The locomotive of Trevithick, according to the most authorized references, was very similar to the attached figure in this page . The boiler was made of strained iron with inner furnace, and the products of the combustion were directed to a chimney located in the same end of the mouth of the firebox . The steam engine, that is to say, the cylinder with the piston, was arranged vertically, and the connecting bars represented in the figure by the D, that acted as a connecting rod, and the L, connected with the motor axis.The steam, after having operated, escaped by the chimney to increase the shot, and this system it depended on the friction of the driving wheels on the tracks to assure sufficient traction power . The pressure of the steam was about 40 pounds by square inch; so that strictly speaking it was a machine of high pressure. The safety valve, E , prevented an excessive pressure in the boiler. This locomotive worked well, but its economic results were not satisfactory.
The following successful attempt to obtain a steam locomotive was done by Blenkinsop in 1812. This machine, as it appears in the corresponding figure , had two cylinders of 203 millimeters of diameter each one and arranged vertically , like in the machine of Trevithick. The connecting bars, nevertheless, acted on axes with pinions that rotated a great dented wheel, that matched as well in the edges of the rails of the track . The supporting wheels of the machine were not, then, driving wheels. The machine of Blenkinsop was followed, in 1813, by another denominated " Puffing Billy ", devised by Blackett, that almost completely agreed upon the same Blenkínsop's system in the general structure of the vehicle, but that obtained the effect of traction by means of the supporting wheels, like in the locomotive invented by Trevithick.