Optimization Of The Large Precision Shafting

Four hundred years after the invention of telescope by Galileo, the telescope has been evolving toward greater caliber. The increase of the telescope caliber, weight and demand for accuracy give a higher shafting design requirement. This paper analyzed the plane thrust bearing which has been widely used. Then, we studied the structure of large precision shafting by experiment and finite element analysis. The study has laid an important technical foundation for solving the development challenges of several meters telescope project. Specifically, the technical route taken in the paper and the results are as follows:1. After using the method of classical Hertz theory combined with finite element analysis, we established a two-dimensional finite element analysis model of the plane thrust bearing which can be solved faster and more accurate. The results showed that compared with the results of Hertz theory, the errors of finite element analysis results were less than 1.87%.2. We designed and built an experimental platform to measure the elastic approaching of the plane thrust bearing. The experimental platform was based on the optical non-contact measurement and analysis system for displacement. The platform can measure the approach of plane thrust bearing’s raceways under different loads. In other words, it is the stiffness curve of the plane thrust bearing. The results showed that the test system’s accuracy is within ±8.3%, which can meet the demand of mechanics measurement of design stage.3. We carried on the analysis to the parameters which can affect the results of finite element analysis. Based on this, we modified "Elastic modulus" and "Poisson’s ratio" according to the experimental results. Then a finite element model in line with the actual working conditions was established and the recommended values of key parameters were given. The results showed that compared with the results of the experiment, the errors of finite element analysis results were less than 13.8%.4. According to the finite element model in line with the actual working conditions, we established the finite element analysis models of plane thrust bearings, angular-contact ball bearings and cylindrical roller bearings. And we plotted the static bearing capacity curves of the bearings. Under the conditions of same diameter and number of the rollers, the results showed that the angular-contact ball bearing’s axial ultimate bearing capacity is 6.8 times of the plane thrust bearing’s, and the cylindrical roller bearing’s ultimate bearing capacity is 8.7 times of the plane thrust bearing’s.5. After studying the working conditions of the large aperture telescope which can be transported, we got the design requirements of the shafting structures.6. We carried on the analysis to the parameters which can affect the bearing capacity of plane thrust bearings, angular-contact ball bearings and cylindrical roller bearings by using the finite element analysis models and got the design parameters of the shafting structures which meet the requirements of the subject. The results showed that the plane thrust bearing can meet the design requirements, and it was suggested to use this type of bearing. In the future, if the shafting structure we designed needs to carry larger aperture telescope or stronger impact load and the plane thrust bearing can’t meet the design requirements, we propose the use of angular-contact ball bearings or cylindrical roller bearings.