I've seen blacksmiths using a pedal-operated portable forge (or furnace? How does this terminology actually go in English? Anyway, here I'm not referring to the building of a blacksmith, but the actual heater thing.)

Something like this. I think there is a pedal which makes the big wheel go round, and then there is a belt transmitting the rotation to the fan of the blower.

EDIT: changed the link to direct to a better picture - nah, seems like I can't get a direct link to the exact picture... So the above link takes to an index page, and I mean the image which is second from right on the lower row =)