Strong Universal Joint

Universal joint for linking motor to drive shaft. I use to drive a ball mill/rock tumbler. need to print 2 UJbottoms with one UJmiddle per joint. The Universal Joint is needed in this application to reduce vibration caused by slight miss-alignment between motor and rollers. made using recycled nuts and bolts, steel shaft is from an old inkjet printer.
Will need to be printed with 100% infill to take the stress of months of continuous use.
Development file from 123d design included for you to improve on this design if you like.