ill do a sketch if i find time.

Why do you want such a high ratio anyway?
i want to cut holes and bearing recesses in a 50mm acetal cylinder and also engrave fine markings and im trying to avoid the complications of adding a disk brake... it feels like i might get the holding torqe i need at 50:1 (i should really do the maths)
i may well use timing belts and pullies, im not fully commited to one thing or another at the moment

with all the ice i managed to burn out my windscreen wiper motor so iv even pulled the old one apart to look at the worm gear as a possibility... thats 55:1 ratio, i think id struggle tameing the backlash on that though