  We use the bond fluctuation model to study the contraction process of two
polymer loops with $N$ segments that are connected each to the bottom and top
part of a Feringa engine. The change in the size of the molecules as well as
the folding of the two strands follows approximately scaling predictions that
are derived by assuming that the strands are confined inside an effective tube.
Conformation data can be overlapped when plotting it as a function of
$W_{\text{n}}N^{-1/4}$, where $W_{\text{n}}$ is the winding number of the two
strands that is proportional to the number of blobs inside the ``knotted''
region of the molecule and $N$ is the degree of polymerization of the strands.
Our data also supports a weak localization of the knots along the contour of
a-thermal polymers with a localization exponent $t\approx0.78$.
