One other important thing to note (not sure if its in the videos) is that the flywheel key must be an aluminium key. If you put a regular steel woodruff key, the shear strength will be higher than the bits its supposed to protect - meaning next time it will go bang.
Easy to clout things under thick grass - I hit a large chunk of concrete left protruding 10cm from the ground by a council road crew when they put in a footpath a few months ago with my slasher mower. Luckily no damage.
Took 2 more steps and fell down a 30cm deep hole.
Council didn't give 2 figs about the problem for a month until I used the word 'trip hazard'.
Or maybe it was my offer to jackhammer the offending chunk out of the footpath for them.
Either way, I need to brush cut it next time as I worked out they so kindly smashed the concrete chunk up and randomly littered it through for me to hit.
How good are councils
