(* Klein Bootle 1.10.1997 *) (* author: Pavel.Pokorny@vscht.cz *) x = { Cos[t], Sin[t](1-Cos[t]), 0}; v = D[x,t]; w = Sqrt[v.v]; r = 0.3 + 0.2 Sin [t] ; a = r {0,0,1}; b = r {-v[[2]],v[[1]],0}/w; y = x + a Cos[u] + b Sin[u]; e = 10^-7; p = ParametricPlot3D [y,{t,e,2Pi-e},{u,0,2Pi}, PlotPoints -> {70,30}, ViewPoint -> {2.4, -1.3, 2.} , Axes -> None, Boxed -> False ];