Caution this toy is very dangerous for children under 8 years, see below Warning: Small parts kill children if aspirated, see below This 3Dmodel is a toy for age 8 and up, it is inappropriate for children outside this age group, the parts are small and fragile, very easy to be broken and can cause fatal injuries if aspirated by children. Please look into: http://en.wikipedia.org/wiki/Toy_safety http://en.wikipedia.org/wiki/Home_Safety_Council input the parameters, make one by one and play recommended minimum set one Normal gear and one Ring gear Gears to make hypotrochoids and epitrochoids. No... realy, very lovely curves although the names. source of data: http://en.wikipedia.org/wiki/Bruno_Abakanowicz http://en.wikipedia.org/wiki/Spirograph http://en.wikipedia.org/wiki/Hypotrochoid http://en.wikipedia.org/wiki/Epitrochoid