Hawk is a Kitson Meyer 0-4+4-0 articulated loco based on a design built by Andrew Barclay Sons & Co for the 2'5.5" Anglo Greek Magnesite Company in 1903. She was the first steam locomotive to be completely outshopped from the Clayton West workshops. Hawk has 14" driving wheels with 4 cylinders each having 5" bore and 8" stroke. She has Walschearts valve gear and has roller bearings on the main axleboxes, coupling and connecting rods. Hawk was completed in 1998 and originally sported only one chimney with the exhaust from both bogies being piped to the smokebox. Later in 1998 the second chimney (in the coal bunker) was added. Hawk runs with a multiple jet blast nozzle and a future modification is to introduce the gas producer combustion system now well proven on both Fox and Badger. This will involve some additional pipework to carry some of the rear exhaust to the ashpan. Like Fox and Badger Hawk runs with a saturated steam welded steel boiler which combines with its two power bogies to give her a tractive effort of 4371lbs making her not just the largest but also the most powerful loco on the line, and arguably the most powerful 15" gauge locomotive in the country and possibly the world.
During her overhaul in 2007 Hawk received a new main frame and the revised steam pipework. This has resulted in a many of the restrictions in the pipework being removed and the locomotive has now reverted to having only one chimney, the rear one being removed.