The previous answer is a little unfair - it was YOU that hit an immoveable object, not the mower! ANY crank will bend under these conditions - assumng you have (had) a mountfield with a Chinese engine, a new crank will cost about £20. Briggs or Tecumseh about £30, and a Honda a massive £115. ANY of these can be - and are on a regular basis - bent by a hard object. Top end models are fitted with a clutch that absorbs shock loads and prevents this kind of damage. A replacement Tecumseh engine (which will bolt straight on, regardless of what was fitted before) can be bought for about £50.
Basically, it's a 'put it down to experience' job! (Or pay £600 for a mower with a blade brake clutch).
phil_saunders@bigfoot.com
Phil Saunders, July 2008