The first Steam Battle Engine was introduced by the british in the early 50's of the XIX century. These were ordinary steam engines put on iron-reinforced carts, pulling a wagon with small-calibre gun. The proved to be very unreliable and never saw combat during the Crimean War. However, the British government asked for serious research on further Battle Engines. The machine shown here is of Robert Stephenson workshop's production and it has a B1 (or 0-4-2) layout - four powered wheels and two free in the rear.
Its prototype was built in 1858 and was soon put to trials. The prototype displayed several engine problems which have been eliminated quickly afterwards. The machine was accepted by the military and put into production. First fifty Battle Engines of that type were completed by January 1860. The manufcturers were: GWR Railroads' and Robert Stephenson & Co.'s workshops in Swindon and Newcastle respectively. The first production series' Engines carried a brand-new, breech-loading 3in howitzer with a revolutionary recoil system.
It's based a little bit on a steam tank shown in anime Steamboy
2-3 hours, HB and 2B mechanical pencils.