just been looking around the net for some ideas for my new wrapper that i'm building. i came across this - http://www.okierodbuildingtools.com/POWER_CHUCK.html
i really like the idea, with a little modification it could make a really nice chuck. i'm not sure about most of the products on this site though, they look a bit plasticky and flimsy for me, but some of their ideas with a bit of tuning could work well. if this chuck had two plates to support the bolts, and was made out of metal, it could be a nice piece of gear. i think i'll have a go at making one and see how it turns out.