Hi,
somewhere on this forum someone looked for a manual degrainer for corn, and someone else used an old
cast iron tool.
mayapedal.org builds (and gives away plans for free) bicycle powered mills and degrainer for corn, soy... which can mill 3 lbs per minute.
And, citing the plans:
The Corn Degrainer is used post-harvest and easily degrains 12 to 15 quintales (1 quintal = 100 lbs.) per day.
Link to the pdf plan
http://www.mayapedal.org/Mill.pdf
Link to the homepage with other tools powered by bicycle, (and sketchup plans)
http://www.mayapedal.org/machines.en