Gearbox design requirements and so forth

[darren.g]

Hi, I am looking to design a gearbox that outputs 200Nm from an input of 0.25-0.3Nm. My question is which gear train method would be more efficient. Also any design guidelines if there are any.

The gear box is to be rotated at the input by a users own strength

 

[Danger]

Welcome to PF, Darren.
I'd recommend looking into an epicyclic train first, although it could be done otherwise.