. .Indeed,thanks to the good ideas of lots of people,like the cycling fans in the 1960s,many people around the world______the city centre streets without cars for many years.
【简答题】某传动装置中有一对外啮合渐开线标准直齿圆柱齿轮(正常齿),大齿轮已损坏,小齿轮的齿数 z 1 =2 4 ,齿顶圆直径 d a1 = 78 mm ,中心距a=135mm,试计算大齿轮的主要尺寸: d 2 = _____mm ; z 2 = _____ ; d a2 =______mm ; d f2 = _____mm ; p=____mm;s=____mm。