No-I've thought about them before but trying to make a class like the steam knight balanced but also true to the source material would be quite hard. I think it'd be a matter of a 'Steam Knight's Apprentice' being a class in which you gain average BAB progression and good Will and Fort save progression and otherwise just get lots of stat boosts to your Str and a few to your Con and also learn to use , repair and even create steam armour. After that you'd go into a prestiege class which would be 'Steam Knight'.

This class would give more boosts to your Str stat, superior BAB progression, good Fort and Will save progression and would let you customise your steam armour with various boosts to defence and offensive capability. That would be how I'd approach it in 3.5 or Pathfinder. It's doable but getting it right would be tough