the filament wound composite tapered beam. Concerns in composite skid landing gear designs, testing requirements and future opportunities are addressed.

M. Ing. / Reliability is basically the measure of performance, it is the probability that a system or component will perform its required task without failure under certain conditions for a given period of time [1]. As systems have become more complex in recent time the need for reliability within that system has become more and more important, safety, productivity and profit are three factors that have also demanded an increased level of reliability [2]. The reliability of an industrial gear unit comes from the reliability of all the individual components within the gear unit. Bearing lives are often the limiting factor of a gear unit and more often than not the lubrication becomes contaminated through insufficient maintenance practices, operational practices and harsh environments. This then results in the premature bearing failures within the gear unit. If the gear unit’s “health” can be monitored and imminent failures are known then the unit can be taken out of service and replaced or repaired prior to failure and during scheduled maintenance periods, this will then reduce overall repair costs and drastically reduce unscheduled maintenance time and cost.

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No description available.