We present numerical simulations of the interaction between a collimated, bipolar ``pulse ejected from a star and a continuous wind ejected from a stellar companion. We explore the characteristics of the predicted H$alpha$ intensity maps by varying selected input parameters. We find that the asymmetry (in size and strength) between the two lobes of the proto-planetary nebula OH 231.8+4.2 is reproduced in this scenario if the wind ejected by the companion star has a strong latitude dependence.
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