Aganst the problems in the use of MDD 6—9 6t drop-bottom car,its main frame,weel seal and connecting form were analysed, a reform scheme was put foreward and good results were obtained.

Analysis and design for the solid dump track of bottom dumping skip;

Some issues need to be noticed in dump track design of bottom dumping skip;

The special structure of the new type of bottom unloading bucket is illustrated, and the principle and the properties of the self locking structure as well as the ways of deciding on and calculating the self locking protection angles are discussed.