Ok, when nest a railclone object,instance engine should turn off. I got it,thanks for taking time answering my dumb question.,big thanks.
I have a question though: Is instance engine being used to speed up parsing process of rendering or what? I am quite new to 3dsmax,but really love FP and RC,really don't know what's instance engine all about. The only little thing I knew about instance engine is that the instance engine is not fully compatible with corona render...