"The key is to get rid of sharp corners, hence the octagonal shape and a slight taper from top to bottom. Discs tend to glance off angled faces, and if you hit the disc hard enough it destroys it's bearings, flips itself out or breaks whatever belt or chain is driving it.
Tiny Toon was originally built by John Bell who deliberately took on the hardest discs until it stopped breaking so look there for inspiration."

I have been going through the pictures I can find all afternoon and I understand. The sloping sides and shape deflect the energy away and don't present anything for it to bite to.

"BonX main problem was a self inflicted design flaw... It either didn't move, or was too fast."

Bonx looks a right weapon. I think you smashed me round the walls at Doncaster. You bent a GR01 output shaft so must be doing something right!!