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The Doble Detroit incorporated key ignition, doing away with the need for manual ignition of the boiler system. John Doble also constructed a flash boiler with rectangular casing in which atomized kerosene fuel was ignited with a spark plug, in a carburettor-type venturi and used forced draught provided by an electrically driven fan. This rapidly heated the feedwater contained in vertical grids of tubes welded to horizontal headers. The steam-raising part of the boiler was partitioned off by a wall of heat-resisting material jacketed with planished steel from a smaller compartment in which were similar grids of tubes for feedwater heating. There seem to have been at least two versions of this boiler, the first with the burner and combustion chamber at the bottom, the other with them at the top of the casing; we can already see the thinking that led to the subsequent counterflow monotube boiler arrangement. Boiler operation was fully electro-mechanically automated: the bottom of the boiler housed a metal tray with a row of quartz rods. As heat increased, the tray expanded, pushing the rods forward and shutting off the burner. As the system cooled, the quartz rods contracted, engaging the burner.

The Detroit could start from cold in as little as 90 seconds. A two-cylinder double-acting uniflow engine was mounted under the floor driving the back axle; double slide valves were driven by Joy’s valve gear. The car had only four controls — a steering wheel, a brake pedal, a trip pedal for variable cut-off and reversing, and a foot-operated throttle. The layout of the chassis put the boiler at the front end of the car under the bonnet, the engine and the rear axle forming an integrated unit. The even weight distribution and low center of gravity contributed much to the ride and handling of all Doble cars.

These improvements promised a steam car that would at last provide virtually all of the convenience associated with a conventional automobile, but with higher speed, simpler controls, and what was a virtually noiseless power plant. The only defect sometimes noted throughout the Doble car era was less than perfect braking, which was common in automobiles of all types before 1930. Typically, a car of 1920s only had two rear-mounted mechanical drum brakes, although those fitted to Dobles were of larger than usual proportions. Dobles achieved reliability by eliminating most of the mechanical items that tended to malfunction in conventional automobiles: they had no clutch, no transmission, no distributor, no points. Later Doble steam cars often achieved several hundred thousand miles of use before a major mechanical service was necessary.

The Doble Detroit caused a sensation at the 1917 New York Motor Show and over 5000 deposits were received for the car, with deliveries scheduled to begin in early 1918. However, the Doble brothers had not entirely worked out various design and manufacturing issues, and although the car received good notices and several thousand advance orders were placed, very few were actually built, estimates ranging from 11 to as many as 80. Abner Doble blamed his company's production failure on the steel shortages caused by World War I, but the Doble Detroit was mechanically unsatisfactory. Those few customers who had received completed cars complained that they were sluggish and unpredictable, some even reversing when they should have gone forward. In addition, the Doble brothers were divided by Abner's insistence on taking credit for the company's technical achievements, and John Doble ended up suing Abner for patent infringement, whereupon Abner left Detroit for California. They used 135-inch (3,400 mm) wheelbases.

John Doble died of lymphatic cancer at the age of 28 in 1921, and the surviving brothers reunited in Emeryville, California, setting up under the name of Doble Steam Motors. They managed to solve most of the remaining engineering problems and added even more innovations which increased the cars' acceleration and reliability.