Here’s a two-part article that I think was originally published in White Dwarf, unfortunately we currently don't have access to those, so this version comes from Gubbinz and therefore is in black and white. It was originally in two bits but we've included both parts in the PDF below, worry ye not.
It covers rules and how to model some extra gubbins, including wheel slashas and boosta rokkits, amongst other random odds and ends.
(image by rpeschetz licensed under a Attribution-Non-Commercial 2.0 license)