Ned Simnel was the blacksmith and tinkerer on the stifling plains where Miss Renata Flitworth had her farm, and where Death in his disguise as Bill Door once came a-knocking with a task. He was one of those difficult men who not only knew what a three-eighths Gripley was, but also how to use it...
Ned was charged with destroying - "Killing utterly" - a common-or-garden scythe so that it could be used in the shadowy world between life and death. However, he could not bring himself to destroy the blade which Bill Door had honed to perfection.
Ned was also the inventor of the Combination Harvester, a reaper of corn that horrified Bill Door utterly. This mechanical contrivance was to be the dawning of a new technological age on the Disc, but unfortunately came to grief when Bill Door needed the tarpaulin from around it during a very fierce storm, and at the same time removed a small but vital part, a three-eighths Gripley.
As of the beginning of Raising Steam, Ned is deceased following a miscalculation while building a steam engine. The boiler explodes when a 3/8ths Gripley fails leaving assorted metal bits, a ruined forge, and a cloud of bright pink steam (not surprising given the small bits of Ned that are left). A 3/8ths Gripley is a cotter pin.
He is succeeded in his investigations into the nature of steam by his son Dick Simnel, who gets the engineering right and builds a functioning steam engine and railway network. He leaves a widow, Elsie Simnel, who returns to her hometown of Sheepridge in the hopes that Dick will not follow in his father's footsteps. This proves a vain hope so she uses her legacy from a grandfather who was a pirate to make sure that Dick is properly educated to do it right.