Just finished disassembling and testing hornet and worked out what went wrong (bar the obvious disc coming loose :P)

It seems that when the disc jammed against the small sprocket on the mag the mag stalled drawing a huge current. This heated up the batteries and caused the plastic end caps on the batteries to melt and smoke (causing me to run like a loon through the pits to get the batts out!).

Tested the batteries and apart from being slightly unbalanced they seem to be unscathed from their ordeal and the mag works but it sounds a little rough. Gonna open it up next time Im back in the workshop.

Things are looking good for hornet to make an appearance at robochallenge in Newcastle