Muscle-powered rotary weed whacker

A rotary weed whacker using a linear-to-rotary power mechanism, as used in salad spinners and toy cars. I'm not a farmer but this seems like something which readers here could develop quickly; thanks for having me. I assembled this tool with an actual salad spinner mechanism, which does not provide enough rpm; but a higher-geared mechanism with a flywheel design might, I suspect, work.