The article deals with the design of the internal combustion engines. Disadvantages of piston engine are pointed out and advantages of rotary engines are stressed. The simply calculations are added in order to convince the opponents. The very early development procedures of the two rotary engines design are described. The important parts of first rotary engine are machined out and the difficulties that occur already during the assembly phase are pointed out. On the basis of the analysis of the troubles that we have with this first rotary engine the second rotary engine is proposed. The working concept for this second rotary engine is described.