Early Stanley cars had light wooden bodies mounted on wooden "perch poles" with
full-elliptic springs. Steam was generated in a
vertical fire-tube boiler mounted beneath the seat with a vaporizing
gasoline (later
kerosene) burner underneath. The boiler was reinforced by several layers of
piano wire wound around it, which gave it a strong but relatively lightweight shell. In early models, the vertical fire-tubes were made of copper and were expanded into holes in the upper and lower
crown sheets. In later models, the installation of a condenser caused oil-fouling in the
expansion joints, and welded steel fire-tubes had to be used. The boilers were reasonably safe since they were fitted with safety valves. Even if these failed, any dangerous over pressure would rupture one of the joints long before the boiler shell itself could burst. The resulting leakage would relieve the boiler pressure and douse the burner with very little risk to the passenger. There is not a single documented incident of a Stanley boiler exploding. The engine had two double-acting cylinders side by side and equipped with slide-valves, and it was a simple-expansion type. Drive was transmitted directly by the crankshaft to a rear-mounted
differential using a chain. Owners often modified their Locomobiles by adding third-party accessories, including improved lubricators, condensers, and devices which eased the laborious starting procedure. To overcome patent difficulties with the design they had sold to Locomobile, the Stanley brothers developed a new model with twin-cylinder engines geared directly to the rear axle. Later models had aluminium coachwork that resembled the internal combustion cars of the time, but they retained steam-car features by having no transmission, clutch, or driveshaft. They also had a fully sprung tubular steel frame. When they later moved the steam boiler to the front of the vehicle, the owners dubbed it the "coffin nose". The compact engine ran at considerable steam pressure, with the boiler described in 1912 as having the safety valve set at , with the burner set to automatically cut back when pressure reached . The twin-cylinder steam engines were at that time 10 horsepower, with bore and stroke, and with bore and stroke, and made extensive use of ball bearings. In order to improve range,
condensers were added from 1915. A Stanley Steamer set the world record for the fastest mile in an automobile (28.2 seconds) in 1906. This record () was not broken by any automobile until 1911, although
Glen Curtiss beat the record in 1907 with a V-8-powered motorcycle at . The record for steam-powered automobiles was not broken until 2009 by Charles Burnett III driving
Inspiration. Production rose to 519 cars in 1917. The Stanley Steamer was sometimes nicknamed "The Flying Teapot". At least one Stanley Steamer found its way to
Castle Hill, New South Wales,
Australia, where it was driven in the late 1920s. == Overview of production figures ==